Hi Dmitri, Thanks for the feedback! I'm glad that we could start a conversation on the lists, and happy to see people offering their unvarnished opinions.
I think conditional conformances upon Array<UInt8> is definitely an avenue worth exploring. I'm not sure what the performance implications are - Zach brought up use cases in which the ability for a data type to be backed by non-contiguous storage was important. More generally, I wanted to open up discussion as to what people wanted from a native Data type. It seems like a DataProtocol-like protocol may be a good idea. Array<UInt8> could conform through conditional conformances to provide an implementation for people wanting a simple contiguous buffer that could be punned to an array or other linear collection, while a more robust dispatch_data_t-like conforming Swift stdlib type could be provided for more demanding use cases. This actually seems to be a good fit - if you only care about a data buffer as an arbitrary collection of bytes, the abstract protocol interface gives you flexibility, while if you have requirements that require a specific representation of data in memory you should use a concrete type. Best, Austin On Wed, May 11, 2016 at 11:01 AM, Dmitri Gribenko <griboz...@gmail.com> wrote: > On Wed, May 11, 2016 at 2:37 AM, Austin Zheng via swift-evolution > <swift-evolution@swift.org> wrote: > > Hello swift-evolution, > > > > I've been thinking about a standard library 'Data' type for a while, > > analogous to NSData in the same way Swift's Arrays and Dictionaries are > > analogous to NSArrays and NSDictionaries. A first-class container for > binary > > data that is available to every Swift user, conforms to Swift semantics, > and > > is safer and easier to work with than UnsafeBufferPointer seems like a > > natural fit for the standard library. > > Hi Austin, > > This is an interesting territory! > > One thing that I would like to suggest for us to consider is > justifying why Data needs to be a separate type from Array<Int8> and > Array<UInt8>. We can add conditional extensions to Array of Int8 and > UInt8 if we find that existing NSData/dispatch_data_t usecases need a > few special APIs that won't make sense on arrays in general. > > For example, something that I would imagine people want to do with > "data buffer" types is being able to make an unaligned or type punned > load or store. For example, in Java, this is one of the primary > usecases for a type similar in spirit, java.nio.ByteBuffer > (https://docs.oracle.com/javase/7/docs/api/java/nio/ByteBuffer.html). > > Another usecase that is a crossover between Array and Data, allow > Array to (unsafely) adopt ownership of an existing initialized unsafe > buffer pointer. We had quite a few requests for this. Do you think > this is an interesting usecase? Does it overlap with this discussion? > > Dmitri > > -- > main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if > (j){printf("%d\n",i);}}} /*Dmitri Gribenko <griboz...@gmail.com>*/ >
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