Hello developers, After considering everyone's feedback, I decided to completely rewrite my trial balloon proposal (https://github.com/austinzheng/swift-evolution/blob/d2/proposals/XXXX-stdlib-data.md <https://github.com/austinzheng/swift-evolution/blob/d2/proposals/XXXX-stdlib-data.md>).
In short, much of the API interface has been extracted into a `Data` protocol; two concrete implementations (one exploiting Swift 3's conditional protocol conformances) can be used for different purposes. The API should properly model data objects using both contiguous and non-contiguous backing stores. Further thoughts, opinions, criticism, or just ideas as to what a great `Data` type would be capable of doing are much appreciated. Thanks again! Best, Austin > On May 11, 2016, at 11:29 AM, Austin Zheng <[email protected]> wrote: > > 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 <[email protected] > <mailto:[email protected]>> wrote: > On Wed, May 11, 2016 at 2:37 AM, Austin Zheng via swift-evolution > <[email protected] <mailto:[email protected]>> 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 > <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 <[email protected] > <mailto:[email protected]>>*/ >
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