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StringRangeReplaceableCollection.swift
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StringRangeReplaceableCollection.swift
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//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
extension String : StringProtocol, RangeReplaceableCollection {
/// A type that represents the number of steps between two `String.Index`
/// values, where one value is reachable from the other.
///
/// In Swift, *reachability* refers to the ability to produce one value from
/// the other through zero or more applications of `index(after:)`.
public typealias IndexDistance = Int
public typealias SubSequence = Substring
/// Creates a string representing the given character repeated the specified
/// number of times.
///
/// For example, use this initializer to create a string with ten `"0"`
/// characters in a row.
///
/// let zeroes = String(repeating: "0" as Character, count: 10)
/// print(zeroes)
/// // Prints "0000000000"
///
/// - Parameters:
/// - repeatedValue: The character to repeat.
/// - count: The number of times to repeat `repeatedValue` in the
/// resulting string.
@inlinable // FIXME(sil-serialize-all)
public init(repeating repeatedValue: Character, count: Int) {
self.init(repeating: String(repeatedValue), count: count)
}
// This initializer disambiguates between the following intitializers, now
// that String conforms to Collection:
// - init<T>(_ value: T) where T : LosslessStringConvertible
// - init<S>(_ characters: S) where S : Sequence, S.Element == Character
/// Creates a new string containing the characters in the given sequence.
///
/// You can use this initializer to create a new string from the result of
/// one or more collection operations on a string's characters. For example:
///
/// let str = "The rain in Spain stays mainly in the plain."
///
/// let vowels: Set<Character> = ["a", "e", "i", "o", "u"]
/// let disemvoweled = String(str.lazy.filter { !vowels.contains($0) })
///
/// print(disemvoweled)
/// // Prints "Th rn n Spn stys mnly n th pln."
///
/// - Parameter other: A string instance or another sequence of
/// characters.
@inlinable // FIXME(sil-serialize-all)
public init<S : Sequence & LosslessStringConvertible>(_ other: S)
where S.Element == Character {
self = other.description
}
// The defaulted argument prevents this initializer from satisfies the
// LosslessStringConvertible conformance. You can satisfy a protocol
// requirement with something that's not yet available, but not with
// something that has become unavailable. Without this, the code won't
// compile as Swift 4.
@inlinable // FIXME(sil-serialize-all)
@available(swift, obsoleted: 4, message: "String.init(_:String) is no longer failable")
public init?(_ other: String, obsoletedInSwift4: () = ()) {
self.init(other._guts)
}
/// The position of the first character in a nonempty string.
///
/// In an empty string, `startIndex` is equal to `endIndex`.
@inlinable // FIXME(sil-serialize-all)
public var startIndex: Index { return Index(encodedOffset: 0) }
/// A string's "past the end" position---that is, the position one greater
/// than the last valid subscript argument.
///
/// In an empty string, `endIndex` is equal to `startIndex`.
@inlinable // FIXME(sil-serialize-all)
public var endIndex: Index { return Index(encodedOffset: _guts.count) }
/// The number of characters in a string.
public var count: Int {
return distance(from: startIndex, to: endIndex)
}
@inlinable
@inline(__always)
internal func _boundsCheck(_ index: Index) {
_precondition(index.encodedOffset >= 0 && index.encodedOffset < _guts.count,
"String index is out of bounds")
}
@inlinable
@inline(__always)
internal func _boundsCheck(_ range: Range<Index>) {
_precondition(
range.lowerBound.encodedOffset >= 0 &&
range.upperBound.encodedOffset <= _guts.count,
"String index range is out of bounds")
}
@inlinable
@inline(__always)
internal func _boundsCheck(_ range: ClosedRange<Index>) {
_precondition(
range.lowerBound.encodedOffset >= 0 &&
range.upperBound.encodedOffset < _guts.count,
"String index range is out of bounds")
}
internal func _index(atEncodedOffset offset: Int) -> Index {
return _visitGuts(_guts, args: offset,
ascii: { ascii, offset in return ascii.characterIndex(atOffset: offset) },
utf16: { utf16, offset in return utf16.characterIndex(atOffset: offset) },
opaque: { opaque, offset in
return opaque.characterIndex(atOffset: offset) })
}
/// Returns the position immediately after the given index.
///
/// - Parameter i: A valid index of the collection. `i` must be less than
/// `endIndex`.
/// - Returns: The index value immediately after `i`.
public func index(after i: Index) -> Index {
return _visitGuts(_guts, args: i,
ascii: { ascii, i in ascii.characterIndex(after: i) },
utf16: { utf16, i in utf16.characterIndex(after: i) },
opaque: { opaque, i in opaque.characterIndex(after: i) })
}
/// Returns the position immediately before the given index.
///
/// - Parameter i: A valid index of the collection. `i` must be greater than
/// `startIndex`.
/// - Returns: The index value immediately before `i`.
public func index(before i: Index) -> Index {
return _visitGuts(_guts, args: i,
ascii: { ascii, i in ascii.characterIndex(before: i) },
utf16: { utf16, i in utf16.characterIndex(before: i) },
opaque: { opaque, i in opaque.characterIndex(before: i) })
}
/// Returns an index that is the specified distance from the given index.
///
/// The following example obtains an index advanced four positions from a
/// string's starting index and then prints the character at that position.
///
/// let s = "Swift"
/// let i = s.index(s.startIndex, offsetBy: 4)
/// print(s[i])
/// // Prints "t"
///
/// The value passed as `n` must not offset `i` beyond the bounds of the
/// collection.
///
/// - Parameters:
/// - i: A valid index of the collection.
/// - n: The distance to offset `i`.
/// - Returns: An index offset by `n` from the index `i`. If `n` is positive,
/// this is the same value as the result of `n` calls to `index(after:)`.
/// If `n` is negative, this is the same value as the result of `-n` calls
/// to `index(before:)`.
///
/// - Complexity: O(*n*), where *n* is the absolute value of `n`.
public func index(_ i: Index, offsetBy n: IndexDistance) -> Index {
return _visitGuts(_guts, args: (i, n),
ascii: { ascii, args in let (i, n) = args
return ascii.characterIndex(i, offsetBy: n) },
utf16: { utf16, args in let (i, n) = args
return utf16.characterIndex(i, offsetBy: n) },
opaque: { opaque, args in let (i, n) = args
return opaque.characterIndex(i, offsetBy: n) })
}
/// Returns an index that is the specified distance from the given index,
/// unless that distance is beyond a given limiting index.
///
/// The following example obtains an index advanced four positions from a
/// string's starting index and then prints the character at that position.
/// The operation doesn't require going beyond the limiting `s.endIndex`
/// value, so it succeeds.
///
/// let s = "Swift"
/// if let i = s.index(s.startIndex, offsetBy: 4, limitedBy: s.endIndex) {
/// print(s[i])
/// }
/// // Prints "t"
///
/// The next example attempts to retrieve an index six positions from
/// `s.startIndex` but fails, because that distance is beyond the index
/// passed as `limit`.
///
/// let j = s.index(s.startIndex, offsetBy: 6, limitedBy: s.endIndex)
/// print(j)
/// // Prints "nil"
///
/// The value passed as `n` must not offset `i` beyond the bounds of the
/// collection, unless the index passed as `limit` prevents offsetting
/// beyond those bounds.
///
/// - Parameters:
/// - i: A valid index of the collection.
/// - n: The distance to offset `i`.
/// - limit: A valid index of the collection to use as a limit. If `n > 0`,
/// a limit that is less than `i` has no effect. Likewise, if `n < 0`, a
/// limit that is greater than `i` has no effect.
/// - Returns: An index offset by `n` from the index `i`, unless that index
/// would be beyond `limit` in the direction of movement. In that case,
/// the method returns `nil`.
///
/// - Complexity: O(*n*), where *n* is the absolute value of `n`.
public func index(
_ i: Index, offsetBy n: IndexDistance, limitedBy limit: Index
) -> Index? {
return _visitGuts(_guts, args: (i, n, limit),
ascii: { ascii, args in let (i, n, limit) = args
return ascii.characterIndex(i, offsetBy: n, limitedBy: limit) },
utf16: { utf16, args in let (i, n, limit) = args
return utf16.characterIndex(i, offsetBy: n, limitedBy: limit) },
opaque: { opaque, args in let (i, n, limit) = args
return opaque.characterIndex(i, offsetBy: n, limitedBy: limit) })
}
/// Returns the distance between two indices.
///
/// - Parameters:
/// - start: A valid index of the collection.
/// - end: Another valid index of the collection. If `end` is equal to
/// `start`, the result is zero.
/// - Returns: The distance between `start` and `end`.
///
/// - Complexity: O(*n*), where *n* is the resulting distance.
public func distance(from start: Index, to end: Index) -> IndexDistance {
return _visitGuts(_guts, args: (start, end),
ascii: { ascii, args in let (start, end) = args
return ascii.characterDistance(from: start, to: end) },
utf16: { utf16, args in let (start, end) = args
return utf16.characterDistance(from: start, to: end) },
opaque: { opaque, args in let (start, end) = args
return opaque.characterDistance(from: start, to: end) })
}
/// Accesses the character at the given position.
///
/// You can use the same indices for subscripting a string and its substring.
/// For example, this code finds the first letter after the first space:
///
/// let str = "Greetings, friend! How are you?"
/// let firstSpace = str.firstIndex(of: " ") ?? str.endIndex
/// let substr = str[firstSpace...]
/// if let nextCapital = substr.firstIndex(where: { $0 >= "A" && $0 <= "Z" }) {
/// print("Capital after a space: \(str[nextCapital])")
/// }
/// // Prints "Capital after a space: H"
///
/// - Parameter i: A valid index of the string. `i` must be less than the
/// string's end index.
public subscript(i: Index) -> Character {
return _visitGuts(_guts, args: i,
ascii: { ascii, i in return ascii.character(at: i) },
utf16: { utf16, i in return utf16.character(at: i) },
opaque: { opaque, i in return opaque.character(at: i) })
}
}
extension String {
/// Creates a new string containing the characters in the given sequence.
///
/// You can use this initializer to create a new string from the result of
/// one or more collection operations on a string's characters. For example:
///
/// let str = "The rain in Spain stays mainly in the plain."
///
/// let vowels: Set<Character> = ["a", "e", "i", "o", "u"]
/// let disemvoweled = String(str.lazy.filter { !vowels.contains($0) })
///
/// print(disemvoweled)
/// // Prints "Th rn n Spn stys mnly n th pln."
///
/// - Parameter characters: A string instance or another sequence of
/// characters.
@inlinable // FIXME(sil-serialize-all)
public init<S : Sequence>(_ characters: S)
where S.Iterator.Element == Character {
self = ""
self.append(contentsOf: characters)
}
/// Reserves enough space in the string's underlying storage to store the
/// specified number of ASCII characters.
///
/// Because each character in a string can require more than a single ASCII
/// character's worth of storage, additional allocation may be necessary
/// when adding characters to a string after a call to
/// `reserveCapacity(_:)`.
///
/// - Parameter n: The minimum number of ASCII character's worth of storage
/// to allocate.
///
/// - Complexity: O(*n*)
public mutating func reserveCapacity(_ n: Int) {
_guts.reserveCapacity(n)
}
/// Appends the given character to the string.
///
/// The following example adds an emoji globe to the end of a string.
///
/// var globe = "Globe "
/// globe.append("🌍")
/// print(globe)
/// // Prints "Globe 🌍"
///
/// - Parameter c: The character to append to the string.
public mutating func append(_ c: Character) {
if let small = c._smallUTF16 {
_guts.append(contentsOf: small)
} else {
_guts.append(c._largeUTF16!.unmanagedView)
_fixLifetime(c)
}
}
public mutating func append(contentsOf newElements: String) {
append(newElements)
}
public mutating func append(contentsOf newElements: Substring) {
_guts.append(
newElements._wholeString._guts,
range: newElements._encodedOffsetRange)
}
/// Appends the characters in the given sequence to the string.
///
/// - Parameter newElements: A sequence of characters.
@inlinable // FIXME(sil-serialize-all)
public mutating func append<S : Sequence>(contentsOf newElements: S)
where S.Iterator.Element == Character {
if _fastPath(newElements is _SwiftStringView) {
let v = newElements as! _SwiftStringView
_guts.append(v._wholeString._guts, range: v._encodedOffsetRange)
return
}
_guts.reserveUnusedCapacity(
newElements.underestimatedCount,
ascii: _guts.isASCII)
for c in newElements { self.append(c) }
}
/// Replaces the text within the specified bounds with the given characters.
///
/// Calling this method invalidates any existing indices for use with this
/// string.
///
/// - Parameters:
/// - bounds: The range of text to replace. The bounds of the range must be
/// valid indices of the string.
/// - newElements: The new characters to add to the string.
///
/// - Complexity: O(*m*), where *m* is the combined length of the string and
/// `newElements`. If the call to `replaceSubrange(_:with:)` simply
/// removes text at the end of the string, the complexity is O(*n*), where
/// *n* is equal to `bounds.count`.
@inlinable // FIXME(sil-serialize-all)
public mutating func replaceSubrange<C>(
_ bounds: Range<Index>,
with newElements: C
) where C : Collection, C.Iterator.Element == Character {
let offsetRange: Range<Int> =
bounds.lowerBound.encodedOffset ..< bounds.upperBound.encodedOffset
let lazyUTF16 = newElements.lazy.flatMap { $0.utf16 }
_guts.replaceSubrange(offsetRange, with: lazyUTF16)
}
/// Inserts a new character at the specified position.
///
/// Calling this method invalidates any existing indices for use with this
/// string.
///
/// - Parameters:
/// - newElement: The new character to insert into the string.
/// - i: A valid index of the string. If `i` is equal to the string's end
/// index, this methods appends `newElement` to the string.
///
/// - Complexity: O(*n*), where *n* is the length of the string.
@inlinable // FIXME(sil-serialize-all)
public mutating func insert(_ newElement: Character, at i: Index) {
let offset = i.encodedOffset
_guts.replaceSubrange(offset..<offset, with: newElement.utf16)
}
/// Inserts a collection of characters at the specified position.
///
/// Calling this method invalidates any existing indices for use with this
/// string.
///
/// - Parameters:
/// - newElements: A collection of `Character` elements to insert into the
/// string.
/// - i: A valid index of the string. If `i` is equal to the string's end
/// index, this methods appends the contents of `newElements` to the
/// string.
///
/// - Complexity: O(*n*), where *n* is the combined length of the string and
/// `newElements`.
@inlinable // FIXME(sil-serialize-all)
public mutating func insert<S : Collection>(
contentsOf newElements: S, at i: Index
) where S.Iterator.Element == Character {
let offset = i.encodedOffset
let utf16 = newElements.lazy.flatMap { $0.utf16 }
_guts.replaceSubrange(offset..<offset, with: utf16)
}
/// Removes and returns the character at the specified position.
///
/// All the elements following `i` are moved to close the gap. This example
/// removes the hyphen from the middle of a string.
///
/// var nonempty = "non-empty"
/// if let i = nonempty.firstIndex(of: "-") {
/// nonempty.remove(at: i)
/// }
/// print(nonempty)
/// // Prints "nonempty"
///
/// Calling this method invalidates any existing indices for use with this
/// string.
///
/// - Parameter i: The position of the character to remove. `i` must be a
/// valid index of the string that is not equal to the string's end index.
/// - Returns: The character that was removed.
@inlinable // FIXME(sil-serialize-all)
@discardableResult
public mutating func remove(at i: Index) -> Character {
let offset = i.encodedOffset
let stride = _stride(of: i)
let range: Range<Int> = offset ..< offset + stride
let old = Character(_unverified: _guts, range: range)
_guts.replaceSubrange(range, with: EmptyCollection())
return old
}
@inlinable // FIXME(sil-serialize-all)
internal func _stride(of i: Index) -> Int {
if case .character(let stride) = i._cache {
// TODO: should _fastPath the case somehow
_sanityCheck(stride > 0)
return Int(stride)
}
let offset = i.encodedOffset
return _visitGuts(_guts, args: offset,
ascii: { ascii, offset in
return ascii.characterStride(atOffset: offset) },
utf16: { utf16, offset in
return utf16.characterStride(atOffset: offset) },
opaque: { opaque, offset in
return opaque.characterStride(atOffset: offset) })
}
/// Removes the characters in the given range.
///
/// Calling this method invalidates any existing indices for use with this
/// string.
///
/// - Parameter bounds: The range of the elements to remove. The upper and
/// lower bounds of `bounds` must be valid indices of the string and not
/// equal to the string's end index.
/// - Parameter bounds: The range of the elements to remove. The upper and
/// lower bounds of `bounds` must be valid indices of the string.
@inlinable // FIXME(sil-serialize-all)
public mutating func removeSubrange(_ bounds: Range<Index>) {
let start = bounds.lowerBound.encodedOffset
let end = bounds.upperBound.encodedOffset
_guts.replaceSubrange(start..<end, with: EmptyCollection())
}
/// Replaces this string with the empty string.
///
/// Calling this method invalidates any existing indices for use with this
/// string.
///
/// - Parameter keepCapacity: Pass `true` to prevent the release of the
/// string's allocated storage. Retaining the storage can be a useful
/// optimization when you're planning to grow the string again. The
/// default value is `false`.
@inlinable // FIXME(sil-serialize-all)
public mutating func removeAll(keepingCapacity keepCapacity: Bool = false) {
if keepCapacity {
_guts.replaceSubrange(0..<_guts.count, with: EmptyCollection())
} else {
_guts = _StringGuts()
}
}
}
extension String {
// This is needed because of the issue described in SR-4660 which causes
// source compatibility issues when String becomes a collection
@inlinable // FIXME(sil-serialize-all)
@_transparent
public func max<T : Comparable>(_ x: T, _ y: T) -> T {
return Swift.max(x,y)
}
// This is needed because of the issue described in SR-4660 which causes
// source compatibility issues when String becomes a collection
@inlinable // FIXME(sil-serialize-all)
@_transparent
public func min<T : Comparable>(_ x: T, _ y: T) -> T {
return Swift.min(x,y)
}
}
//===----------------------------------------------------------------------===//
// The following overloads of flatMap are carefully crafted to allow the code
// like the following:
// ["hello"].flatMap { $0 }
// return an array of strings without any type context in Swift 3 mode, at the
// same time allowing the following code snippet to compile:
// [0, 1].flatMap { x in
// if String(x) == "foo" { return "bar" } else { return nil }
// }
// Note that the second overload is declared on a more specific protocol.
// See: test/stdlib/StringFlatMap.swift for tests.
extension Sequence {
@inlinable // FIXME(sil-serialize-all)
@available(swift, obsoleted: 4)
public func flatMap(
_ transform: (Element) throws -> String
) rethrows -> [String] {
return try map(transform)
}
}
extension Collection {
@available(swift, deprecated: 4.1, renamed: "compactMap(_:)",
message: "Please use compactMap(_:) for the case where closure returns an optional value")
@inline(__always)
public func flatMap(
_ transform: (Element) throws -> String?
) rethrows -> [String] {
return try _compactMap(transform)
}
}
//===----------------------------------------------------------------------===//
extension Sequence where Element == String {
@available(*, unavailable, message: "Operator '+' cannot be used to append a String to a sequence of strings")
public static func + (lhs: Self, rhs: String) -> Never {
fatalError()
}
@available(*, unavailable, message: "Operator '+' cannot be used to append a String to a sequence of strings")
public static func + (lhs: String, rhs: Self) -> Never {
fatalError()
}
}