[swift-evolution] [SHORT Review] SE-0134: Rename two UTF8-related properties on String

[Ben Rimmington]

> On 25 Jul 2016, at 15:27, Ben Rimmington wrote:
> 
> <https://github.com/apple/swift-evolution/blob/master/proposals/0134-rename-string-properties.md>
> 
> My suggestion for SE-0134 is to use the `utf8CString` name, overloading for CSignedChar and CUnsignedChar:
> 
> 	<https://github.com/apple/swift/blob/master/stdlib/public/core/CString.swift>
> 
> 	extension String {
> 	- init(cString: UnsafePointer<CChar>)
> 	- init(cString: UnsafePointer<UInt8>)
> 	- init?(validatingUTF8 cString: UnsafePointer<CChar>)
> 
> 	+ init(utf8CString: UnsafePointer<CSignedChar>)
> 	+ init(utf8CString: UnsafePointer<CUnsignedChar>)
> 	+ init?(validatingUTF8CString: UnsafePointer<CSignedChar>)
> 	+ init?(validatingUTF8CString: UnsafePointer<CUnsignedChar>)
> 	}
> 
> The properties would change to methods, overloaded by return type:
> 
> 	<https://github.com/apple/swift/blob/master/stdlib/public/core/StringUTF8.swift>
> 
> 	extension String {
> 	- var nulTerminatedUTF8CString: ContiguousArray<CChar>
> 	- var nulTerminatedUTF8: ContiguousArray<UTF8.CodeUnit>
> 
> 	+ func utf8CString() -> ContiguousArray<CSignedChar>
> 	+ func utf8CString() -> ContiguousArray<CUnsignedChar>
> 	}
> 
> ## NOTES ##
> 
> UTF8.CodeUnit is defined as UInt8, and CChar is currently defined as Int8:
> 
> 	<https://github.com/apple/swift/blob/master/stdlib/public/core/CTypes.swift>
> 
> 	/// The C 'char' type.
> 	///
> 	/// This will be the same as either `CSignedChar` (in the common
> 	/// case) or `CUnsignedChar`, depending on the platform.
> 	public typealias CChar = Int8
> 
> 	/// The C 'signed char' type.
> 	public typealias CSignedChar = Int8
> 
> 	/// The C 'unsigned char' type.
> 	public typealias CUnsignedChar = UInt8
> 
> There's an abandoned proposal to update CChar:
> 
> 	<http://thread.gmane.org/gmane.comp.lang.swift.evolution/7925/focus=8158>
> 
> 	<http://thread.gmane.org/gmane.comp.lang.swift.evolution/8419>
> 
> String.init(cString: UnsafePointer<UInt8>) and nulTerminatedUTF8CString were added by SE-0107:
> 
> 	<https://github.com/apple/swift-evolution/blob/master/proposals/0107-unsaferawpointer.md#cstring-conversion>
> 
> 	<https://github.com/apple/swift/commit/c7aa8284c905a73959ad69255cb56c38db80d039>
> 
> Foundation.NSString uses the `utf8String` name instead:
> 
> 	<https://developer.apple.com/reference/foundation/nsstring/1412128-init>
> 
> 	<https://developer.apple.com/reference/foundation/nsstring/1411189-utf8string>

<https://github.com/apple/swift-evolution/blob/master/proposals/0134-rename-string-properties.md>

There's another method for SE-0134 which could be renamed or removed:

	<https://github.com/apple/swift/blob/master/stdlib/public/core/LifetimeManager.swift>

	extension String {
	- func withCString<Result>(
	-   _ body: @noescape (UnsafePointer<Int8>) throws -> Result
	- ) rethrows -> Result

	+ func withUTF8CString<Result>(
	+   _ body: @noescape (UnsafePointer<CSignedChar>) throws -> Result
	+ ) rethrows -> Result

	+ func withUTF8CString<Result>(
	+   _ body: @noescape (UnsafePointer<CUnsignedChar>) throws -> Result
	+ ) rethrows -> Result
	}

The overloads (CSignedChar and CUnsignedChar) are needed if CChar will become UInt8 on some platforms.

-- Ben