> 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 >
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