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.send { color:#77bb77; }
.server { color:#7799bb; }
.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>I’ve got an answer on Twitter for that behavior: https://twitter.com/phausler/status/743927492096851969</p>
<p>I’ve anyone like me needs <code>Data</code> to have a specific capacity and still be non-optional, here is how I build a workaround (<code>Data</code> and <code>Data.Deallocator</code> aren’t fully implemented yet, thats why I’m using a custom deallocator rather then <code>.free</code>):</p>
<pre><code class="swift">let capacity = 42 // or get the value somehow
let dataBufferPointer = UnsafeMutablePointer<UInt8>(allocatingCapacity: capacity)
dataBufferPointer.initialize(with: 0, count: capacity)
// do some work and mutation to the data here
let deallocator = Data.Deallocator.custom {
(buffer, _) in
free(buffer)
}
// this initializer says you should not mutate that data after constructing it
let data = Data(bytesNoCopy: dataBufferPointer, count: capacity, deallocator: deallocator)
</code></pre>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1466358266502991872" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 19. Juni 2016 um 19:27:21, Saagar Jha (<a href="mailto:saagarjha28@gmail.com">saagarjha28@gmail.com</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>
<title></title>
<div dir="ltr">
<p>Not quite:</p>
<blockquote>
<p>Swift’s policy on memory allocation failure is that fixed-size
object allocation is considered to be a runtime failure if it
cannot be handled. OTOH, APIs that can take a variable and
arbitrarily large amount to allocate should be failable. NSData
falls into the later category. </p>
</blockquote>
<p><a href="http://article.gmane.org/gmane.comp.lang.swift.user/1709">Source</a></p>
<br>
<br>
<div class="gmail_quote">
<div dir="ltr">On Sun, Jun 19, 2016 at 10:00 AM Karl <<a href="mailto:razielim@gmail.com">razielim@gmail.com</a>>
wrote:<br></div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word">As I understand it, that’s not an
error in the ‘try’ sense of the word. If that failure happens, it’s
a catastrophic issue which should bring down the application.
<div><br></div>
<div>So the initialiser shouldn’t be failable; you’re right. File a
bug at <a href="http://bugs.swift.org" target="_blank">bugs.swift.org</a>.</div>
</div>
<div style="word-wrap:break-word">
<div><br></div>
<div>Karl</div>
</div>
<div style="word-wrap:break-word">
<div><br>
<div>
<blockquote type="cite">
<div>On 18 Jun 2016, at 06:06, Saagar Jha via swift-users
<<a href="mailto:swift-users@swift.org" target="_blank">swift-users@swift.org</a>> wrote:</div>
<br>
<div>
<div dir="ltr">
<p><a href="http://article.gmane.org/gmane.comp.lang.swift.user/1702" target="_blank">This</a> might be relavant. Basically, <code>Data</code>’s
<code>init</code> will fail if memory can’t be allocated for
it.</p>
<br>
<br>
<div class="gmail_quote">
<div dir="ltr">On Fri, Jun 17, 2016 at 11:38 AM Adrian Zubarev via
swift-users <<a href="mailto:swift-users@swift.org" target="_blank">swift-users@swift.org</a>> wrote:<br></div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word">
<div>
<p>Hello there, I’m trying to optimize my code and reduce copying
from different buffers into a new one.</p>
<p>I thought I just create a Data value with enough capacity and
write directly into it. My problem is that
<code>Data.init?(capacity:)</code> can fail, but why and when?</p>
<p>Can someone explain this behavior to me?</p>
<p>I’m sending data via TCP sockets and when <code>recn</code>
function write directly into a <code>Data</code> struct.</p>
<div><br></div>
</div>
<div>
<div style="font-family:Helvetica,Arial;font-size:13px;margin:0px">
<br></div>
<br>
<div>
<div style="font-family:helvetica,arial;font-size:13px">
-- <br>
Adrian Zubarev<br>
Sent with Airmail</div>
</div>
</div>
<div>
<div><br></div>
</div>
</div>
_______________________________________________<br>
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<a href="https://lists.swift.org/mailman/listinfo/swift-users" rel="noreferrer" target="_blank">https://lists.swift.org/mailman/listinfo/swift-users</a><br>
</blockquote>
</div>
</div>
<div dir="ltr">--<br></div>
<div data-smartmail="gmail_signature">
<div dir="ltr">-Saagar Jha</div>
</div>
_______________________________________________<br>
swift-users mailing list<br>
<a href="mailto:swift-users@swift.org" target="_blank">swift-users@swift.org</a><br>
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</div>
</blockquote>
</div>
<br></div>
</div>
</blockquote>
</div>
</div>
<div dir="ltr">--<br></div>
<div data-smartmail="gmail_signature">
<div dir="ltr">-Saagar Jha</div>
</div>
</div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>