[swift-evolution] [Review] SE-0147: Move UnsafeMutablePointer.initialize(from:) to UnsafeMutableBufferPointer

[Ben Cohen]

> On Dec 12, 2016, at 1:32 PM, Andrew Trick <atrick at apple.com> wrote:
> 
>> 
>> On Dec 7, 2016, at 10:07 PM, Douglas Gregor via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Hello Swift community,
>> 
>> The review of SE-0147 "Move UnsafeMutablePointer.initialize(from:) to UnsafeMutableBufferPointer" begins now and runs through December 12, 2016. The proposal is available here:
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0147-move-unsafe-initialize-from.md <https://github.com/apple/swift-evolution/blob/master/proposals/0147-move-unsafe-initialize-from.md>
>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>> 
>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>> or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:
>> 
>> Proposal link:
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0147-move-unsafe-initialize-from.md <https://github.com/apple/swift-evolution/blob/master/proposals/0147-move-unsafe-initialize-from.md>
> For UnsafeMutableRawBufferPointer.initializeMemory:
> 
> We have this doc comment:
> 
>   /// Returns an iterator to any elements of `source` that didn't fit in the 
>   /// buffer, and an index into the buffer one past the last byte written.
> 
> Which is consistent with the PR https://github.com/apple/swift/pull/5718 <https://github.com/apple/swift/pull/5718>
> 
> + public func initializeMemory<S: Sequence>(
> +    as: S.Iterator.Element.Type, from source: S
> +  ) -> (unwritten: S.Iterator, initializedUpTo: Index) {
> 
> However, the proposal reads:
> 
> public func initializeMemory<S: Sequence>(
>      as: S.Iterator.Element.Type, from source: S
>   ) -> (unwritten: S.Iterator, initialized: UnsafeMutableBufferPointer<S.Iterator.Element>)
> 
> Which API did we end up deciding on?
> 
> (unwritten:, initialized:) makes sense to me, but I can’t remember if we ditched that approach for some reason (e.g. consistency with UnsafeMutableBufferPointer).
> 
> -Andy

The proposed API in the proposal is right, the comment above it should have been updated. The intention is for the raw buffer version to return an initialized typed buffer not an index into the raw buffer. While this means it’s inconsistent with the typed equivalent, an index into the raw buffer isn’t all that useful as usually you want to operate on typed values after you’ve initialized them, and the calculation to get to the raw buffer index from the typed buffer if you need it is easy i.e. initialized.count * the stride of the type.

(I haven’t yet updated the PR to reflect this change yet either, was waiting to see if there was more feedback first to incorporate)


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20161212/9eb25264/attachment.html>