mirror of
https://github.com/apple/swift.git
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428 lines
15 KiB
Swift
428 lines
15 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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extension _StringGuts {
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@usableFromInline @inline(__always)
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internal func fastUTF8Scalar(startingAt i: Int) -> Unicode.Scalar {
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return fastUTF8ScalarAndLength(startingAt: i).0
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}
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@usableFromInline @inline(__always)
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internal func fastUTF8ScalarAndLength(startingAt i: Int) -> (Unicode.Scalar, Int) {
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_sanityCheck(isFastUTF8)
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return self.withFastUTF8 { utf8 in
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return utf8.utf8ScalarAndLength(startingAt: i)
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}
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}
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}
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extension UnsafeBufferPointer where Element == UInt8 {
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@usableFromInline @inline(__always)
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internal func utf8ScalarAndLength(startingAt i: Int) -> (Unicode.Scalar, Int) {
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let cu0 = self[i]
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assert(!_isContinuation(cu0))
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let length = Swift._utf8ScalarLength(cu0)
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let scalar: Unicode.Scalar
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switch length {
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case 1: scalar = _decodeUTF8(cu0)
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case 2: scalar = _decodeUTF8(cu0, self[i &+ 1])
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case 3: scalar = _decodeUTF8(cu0, self[i &+ 1], self[i &+ 2])
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case 4: scalar = _decodeUTF8(cu0, self[i &+ 1], self[i &+ 2], self[i &+ 3])
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default: Builtin.unreachable()
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}
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return (scalar, length)
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}
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@usableFromInline @inline(__always)
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internal func utf8Scalar(startingAt i: Int) -> Unicode.Scalar {
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return utf8ScalarAndLength(startingAt: i).0
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}
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}
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extension String.UnicodeScalarView {
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#if !INTERNAL_CHECKS_ENABLED
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@inlinable @inline(__always) internal func _invariantCheck() {}
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#else
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@usableFromInline @inline(never) @_effects(releasenone)
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internal func _invariantCheck() {
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// TODO: Assert start/end are scalar aligned
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}
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#endif // INTERNAL_CHECKS_ENABLED
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}
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extension String.UnicodeScalarView: BidirectionalCollection {
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public typealias Index = String.Index
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/// The position of the first Unicode scalar value if the string is
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/// nonempty.
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///
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/// If the string is empty, `startIndex` is equal to `endIndex`.
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@inlinable
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public var startIndex: Index {
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@inline(__always) get { return _guts.startIndex }
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}
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/// The "past the end" position---that is, the position one greater than
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/// the last valid subscript argument.
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///
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/// In an empty Unicode scalars view, `endIndex` is equal to `startIndex`.
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@inlinable
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public var endIndex: Index {
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@inline(__always) get { return _guts.endIndex }
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}
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/// Returns the next consecutive location after `i`.
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///
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/// - Precondition: The next location exists.
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@inlinable @inline(__always)
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public func index(after i: Index) -> Index {
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_sanityCheck(i < endIndex)
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// TODO(UTF8): isKnownASCII bit fast-path...
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if _fastPath(_guts.isFastUTF8) {
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let len = _guts.fastUTF8ScalarLength(startingAt: i.encodedOffset)
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return Index(encodedOffset: i.encodedOffset &+ len)
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}
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return _foreignIndex(after: i)
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}
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/// Returns the previous consecutive location before `i`.
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///
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/// - Precondition: The previous location exists.
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@inlinable @inline(__always)
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public func index(before i: Index) -> Index {
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precondition(i.encodedOffset > 0)
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if _fastPath(_guts.isFastUTF8) {
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// TODO(UTF8): isKnownASCII bit fast-path...
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let len = _guts.withFastUTF8 { utf8 -> Int in
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return _utf8ScalarLength(utf8, endingAt: i.encodedOffset)
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}
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_sanityCheck(len <= 4, "invalid UTF8")
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return Index(encodedOffset: i.encodedOffset &- len)
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}
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return _foreignIndex(before: i)
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}
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/// Accesses the Unicode scalar value at the given position.
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///
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/// The following example searches a string's Unicode scalars view for a
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/// capital letter and then prints the character and Unicode scalar value
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/// at the found index:
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///
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/// let greeting = "Hello, friend!"
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/// if let i = greeting.unicodeScalars.firstIndex(where: { "A"..."Z" ~= $0 }) {
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/// print("First capital letter: \(greeting.unicodeScalars[i])")
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/// print("Unicode scalar value: \(greeting.unicodeScalars[i].value)")
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/// }
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/// // Prints "First capital letter: H"
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/// // Prints "Unicode scalar value: 72"
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///
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/// - Parameter position: A valid index of the character view. `position`
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/// must be less than the view's end index.
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@inlinable
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public subscript(position: Index) -> Unicode.Scalar {
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@inline(__always) get {
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String(_guts)._boundsCheck(position)
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let i = _guts.scalarAlign(position)
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if _fastPath(_guts.isFastUTF8) {
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return _guts.fastUTF8Scalar(startingAt: i.encodedOffset)
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}
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return _foreignSubscript(aligned: i)
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}
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}
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}
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// TODO(UTF8): design specialized iterator, rather than default indexing one
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// extension String.UnicodeScalarView {
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// /// An iterator over the Unicode scalars that make up a `UnicodeScalarView`
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// /// collection.
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// @_fixed_layout
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// public struct Iterator : IteratorProtocol {
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// // TODO:
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// /// Advances to the next element and returns it, or `nil` if no next
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// /// element exists.
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// ///
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// /// Once `nil` has been returned, all subsequent calls return `nil`.
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// ///
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// /// - Precondition: `next()` has not been applied to a copy of `self`
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// /// since the copy was made.
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// @inlinable @inline(__always)
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// public mutating func next() -> Unicode.Scalar? {
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// unimplemented_utf8()
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// }
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// }
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// }
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// extension String.UnicodeScalarView {
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// /// Returns an iterator over the Unicode scalars that make up this view.
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// ///
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// /// - Returns: An iterator over this collection's `Unicode.Scalar` elements.
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// @inlinable @inline(__always)
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// public func makeIterator() -> Iterator {
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// unimplemented_utf8()
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// }
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// }
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extension String.UnicodeScalarView: CustomStringConvertible {
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@inlinable
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public var description: String {
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@inline(__always) get { return String(_guts) }
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}
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}
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extension String.UnicodeScalarView: CustomDebugStringConvertible {
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public var debugDescription: String {
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return "StringUnicodeScalarView(\(self.description.debugDescription))"
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}
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}
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extension String {
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/// Creates a string corresponding to the given collection of Unicode
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/// scalars.
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///
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/// You can use this initializer to create a new string from a slice of
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/// another string's `unicodeScalars` view.
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///
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/// let picnicGuest = "Deserving porcupine"
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/// if let i = picnicGuest.unicodeScalars.firstIndex(of: " ") {
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/// let adjective = String(picnicGuest.unicodeScalars[..<i])
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/// print(adjective)
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/// }
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/// // Prints "Deserving"
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///
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/// The `adjective` constant is created by calling this initializer with a
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/// slice of the `picnicGuest.unicodeScalars` view.
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///
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/// - Parameter unicodeScalars: A collection of Unicode scalar values.
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@inlinable @inline(__always)
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public init(_ unicodeScalars: UnicodeScalarView) {
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self.init(unicodeScalars._guts)
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}
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/// The index type for a string's `unicodeScalars` view.
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public typealias UnicodeScalarIndex = UnicodeScalarView.Index
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/// The string's value represented as a collection of Unicode scalar values.
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@inlinable
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public var unicodeScalars: UnicodeScalarView {
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@inline(__always) get { return UnicodeScalarView(_guts) }
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@inline(__always) set { _guts = newValue._guts }
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}
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}
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extension String.UnicodeScalarView : RangeReplaceableCollection {
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/// Creates an empty view instance.
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@inlinable @inline(__always)
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public init() {
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self.init(_StringGuts())
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}
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/// Reserves enough space in the view's underlying storage to store the
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/// specified number of ASCII characters.
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///
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/// Because a Unicode scalar value can require more than a single ASCII
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/// character's worth of storage, additional allocation may be necessary
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/// when adding to a Unicode scalar view after a call to
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/// `reserveCapacity(_:)`.
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///
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/// - Parameter n: The minimum number of ASCII character's worth of storage
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/// to allocate.
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///
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/// - Complexity: O(*n*), where *n* is the capacity being reserved.
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public mutating func reserveCapacity(_ n: Int) {
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self._guts.reserveCapacity(n)
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}
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/// Appends the given Unicode scalar to the view.
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///
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/// - Parameter c: The character to append to the string.
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public mutating func append(_ c: Unicode.Scalar) {
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// TODO(UTF8 perf): This is a horribly slow means...
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self.append(contentsOf: [c])
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}
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/// Appends the Unicode scalar values in the given sequence to the view.
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///
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/// - Parameter newElements: A sequence of Unicode scalar values.
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///
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/// - Complexity: O(*n*), where *n* is the length of the resulting view.
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public mutating func append<S : Sequence>(contentsOf newElements: S)
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where S.Element == Unicode.Scalar {
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// TODO(UTF8 perf): This is a horribly slow means...
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let scalars = String(decoding: newElements.map { $0.value }, as: UTF32.self)
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self = (String(self._guts) + scalars).unicodeScalars
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}
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/// Replaces the elements within the specified bounds with the given Unicode
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/// scalar values.
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///
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/// Calling this method invalidates any existing indices for use with this
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/// string.
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///
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/// - Parameters:
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/// - bounds: The range of elements to replace. The bounds of the range
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/// must be valid indices of the view.
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/// - newElements: The new Unicode scalar values to add to the string.
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///
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/// - Complexity: O(*m*), where *m* is the combined length of the view and
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/// `newElements`. If the call to `replaceSubrange(_:with:)` simply
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/// removes elements at the end of the string, the complexity is O(*n*),
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/// where *n* is equal to `bounds.count`.
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public mutating func replaceSubrange<C>(
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_ bounds: Range<Index>,
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with newElements: C
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) where C : Collection, C.Element == Unicode.Scalar {
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// TODO(UTF8 perf): This is a horribly slow means...
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//
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// TODO(UTF8 perf): Consider storing a string directly, or implemeting RSR
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// on guts.
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let utf8Replacement = newElements.flatMap { String($0).utf8 }
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let replacement = utf8Replacement.withUnsafeBufferPointer {
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return String._uncheckedFromUTF8($0)
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}
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var copy = String(_guts)
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copy.replaceSubrange(bounds, with: replacement)
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self = copy.unicodeScalars
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}
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}
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// Index conversions
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extension String.UnicodeScalarIndex {
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/// Creates an index in the given Unicode scalars view that corresponds
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/// exactly to the specified `UTF16View` position.
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///
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/// The following example finds the position of a space in a string's `utf16`
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/// view and then converts that position to an index in the string's
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/// `unicodeScalars` view:
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///
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/// let cafe = "Café 🍵"
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///
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/// let utf16Index = cafe.utf16.firstIndex(of: 32)!
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/// let scalarIndex = String.Index(utf16Index, within: cafe.unicodeScalars)!
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///
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/// print(String(cafe.unicodeScalars[..<scalarIndex]))
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/// // Prints "Café"
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///
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/// If the index passed as `sourcePosition` doesn't have an exact
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/// corresponding position in `unicodeScalars`, the result of the
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/// initializer is `nil`. For example, an attempt to convert the position of
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/// the trailing surrogate of a UTF-16 surrogate pair results in `nil`.
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///
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/// - Parameters:
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/// - sourcePosition: A position in the `utf16` view of a string.
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/// `utf16Index` must be an element of
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/// `String(unicodeScalars).utf16.indices`.
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/// - unicodeScalars: The `UnicodeScalarView` in which to find the new
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/// position.
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public init?(
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_ sourcePosition: String.Index,
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within unicodeScalars: String.UnicodeScalarView
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) {
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guard unicodeScalars._guts.isOnUnicodeScalarBoundary(sourcePosition) else {
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return nil
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}
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self = sourcePosition
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}
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/// Returns the position in the given string that corresponds exactly to this
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/// index.
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///
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/// This example first finds the position of a space (UTF-8 code point `32`)
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/// in a string's `utf8` view and then uses this method find the same position
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/// in the string.
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///
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/// let cafe = "Café 🍵"
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/// let i = cafe.unicodeScalars.firstIndex(of: "🍵")
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/// let j = i.samePosition(in: cafe)!
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/// print(cafe[j...])
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/// // Prints "🍵"
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///
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/// - Parameter characters: The string to use for the index conversion.
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/// This index must be a valid index of at least one view of `characters`.
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/// - Returns: The position in `characters` that corresponds exactly to
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/// this index. If this index does not have an exact corresponding
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/// position in `characters`, this method returns `nil`. For example,
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/// an attempt to convert the position of a UTF-8 continuation byte
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/// returns `nil`.
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public func samePosition(in characters: String) -> String.Index? {
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return String.Index(self, within: characters)
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}
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}
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// Reflection
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extension String.UnicodeScalarView : CustomReflectable {
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/// Returns a mirror that reflects the Unicode scalars view of a string.
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public var customMirror: Mirror {
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return Mirror(self, unlabeledChildren: self)
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}
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}
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//===--- Slicing Support --------------------------------------------------===//
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/// In Swift 3.2, in the absence of type context,
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///
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/// someString.unicodeScalars[
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/// someString.unicodeScalars.startIndex
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/// ..< someString.unicodeScalars.endIndex]
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///
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/// was deduced to be of type `String.UnicodeScalarView`. Provide a
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/// more-specific Swift-3-only `subscript` overload that continues to produce
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/// `String.UnicodeScalarView`.
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extension String.UnicodeScalarView {
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public typealias SubSequence = Substring.UnicodeScalarView
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@available(swift, introduced: 4)
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public subscript(r: Range<Index>) -> String.UnicodeScalarView.SubSequence {
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return String.UnicodeScalarView.SubSequence(self, _bounds: r)
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}
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}
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// Foreign string Support
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extension String.UnicodeScalarView {
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@usableFromInline @inline(never)
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@_effects(releasenone)
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internal func _foreignIndex(after i: Index) -> Index {
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_sanityCheck(_guts.isForeign)
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let cu = _guts.foreignErrorCorrectedUTF16CodeUnit(at: i)
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let len = _isLeadingSurrogate(cu) ? 2 : 1
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return Index(encodedOffset: i.encodedOffset + len)
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}
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@usableFromInline @inline(never)
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@_effects(releasenone)
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internal func _foreignIndex(before i: Index) -> Index {
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_sanityCheck(_guts.isForeign)
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let priorIdx = String.Index(encodedOffset: i.encodedOffset - 1)
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let cu = _guts.foreignErrorCorrectedUTF16CodeUnit(at: priorIdx)
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let len = _isTrailingSurrogate(cu) ? 2 : 1
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return Index(encodedOffset: i.encodedOffset - len)
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}
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@usableFromInline @inline(never)
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@_effects(releasenone)
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internal func _foreignSubscript(aligned i: Index) -> Unicode.Scalar {
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_sanityCheck(_guts.isForeign)
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_sanityCheck(_guts.isOnUnicodeScalarBoundary(i),
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"should of been aligned prior")
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return _guts.foreignErrorCorrectedScalar(startingAt: i)
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}
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}
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