[swift-evolution] SE-163: String Revision: Collection Conformance, C Interop, Transcoding

[Félix Cloutier]

It probably depends on the positioning of the initializer. I strongly associate the collection initializer to the special case of UnsafeBufferPointer<CChar>, and the result strings will probably be passed back to C at some point, where an embedded NUL terminates the string (inconsistently with what Swift does). As a Swift-first feature, parsing the whole buffer regardless of embedded NULs makes sense, but as an interop feature, that's almost certainly not what developers will be looking for.

That probably passes the bar of being reasonable, though. I'd advise documenting that it doesn't stop on NUL characters.

Félix

> Le 6 avr. 2017 à 17:34, Ben Cohen <ben_cohen at apple.com> a écrit :
> 
> 
>> On Apr 5, 2017, at 10:32 PM, Félix Cloutier <felixcca at yahoo.ca <mailto:felixcca at yahoo.ca>> wrote:
>> 
>> During the proposal phase, we asked how this would handle fixed-length strings with an optional NUL terminator. For instance, in a C `struct Foo { char name[8]; };`, `name` stops at the first \0, or at the eighth byte, whichever comes first. IIRC, Ben said that it would be handled, but I'd like to have it clarified.
>> 
>> Is it correct to assume that a UnicodeEncoding is expected to return UnicodeParseResult.emptyInput when it sees a NUL character (thus stopping before the end of the buffer if necessary)? Is it also correct to assume that if you need this functionality, you'll be looking at code like this?
>> 
>> var result = ""
>> UnicodeEncoding.parseForward(bufferPointer) { result += $0 }
>> 
> 
> 
> Hi Félix,
> 
> Having talked about it among the team, it feels like we should add an initializer from a Collection of code units to this proposal.  Therefore given a pointer p to some utf8 and a length n, you would write:
> 
> let b = UnsafeBuffer(start: p, count: n)
> // naming opinions on the argument labels welcomed, this is probably what I’d go for...
> let s = String(b, fromEncoding: UTF8.self)
> 
> Similar to the C string inits, this would only be a repairing initializer.
> 
> Your request goes a little bit further though. For that, I would say that it probably doesn’t deserve a special dedicated initializer. You could instead search for the nil using index(of:):
> 
> let i = b.index(of: 0)
> let s = String(b[..<i], UTF8.self)  // one-sided ranges pitch forthcoming ;)
> 
> Does this sound reasonable?
> 
>>> Le 5 avr. 2017 à 11:39, John McCall via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> a écrit :
>>> 
>>> Hello, Swift community!
>>> 
>>> The review of "SE-163: String Revision: Collection Conformance, C Interop, Transcoding" begins now and runs through next Tuesday, April 11th. The proposal is available here:
>>> 	https://github.com/apple/swift-evolution/blob/master/proposals/0163-string-revision-1.md <https://github.com/apple/swift-evolution/blob/master/proposals/0163-string-revision-1.md>
>>> 
>>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>>> 	https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>> or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:
>>> 
>>> 	Proposal link: https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md <https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md>
>>> 
>>> 	Reply text
>>> 
>>> 	Other replies
>>> 
>>> What goes into a review?
>>> 
>>> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
>>> 
>>> 	• What is your evaluation of the proposal?
>>> 	• Is the problem being addressed significant enough to warrant a change to Swift?
>>> 	• Does this proposal fit well with the feel and direction of Swift?
>>> 	• If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
>>> 	• How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
>>> 
>>> More information about the Swift evolution process is available at https://github.com/apple/swift-evolution/blob/master/process.md <https://github.com/apple/swift-evolution/blob/master/process.md>
>>> 
>>> Thank you,
>>> 
>>> John McCall
>>> Review Manager
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20170407/c854c4b4/attachment.html>