> On Jul 14, 2017, at 9:33 AM, Taylor Swift <kelvin1...@gmail.com> wrote:
>
> How would you feel about:
>
> struct UnsafeMutableRawBufferPointer
> {
>
> --- static func allocate(count:Int) -> UnsafeMutableRawBufferPointer
> +++ static func allocate(bytes:Int, alignedTo:Int) ->
> UnsafeMutableRawBufferPointer
> func deallocate()
> +++ func bindMemory<Element>(to:Element.Type, capacity:Int)
> +++ func copy(from:UnsafeRawBufferPointer, bytes:Int)
> +++ func initializeMemory<Element>(as:Element.Type, at:Int, to:Element,
> count:Int)
> +++ func initializeMemory<Element>(as:Element.Type,
> from:UnsafeBufferPointer<Element>, count:Int)
> +++ func moveInitializeMemory<Element>(as:Element.Type,
> from:UnsafeMutableBufferPointer<Element>, count:Int
> }
>
> “bytes” = 8 bit quantities (don’t @ me we’re assuming 8 bit bytes)
> “capacity” = strided quantities, not assumed to be initialized
> “count” = strided quantities, assumed to be initialized
>
> It’s also worth nothing that a lot of what the proposal tries to add to
> UnsafeBufferPointer is already present in UnsafeMutableRawPointer like a
> sizeless deallocate() and a sizeless copyBytes(from:).
>
> Although I’m not sure what’s going on with the latter one
> <https://developer.apple.com/documentation/swift/unsafemutablerawbufferpointer/2635415-copybytes>…lol
> swiftdoc
Purely in terms of label names, what you have above is perfectly fine.
You’re going to have a problem adding the alignment constraint to buffer
pointer, but that’s another topic.
-Andy
> On Fri, Jul 14, 2017 at 1:57 AM, Andrew Trick <atr...@apple.com
> <mailto:atr...@apple.com>> wrote:
>
>> On Jul 13, 2017, at 10:30 PM, Taylor Swift <kelvin1...@gmail.com
>> <mailto:kelvin1...@gmail.com>> wrote:
>>
>> I’m confused I thought we were talking about the naming choices for the
>> argument labels in those functions. I think defining and abiding by
>> consistent meanings for `count`, `capacity`, and `bytes` is a good idea, and
>> it’s part of what this proposal tries to accomplish. Right now half the time
>> we use `count` to refer to “bytes” and half the time we use it to refer to
>> “instances”. The same goes for the word “capacity”. This is all laid out in
>> the document:
>>
>> “““
>> Finally, the naming and design of some UnsafeMutableRawPointer members
>> deserves to be looked at. The usage of capacity, bytes, and count as
>> argument labels is wildly inconsistent and confusing. In
>> copyBytes(from:count:), count refers to the number of bytes, while in
>> initializeMemory<T>(as:at:count:to:) and
>> initializeMemory<T>(as:from:count:), count refers to the number of strides.
>> Meanwhile bindMemory<T>(to:capacity:) uses capacity to refer to this
>> quantity. The always-problematic deallocate(bytes:alignedTo) method and
>> allocate(bytes:alignedTo:) type methods use bytes to refer to
>> byte-quantities. Adding to the confusion, UnsafeMutableRawBufferPointer
>> offers an allocate(count:) type method (the same signature method we’re
>> trying to add to UnsafeMutableBufferPointer), except the count in this
>> method refers to bytes. This kind of API naming begets stride bugs and makes
>> Swift needlessly difficult to learn.
>> ”””
>>
>> The only convenience methods this proposal is trying to add is the
>> functionality on the buffer pointer types. There seems to be broad support
>> for adding this functionality as no one has really opposed that part of the
>> proposal yet. Any other new methods like `UnsafeMutablePointer.assign(to:)`
>> are there for API consistency.
>>
>> This proposal also calls for getting rid of one of those “redundant
>> initializers” :)
>
> Since we’re not bike-shedding the specifics yet, I’ll just give you some
> background.
>
> We would ultimately like APIs that allocate and initialize in one go. It’s
> important that the current lower-level (dangerous) APIs make a clear
> distinction between initialized and uninitialized memory to avoid confusing
> them with future (safer) APIs. `capacity` always refers to memory that may be
> uninitialized. I think that’s very clear and helpful.
>
> In the context of pointers `count` should always be in strides. For raw
> pointers, that happens to be the same as as `bytes`.
>
> I initially proposed copy(bytes:from:), but someone thought that `bytes` in
> this particular context did not properly convey the "count of bytes" as
> opposed to the source of the bytes. You’re right, that’s inconsistent with
> allocate/deallocate(bytes:), because allocateBytes(count:) would be silly.
> Just be aware that the inconsistency is a result of over-thinking and
> excessive bike shedding to the detriment of something that looks nice and is
> easy to remember.
>
> I should also point out that the inconsistencies in functionality across
> pointer types, in terms of collection support and other convenience, is also
> known but was deliberately stripped from proposals as “additive”.
>
> -Andy
>
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
