| //===--- StringUTF8.swift - A UTF8 view of _StringCore --------------------===// |
| // |
| // This source file is part of the Swift.org open source project |
| // |
| // Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors |
| // Licensed under Apache License v2.0 with Runtime Library Exception |
| // |
| // See https://swift.org/LICENSE.txt for license information |
| // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // _StringCore currently has three representations: Native ASCII, |
| // Native UTF-16, and Opaque Cocoa. Expose each of these as UTF-8 in a |
| // way that will hopefully be efficient to traverse |
| // |
| //===----------------------------------------------------------------------===// |
| |
| extension String { |
| /// A view of a string's contents as a collection of UTF-8 code units. |
| /// |
| /// You can access a string's view of UTF-8 code units by using its `utf8` |
| /// property. A string's UTF-8 view encodes the string's Unicode scalar |
| /// values as 8-bit integers. |
| /// |
| /// let flowers = "Flowers 💐" |
| /// for v in flowers.utf8 { |
| /// print(v) |
| /// } |
| /// // 70 |
| /// // 108 |
| /// // 111 |
| /// // 119 |
| /// // 101 |
| /// // 114 |
| /// // 115 |
| /// // 32 |
| /// // 240 |
| /// // 159 |
| /// // 146 |
| /// // 144 |
| /// |
| /// A string's Unicode scalar values can be up to 21 bits in length. To |
| /// represent those scalar values using 8-bit integers, more than one UTF-8 |
| /// code unit is often required. |
| /// |
| /// let flowermoji = "💐" |
| /// for v in flowermoji.unicodeScalars { |
| /// print(v, v.value) |
| /// } |
| /// // 💐 128144 |
| /// |
| /// for v in flowermoji.utf8 { |
| /// print(v) |
| /// } |
| /// // 240 |
| /// // 159 |
| /// // 146 |
| /// // 144 |
| /// |
| /// In the encoded representation of a Unicode scalar value, each UTF-8 code |
| /// unit after the first is called a *continuation byte*. |
| /// |
| /// UTF8View Elements Match Encoded C Strings |
| /// ========================================= |
| /// |
| /// Swift streamlines interoperation with C string APIs by letting you pass a |
| /// `String` instance to a function as an `Int8` or `UInt8` pointer. When you |
| /// call a C function using a `String`, Swift automatically creates a buffer |
| /// of UTF-8 code units and passes a pointer to that buffer. The code units |
| /// of that buffer match the code units in the string's `utf8` view. |
| /// |
| /// The following example uses the C `strncmp` function to compare the |
| /// beginning of two Swift strings. The `strncmp` function takes two |
| /// `const char*` pointers and an integer specifying the number of characters |
| /// to compare. Because the strings are identical up to the 14th character, |
| /// comparing only those characters results in a return value of `0`. |
| /// |
| /// let s1 = "They call me 'Bell'" |
| /// let s2 = "They call me 'Stacey'" |
| /// |
| /// print(strncmp(s1, s2, 14)) |
| /// // Prints "0" |
| /// print(String(s1.utf8.prefix(14))) |
| /// // Prints "They call me '" |
| /// |
| /// Extending the compared character count to 15 includes the differing |
| /// characters, so a nonzero result is returned. |
| /// |
| /// print(strncmp(s1, s2, 15)) |
| /// // Prints "-17" |
| /// print(String(s1.utf8.prefix(15))) |
| /// // Prints "They call me 'B" |
| public struct UTF8View |
| : BidirectionalCollection, |
| CustomStringConvertible, |
| CustomDebugStringConvertible { |
| |
| /// Underlying UTF-16-compatible representation |
| @_versioned |
| internal let _core: _StringCore |
| |
| /// Distances to `(startIndex, endIndex)` from the endpoints of _core, |
| /// measured in UTF-8 code units. |
| /// |
| /// Note: this is *only* here to support legacy Swift3-style slicing where |
| /// `s.utf8[i..<j]` produces a `String.UTF8View`, and should be removed when |
| /// those semantics are no longer supported. |
| @_versioned |
| internal let _legacyOffsets: (start: Int8, end: Int8) |
| |
| init(_ _core: _StringCore, |
| legacyOffsets: (Int, Int) = (0, 0) |
| ) { |
| self._core = _core |
| self._legacyOffsets = (Int8(legacyOffsets.0), Int8(legacyOffsets.1)) |
| } |
| |
| public typealias Index = String.Index |
| public typealias IndexDistance = Int |
| |
| /// The position of the first code unit if the UTF-8 view is |
| /// nonempty. |
| /// |
| /// If the UTF-8 view is empty, `startIndex` is equal to `endIndex`. |
| public var startIndex: Index { |
| let r = _index(atEncodedOffset: _core.startIndex) |
| if _legacyOffsets.start == 0 { return r } |
| return index(r, offsetBy: numericCast(_legacyOffsets.start)) |
| } |
| |
| /// The "past the end" position---that is, the position one |
| /// greater than the last valid subscript argument. |
| /// |
| /// In an empty UTF-8 view, `endIndex` is equal to `startIndex`. |
| public var endIndex: Index { |
| _sanityCheck(_legacyOffsets.end >= -3 && _legacyOffsets.end <= 0, |
| "out of bounds legacy end") |
| |
| var r = Index(encodedOffset: _core.endIndex) |
| if _fastPath(_legacyOffsets.end == 0) { |
| return r |
| } |
| switch _legacyOffsets.end { |
| case -3: r = index(before: r); fallthrough |
| case -2: r = index(before: r); fallthrough |
| case -1: return index(before: r) |
| default: Builtin.unreachable() |
| } |
| } |
| |
| @_versioned |
| internal func _index(atEncodedOffset n: Int) -> Index { |
| if _fastPath(_core.isASCII) { return Index(encodedOffset: n) } |
| if n == _core.endIndex { return endIndex } |
| |
| var p = UTF16.ForwardParser() |
| var i = _core[n...].makeIterator() |
| var buffer = Index._UTF8Buffer() |
| Loop: |
| while true { |
| switch p.parseScalar(from: &i) { |
| case .valid(let u16): |
| let u8 = Unicode.UTF8.transcode(u16, from: Unicode.UTF16.self) |
| ._unsafelyUnwrappedUnchecked |
| if buffer.count + u8.count > buffer.capacity { break Loop } |
| buffer.append(contentsOf: u8) |
| case .error: |
| let u8 = Unicode.UTF8.encodedReplacementCharacter |
| if buffer.count + u8.count > buffer.capacity { break Loop } |
| buffer.append(contentsOf: u8) |
| case .emptyInput: |
| break Loop |
| } |
| } |
| return Index(encodedOffset: n, .utf8(buffer: buffer)) |
| } |
| |
| /// Returns the next consecutive position after `i`. |
| /// |
| /// - Precondition: The next position is representable. |
| @inline(__always) |
| public func index(after i: Index) -> Index { |
| if _fastPath(_core.isASCII) { |
| precondition(i.encodedOffset < _core.count) |
| return Index(encodedOffset: i.encodedOffset + 1) |
| } |
| |
| var j = i |
| |
| // Ensure j's cache is utf8 |
| if _slowPath(j._cache.utf8 == nil) { |
| j = _index(atEncodedOffset: j.encodedOffset) |
| precondition(j != endIndex, "Index out of bounds") |
| } |
| |
| let buffer = j._cache.utf8._unsafelyUnwrappedUnchecked |
| |
| var scalarLength16 = 1 |
| let b0 = buffer.first._unsafelyUnwrappedUnchecked |
| var nextBuffer = buffer |
| |
| let leading1s = (~b0).leadingZeroBitCount |
| if _fastPath(leading1s == 0) { // ASCII in buffer; just consume it |
| nextBuffer.removeFirst() |
| } |
| else { |
| // Number of bytes consumed in this scalar |
| let n8 = j._transcodedOffset + 1 |
| // If we haven't reached a scalar boundary... |
| if _fastPath(n8 < leading1s) { |
| // Advance to the next position in this scalar |
| return Index( |
| encodedOffset: j.encodedOffset, |
| transcodedOffset: n8, .utf8(buffer: buffer)) |
| } |
| // We reached a scalar boundary; compute the underlying utf16's width |
| // based on the number of utf8 code units |
| scalarLength16 = n8 >> 2 + 1 |
| nextBuffer.removeFirst(n8) |
| } |
| |
| if _fastPath(!nextBuffer.isEmpty) { |
| return Index( |
| encodedOffset: j.encodedOffset + scalarLength16, |
| .utf8(buffer: nextBuffer)) |
| } |
| // If nothing left in the buffer, refill it. |
| return _index(atEncodedOffset: j.encodedOffset + scalarLength16) |
| } |
| |
| public func index(before i: Index) -> Index { |
| if _fastPath(_core.isASCII) { |
| precondition(i.encodedOffset > 0) |
| return Index(encodedOffset: i.encodedOffset - 1) |
| } |
| |
| if i._transcodedOffset != 0 { |
| _sanityCheck(i._cache.utf8 != nil) |
| var r = i |
| r._compoundOffset = r._compoundOffset &- 1 |
| return r |
| } |
| |
| // Handle the scalar boundary the same way as the not-a-utf8-index case. |
| |
| // Parse a single scalar |
| var p = Unicode.UTF16.ReverseParser() |
| var s = _core[..<i.encodedOffset].reversed().makeIterator() |
| let u8: Unicode.UTF8.EncodedScalar |
| switch p.parseScalar(from: &s) { |
| case .valid(let u16): |
| u8 = Unicode.UTF8.transcode( |
| u16, from: Unicode.UTF16.self)._unsafelyUnwrappedUnchecked |
| case .error: |
| u8 = Unicode.UTF8.encodedReplacementCharacter |
| case .emptyInput: |
| _preconditionFailure("Index out of bounds") |
| } |
| return Index( |
| encodedOffset: i.encodedOffset &- (u8.count < 4 ? 1 : 2), |
| transcodedOffset: u8.count &- 1, |
| .utf8(buffer: String.Index._UTF8Buffer(u8)) |
| ) |
| } |
| |
| public func distance(from i: Index, to j: Index) -> IndexDistance { |
| if _fastPath(_core.isASCII) { |
| return j.encodedOffset - i.encodedOffset |
| } |
| return j >= i |
| ? _forwardDistance(from: i, to: j) : -_forwardDistance(from: j, to: i) |
| } |
| |
| @_versioned |
| @inline(__always) |
| internal func _forwardDistance(from i: Index, to j: Index) -> IndexDistance { |
| var r: IndexDistance = j._transcodedOffset - i._transcodedOffset |
| UTF8._transcode( |
| _core[i.encodedOffset..<j.encodedOffset], from: UTF16.self) { |
| r += $0.count |
| } |
| return r |
| } |
| |
| /// Accesses the code unit at the given position. |
| /// |
| /// The following example uses the subscript to print the value of a |
| /// string's first UTF-8 code unit. |
| /// |
| /// let greeting = "Hello, friend!" |
| /// let i = greeting.utf8.startIndex |
| /// print("First character's UTF-8 code unit: \(greeting.utf8[i])") |
| /// // Prints "First character's UTF-8 code unit: 72" |
| /// |
| /// - Parameter position: A valid index of the view. `position` |
| /// must be less than the view's end index. |
| public subscript(position: Index) -> UTF8.CodeUnit { |
| @inline(__always) |
| get { |
| if _fastPath(_core.asciiBuffer != nil), let ascii = _core.asciiBuffer { |
| _precondition(position < endIndex, "Index out of bounds") |
| return ascii[position.encodedOffset] |
| } |
| var j = position |
| while true { |
| if case .utf8(let buffer) = j._cache { |
| _onFastPath() |
| return buffer[ |
| buffer.index(buffer.startIndex, offsetBy: j._transcodedOffset)] |
| } |
| j = _index(atEncodedOffset: j.encodedOffset) |
| precondition(j < endIndex, "Index out of bounds") |
| } |
| } |
| } |
| |
| public var description: String { |
| return String(_core) |
| } |
| |
| public var debugDescription: String { |
| return "UTF8View(\(self.description.debugDescription))" |
| } |
| } |
| |
| /// A UTF-8 encoding of `self`. |
| public var utf8: UTF8View { |
| get { |
| return UTF8View(self._core) |
| } |
| set { |
| self = String(describing: newValue) |
| } |
| } |
| |
| /// A contiguously stored null-terminated UTF-8 representation of the string. |
| /// |
| /// To access the underlying memory, invoke `withUnsafeBufferPointer` on the |
| /// array. |
| /// |
| /// let s = "Hello!" |
| /// let bytes = s.utf8CString |
| /// print(bytes) |
| /// // Prints "[72, 101, 108, 108, 111, 33, 0]" |
| /// |
| /// bytes.withUnsafeBufferPointer { ptr in |
| /// print(strlen(ptr.baseAddress!)) |
| /// } |
| /// // Prints "6" |
| public var utf8CString: ContiguousArray<CChar> { |
| var result = ContiguousArray<CChar>() |
| result.reserveCapacity(utf8.count + 1) |
| for c in utf8 { |
| result.append(CChar(bitPattern: c)) |
| } |
| result.append(0) |
| return result |
| } |
| |
| internal func _withUnsafeBufferPointerToUTF8<R>( |
| _ body: (UnsafeBufferPointer<UTF8.CodeUnit>) throws -> R |
| ) rethrows -> R { |
| if let asciiBuffer = self._core.asciiBuffer { |
| return try body(UnsafeBufferPointer( |
| start: asciiBuffer.baseAddress, |
| count: asciiBuffer.count)) |
| } |
| var nullTerminatedUTF8 = ContiguousArray<UTF8.CodeUnit>() |
| nullTerminatedUTF8.reserveCapacity(utf8.count + 1) |
| nullTerminatedUTF8 += utf8 |
| nullTerminatedUTF8.append(0) |
| return try nullTerminatedUTF8.withUnsafeBufferPointer(body) |
| } |
| |
| /// Creates a string corresponding to the given sequence of UTF-8 code units. |
| /// |
| /// If `utf8` is an ill-formed UTF-8 code sequence, the result is `nil`. |
| /// |
| /// You can use this initializer to create a new string from a slice of |
| /// another string's `utf8` view. |
| /// |
| /// let picnicGuest = "Deserving porcupine" |
| /// if let i = picnicGuest.utf8.index(of: 32) { |
| /// let adjective = String(picnicGuest.utf8[..<i]) |
| /// print(adjective) |
| /// } |
| /// // Prints "Optional(Deserving)" |
| /// |
| /// The `adjective` constant is created by calling this initializer with a |
| /// slice of the `picnicGuest.utf8` view. |
| /// |
| /// - Parameter utf8: A UTF-8 code sequence. |
| @available(swift, deprecated: 3.2, |
| message: "Failable initializer was removed in Swift 4. When upgrading to Swift 4, please use non-failable String.init(_:UTF8View)") |
| @available(swift, obsoleted: 4.0, |
| message: "Please use non-failable String.init(_:UTF8View) instead") |
| public init?(_ utf8: UTF8View) { |
| if utf8.startIndex._transcodedOffset != 0 |
| || utf8.endIndex._transcodedOffset != 0 { |
| return nil |
| } |
| // Attempt to recover the whole string, the better to implement the actual |
| // Swift 3.1 semantics, which are not as documented above! Full Swift 3.1 |
| // semantics may be impossible to preserve in the case of string literals, |
| // since we no longer have access to the length of the original string when |
| // there is no owner and elements have been dropped from the end. |
| if let nativeBuffer = utf8._core.nativeBuffer { |
| let wholeString = String(_StringCore(nativeBuffer)) |
| let offset = (utf8._core._baseAddress! - nativeBuffer.start) |
| &>> utf8._core.elementShift |
| |
| if Index( |
| encodedOffset: utf8.startIndex.encodedOffset + offset |
| ).samePosition(in: wholeString) == nil |
| || Index( |
| encodedOffset: utf8.endIndex.encodedOffset + offset |
| ).samePosition(in: wholeString) == nil { |
| return nil |
| } |
| } |
| self = String(utf8._core) |
| } |
| |
| /// Creates a string corresponding to the given sequence of UTF-8 code units. |
| @available(swift, introduced: 4.0, message: |
| "Please use failable String.init?(_:UTF8View) when in Swift 3.2 mode") |
| public init(_ utf8: UTF8View) { |
| self = String(utf8._core) |
| } |
| |
| /// The index type for subscripting a string. |
| public typealias UTF8Index = UTF8View.Index |
| } |
| |
| extension String.UTF8View : _SwiftStringView { |
| var _persistentContent : String { return String(self._core) } |
| } |
| |
| extension String.UTF8View { |
| public struct Iterator { |
| typealias _OutputBuffer = UInt64 |
| internal let _source: _StringCore |
| internal var _sourceIndex: Int |
| internal var _buffer: _OutputBuffer |
| } |
| public func makeIterator() -> Iterator { |
| return Iterator(_core) |
| } |
| } |
| |
| extension String.UTF8View.Iterator : IteratorProtocol { |
| internal init(_ source: _StringCore) { |
| _source = source |
| _sourceIndex = 0 |
| _buffer = 0 |
| } |
| |
| public mutating func next() -> Unicode.UTF8.CodeUnit? { |
| if _fastPath(_buffer != 0) { |
| let r = UInt8(truncatingIfNeeded: _buffer) &- 1 |
| _buffer >>= 8 |
| return r |
| } |
| if _slowPath(_sourceIndex == _source.count) { return nil } |
| |
| defer { _fixLifetime(_source) } |
| |
| if _fastPath(_source._unmanagedASCII != nil), |
| let ascii = _source._unmanagedASCII { |
| let result = ascii[_sourceIndex] |
| _sourceIndex += 1 |
| for i in 0 ..< _OutputBuffer.bitWidth>>3 { |
| if _sourceIndex == _source.count { break } |
| _buffer |= _OutputBuffer(ascii[_sourceIndex] &+ 1) &<< (i << 3) |
| _sourceIndex += 1 |
| } |
| return result |
| } |
| |
| if _fastPath(_source._unmanagedUTF16 != nil), |
| let utf16 = _source._unmanagedUTF16 { |
| return _next(refillingFrom: utf16) |
| } |
| return _next(refillingFrom: _source) |
| } |
| |
| internal mutating func _next<Source: Collection>( |
| refillingFrom source: Source |
| ) -> Unicode.UTF8.CodeUnit? |
| where Source.Element == Unicode.UTF16.CodeUnit, |
| Source.Index == Int |
| { |
| _sanityCheck(_buffer == 0) |
| var shift = 0 |
| |
| // ASCII fastpath |
| while _sourceIndex != _source.endIndex && shift < _OutputBuffer.bitWidth { |
| let u = _source[_sourceIndex] |
| if u >= 0x80 { break } |
| _buffer |= _OutputBuffer(UInt8(truncatingIfNeeded: u &+ 1)) &<< shift |
| _sourceIndex += 1 |
| shift = shift &+ 8 |
| } |
| |
| var i = IndexingIterator(_elements: source, _position: _sourceIndex) |
| var parser = Unicode.UTF16.ForwardParser() |
| Loop: |
| while true { |
| let u8: UTF8.EncodedScalar |
| switch parser.parseScalar(from: &i) { |
| case .valid(let s): |
| u8 = UTF8.transcode(s, from: UTF16.self)._unsafelyUnwrappedUnchecked |
| case .error(_): |
| u8 = UTF8.encodedReplacementCharacter |
| case .emptyInput: |
| break Loop |
| } |
| var newBuffer = _buffer |
| for x in u8 { |
| newBuffer |= _OutputBuffer(x &+ 1) &<< shift |
| shift = shift &+ 8 |
| } |
| guard _fastPath(shift <= _OutputBuffer.bitWidth) else { break Loop } |
| _buffer = newBuffer |
| _sourceIndex = i._position &- parser._buffer.count |
| } |
| guard _fastPath(_buffer != 0) else { return nil } |
| let result = UInt8(truncatingIfNeeded: _buffer) &- 1 |
| _buffer >>= 8 |
| return result |
| } |
| } |
| |
| extension String.UTF8View { |
| public var count: Int { |
| if _fastPath(_core.isASCII) { return _core.count } |
| let b = _core._unmanagedUTF16 |
| if _fastPath(b != nil) { |
| defer { _fixLifetime(_core) } |
| return _count(fromUTF16: b!) |
| } |
| return _count(fromUTF16: self._core) |
| } |
| |
| internal func _count<Source: Sequence>(fromUTF16 source: Source) -> Int |
| where Source.Element == Unicode.UTF16.CodeUnit |
| { |
| var result = 0 |
| var prev: Unicode.UTF16.CodeUnit = 0 |
| for u in source { |
| switch u { |
| case 0..<0x80: result += 1 |
| case 0x80..<0x800: result += 2 |
| case 0x800..<0xDC00: result += 3 |
| case 0xDC00..<0xE000: result += UTF16.isLeadSurrogate(prev) ? 1 : 3 |
| default: result += 3 |
| } |
| prev = u |
| } |
| return result |
| } |
| } |
| |
| // Index conversions |
| extension String.UTF8View.Index { |
| /// Creates an index in the given UTF-8 view that corresponds exactly to the |
| /// specified `UTF16View` position. |
| /// |
| /// The following example finds the position of a space in a string's `utf16` |
| /// view and then converts that position to an index in the string's |
| /// `utf8` view. |
| /// |
| /// let cafe = "Café 🍵" |
| /// |
| /// let utf16Index = cafe.utf16.index(of: 32)! |
| /// let utf8Index = String.UTF8View.Index(utf16Index, within: cafe.utf8)! |
| /// |
| /// print(Array(cafe.utf8[..<utf8Index])) |
| /// // Prints "[67, 97, 102, 195, 169]" |
| /// |
| /// If the position passed in `utf16Index` doesn't have an exact |
| /// corresponding position in `utf8`, the result of the initializer is |
| /// `nil`. For example, because UTF-8 and UTF-16 represent high Unicode code |
| /// points differently, an attempt to convert the position of the trailing |
| /// surrogate of a UTF-16 surrogate pair fails. |
| /// |
| /// The next example attempts to convert the indices of the two UTF-16 code |
| /// points that represent the teacup emoji (`"🍵"`). The index of the lead |
| /// surrogate is successfully converted to a position in `utf8`, but the |
| /// index of the trailing surrogate is not. |
| /// |
| /// let emojiHigh = cafe.utf16.index(after: utf16Index) |
| /// print(String.UTF8View.Index(emojiHigh, within: cafe.utf8)) |
| /// // Prints "Optional(String.Index(...))" |
| /// |
| /// let emojiLow = cafe.utf16.index(after: emojiHigh) |
| /// print(String.UTF8View.Index(emojiLow, within: cafe.utf8)) |
| /// // Prints "nil" |
| /// |
| /// - Parameters: |
| /// - sourcePosition: A position in a `String` or one of its views. |
| /// - target: The `UTF8View` in which to find the new position. |
| public init?(_ sourcePosition: String.Index, within target: String.UTF8View) { |
| switch sourcePosition._cache { |
| case .utf8: |
| self.init(encodedOffset: sourcePosition.encodedOffset, |
| transcodedOffset:sourcePosition._transcodedOffset, sourcePosition._cache) |
| |
| default: |
| guard String.UnicodeScalarView(target._core)._isOnUnicodeScalarBoundary( |
| sourcePosition) else { return nil } |
| self.init(encodedOffset: sourcePosition.encodedOffset) |
| } |
| } |
| } |
| |
| // Reflection |
| extension String.UTF8View : CustomReflectable { |
| /// Returns a mirror that reflects the UTF-8 view of a string. |
| public var customMirror: Mirror { |
| return Mirror(self, unlabeledChildren: self) |
| } |
| } |
| |
| extension String.UTF8View : CustomPlaygroundQuickLookable { |
| public var customPlaygroundQuickLook: PlaygroundQuickLook { |
| return .text(description) |
| } |
| } |
| |
| // backward compatibility for index interchange. |
| extension String.UTF8View { |
| @available( |
| swift, obsoleted: 4.0, |
| message: "Any String view index conversion can fail in Swift 4; please unwrap the optional index") |
| public func index(after i: Index?) -> Index { |
| return index(after: i!) |
| } |
| @available( |
| swift, obsoleted: 4.0, |
| message: "Any String view index conversion can fail in Swift 4; please unwrap the optional index") |
| public func index(_ i: Index?, offsetBy n: IndexDistance) -> Index { |
| return index(i!, offsetBy: n) |
| } |
| @available( |
| swift, obsoleted: 4.0, |
| message: "Any String view index conversion can fail in Swift 4; please unwrap the optional indices") |
| public func distance( |
| from i: Index?, to j: Index?) -> IndexDistance { |
| return distance(from: i!, to: j!) |
| } |
| @available( |
| swift, obsoleted: 4.0, |
| message: "Any String view index conversion can fail in Swift 4; please unwrap the optional index") |
| public subscript(i: Index?) -> Unicode.UTF8.CodeUnit { |
| return self[i!] |
| } |
| } |
| |
| //===--- Slicing Support --------------------------------------------------===// |
| /// In Swift 3.2, in the absence of type context, |
| /// |
| /// someString.utf8[someString.utf8.startIndex..<someString.utf8.endIndex] |
| /// |
| /// was deduced to be of type `String.UTF8View`. Provide a more-specific |
| /// Swift-3-only `subscript` overload that continues to produce |
| /// `String.UTF8View`. |
| extension String.UTF8View { |
| public typealias SubSequence = Substring.UTF8View |
| |
| @available(swift, introduced: 4) |
| public subscript(r: Range<Index>) -> String.UTF8View.SubSequence { |
| return String.UTF8View.SubSequence(self, _bounds: r) |
| } |
| |
| @available(swift, obsoleted: 4) |
| public subscript(r: Range<Index>) -> String.UTF8View { |
| if r.upperBound._transcodedOffset == 0 { |
| return String.UTF8View( |
| _core[r.lowerBound.encodedOffset..<r.upperBound.encodedOffset], |
| legacyOffsets: (r.lowerBound._transcodedOffset, 0)) |
| } |
| |
| let b0 = r.upperBound._cache.utf8!.first! |
| let scalarLength8 = (~b0).leadingZeroBitCount |
| let scalarLength16 = scalarLength8 == 4 ? 2 : 1 |
| let coreEnd = r.upperBound.encodedOffset + scalarLength16 |
| return String.UTF8View( |
| _core[r.lowerBound.encodedOffset..<coreEnd], |
| legacyOffsets: ( |
| r.lowerBound._transcodedOffset, |
| r.upperBound._transcodedOffset - scalarLength8)) |
| } |
| |
| @available(swift, obsoleted: 4) |
| public subscript(bounds: ClosedRange<Index>) -> String.UTF8View { |
| return self[bounds.relative(to: self)] |
| } |
| } |
| |