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String comparison iterator for UTF8 strings

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This commit is contained in:
Lance Parker
2018-09-22 09:58:51 -07:00
committed by Michael Ilseman
parent a0e639eaf5
commit f1a35bd1c9
7 changed files with 702 additions and 13 deletions
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38
stdlib/public/core/StringUnicodeScalarView.swift
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@@ -10,6 +10,44 @@
//
//===----------------------------------------------------------------------===//
extension _StringGuts {
@usableFromInline @inline(__always)
internal func fastUTF8Scalar(startingAt i: Int) -> Unicode.Scalar {
return fastUTF8ScalarAndLength(startingAt: i).0
}
@usableFromInline @inline(__always)
internal func fastUTF8ScalarAndLength(startingAt i: Int) -> (Unicode.Scalar, Int) {
_sanityCheck(isFastUTF8)
return self.withFastUTF8 { utf8 in
return utf8.utf8ScalarAndLength(startingAt: i)
}
}
}
extension UnsafeBufferPointer where Element == UInt8 {
@usableFromInline @inline(__always)
internal func utf8ScalarAndLength(startingAt i: Int) -> (Unicode.Scalar, Int) {
let cu0 = self[i]
assert(!_isContinuation(cu0))
let length = Swift._utf8ScalarLength(cu0)
let scalar: Unicode.Scalar
switch length {
case 1: scalar = _decodeUTF8(cu0)
case 2: scalar = _decodeUTF8(cu0, self[i &+ 1])
case 3: scalar = _decodeUTF8(cu0, self[i &+ 1], self[i &+ 2])
case 4: scalar = _decodeUTF8(cu0, self[i &+ 1], self[i &+ 2], self[i &+ 3])
default: Builtin.unreachable()
}
return (scalar, length)
}
@usableFromInline @inline(__always)
internal func utf8Scalar(startingAt i: Int) -> Unicode.Scalar {
return utf8ScalarAndLength(startingAt: i).0
}
}
extension String.UnicodeScalarView {
#if !INTERNAL_CHECKS_ENABLED
@inlinable @inline(__always) internal func _invariantCheck() {}