[swift-evolution] [Review] SE-0184: Unsafe[Mutable][Raw][Buffer]Pointer: add missing methods, adjust existing labels for clarity, and remove deallocation size

[Andrew Trick]

> On Sep 3, 2017, at 8:38 PM, Taylor Swift <kelvin13ma at gmail.com> wrote:
> 
> what was the reasoning for making raw at: offset in strides and not bytes?

So, you’re talking about UnsafeMutableRawPointer(as:at:count:to:)…

The thinking was that it was typical for users to continue filling in the memory using the same type, and that manually performing address arithmetic is error prone.

Now that we're considering consistency with the raw buffer pointer API, which didn’t exist at the time, the thinking is that `at` can be ambiguous and that manual address arithmetic is actually less error prone and increases clarity at the call site.

Does that adequately sum of the last few messages in this thread?

-Andy


> On Sep 3, 2017, at 10:22 PM, Andrew Trick <atrick at apple.com <mailto:atrick at apple.com>> wrote:
> 
>> 
>>> On Sep 3, 2017, at 8:05 PM, Xiaodi Wu <xiaodi.wu at gmail.com <mailto:xiaodi.wu at gmail.com>> wrote:
>>> 
>>> If we use byte offset, then the at parameter in UnsafeMutableRawPointer should be removed, since pointer arithmetic can be used instead (just like with UnsafeMutablePointer).
>>> 
>>> I agree that it seems quite sensible to remove the ‘at’ parameter altogether from the UMRP method.
>> 
>> No code in tree or on github is using the `at` argument. I think it can be removed. A fixit should still be possible.
>> 
>>> Not convinced moving the at: argument to come before the as: argument is worth it in terms of source breakage.
>>> 
>>> Since much of this proposal involves shuffling and relabeling arguments, I’d argue it’s better to break slight more source in one go for the optimal API than to break slightly less for a slightly less optimal API, no? (This is assuming there is agreement that ‘at:as:’ is less prone to misinterpretation than ‘as:at:’.)
>> 
>> 
>> To be clear, we’re just talking about UnsafeMutableRawBufferPointer.initializeMemory now, so this is purely additive.
>> I think the label needs to be `atByteOffset`, and placing it before `as` makes a lot of sense because it no longer depends on the type’s stride. 
>> 
>> -Andy

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