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[String] NFC iterator fast-paths

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Refactor and rename _StringGutsSlice, apply NFC-aware fast paths to a
new buffered iterator.

Also, fix bug in _typeName which used to assume ASCIIness and better
SIL optimizations on StringObject.
This commit is contained in:
Michael Ilseman
2018-10-28 15:47:49 -07:00
parent 7376009ccc
commit 7aea40680d
27 changed files with 716 additions and 285 deletions
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12
stdlib/public/core/StringUnicodeScalarView.swift
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@@ -52,7 +52,7 @@ extension String.UnicodeScalarView: BidirectionalCollection {
if _fastPath(_guts.isFastUTF8) {
let len = _guts.fastUTF8ScalarLength(startingAt: i.encodedOffset)
return Index(encodedOffset: i.encodedOffset &+ len)
return i.encoded(offsetBy: len)
}
return _foreignIndex(after: i)
@@ -71,7 +71,7 @@ extension String.UnicodeScalarView: BidirectionalCollection {
return _utf8ScalarLength(utf8, endingAt: i.encodedOffset)
}
_sanityCheck(len <= 4, "invalid UTF8")
return Index(encodedOffset: i.encodedOffset &- len)
return i.encoded(offsetBy: -len)
}
return _foreignIndex(before: i)
@@ -362,18 +362,18 @@ extension String.UnicodeScalarView {
let cu = _guts.foreignErrorCorrectedUTF16CodeUnit(at: i)
let len = _isLeadingSurrogate(cu) ? 2 : 1
return Index(encodedOffset: i.encodedOffset + len)
return i.encoded(offsetBy: len)
}
@usableFromInline @inline(never)
@_effects(releasenone)
internal func _foreignIndex(before i: Index) -> Index {
_sanityCheck(_guts.isForeign)
let priorIdx = String.Index(encodedOffset: i.encodedOffset - 1)
let priorIdx = i.priorEncoded
let cu = _guts.foreignErrorCorrectedUTF16CodeUnit(at: priorIdx)
let len = _isTrailingSurrogate(cu) ? 2 : 1
return Index(encodedOffset: i.encodedOffset - len)
return i.encoded(offsetBy: -len)
}
@usableFromInline @inline(never)
@@ -383,6 +383,6 @@ extension String.UnicodeScalarView {
_sanityCheck(_guts.isOnUnicodeScalarBoundary(i),
"should of been aligned prior")
return _guts.foreignErrorCorrectedScalar(startingAt: i)
return _guts.foreignErrorCorrectedScalar(startingAt: i).0
}
}