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Substring.swift
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Substring.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 {
// FIXME(strings): at least temporarily remove it to see where it was applied
/// Creates a new string from the given substring.
///
/// - Parameter substring: A substring to convert to a standalone `String`
/// instance.
///
/// - Complexity: O(*n*), where *n* is the length of `substring`.
@inlinable
public init(_ substring: __shared Substring) {
self = String._fromSubstring(substring)
}
}
/// A slice of a string.
///
/// When you create a slice of a string, a `Substring` instance is the result.
/// Operating on substrings is fast and efficient because a substring shares
/// its storage with the original string. The `Substring` type presents the
/// same interface as `String`, so you can avoid or defer any copying of the
/// string's contents.
///
/// The following example creates a `greeting` string, and then finds the
/// substring of the first sentence:
///
/// let greeting = "Hi there! It's nice to meet you! 👋"
/// let endOfSentence = greeting.firstIndex(of: "!")!
/// let firstSentence = greeting[...endOfSentence]
/// // firstSentence == "Hi there!"
///
/// You can perform many string operations on a substring. Here, we find the
/// length of the first sentence and create an uppercase version.
///
/// print("'\(firstSentence)' is \(firstSentence.count) characters long.")
/// // Prints "'Hi there!' is 9 characters long."
///
/// let shoutingSentence = firstSentence.uppercased()
/// // shoutingSentence == "HI THERE!"
///
/// Converting a Substring to a String
/// ==================================
///
/// This example defines a `rawData` string with some unstructured data, and
/// then uses the string's `prefix(while:)` method to create a substring of
/// the numeric prefix:
///
/// let rawInput = "126 a.b 22219 zzzzzz"
/// let numericPrefix = rawInput.prefix(while: { "0"..."9" ~= $0 })
/// // numericPrefix is the substring "126"
///
/// When you need to store a substring or pass it to a function that requires a
/// `String` instance, you can convert it to a `String` by using the
/// `String(_:)` initializer. Calling this initializer copies the contents of
/// the substring to a new string.
///
/// func parseAndAddOne(_ s: String) -> Int {
/// return Int(s, radix: 10)! + 1
/// }
/// _ = parseAndAddOne(numericPrefix)
/// // error: cannot convert value...
/// let incrementedPrefix = parseAndAddOne(String(numericPrefix))
/// // incrementedPrefix == 127
///
/// Alternatively, you can convert the function that takes a `String` to one
/// that is generic over the `StringProtocol` protocol. The following code
/// declares a generic version of the `parseAndAddOne(_:)` function:
///
/// func genericParseAndAddOne<S: StringProtocol>(_ s: S) -> Int {
/// return Int(s, radix: 10)! + 1
/// }
/// let genericallyIncremented = genericParseAndAddOne(numericPrefix)
/// // genericallyIncremented == 127
///
/// You can call this generic function with an instance of either `String` or
/// `Substring`.
///
/// - Important: Don't store substrings longer than you need them to perform a
/// specific operation. A substring holds a reference to the entire storage
/// of the string it comes from, not just to the portion it presents, even
/// when there is no other reference to the original string. Storing
/// substrings may, therefore, prolong the lifetime of string data that is
/// no longer otherwise accessible, which can appear to be memory leakage.
@_fixed_layout
public struct Substring {
@usableFromInline
internal var _slice: Slice<String>
@inlinable @inline(__always)
internal init(_ slice: Slice<String>) {
self._slice = slice
_invariantCheck()
}
@inline(__always)
internal init(_ slice: _StringGutsSlice) {
self.init(String(slice._guts)[slice.range])
}
/// Creates an empty substring.
@inlinable @inline(__always)
public init() {
self.init(Slice())
}
}
extension Substring {
@inlinable
internal var _wholeGuts: _StringGuts {
@inline(__always) get { return _slice.base._guts }
}
@inlinable
internal var _wholeString: String {
@inline(__always) get { return String(self._wholeGuts) }
}
@inlinable
internal var _offsetRange: Range<Int> {
@inline(__always) get {
let start = _slice.startIndex
let end = _slice.endIndex
_internalInvariant(start.transcodedOffset == 0 && end.transcodedOffset == 0)
return Range(uncheckedBounds: (start.encodedOffset, end.encodedOffset))
}
}
#if !INTERNAL_CHECKS_ENABLED
@inlinable @inline(__always) internal func _invariantCheck() {}
#else
@usableFromInline @inline(never) @_effects(releasenone)
internal func _invariantCheck() {
self._wholeString._invariantCheck()
}
#endif // INTERNAL_CHECKS_ENABLED
}
extension Substring: StringProtocol {
public typealias Index = String.Index
public typealias SubSequence = Substring
@inlinable
public var startIndex: Index {
@inline(__always) get { return _slice.startIndex }
}
@inlinable
public var endIndex: Index {
@inline(__always) get { return _slice.endIndex }
}
@inlinable @inline(__always)
public func index(after i: Index) -> Index {
_precondition(i < endIndex, "Cannot increment beyond endIndex")
_precondition(i >= startIndex, "Cannot increment an invalid index")
return _slice.index(after: i)
}
@inlinable @inline(__always)
public func index(before i: Index) -> Index {
_precondition(i <= endIndex, "Cannot decrement an invalid index")
_precondition(i > startIndex, "Cannot decrement beyond startIndex")
return _slice.index(before: i)
}
@inlinable @inline(__always)
public func index(_ i: Index, offsetBy n: Int) -> Index {
let result = _slice.index(i, offsetBy: n)
_precondition(
(_slice._startIndex ... _slice.endIndex).contains(result),
"Operation results in an invalid index")
return result
}
@inlinable @inline(__always)
public func index(
_ i: Index, offsetBy n: Int, limitedBy limit: Index
) -> Index? {
let result = _slice.index(i, offsetBy: n, limitedBy: limit)
_precondition(result.map {
(_slice._startIndex ... _slice.endIndex).contains($0)
} ?? true,
"Operation results in an invalid index")
return result
}
@inlinable @inline(__always)
public func distance(from start: Index, to end: Index) -> Int {
return _slice.distance(from: start, to: end)
}
public subscript(i: Index) -> Character {
return _slice[i]
}
public mutating func replaceSubrange<C>(
_ bounds: Range<Index>,
with newElements: C
) where C : Collection, C.Iterator.Element == Iterator.Element {
_slice.replaceSubrange(bounds, with: newElements)
}
public mutating func replaceSubrange(
_ bounds: Range<Index>, with newElements: Substring
) {
replaceSubrange(bounds, with: newElements._slice)
}
/// Creates a string from the given Unicode code units in the specified
/// encoding.
///
/// - Parameters:
/// - codeUnits: A collection of code units encoded in the encoding
/// specified in `sourceEncoding`.
/// - sourceEncoding: The encoding in which `codeUnits` should be
/// interpreted.
@inlinable // specialization
public init<C: Collection, Encoding: _UnicodeEncoding>(
decoding codeUnits: C, as sourceEncoding: Encoding.Type
) where C.Iterator.Element == Encoding.CodeUnit {
self.init(String(decoding: codeUnits, as: sourceEncoding))
}
/// Creates a string from the null-terminated, UTF-8 encoded sequence of
/// bytes at the given pointer.
///
/// - Parameter nullTerminatedUTF8: A pointer to a sequence of contiguous,
/// UTF-8 encoded bytes ending just before the first zero byte.
public init(cString nullTerminatedUTF8: UnsafePointer<CChar>) {
self.init(String(cString: nullTerminatedUTF8))
}
/// Creates a string from the null-terminated sequence of bytes at the given
/// pointer.
///
/// - Parameters:
/// - nullTerminatedCodeUnits: A pointer to a sequence of contiguous code
/// units in the encoding specified in `sourceEncoding`, ending just
/// before the first zero code unit.
/// - sourceEncoding: The encoding in which the code units should be
/// interpreted.
@inlinable // specialization
public init<Encoding: _UnicodeEncoding>(
decodingCString nullTerminatedCodeUnits: UnsafePointer<Encoding.CodeUnit>,
as sourceEncoding: Encoding.Type
) {
self.init(
String(decodingCString: nullTerminatedCodeUnits, as: sourceEncoding))
}
/// Calls the given closure with a pointer to the contents of the string,
/// represented as a null-terminated sequence of UTF-8 code units.
///
/// The pointer passed as an argument to `body` is valid only during the
/// execution of `withCString(_:)`. Do not store or return the pointer for
/// later use.
///
/// - Parameter body: A closure with a pointer parameter that points to a
/// null-terminated sequence of UTF-8 code units. If `body` has a return
/// value, that value is also used as the return value for the
/// `withCString(_:)` method. The pointer argument is valid only for the
/// duration of the method's execution.
/// - Returns: The return value, if any, of the `body` closure parameter.
@inlinable // specialization
public func withCString<Result>(
_ body: (UnsafePointer<CChar>) throws -> Result) rethrows -> Result {
// TODO(String performance): Detect when we cover the rest of a nul-
// terminated String, and thus can avoid a copy.
return try String(self).withCString(body)
}
/// Calls the given closure with a pointer to the contents of the string,
/// represented as a null-terminated sequence of code units.
///
/// The pointer passed as an argument to `body` is valid only during the
/// execution of `withCString(encodedAs:_:)`. Do not store or return the
/// pointer for later use.
///
/// - Parameters:
/// - body: A closure with a pointer parameter that points to a
/// null-terminated sequence of code units. If `body` has a return
/// value, that value is also used as the return value for the
/// `withCString(encodedAs:_:)` method. The pointer argument is valid
/// only for the duration of the method's execution.
/// - targetEncoding: The encoding in which the code units should be
/// interpreted.
/// - Returns: The return value, if any, of the `body` closure parameter.
@inlinable // specialization
public func withCString<Result, TargetEncoding: _UnicodeEncoding>(
encodedAs targetEncoding: TargetEncoding.Type,
_ body: (UnsafePointer<TargetEncoding.CodeUnit>) throws -> Result
) rethrows -> Result {
// TODO(String performance): Detect when we cover the rest of a nul-
// terminated String, and thus can avoid a copy.
return try String(self).withCString(encodedAs: targetEncoding, body)
}
}
extension Substring : CustomReflectable {
public var customMirror: Mirror { return String(self).customMirror }
}
extension Substring : CustomStringConvertible {
@inlinable
public var description: String {
@inline(__always) get { return String(self) }
}
}
extension Substring : CustomDebugStringConvertible {
public var debugDescription: String { return String(self).debugDescription }
}
extension Substring : LosslessStringConvertible {
@inlinable
public init(_ content: String) {
self = content[...]
}
}
extension Substring {
@_fixed_layout
public struct UTF8View {
@usableFromInline
internal var _slice: Slice<String.UTF8View>
}
}
extension Substring.UTF8View : BidirectionalCollection {
public typealias Index = String.UTF8View.Index
public typealias Indices = String.UTF8View.Indices
public typealias Element = String.UTF8View.Element
public typealias SubSequence = Substring.UTF8View
/// Creates an instance that slices `base` at `_bounds`.
@inlinable
internal init(_ base: String.UTF8View, _bounds: Range<Index>) {
_slice = Slice(
base: String(base._guts).utf8,
bounds: _bounds)
}
//
// Plumb slice operations through
//
@inlinable
public var startIndex: Index { return _slice.startIndex }
@inlinable
public var endIndex: Index { return _slice.endIndex }
@inlinable
public subscript(index: Index) -> Element { return _slice[index] }
@inlinable
public var indices: Indices { return _slice.indices }
@inlinable
public func index(after i: Index) -> Index { return _slice.index(after: i) }
@inlinable
public func formIndex(after i: inout Index) {
_slice.formIndex(after: &i)
}
@inlinable
public func index(_ i: Index, offsetBy n: Int) -> Index {
return _slice.index(i, offsetBy: n)
}
@inlinable
public func index(
_ i: Index, offsetBy n: Int, limitedBy limit: Index
) -> Index? {
return _slice.index(i, offsetBy: n, limitedBy: limit)
}
@inlinable
public func distance(from start: Index, to end: Index) -> Int {
return _slice.distance(from: start, to: end)
}
@inlinable
public func _failEarlyRangeCheck(_ index: Index, bounds: Range<Index>) {
_slice._failEarlyRangeCheck(index, bounds: bounds)
}
@inlinable
public func _failEarlyRangeCheck(
_ range: Range<Index>, bounds: Range<Index>
) {
_slice._failEarlyRangeCheck(range, bounds: bounds)
}
public func index(before i: Index) -> Index { return _slice.index(before: i) }
public func formIndex(before i: inout Index) {
_slice.formIndex(before: &i)
}
public subscript(r: Range<Index>) -> Substring.UTF8View {
// FIXME(strings): tests.
_precondition(r.lowerBound >= startIndex && r.upperBound <= endIndex,
"UTF8View index range out of bounds")
return Substring.UTF8View(_slice.base, _bounds: r)
}
}
extension Substring {
@inlinable
public var utf8: UTF8View {
get {
return _wholeString.utf8[startIndex..<endIndex]
}
set {
self = Substring(newValue)
}
}
/// Creates a Substring having the given content.
///
/// - Complexity: O(1)
public init(_ content: UTF8View) {
self = String(
content._slice.base._guts
)[content.startIndex..<content.endIndex]
}
}
extension String {
/// Creates a String having the given content.
///
/// If `codeUnits` is an ill-formed code unit sequence, the result is `nil`.
///
/// - Complexity: O(N), where N is the length of the resulting `String`'s
/// UTF-16.
public init?(_ codeUnits: Substring.UTF8View) {
let guts = codeUnits._slice.base._guts
guard guts.isOnUnicodeScalarBoundary(codeUnits._slice.startIndex),
guts.isOnUnicodeScalarBoundary(codeUnits._slice.endIndex) else {
return nil
}
self = String(Substring(codeUnits))
}
}
extension Substring {
@_fixed_layout
public struct UTF16View {
@usableFromInline
internal var _slice: Slice<String.UTF16View>
}
}
extension Substring.UTF16View : BidirectionalCollection {
public typealias Index = String.UTF16View.Index
public typealias Indices = String.UTF16View.Indices
public typealias Element = String.UTF16View.Element
public typealias SubSequence = Substring.UTF16View
/// Creates an instance that slices `base` at `_bounds`.
@inlinable
internal init(_ base: String.UTF16View, _bounds: Range<Index>) {
_slice = Slice(
base: String(base._guts).utf16,
bounds: _bounds)
}
//
// Plumb slice operations through
//
@inlinable
public var startIndex: Index { return _slice.startIndex }
@inlinable
public var endIndex: Index { return _slice.endIndex }
@inlinable
public subscript(index: Index) -> Element { return _slice[index] }
@inlinable
public var indices: Indices { return _slice.indices }
@inlinable
public func index(after i: Index) -> Index { return _slice.index(after: i) }
@inlinable
public func formIndex(after i: inout Index) {
_slice.formIndex(after: &i)
}
@inlinable
public func index(_ i: Index, offsetBy n: Int) -> Index {
return _slice.index(i, offsetBy: n)
}
@inlinable
public func index(
_ i: Index, offsetBy n: Int, limitedBy limit: Index
) -> Index? {
return _slice.index(i, offsetBy: n, limitedBy: limit)
}
@inlinable
public func distance(from start: Index, to end: Index) -> Int {
return _slice.distance(from: start, to: end)
}
@inlinable
public func _failEarlyRangeCheck(_ index: Index, bounds: Range<Index>) {
_slice._failEarlyRangeCheck(index, bounds: bounds)
}
@inlinable
public func _failEarlyRangeCheck(
_ range: Range<Index>, bounds: Range<Index>
) {
_slice._failEarlyRangeCheck(range, bounds: bounds)
}
@inlinable
public func index(before i: Index) -> Index { return _slice.index(before: i) }
@inlinable
public func formIndex(before i: inout Index) {
_slice.formIndex(before: &i)
}
@inlinable
public subscript(r: Range<Index>) -> Substring.UTF16View {
return Substring.UTF16View(_slice.base, _bounds: r)
}
}
extension Substring {
@inlinable
public var utf16: UTF16View {
get {
return _wholeString.utf16[startIndex..<endIndex]
}
set {
self = Substring(newValue)
}
}
/// Creates a Substring having the given content.
///
/// - Complexity: O(1)
public init(_ content: UTF16View) {
self = String(
content._slice.base._guts
)[content.startIndex..<content.endIndex]
}
}
extension String {
/// Creates a String having the given content.
///
/// If `codeUnits` is an ill-formed code unit sequence, the result is `nil`.
///
/// - Complexity: O(N), where N is the length of the resulting `String`'s
/// UTF-16.
public init?(_ codeUnits: Substring.UTF16View) {
let guts = codeUnits._slice.base._guts
guard guts.isOnUnicodeScalarBoundary(codeUnits._slice.startIndex),
guts.isOnUnicodeScalarBoundary(codeUnits._slice.endIndex) else {
return nil
}
self = String(Substring(codeUnits))
}
}
extension Substring {
@_fixed_layout
public struct UnicodeScalarView {
@usableFromInline
internal var _slice: Slice<String.UnicodeScalarView>
}
}
extension Substring.UnicodeScalarView : BidirectionalCollection {
public typealias Index = String.UnicodeScalarView.Index
public typealias Indices = String.UnicodeScalarView.Indices
public typealias Element = String.UnicodeScalarView.Element
public typealias SubSequence = Substring.UnicodeScalarView
/// Creates an instance that slices `base` at `_bounds`.
@inlinable
internal init(_ base: String.UnicodeScalarView, _bounds: Range<Index>) {
_slice = Slice(
base: String(base._guts).unicodeScalars,
bounds: _bounds)
}
//
// Plumb slice operations through
//
@inlinable
public var startIndex: Index { return _slice.startIndex }
@inlinable
public var endIndex: Index { return _slice.endIndex }
@inlinable
public subscript(index: Index) -> Element { return _slice[index] }
@inlinable
public var indices: Indices { return _slice.indices }
@inlinable
public func index(after i: Index) -> Index { return _slice.index(after: i) }
@inlinable
public func formIndex(after i: inout Index) {
_slice.formIndex(after: &i)
}
@inlinable
public func index(_ i: Index, offsetBy n: Int) -> Index {
return _slice.index(i, offsetBy: n)
}
@inlinable
public func index(
_ i: Index, offsetBy n: Int, limitedBy limit: Index
) -> Index? {
return _slice.index(i, offsetBy: n, limitedBy: limit)
}
@inlinable
public func distance(from start: Index, to end: Index) -> Int {
return _slice.distance(from: start, to: end)
}
@inlinable
public func _failEarlyRangeCheck(_ index: Index, bounds: Range<Index>) {
_slice._failEarlyRangeCheck(index, bounds: bounds)
}
@inlinable
public func _failEarlyRangeCheck(
_ range: Range<Index>, bounds: Range<Index>
) {
_slice._failEarlyRangeCheck(range, bounds: bounds)
}
@inlinable
public func index(before i: Index) -> Index { return _slice.index(before: i) }
@inlinable
public func formIndex(before i: inout Index) {
_slice.formIndex(before: &i)
}
@inlinable
public subscript(r: Range<Index>) -> Substring.UnicodeScalarView {
return Substring.UnicodeScalarView(_slice.base, _bounds: r)
}
}
extension Substring {
@inlinable
public var unicodeScalars: UnicodeScalarView {
get {
return _wholeString.unicodeScalars[startIndex..<endIndex]
}
set {
self = Substring(newValue)
}
}
/// Creates a Substring having the given content.
///
/// - Complexity: O(1)
public init(_ content: UnicodeScalarView) {
self = String(
content._slice.base._guts
)[content.startIndex..<content.endIndex]
}
}
extension String {
/// Creates a String having the given content.
///
/// - Complexity: O(N), where N is the length of the resulting `String`'s
/// UTF-16.
public init(_ content: Substring.UnicodeScalarView) {
self = String(Substring(content))
}
}
// FIXME: The other String views should be RangeReplaceable too.
extension Substring.UnicodeScalarView : RangeReplaceableCollection {
@inlinable
public init() { _slice = Slice.init() }
public mutating func replaceSubrange<C : Collection>(
_ target: Range<Index>, with replacement: C
) where C.Element == Element {
_slice.replaceSubrange(target, with: replacement)
}
}
extension Substring : RangeReplaceableCollection {
@_specialize(where S == String)
@_specialize(where S == Substring)
@_specialize(where S == Array<Character>)
public init<S : Sequence>(_ elements: S)
where S.Element == Character {
if let str = elements as? String {
self = str[...]
return
}
if let subStr = elements as? Substring {
self = subStr
return
}
self = String(elements)[...]
}
@inlinable // specialize
public mutating func append<S : Sequence>(contentsOf elements: S)
where S.Element == Character {
var string = String(self)
self = Substring() // Keep unique storage if possible
string.append(contentsOf: elements)
self = Substring(string)
}
}
extension Substring {
public func lowercased() -> String {
return String(self).lowercased()
}
public func uppercased() -> String {
return String(self).uppercased()
}
public func filter(
_ isIncluded: (Element) throws -> Bool
) rethrows -> String {
return try String(self.lazy.filter(isIncluded))
}
}
extension Substring : TextOutputStream {
public mutating func write(_ other: String) {
append(contentsOf: other)
}
}
extension Substring : TextOutputStreamable {
@inlinable // specializable
public func write<Target : TextOutputStream>(to target: inout Target) {
target.write(String(self))
}
}
extension Substring : ExpressibleByUnicodeScalarLiteral {
@inlinable
public init(unicodeScalarLiteral value: String) {
self.init(value)
}
}
extension Substring : ExpressibleByExtendedGraphemeClusterLiteral {
@inlinable
public init(extendedGraphemeClusterLiteral value: String) {
self.init(value)
}
}
extension Substring : ExpressibleByStringLiteral {
@inlinable
public init(stringLiteral value: String) {
self.init(value)
}
}
// String/Substring Slicing
extension String {
@inlinable
@available(swift, introduced: 4)
public subscript(r: Range<Index>) -> Substring {
_boundsCheck(r)
return Substring(Slice(base: self, bounds: r))
}
}
extension Substring {
@inlinable
@available(swift, introduced: 4)
public subscript(r: Range<Index>) -> Substring {
return Substring(_slice[r])
}
}