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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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32
stdlib/public/core/StringUTF8View.swift
View File

@@ -50,7 +50,7 @@ extension String.UTF8View: BidirectionalCollection {
@inlinable @inline(__always)
public func index(after i: Index) -> Index {
if _fastPath(_guts.isFastUTF8) {
return Index(encodedOffset: i.encodedOffset &+ 1)
return i.nextEncoded
}
return _foreignIndex(after: i)
@@ -60,7 +60,7 @@ extension String.UTF8View: BidirectionalCollection {
public func index(before i: Index) -> Index {
precondition(!i.isZeroPosition)
if _fastPath(_guts.isFastUTF8) {
return Index(encodedOffset: i.encodedOffset &- 1)
return i.priorEncoded
}
return _foreignIndex(before: i)
@@ -69,9 +69,8 @@ extension String.UTF8View: BidirectionalCollection {
@inlinable @inline(__always)
public func index(_ i: Index, offsetBy n: Int) -> Index {
if _fastPath(_guts.isFastUTF8) {
let offset = i.encodedOffset + n
_precondition(offset >= 0 && offset <= _guts.count)
return Index(encodedOffset: offset)
_precondition(n + i.encodedOffset <= _guts.count)
return i.encoded(offsetBy: n)
}
return _foreignIndex(i, offsetBy: n)
@@ -347,23 +346,22 @@ extension String.UTF8View {
internal func _foreignIndex(after i: Index) -> Index {
_sanityCheck(_guts.isForeign)
let scalar = _guts.foreignErrorCorrectedScalar(
let (scalar, scalarLen) = _guts.foreignErrorCorrectedScalar(
startingAt: i.strippingTranscoding)
let utf8Len = _numUTF8CodeUnits(scalar)
let utf16Len = _numUTF16CodeUnits(scalar)
if utf8Len == 1 {
_sanityCheck(i.transcodedOffset == 0)
return Index(encodedOffset: i.encodedOffset + 1)
return i.nextEncoded
}
// Check if we're still transcoding sub-scalar
if i.transcodedOffset < utf8Len - 1 {
return Index(transcodedAfter: i)
return i.nextTranscoded
}
// Skip to the next scalar
return Index(encodedOffset: i.encodedOffset + utf16Len)
return i.encoded(offsetBy: scalarLen)
}
@usableFromInline @inline(never)
@@ -372,15 +370,13 @@ extension String.UTF8View {
_sanityCheck(_guts.isForeign)
if i.transcodedOffset != 0 {
_sanityCheck((1...3) ~= i.transcodedOffset)
return Index(transcodedBefore: i)
return i.priorTranscoded
}
let scalar = _guts.foreignErrorCorrectedScalar(endingAt: i)
let (scalar, scalarLen) = _guts.foreignErrorCorrectedScalar(
endingAt: i)
let utf8Len = _numUTF8CodeUnits(scalar)
let utf16Len = _numUTF16CodeUnits(scalar)
return Index(
encodedOffset: i.encodedOffset &- utf16Len,
transcodedOffset: utf8Len &- 1)
return i.encoded(offsetBy: -scalarLen).transcoded(withOffset: utf8Len &- 1)
}
@usableFromInline @inline(never)
@@ -389,7 +385,7 @@ extension String.UTF8View {
_sanityCheck(_guts.isForeign)
let scalar = _guts.foreignErrorCorrectedScalar(
startingAt: _guts.scalarAlign(i))
startingAt: _guts.scalarAlign(i)).0
let encoded = Unicode.UTF8.encode(scalar)._unsafelyUnwrappedUnchecked
_sanityCheck(i.transcodedOffset < 1+encoded.count)
@@ -436,7 +432,7 @@ extension String.Index {
// Currently, foreign means UTF-16.
// If we're transcoding, we're already a UTF8 view index.
if self.encodedOffset != 0 { return true }
if self.transcodedOffset != 0 { return true }
// Otherwise, we must be scalar-aligned, i.e. not pointing at a trailing
// surrogate.