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[stdlib] Fix string index sharing (#4896)

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* [stdlib] Fix String.UTF16View index sharing

* [stdlib] Fix String.UnicodeScalarView index sharing

* [stdlib] Fix String.CharacterView index sharing

* [stdlib] Test advancing string indices past their ends

* [stdlib] Simplify CharacterView ranged subscript
This commit is contained in:
Nate Cook
2016-10-13 12:19:38 -05:00
committed by Maxim Moiseev
parent 91bba4d425
commit c2bc72d9d6
4 changed files with 93 additions and 55 deletions
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27
stdlib/public/core/StringCharacterView.swift
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@@ -54,14 +54,22 @@ extension String {
public struct CharacterView {
internal var _core: _StringCore
/// The offset of this view's `_core` from an original core. This works
/// around the fact that `_StringCore` is always zero-indexed.
/// `_coreOffset` should be subtracted from `UnicodeScalarIndex._position`
/// before that value is used as a `_core` index.
internal var _coreOffset: Int
/// Creates a view of the given string.
public init(_ text: String) {
self._core = text._core
self._coreOffset = 0
}
public // @testable
init(_ _core: _StringCore) {
init(_ _core: _StringCore, coreOffset: Int = 0) {
self._core = _core
self._coreOffset = coreOffset
}
}
@@ -139,7 +147,7 @@ extension String {
extension String.CharacterView : BidirectionalCollection {
internal typealias UnicodeScalarView = String.UnicodeScalarView
internal var unicodeScalars: UnicodeScalarView {
return UnicodeScalarView(_core)
return UnicodeScalarView(_core, coreOffset: _coreOffset)
}
/// A position in a string's `CharacterView` instance.
@@ -246,7 +254,7 @@ extension String.CharacterView : BidirectionalCollection {
from start: UnicodeScalarView.Index
) -> Int {
var start = start
let end = UnicodeScalarView.Index(_position: _core.count)
let end = unicodeScalars.endIndex
if start == end {
return 0
}
@@ -288,7 +296,7 @@ extension String.CharacterView : BidirectionalCollection {
internal func _measureExtendedGraphemeClusterBackward(
from end: UnicodeScalarView.Index
) -> Int {
let start = UnicodeScalarView.Index(_position: 0)
let start = unicodeScalars.startIndex
if start == end {
return 0
}
@@ -363,8 +371,8 @@ extension String.CharacterView : RangeReplaceableCollection {
with newElements: C
) where C : Collection, C.Iterator.Element == Character {
let rawSubRange: Range<Int> =
bounds.lowerBound._base._position
..< bounds.upperBound._base._position
bounds.lowerBound._base._position - _coreOffset
..< bounds.upperBound._base._position - _coreOffset
let lazyUTF16 = newElements.lazy.flatMap { $0.utf16 }
_core.replaceSubrange(rawSubRange, with: lazyUTF16)
}
@@ -436,10 +444,9 @@ extension String.CharacterView {
/// - Complexity: O(*n*) if the underlying string is bridged from
/// Objective-C, where *n* is the length of the string; otherwise, O(1).
public subscript(bounds: Range<Index>) -> String.CharacterView {
let unicodeScalarRange =
bounds.lowerBound._base..<bounds.upperBound._base
return String.CharacterView(
String(_core).unicodeScalars[unicodeScalarRange]._core)
let unicodeScalarRange = bounds.lowerBound._base..<bounds.upperBound._base
return String.CharacterView(unicodeScalars[unicodeScalarRange]._core,
coreOffset: unicodeScalarRange.lowerBound._position)
}
}