<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Hello Swift evolution,</div><div class=""><br class=""></div><div class="">I'm sending this proposal out again for another round of RFC. The first round did not get much specific feedback, and nothing has fundamentally changed. In this updated version I beefed up the explanation a bit and clarified the language.</div><div class=""><br class=""></div><div class="">-Andy</div><div class=""><br class=""></div><div><blockquote type="cite" class=""><div class="">On May 9, 2016, at 11:14 AM, Andrew Trick via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><div class=""><div class="">Hello Swift evolution,</div><div class=""><br class=""></div><div class="">I sent this to swift-dev last week. Sorry to post on two lists!</div><div class=""><br class=""></div><div class="">Swift does a great job of protecting against undefined behavior--as long as you avoid "unsafe" APIs, that is. However, unsafe APIs are important for giving developers control over implementation details and performance. Naturally, the contract between unsafe APIs and the optimizer is crucial. When a developer uses an unsafe API, the rules governing safe, well-defined behavior must be clear. On the opposite end, the optimizer must know which assumptions it can make based on those rules. Simply saying that anything goes because "unsafe" is in the name is not helpful to this effort.</div><div class=""><br class=""></div><div class="">For a long time, I've wanted these rules nailed down. We have more users taking advantage of advanced features, and more optimizations that take advantage of assumptions guided by the type system. This seems like a particularly good time to resolve UnsafePointer semantics, considering the type system and UnsafePointer work that's been going on recently. Strict aliasing is something I would like addressed. If we do nothing here, then we will end up by default inheriting C/C++ semantics, as with any language that relies on a C/C++ backend. In other words, developers will be forced to write code with technically undefined behavior and rely on the compiler to be smart enough to recognize and recover from common patterns. Or we can take advantage of this opportunity and instead adopt a sound memory model with respect to aliasing.</div><div class=""><br class=""></div><div class="">This proposal is only an RFC at this point. I'm sending it out now to allow for plenty of time for discussion (or advance warning). Keep in mind that it could change considerably before it goes up for review.</div></div><div class=""><br class=""></div><div class="">-Andy</div></div><div class=""><br class=""></div></div></div></blockquote><div><br class=""></div><h1 style="box-sizing: border-box; font-size: 2.25em; margin-right: 0px; margin-bottom: 16px; margin-left: 0px; line-height: 1.2; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255); margin-top: 0px !important;" class="">UnsafeBytePointer API for In-Memory Layout</h1><ul style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><li style="box-sizing: border-box;" class="">Proposal: <a href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">SE-NNNN</a></li><li style="box-sizing: border-box;" class="">Author(s): <a href="https://github.com/atrick" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">Andrew Trick</a></li><li style="box-sizing: border-box;" class="">Status: <span style="box-sizing: border-box;" class=""><a href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#rationale" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">Awaiting review</a></span></li><li style="box-sizing: border-box;" class="">Review manager: TBD</li></ul><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-introduction" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#introduction" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Introduction</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutable</code> refer to a typed region of memory, and the compiler must be able to assume that <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> element (<code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Pointee</code>) type is consistent with other access to the same memory. See <a href="https://github.com/atrick/swift/blob/type-safe-mem-docs/docs/TypeSafeMemory.rst" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">proposed Type Safe Memory Access documentation</a>. Consequently, conversion between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> element types exposes an easy way to abuse the type system.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">In the following example, <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">takesUIntPtr</code> accesses a memory location as a <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UInt</code>, which is incompatible with the declared type of the pointer passed to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">takesIntPtr</code>, yet the statement that performs the pointer conversion provides no indication that type punning may be taking place:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">takesUIntPtr</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">p</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> p[<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>]
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">takesIntPtr</span>(q: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> takesUIntPtr(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span>(q))
}
</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">If this pointer conversion was accidental, then it is likely a serious bug. Type punning via <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> is semantically undefined behavior and de facto undefined behavior given the optimizer's long-time treatment of <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code>.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">If the user's intention is to perform type punning, then <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> is the wrong API. Swift does not currently provide an API that permits safe, legal, type punning.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Swift-evolution thread: <a href="https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160509/thread.html#16909" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">[RFC] UnsafeBytePointer API for In-Memory Layout</a></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">In this document, all mentions of <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> also apply to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer</code>.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-motivation" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#motivation" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Motivation</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Type punning is not a normal use case for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> and will likely lead to undefined behavior. To avoid accidental type punning, we should prohibit inferred conversion between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T></code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<U></code> unless the target of the conversion is an untyped or nondereferenceable pointer (currently represented as <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code>). An "inferred conversion" is one in which a generic type is initialized via type inferrence without the need to spell the destination type:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">struct</span> S {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> ptr <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> p <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">...</span>)
S(ptr: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span>(p))</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; background-color: rgb(255, 255, 255);" class=""><span style="color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px;" class="">To support this change we should introduce a new pointer type that does not bind the type of its <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Pointee</code>. </span><font color="#333333" face="Helvetica Neue, Helvetica, Segoe UI, Arial, freesans, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol" size="3" class="">Such a new pointer type would </font><span style="color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: medium;" class="">allow inferred and implicit conversion from typed to untyped pointers, </span><span style="color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: medium;" class="">which is the common, safe use case for UnsafePointer </span><font color="#333333" face="Helvetica Neue, Helvetica, Segoe UI, Arial, freesans, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol" size="3" class="">conversion. More importantly it would provide</font><span style="color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px;" class=""> an ideal foundation for an API that allows byte-wise pointer arithmetic and a legal, well-defined means to access an untyped region of memory (safe type punning). No alternative currently exists for manual memory layout and direct access to untyped memory. Not only is this a legitimate use case that Swift should support, but the lack a proper API has already lead to dangerous overuse of <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code>.</span></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">As motivation for such an API, consider that an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code> or <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">OpaquePointer</code> may be currently be obtained from an external API. However, the developer may know the memory layout and may want to read or write elements whose types are compatible with that layout. This a reasonable use case, but unless the developer can guarantee that all accesses to the same memory location have the same type, then they cannot use <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> to access the memory without risking undefined behavior.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">An example based on the proposed new <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> API is included below.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-proposed-solution" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#proposed-solution" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Proposed solution</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">This proposal introduces <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutableBytePointer</code> types, along with an API for obtaining an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutableBytePointer</code> value at a relative byte offset and loading and storing arbitrary types at that location.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T></code> to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> conversion will be allowed via an unlabeled initializer and in some cases may be implicit. However, inferred <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T></code> conversion will now be statically prohibited. Converting arbitrary <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T></code> types will instead require a labeled initializer that accepts the destination type:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">struct</span> S {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> ptr <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> p <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">...</span>)
S(ptr: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span>(p, to: T))</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Just as with <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">unsafeBitCast</code>, although the destination of the cast can usually be inferred, we want the developer to explicitly state the intended destination type, both because type inferrence can be surprising, and because it's important to the reader for code comprehension.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">While the new <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> type supports the removal of dangerous <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> conversion, it's API also meets multiple requirements:</p><ol style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><li style="box-sizing: border-box;" class="">An untyped pointer to memory</li><li style="box-sizing: border-box;" class="">Type-unsafe access to memory (legal type punning)</li><li style="box-sizing: border-box;" class="">Pointer arithmetic within byte-addressable memory</li></ol><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutableBytePointer</code> will replace <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer<Void></code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> will replace <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code> as the standard representations for untyped memory. The Swift imported type for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">const void*</code> will be <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutableBytePointer</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> respectively.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Note: For API clarity we could consider a typealias for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">VoidPointer</code>. A separate <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">VoidPointer</code> type would not be very useful--there's no danger that <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> will be casually dereferenced, and no danger in allowing pointer arithmetic since the only reasonable interpretation is that of a byte-addressable memory.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Loading from and storing to memory via an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutable]BytePointer</code> is safe independent of the type of value being loaded or stored and independent of the memory's allocated type as long as layout guarantees are met (per the ABI). This allows legal type punning within Swift and allows Swift code to access a common region of memory that may be shared across an external interface that does not provide type safety guarantees. Accessing type punned memory directly through a designated <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutable]BytePointer</code> type provides sound basis for compiler implementation of strict aliasing. This is in contrast with the approach of simply providing a special unsafe pointer cast operation for bypassing type safety, which cannot be reliably implemented.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Providing an API for type-unsafe memory access would not serve much purpose without the ability to compute byte offsets. Of course, we could require users to convert back and forth using bitPatterns, but that would be awkward and only obscure the purpose of the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> type.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-detailed-design" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#detailed-design" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Detailed design</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The public API is shown here. For details, see the <a href="https://github.com/atrick/swift/commits/unsafeptr_convert" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">unsafeptr_convert branch</a>.</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">struct</span> UnsafeMutableBytePointer <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Hashable</span>, _Pointer {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> _rawValue: Builtin<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>RawPointer
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> hashValue: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span> {<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">...</span>}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>?<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>?)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>?<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>?)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> OpaquePointer<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>?<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> OpaquePointer<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>?)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>?(bitPattern: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>?(bitPattern: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Load a single `T` value from memory.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The underlying pointer is properly aligned for</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// accessing `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Note: The converse of loading a value, storing a value `T` into</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// initialized memory requires the user to know the previously initialized</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// value's type. Full 'store' semantics can be achieved with:</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// `deinitialize(PreviousType)`</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// `initialize(NewType, with: value)`</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// If the previosly initialized type cannot reference any managed objects,</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// then the `deinitialize` call can be skipped.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">load</span><T>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> T
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Load a `T` value at the specified `index` from `self` as if it</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// contains at least `index` + 1 contiguous values of type `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The underlying pointer is properly aligned for</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// accessing `T`.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">load</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">asArrayOf</span> <span class="pl-smi" style="box-sizing: border-box;">_</span>: T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">at</span> <span class="pl-smi" style="box-sizing: border-box;">index</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> T
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Initialize this memory location with `count` consecutive copies</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// of `newValue`</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Returns a `UnsafeBytePointer` to memory one byte past the last</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// initialized value.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The memory is not initialized.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The underlying pointer is properly aligned for</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// accessing `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: `count` is non-negative.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory is initialized; the value should eventually</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// be destroyed or moved from to avoid leaks.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">initialize</span><T>(_: T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">with</span> <span class="pl-smi" style="box-sizing: border-box;">newValue</span>: T, count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">1</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UnsafeBytePointer
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Initialize the memory location at `index` with `newValue` as if `self`</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// holds at least `index` + 1 contiguous values of type `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Returns a `UnsafeBytePointer` to memory one byte past the</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// initialized value.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The memory at `index` is not initialized.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The underlying pointer is properly aligned for</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// accessing `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory is initialized; the value should eventually</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// be destroyed or moved from to avoid leaks.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">initialize</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">asArrayOf</span> <span class="pl-smi" style="box-sizing: border-box;">_</span>: T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>, initialValue: T, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">at</span> <span class="pl-smi" style="box-sizing: border-box;">index</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UnsafeBytePointer
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// De-initialize the `count` `T`s starting at `self`, returning</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// their memory to an uninitialized state.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The `T`s at `self..<self + count` are initialized.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory is uninitialized.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">deinitialize</span><T>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>, count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">1</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// De-initialize `T` at the memory location `index` as if `self` holds at</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// least `index` + 1 contiguous values of type `T`, returning</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// the memory to an uninitialized state.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The `T` value at `index` is initialized.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory at `index` is uninitialized.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">deinitialize</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">asArrayOf</span> <span class="pl-smi" style="box-sizing: border-box;">_</span>: T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">at</span> <span class="pl-smi" style="box-sizing: border-box;">index</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Allocate and point at uninitialized memory for `size` bytes with</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// `alignedTo` alignment.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory is allocated, but not initialized.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">@warn_unused_result</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(allocatingBytes size: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, alignedTo: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Allocate and point at uninitialized memory for `count` values of `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory is allocated, but not initialized.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">@warn_unused_result</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(allocatingCapacity count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, of: T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Deallocate uninitialized memory allocated for `size` bytes with</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// `alignedTo` alignment.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The memory is not initialized.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory has been deallocated.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">deallocateBytes</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">size</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, alignedTo: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Deallocate uninitialized memory allocated for `count` values of `T`.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Precondition: The memory is not initialized.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">///</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// - Postcondition: The memory has been deallocated.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">deallocateCapacity</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">num</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, of: T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>)
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Omitting comments for the following convenient variations on</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// intitialize...</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">initialize</span><T>(from: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>, count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UnsafeBytePointer
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">initializeBackward</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">from</span> <span class="pl-smi" style="box-sizing: border-box;">source</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>, count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">moveInitialize</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">from</span> <span class="pl-smi" style="box-sizing: border-box;">source</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>, count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">moveInitializeBackward</span><T>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">from</span> <span class="pl-smi" style="box-sizing: border-box;">source</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>,
count: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> OpaquePointer {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(_ <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> UnsafeBytePointer)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(bitPattern: UnsafeBytePointer)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(bitPattern: UnsafeBytePointer)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> UnsafeBytePointer <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Strideable</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">distance</span>(to <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> UnsafeBytePointer) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">advanced</span>(by <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UnsafeBytePointer
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">==</span> (lhs: UnsafeBytePointer, rhs: UnsafeBytePointer) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Bool</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);"><</span> (lhs: UnsafeBytePointer, rhs: UnsafeBytePointer) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Bool</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">+</span> (lhs: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, rhs: UnsafeBytePointer) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UnsafeBytePointer
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">-</span> (lhs: UnsafeBytePointer, rhs: UnsafeBytePointer) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span></pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> provides the same interface as <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer</code> except for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">store</code>, variations on <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">initialize</code>, and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">deinitialize</code>.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Occasionally, we need to convert from a <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> to an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code>. This should only be done in very rare circumstances when the author understands the compiler's strict type rules for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code>. Although this could be done by casting through an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">OpaquePointer</code>, an explicit, designated unsafe pointer cast API would makes the risks more obvious and self-documenting. For example:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(_ from: UnsafeBytePointer, to: Pointee<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>type)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(_ from: UnsafeBytePointer, to: Pointee<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>type)
}</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Similarly, conversion between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> types must now be spelled with an explicitly <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Pointee</code> type:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ from: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>, to: Pointee<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ from: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>, to: Pointee<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(_ from: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>, to: Pointee<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">Type</span>)
}</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Some existing conversions between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> types do not convert <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Pointee</code> types but instead coerce an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> to an <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer</code>. This is no longer an inferred conversion, but must be explicitly requested:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">mutating</span> from: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span>Pointee<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>)
}</pre></div><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-impact-on-existing-code" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#impact-on-existing-code" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Impact on existing code</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The largest impact of this change is that <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">const void*</code> are imported as <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutableBytePointer</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>. This impacts many public APIs, but with implicit argument conversion should not affect typical uses of those APIs.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Any Swift projects that rely on type inference to convert between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> types will need to take action. The developer needs to determine whether type punning is necessary. If so, they must migrate to the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> API. Otherwise, they can work around the new restriction by using a <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">to: Pointee</code>, or <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">mutating</code> label.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Disallowing inferred <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> direct conversion requires some standard library code to use an explicit <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">to: Pointee</code> label for unsafe conversions that may violate strict aliasing.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">All occurrences of <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutable]Pointer<Void></code> in the standard library are converted to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>. e.g. <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">unsafeAddress()</code> now returns <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>, not <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code>.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Some occurrences of <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutable]Pointer<Pointee></code> in the standard library are replaced with <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>, either because the code was playing too loosely with strict aliasing rules, or because the code actually wanted to perform pointer arithmetic on byte-addresses.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">StringCore.baseAddress</code> changes from <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">OpaquePointer</code> to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> because it is computing byte offsets and accessing the memory. <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">OpaquePointer</code> is meant for bridging, but should be truly opaque; that is, nondereferenceable and not involved in address computation.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">StringCore</code> implementation does a considerable amount of casting between different views of the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">String</code> storage. The current implementation already demonstrates some awareness of strict aliasing rules. The rules are generally followed by ensuring that the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">StringBuffer</code> only be accessed using the appropriate <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">CodeUnit</code> within Swift code. For interoperability and optimization, String buffers frequently need to be cast to and from <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">CChar</code>. This is valid as long access to the buffer from Swift is guarded by dynamic checks of the encoding type. These unsafe, but dynamically legal conversion points will now be labeled with <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">to: Pointee</code>.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">CoreAudio</code> utilities now use an UnsafeBytePointer.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-implementation-status" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#implementation-status" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Implementation status</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">On my <a href="https://github.com/atrick/swift/commits/unsafeptr_convert" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">unsafeptr_convert branch</a>, I've made most of the necessary changes to support the addition of <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>and the removal of inferred <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> conversion.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">There are a several things going on here in order to make it possible to build the standard library with the changes:</p><ul style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">A new <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> type is defined.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The type system imports <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> as UnsafeBytePointer.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The type system handles implicit conversions to UnsafeBytePointer.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> replaces both <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer<Void></code> (Recent feedback suggestes that <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer</code> should also be introduced).</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The standard library was relying on inferred UnsafePointer conversion in over 100 places. Most of these conversions now either take an explicit label, such as <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">to: Pointee</code>, <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">mutating</code>. Some have been rewritten.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">Several places in the standard library that were playing loosely with strict aliasing or doing bytewise pointer arithmetic now use UnsafeBytePointer instead.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">Explicit labeled <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutable]Pointer</code> initializers are added.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The inferred <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutable]Pointer</code> conversion is removed.</p></li></ul><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">TODO:</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Once this proposal is accepted, and the rules for casting between pointers types have been decided, we need to finish implementing the type system support. The current implementation (intentionally) breaks a few tests in pointer_conversion.swift. We also need to ensure that interoperability requirements are met. Currently, many argument casts to be explicitly labeled. The current implementation also makes it easy for users to hit an "ambiguous use of 'init'" error when relying on implicit argument conversion.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Additionally:</p><ul style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">UnsafeMutableBytePointer needs to be introduced, and we need to distinguish between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">const void*</code>import types.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">A name mangled abbreviation needs to be created for UnsafeBytePointer.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The StringAPI tests should probably be rewritten with <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The NSStringAPI utilities and tests may need to be ported to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code></p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">The CoreAudio utilities and tests may need to be ported to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>.</p></li></ul><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-alternatives-considered" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#alternatives-considered" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Alternatives considered</h2><h3 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.43; font-size: 1.5em; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-existing-workaround" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#existing-workaround" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1.2;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Existing workaround</h3><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">In some cases, developers can safely reinterpret values to achieve the same effect as type punning:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> ptrI32 <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UnsafeMutablePointer</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int32</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span>(allocatingCapacity: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">1</span>)
ptrI32[<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>] <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int32</span>()
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> u <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">unsafeBitCast</span>(ptrI32[<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>], to: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">self</span>)</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Note that all access to the underlying memory is performed with the same element type. This is perfectly legitimate, but simply isn't a complete solution. It also does not eliminate the inherent danger in declaring a typed pointer and expecting it to point to values of a different type.</p><h3 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.43; font-size: 1.5em; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-discarded-alternatives" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#discarded-alternatives" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1.2;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Discarded alternatives</h3><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">We considered adding a <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">typePunnedMemory</code> property to the existing <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutabale]Pointer</code> API. This would provide a legal way to access a potentially type punned <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Unsafe[Mutabale]Pointer</code>. However, it would certainly cause confusion without doing much to reduce likelihood of programmer error. Furthermore, there are no good use cases for such a property evident in the standard library.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The opaque <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">_RawByte</code> struct is a technique that allows for byte-addressable buffers while hiding the dangerous side effects of type punning (a _RawByte could be loaded but it's value cannot be directly inspected). <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<_RawByte></code> is a clever alternative to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>. However, it doesn't do enough to prevent undefined behavior. The loaded <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">_RawByte</code> would naturally be accessed via <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">unsafeBitCast</code>, which would mislead the author into thinking that they have legally bypassed the type system. In actuality, this API blatantly violates strict aliasing. It theoretically results in undefined behavior as it stands, and may actually exhibit undefined behavior if the user recovers the loaded value.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">To solve the safety problem with <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<_RawByte></code>, the compiler could associate special semantics with a <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code> bound to this concrete generic parameter type. Statically enforcing casting rules would be difficult if not impossible without new language features. It would also be impossible to distinguish between typed and untyped pointer APIs. For example, <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T>.load<U></code> would be a nonsensical vestige.</p><h3 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.43; font-size: 1.5em; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-alternate-proposal-for-void-type" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#alternate-proposal-for-void-type" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1.2;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Alternate proposal for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: inherit; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> type</h3><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Changing the imported type for <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> will be somewhat disruptive. Furthermore, this proposal currently drops the distinction between <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">const void*</code>--an obvious loss of API information.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">We could continue to import <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">void*</code> as <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeMutablePointer<Void></code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">const void*</code> as <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code>, which will continue to serve as an "opaque" untyped pointer. Converting to UnsafeBytePointer would be necesarry to perform pointer arithmetic or to conservatively handle possible type punning.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">This alternative is <em style="box-sizing: border-box;" class="">much</em> less disruptive, but we are left with two forms of untyped pointer, one of which (<code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer</code>) the type system somewhat conflates with typed pointers.</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Given the current restrictions of the language, it's not clear how to statically enforce the necessary rules for casting<code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code> once general <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T></code> conversions are disallowed. The following conversions should be inferred, and implied for function arguments (ignoring mutability):</p><ul style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<T></code> to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code></p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafePointer<Void></code> to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code></p></li></ul><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">I did not implement this simpler design because my primary goal was to enforce legal pointer conversion and rid Swift code of undefined behavior. I can't do that while allowing UnsafePointer conversions.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-future-improvements" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#future-improvements" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Future improvements</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code> should eventually support unaligned memory access. I believe that we will eventually have a modifier that allows "packed" struct members. At that time we may also want to add a "packed" flag to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">UnsafeBytePointer</code>'s <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">load</code> and <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">initialize</code> methods.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-unsafebytepointer-example" class="anchor" href="https://github.com/atrick/swift-evolution/blob/voidpointer/proposals/XXXX-unsafebytepointer.md#unsafebytepointer-example" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>UnsafeBytePointer example</h2><div class="highlight highlight-source-swift" style="box-sizing: border-box; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255); margin-bottom: 0px !important;"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// An example of using UnsafeMutableBytePointer to implement manual memory</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// layout.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// A Buffer for reading and writing basic types at a fixed address.</span>
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Indirection allows the buffer to refer to mutable state elsewhere.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">struct</span> MessageBuffer {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> ptr: UnsafeMutableBytePointer
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">enum</span> IndirectFlag { <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> Direct, Indirect }
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">private</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">getPointer</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">atOffset</span> <span class="pl-smi" style="box-sizing: border-box;">n</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">isIndirect</span>: IndirectFlag)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UnsafeMutableBytePointer {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">switch</span> isIndirect {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Indirect:
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> (ptr <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">+</span> n)<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>load(UnsafeMutableBytePointer<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">self</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Direct:
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> ptr <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">+</span> n
}
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">readUInt32</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">atOffset</span> <span class="pl-smi" style="box-sizing: border-box;">n</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">isIndirect</span>: IndirectFlag) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> getPointer(atOffset: n, isIndirect)<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>load(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">self</span>)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">readFloat32</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">atOffset</span> <span class="pl-smi" style="box-sizing: border-box;">n</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">isIndirect</span>: IndirectFlag) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> getPointer(atOffset: n, isIndirect)<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>load(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">self</span>)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">writeUInt32</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">val</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">atOffset</span> <span class="pl-smi" style="box-sizing: border-box;">n</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) {
getPointer(atOffset: n, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Direct)<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">initialize</span>(with: val)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">writeFloat32</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">val</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span>, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">atOffset</span> <span class="pl-smi" style="box-sizing: border-box;">n</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) {
getPointer(atOffset: n, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Direct)<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">initialize</span>(with: val)
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">writeIndirect</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">ptr</span>: UnsafeMutableBytePointer, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">atOffset</span> <span class="pl-smi" style="box-sizing: border-box;">n</span>: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span>) {
getPointer(atOffset: n, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Direct)<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">initialize</span>(with: ptr)
}
}
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Encoded message format.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">struct</span> MessageFormat <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> Sequence, IteratorProtocol {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">typealias</span> Element <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> MessageFormat
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">private</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">static</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> maxFormatFields <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">32</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">/</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">4</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">static</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> maxBufferBytes <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> maxFormatFields <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">*</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">strideof</span>(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span>)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> formatCode: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> elementCode: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> offset: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">init</span>(bitPattern: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span>) {
formatCode <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> bitPattern
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">enum</span> Kind {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> None, Reserved, <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span>, <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span>, IndirectUInt32, IndirectFloat32
}
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// The first field's kind.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> kind <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> Kind {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">get</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">switch</span> elementCode {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> 0x0: <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> Kind<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>None
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> 0x2: <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> Kind<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> 0x3: <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> Kind<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> 0x6: <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> Kind<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>IndirectUInt32
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> 0x7: <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> Kind<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>IndirectFloat32
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">default</span>: <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> Kind<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Reserved
}
}
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">elementStride</span>() <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Int</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> (elementCode <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">&</span> 0x4) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">!=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">?</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">strideof</span>(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">4</span>
}
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">/// Get the format for the next element.</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">mutating</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">next</span>() <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> Element? {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">if</span> elementCode <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">!=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span> {
offset <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">+=</span> elementStride()
}
elementCode <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> formatCode <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">&</span> 0xF
formatCode <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">>>=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">4</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">if</span> kind <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">==</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>None {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">nil</span>
}
<span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">// align to the next element size</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> offsetMask <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> elementStride() <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">1</span>
offset <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> (offset <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">+</span> offsetMask) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">&</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">~</span>offsetMask
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">self</span>
}
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">createBuffer</span>() <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> MessageBuffer {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> MessageBuffer(ptr: UnsafeMutableBytePointer(
allocatingBytes: MessageFormat<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>maxBufferBytes, alignedTo: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">strideof</span>(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span>)))
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">destroy</span>(buffer: MessageBuffer) {
buffer<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>ptr<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>deallocateBytes(MessageFormat<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>maxBufferBytes,
alignedTo: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">strideof</span>(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt</span>))
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> sharedInt: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">42</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">var</span> sharedFloat: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">16</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">25</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">generateMessage</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">inBuffer</span> <span class="pl-smi" style="box-sizing: border-box;">mb</span>: MessageBuffer) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> MessageFormat {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> mf <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> MessageFormat(bitPattern: 0x06727632)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">for</span> field <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">in</span> mf {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">switch</span> field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>kind {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span>:
mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>writeUInt32(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">66</span>, atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span>:
mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>writeFloat32(<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">41</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">625</span>, atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>IndirectUInt32:
mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>writeIndirect(<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">&</span>sharedInt, atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>IndirectFloat32:
mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>writeIndirect(<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">&</span>sharedFloat, atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>None:
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">fallthrough</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Reserved:
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> MessageFormat(bitPattern: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">0</span>)
}
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> mf
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">handleMessage</span>(<span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">buffer</span> <span class="pl-smi" style="box-sizing: border-box;">mb</span>: MessageBuffer, format: MessageFormat) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Bool</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">for</span> field <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">in</span> format {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">switch</span> field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>kind {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">UInt32</span>:
<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">print</span>(mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>readUInt32(atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Direct))
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Float32</span>:
<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">print</span>(mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>readFloat32(atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Direct))
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>IndirectUInt32:
<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">print</span>(mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>readUInt32(atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Indirect))
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>IndirectFloat32:
<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">print</span>(mb<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>readFloat32(atOffset: field<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>offset, <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Indirect))
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>None:
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">fallthrough</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">case</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Reserved:
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">false</span>
}
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">true</span>
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">runProgram</span>() {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> mb <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> createBuffer()
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> mf <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> generateMessage(inBuffer: mb)
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">if</span> handleMessage(buffer: mb, format: mf) {
<span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">print</span>(<span class="pl-s" style="box-sizing: border-box; color: rgb(24, 54, 145);"><span class="pl-pds" style="box-sizing: border-box;">"</span>Done<span class="pl-pds" style="box-sizing: border-box;">"</span></span>)
}
destroy(buffer: mb)
}
runProgram()</pre></div><div class=""><br class=""></div></div><br class=""></body></html>