| //===--- ArraySlice.swift -------------------------------------*- swift -*-===// |
| // |
| // This source file is part of the Swift.org open source project |
| // |
| // Copyright (c) 2014 - 2018 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // - `ArraySlice<Element>` presents an arbitrary subsequence of some |
| // contiguous sequence of `Element`s. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| /// A slice of an `Array`, `ContiguousArray`, or `ArraySlice` instance. |
| /// |
| /// The `ArraySlice` type makes it fast and efficient for you to perform |
| /// operations on sections of a larger array. Instead of copying over the |
| /// elements of a slice to new storage, an `ArraySlice` instance presents a |
| /// view onto the storage of a larger array. And because `ArraySlice` |
| /// presents the same interface as `Array`, you can generally perform the |
| /// same operations on a slice as you could on the original array. |
| /// |
| /// For more information about using arrays, see `Array` and `ContiguousArray`, |
| /// with which `ArraySlice` shares most properties and methods. |
| /// |
| /// Slices Are Views onto Arrays |
| /// ============================ |
| /// |
| /// For example, suppose you have an array holding the number of absences |
| /// from each class during a session. |
| /// |
| /// let absences = [0, 2, 0, 4, 0, 3, 1, 0] |
| /// |
| /// You want to compare the absences in the first half of the session with |
| /// those in the second half. To do so, start by creating two slices of the |
| /// `absences` array. |
| /// |
| /// let midpoint = absences.count / 2 |
| /// |
| /// let firstHalf = absences[..<midpoint] |
| /// let secondHalf = absences[midpoint...] |
| /// |
| /// Neither the `firstHalf` nor `secondHalf` slices allocate any new storage |
| /// of their own. Instead, each presents a view onto the storage of the |
| /// `absences` array. |
| /// |
| /// You can call any method on the slices that you might have called on the |
| /// `absences` array. To learn which half had more absences, use the |
| /// `reduce(_:_:)` method to calculate each sum. |
| /// |
| /// let firstHalfSum = firstHalf.reduce(0, +) |
| /// let secondHalfSum = secondHalf.reduce(0, +) |
| /// |
| /// if firstHalfSum > secondHalfSum { |
| /// print("More absences in the first half.") |
| /// } else { |
| /// print("More absences in the second half.") |
| /// } |
| /// // Prints "More absences in the first half." |
| /// |
| /// - Important: Long-term storage of `ArraySlice` instances is discouraged. A |
| /// slice holds a reference to the entire storage of a larger array, not |
| /// just to the portion it presents, even after the original array's lifetime |
| /// ends. Long-term storage of a slice may therefore prolong the lifetime of |
| /// elements that are no longer otherwise accessible, which can appear to be |
| /// memory and object leakage. |
| /// |
| /// Slices Maintain Indices |
| /// ======================= |
| /// |
| /// Unlike `Array` and `ContiguousArray`, the starting index for an |
| /// `ArraySlice` instance isn't always zero. Slices maintain the same |
| /// indices of the larger array for the same elements, so the starting |
| /// index of a slice depends on how it was created, letting you perform |
| /// index-based operations on either a full array or a slice. |
| /// |
| /// Sharing indices between collections and their subsequences is an important |
| /// part of the design of Swift's collection algorithms. Suppose you are |
| /// tasked with finding the first two days with absences in the session. To |
| /// find the indices of the two days in question, follow these steps: |
| /// |
| /// 1) Call `firstIndex(where:)` to find the index of the first element in the |
| /// `absences` array that is greater than zero. |
| /// 2) Create a slice of the `absences` array starting after the index found in |
| /// step 1. |
| /// 3) Call `firstIndex(where:)` again, this time on the slice created in step |
| /// 2. Where in some languages you might pass a starting index into an |
| /// `indexOf` method to find the second day, in Swift you perform the same |
| /// operation on a slice of the original array. |
| /// 4) Print the results using the indices found in steps 1 and 3 on the |
| /// original `absences` array. |
| /// |
| /// Here's an implementation of those steps: |
| /// |
| /// if let i = absences.firstIndex(where: { $0 > 0 }) { // 1 |
| /// let absencesAfterFirst = absences[(i + 1)...] // 2 |
| /// if let j = absencesAfterFirst.firstIndex(where: { $0 > 0 }) { // 3 |
| /// print("The first day with absences had \(absences[i]).") // 4 |
| /// print("The second day with absences had \(absences[j]).") |
| /// } |
| /// } |
| /// // Prints "The first day with absences had 2." |
| /// // Prints "The second day with absences had 4." |
| /// |
| /// In particular, note that `j`, the index of the second day with absences, |
| /// was found in a slice of the original array and then used to access a value |
| /// in the original `absences` array itself. |
| /// |
| /// - Note: To safely reference the starting and ending indices of a slice, |
| /// always use the `startIndex` and `endIndex` properties instead of |
| /// specific values. |
| @_fixed_layout |
| public struct ArraySlice<Element>: _DestructorSafeContainer { |
| @usableFromInline |
| internal typealias _Buffer = _SliceBuffer<Element> |
| |
| @usableFromInline |
| internal var _buffer: _Buffer |
| |
| /// Initialization from an existing buffer does not have "array.init" |
| /// semantics because the caller may retain an alias to buffer. |
| @inlinable |
| internal init(_buffer: _Buffer) { |
| self._buffer = _buffer |
| } |
| |
| /// Initialization from an existing buffer does not have "array.init" |
| /// semantics because the caller may retain an alias to buffer. |
| @inlinable |
| internal init(_buffer buffer: _ContiguousArrayBuffer<Element>) { |
| self.init(_buffer: _Buffer(_buffer: buffer, shiftedToStartIndex: 0)) |
| } |
| } |
| |
| //===--- private helpers---------------------------------------------------===// |
| extension ArraySlice { |
| /// Returns `true` if the array is native and does not need a deferred |
| /// type check. May be hoisted by the optimizer, which means its |
| /// results may be stale by the time they are used if there is an |
| /// inout violation in user code. |
| @inlinable |
| @_semantics("array.props.isNativeTypeChecked") |
| public // @testable |
| func _hoistableIsNativeTypeChecked() -> Bool { |
| return _buffer.arrayPropertyIsNativeTypeChecked |
| } |
| |
| @inlinable |
| @_semantics("array.get_count") |
| internal func _getCount() -> Int { |
| return _buffer.count |
| } |
| |
| @inlinable |
| @_semantics("array.get_capacity") |
| internal func _getCapacity() -> Int { |
| return _buffer.capacity |
| } |
| |
| @inlinable |
| @_semantics("array.make_mutable") |
| internal mutating func _makeMutableAndUnique() { |
| if _slowPath(!_buffer.isMutableAndUniquelyReferenced()) { |
| _buffer = _Buffer(copying: _buffer) |
| } |
| } |
| |
| /// Check that the given `index` is valid for subscripting, i.e. |
| /// `0 ≤ index < count`. |
| @inlinable |
| @inline(__always) |
| internal func _checkSubscript_native(_ index: Int) { |
| _buffer._checkValidSubscript(index) |
| } |
| |
| /// Check that the given `index` is valid for subscripting, i.e. |
| /// `0 ≤ index < count`. |
| @inlinable |
| @_semantics("array.check_subscript") |
| public // @testable |
| func _checkSubscript( |
| _ index: Int, wasNativeTypeChecked: Bool |
| ) -> _DependenceToken { |
| #if _runtime(_ObjC) |
| _buffer._checkValidSubscript(index) |
| #else |
| _buffer._checkValidSubscript(index) |
| #endif |
| return _DependenceToken() |
| } |
| |
| /// Check that the specified `index` is valid, i.e. `0 ≤ index ≤ count`. |
| @inlinable |
| @_semantics("array.check_index") |
| internal func _checkIndex(_ index: Int) { |
| _precondition(index <= endIndex, "ArraySlice index is out of range") |
| _precondition(index >= startIndex, "ArraySlice index is out of range (before startIndex)") |
| } |
| |
| @_semantics("array.get_element") |
| @inlinable // FIXME(inline-always) |
| @inline(__always) |
| public // @testable |
| func _getElement( |
| _ index: Int, |
| wasNativeTypeChecked: Bool, |
| matchingSubscriptCheck: _DependenceToken |
| ) -> Element { |
| #if false |
| return _buffer.getElement(index, wasNativeTypeChecked: wasNativeTypeChecked) |
| #else |
| return _buffer.getElement(index) |
| #endif |
| } |
| |
| @inlinable |
| @_semantics("array.get_element_address") |
| internal func _getElementAddress(_ index: Int) -> UnsafeMutablePointer<Element> { |
| return _buffer.subscriptBaseAddress + index |
| } |
| } |
| |
| extension ArraySlice: _ArrayProtocol { |
| /// The total number of elements that the array can contain without |
| /// allocating new storage. |
| /// |
| /// Every array reserves a specific amount of memory to hold its contents. |
| /// When you add elements to an array and that array begins to exceed its |
| /// reserved capacity, the array allocates a larger region of memory and |
| /// copies its elements into the new storage. The new storage is a multiple |
| /// of the old storage's size. This exponential growth strategy means that |
| /// appending an element happens in constant time, averaging the performance |
| /// of many append operations. Append operations that trigger reallocation |
| /// have a performance cost, but they occur less and less often as the array |
| /// grows larger. |
| /// |
| /// The following example creates an array of integers from an array literal, |
| /// then appends the elements of another collection. Before appending, the |
| /// array allocates new storage that is large enough store the resulting |
| /// elements. |
| /// |
| /// var numbers = [10, 20, 30, 40, 50] |
| /// // numbers.count == 5 |
| /// // numbers.capacity == 5 |
| /// |
| /// numbers.append(contentsOf: stride(from: 60, through: 100, by: 10)) |
| /// // numbers.count == 10 |
| /// // numbers.capacity == 12 |
| @inlinable |
| public var capacity: Int { |
| return _getCapacity() |
| } |
| |
| /// An object that guarantees the lifetime of this array's elements. |
| @inlinable |
| public // @testable |
| var _owner: AnyObject? { |
| return _buffer.owner |
| } |
| |
| /// If the elements are stored contiguously, a pointer to the first |
| /// element. Otherwise, `nil`. |
| @inlinable |
| public var _baseAddressIfContiguous: UnsafeMutablePointer<Element>? { |
| @inline(__always) // FIXME(TODO: JIRA): Hack around test failure |
| get { return _buffer.firstElementAddressIfContiguous } |
| } |
| |
| @inlinable |
| internal var _baseAddress: UnsafeMutablePointer<Element> { |
| return _buffer.firstElementAddress |
| } |
| } |
| |
| extension ArraySlice: RandomAccessCollection, MutableCollection { |
| /// The index type for arrays, `Int`. |
| /// |
| /// `ArraySlice` instances are not always indexed from zero. Use `startIndex` |
| /// and `endIndex` as the bounds for any element access, instead of `0` and |
| /// `count`. |
| public typealias Index = Int |
| |
| /// The type that represents the indices that are valid for subscripting an |
| /// array, in ascending order. |
| public typealias Indices = Range<Int> |
| |
| /// The type that allows iteration over an array's elements. |
| public typealias Iterator = IndexingIterator<ArraySlice> |
| |
| /// The position of the first element in a nonempty array. |
| /// |
| /// `ArraySlice` instances are not always indexed from zero. Use `startIndex` |
| /// and `endIndex` as the bounds for any element access, instead of `0` and |
| /// `count`. |
| /// |
| /// If the array is empty, `startIndex` is equal to `endIndex`. |
| @inlinable |
| public var startIndex: Int { |
| return _buffer.startIndex |
| } |
| |
| /// The array's "past the end" position---that is, the position one greater |
| /// than the last valid subscript argument. |
| /// |
| /// When you need a range that includes the last element of an array, use the |
| /// half-open range operator (`..<`) with `endIndex`. The `..<` operator |
| /// creates a range that doesn't include the upper bound, so it's always |
| /// safe to use with `endIndex`. For example: |
| /// |
| /// let numbers = [10, 20, 30, 40, 50] |
| /// if let i = numbers.firstIndex(of: 30) { |
| /// print(numbers[i ..< numbers.endIndex]) |
| /// } |
| /// // Prints "[30, 40, 50]" |
| /// |
| /// If the array is empty, `endIndex` is equal to `startIndex`. |
| @inlinable |
| public var endIndex: Int { |
| return _buffer.endIndex |
| } |
| |
| /// 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 immediately after `i`. |
| @inlinable |
| public func index(after i: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| return i + 1 |
| } |
| |
| /// Replaces the given index with its successor. |
| /// |
| /// - Parameter i: A valid index of the collection. `i` must be less than |
| /// `endIndex`. |
| @inlinable |
| public func formIndex(after i: inout Int) { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| i += 1 |
| } |
| |
| /// 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 immediately before `i`. |
| @inlinable |
| public func index(before i: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| return i - 1 |
| } |
| |
| /// Replaces the given index with its predecessor. |
| /// |
| /// - Parameter i: A valid index of the collection. `i` must be greater than |
| /// `startIndex`. |
| @inlinable |
| public func formIndex(before i: inout Int) { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| i -= 1 |
| } |
| |
| /// Returns an index that is the specified distance from the given index. |
| /// |
| /// The following example obtains an index advanced four positions from an |
| /// array's starting index and then prints the element at that position. |
| /// |
| /// let numbers = [10, 20, 30, 40, 50] |
| /// let i = numbers.index(numbers.startIndex, offsetBy: 4) |
| /// print(numbers[i]) |
| /// // Prints "50" |
| /// |
| /// The value passed as `distance` must not offset `i` beyond the bounds of |
| /// the collection. |
| /// |
| /// - Parameters: |
| /// - i: A valid index of the array. |
| /// - distance: The distance to offset `i`. |
| /// - Returns: An index offset by `distance` from the index `i`. If |
| /// `distance` is positive, this is the same value as the result of |
| /// `distance` calls to `index(after:)`. If `distance` is negative, this |
| /// is the same value as the result of `abs(distance)` calls to |
| /// `index(before:)`. |
| @inlinable |
| public func index(_ i: Int, offsetBy distance: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| return i + distance |
| } |
| |
| /// 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 an |
| /// array's starting index and then prints the element at that position. The |
| /// operation doesn't require going beyond the limiting `numbers.endIndex` |
| /// value, so it succeeds. |
| /// |
| /// let numbers = [10, 20, 30, 40, 50] |
| /// if let i = numbers.index(numbers.startIndex, |
| /// offsetBy: 4, |
| /// limitedBy: numbers.endIndex) { |
| /// print(numbers[i]) |
| /// } |
| /// // Prints "50" |
| /// |
| /// The next example attempts to retrieve an index ten positions from |
| /// `numbers.startIndex`, but fails, because that distance is beyond the |
| /// index passed as `limit`. |
| /// |
| /// let j = numbers.index(numbers.startIndex, |
| /// offsetBy: 10, |
| /// limitedBy: numbers.endIndex) |
| /// print(j) |
| /// // Prints "nil" |
| /// |
| /// The value passed as `distance` 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 array. |
| /// - distance: The distance to offset `i`. |
| /// - limit: A valid index of the collection to use as a limit. If |
| /// `distance > 0`, `limit` has no effect if it is less than `i`. |
| /// Likewise, if `distance < 0`, `limit` has no effect if it is greater |
| /// than `i`. |
| /// - Returns: An index offset by `distance` 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(1) |
| @inlinable |
| public func index( |
| _ i: Int, offsetBy distance: Int, limitedBy limit: Int |
| ) -> Int? { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| let l = limit - i |
| if distance > 0 ? l >= 0 && l < distance : l <= 0 && distance < l { |
| return nil |
| } |
| return i + distance |
| } |
| |
| /// 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`. |
| @inlinable |
| public func distance(from start: Int, to end: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for Array performance. The optimizer is not |
| // capable of creating partial specializations yet. |
| // NOTE: Range checks are not performed here, because it is done later by |
| // the subscript function. |
| return end - start |
| } |
| |
| @inlinable |
| public func _failEarlyRangeCheck(_ index: Int, bounds: Range<Int>) { |
| // NOTE: This method is a no-op for performance reasons. |
| } |
| |
| @inlinable |
| public func _failEarlyRangeCheck(_ range: Range<Int>, bounds: Range<Int>) { |
| // NOTE: This method is a no-op for performance reasons. |
| } |
| |
| /// Accesses the element at the specified position. |
| /// |
| /// The following example uses indexed subscripting to update an array's |
| /// second element. After assigning the new value (`"Butler"`) at a specific |
| /// position, that value is immediately available at that same position. |
| /// |
| /// var streets = ["Adams", "Bryant", "Channing", "Douglas", "Evarts"] |
| /// streets[1] = "Butler" |
| /// print(streets[1]) |
| /// // Prints "Butler" |
| /// |
| /// - Parameter index: The position of the element to access. `index` must be |
| /// greater than or equal to `startIndex` and less than `endIndex`. |
| /// |
| /// - Complexity: Reading an element from an array is O(1). Writing is O(1) |
| /// unless the array's storage is shared with another array or uses a |
| /// bridged `NSArray` instance as its storage, in which case writing is |
| /// O(*n*), where *n* is the length of the array. |
| @inlinable |
| public subscript(index: Int) -> Element { |
| get { |
| // This call may be hoisted or eliminated by the optimizer. If |
| // there is an inout violation, this value may be stale so needs to be |
| // checked again below. |
| let wasNativeTypeChecked = _hoistableIsNativeTypeChecked() |
| |
| // Make sure the index is in range and wasNativeTypeChecked is |
| // still valid. |
| let token = _checkSubscript( |
| index, wasNativeTypeChecked: wasNativeTypeChecked) |
| |
| return _getElement( |
| index, wasNativeTypeChecked: wasNativeTypeChecked, |
| matchingSubscriptCheck: token) |
| } |
| _modify { |
| _makeMutableAndUnique() // makes the array native, too |
| _checkSubscript_native(index) |
| let address = _buffer.subscriptBaseAddress + index |
| yield &address.pointee |
| } |
| } |
| |
| /// Accesses a contiguous subrange of the array's elements. |
| /// |
| /// The returned `ArraySlice` instance uses the same indices for the same |
| /// elements as the original array. In particular, that slice, unlike an |
| /// array, may have a nonzero `startIndex` and an `endIndex` that is not |
| /// equal to `count`. Always use the slice's `startIndex` and `endIndex` |
| /// properties instead of assuming that its indices start or end at a |
| /// particular value. |
| /// |
| /// This example demonstrates getting a slice of an array of strings, finding |
| /// the index of one of the strings in the slice, and then using that index |
| /// in the original array. |
| /// |
| /// let streets = ["Adams", "Bryant", "Channing", "Douglas", "Evarts"] |
| /// let streetsSlice = streets[2 ..< streets.endIndex] |
| /// print(streetsSlice) |
| /// // Prints "["Channing", "Douglas", "Evarts"]" |
| /// |
| /// let i = streetsSlice.firstIndex(of: "Evarts") // 4 |
| /// print(streets[i!]) |
| /// // Prints "Evarts" |
| /// |
| /// - Parameter bounds: A range of integers. The bounds of the range must be |
| /// valid indices of the array. |
| @inlinable |
| public subscript(bounds: Range<Int>) -> ArraySlice<Element> { |
| get { |
| _checkIndex(bounds.lowerBound) |
| _checkIndex(bounds.upperBound) |
| return ArraySlice(_buffer: _buffer[bounds]) |
| } |
| set(rhs) { |
| _checkIndex(bounds.lowerBound) |
| _checkIndex(bounds.upperBound) |
| // If the replacement buffer has same identity, and the ranges match, |
| // then this was a pinned in-place modification, nothing further needed. |
| if self[bounds]._buffer.identity != rhs._buffer.identity |
| || bounds != rhs.startIndex..<rhs.endIndex { |
| self.replaceSubrange(bounds, with: rhs) |
| } |
| } |
| } |
| |
| /// The number of elements in the array. |
| @inlinable |
| public var count: Int { |
| return _getCount() |
| } |
| } |
| |
| extension ArraySlice: ExpressibleByArrayLiteral { |
| /// Creates an array from the given array literal. |
| /// |
| /// Do not call this initializer directly. It is used by the compiler when |
| /// you use an array literal. Instead, create a new array by using an array |
| /// literal as its value. To do this, enclose a comma-separated list of |
| /// values in square brackets. |
| /// |
| /// Here, an array of strings is created from an array literal holding only |
| /// strings: |
| /// |
| /// let ingredients: ArraySlice = |
| /// ["cocoa beans", "sugar", "cocoa butter", "salt"] |
| /// |
| /// - Parameter elements: A variadic list of elements of the new array. |
| @inlinable |
| public init(arrayLiteral elements: Element...) { |
| self.init(_buffer: ContiguousArray(elements)._buffer) |
| } |
| } |
| |
| extension ArraySlice: RangeReplaceableCollection { |
| /// Creates a new, empty array. |
| /// |
| /// This is equivalent to initializing with an empty array literal. |
| /// For example: |
| /// |
| /// var emptyArray = Array<Int>() |
| /// print(emptyArray.isEmpty) |
| /// // Prints "true" |
| /// |
| /// emptyArray = [] |
| /// print(emptyArray.isEmpty) |
| /// // Prints "true" |
| @inlinable |
| @_semantics("array.init") |
| public init() { |
| _buffer = _Buffer() |
| } |
| |
| /// Creates an array containing the elements of a sequence. |
| /// |
| /// You can use this initializer to create an array from any other type that |
| /// conforms to the `Sequence` protocol. For example, you might want to |
| /// create an array with the integers from 1 through 7. Use this initializer |
| /// around a range instead of typing all those numbers in an array literal. |
| /// |
| /// let numbers = Array(1...7) |
| /// print(numbers) |
| /// // Prints "[1, 2, 3, 4, 5, 6, 7]" |
| /// |
| /// You can also use this initializer to convert a complex sequence or |
| /// collection type back to an array. For example, the `keys` property of |
| /// a dictionary isn't an array with its own storage, it's a collection |
| /// that maps its elements from the dictionary only when they're |
| /// accessed, saving the time and space needed to allocate an array. If |
| /// you need to pass those keys to a method that takes an array, however, |
| /// use this initializer to convert that list from its type of |
| /// `LazyMapCollection<Dictionary<String, Int>, Int>` to a simple |
| /// `[String]`. |
| /// |
| /// func cacheImagesWithNames(names: [String]) { |
| /// // custom image loading and caching |
| /// } |
| /// |
| /// let namedHues: [String: Int] = ["Vermillion": 18, "Magenta": 302, |
| /// "Gold": 50, "Cerise": 320] |
| /// let colorNames = Array(namedHues.keys) |
| /// cacheImagesWithNames(colorNames) |
| /// |
| /// print(colorNames) |
| /// // Prints "["Gold", "Cerise", "Magenta", "Vermillion"]" |
| /// |
| /// - Parameter s: The sequence of elements to turn into an array. |
| @inlinable |
| public init<S: Sequence>(_ s: S) |
| where S.Element == Element { |
| |
| self.init(_buffer: s._copyToContiguousArray()._buffer) |
| } |
| |
| /// Creates a new array containing the specified number of a single, repeated |
| /// value. |
| /// |
| /// Here's an example of creating an array initialized with five strings |
| /// containing the letter *Z*. |
| /// |
| /// let fiveZs = Array(repeating: "Z", count: 5) |
| /// print(fiveZs) |
| /// // Prints "["Z", "Z", "Z", "Z", "Z"]" |
| /// |
| /// - Parameters: |
| /// - repeatedValue: The element to repeat. |
| /// - count: The number of times to repeat the value passed in the |
| /// `repeating` parameter. `count` must be zero or greater. |
| @inlinable |
| @_semantics("array.init") |
| public init(repeating repeatedValue: Element, count: Int) { |
| var p: UnsafeMutablePointer<Element> |
| (self, p) = ArraySlice._allocateUninitialized(count) |
| for _ in 0..<count { |
| p.initialize(to: repeatedValue) |
| p += 1 |
| } |
| } |
| |
| @inline(never) |
| @usableFromInline |
| internal static func _allocateBufferUninitialized( |
| minimumCapacity: Int |
| ) -> _Buffer { |
| let newBuffer = _ContiguousArrayBuffer<Element>( |
| _uninitializedCount: 0, minimumCapacity: minimumCapacity) |
| return _Buffer(_buffer: newBuffer, shiftedToStartIndex: 0) |
| } |
| |
| /// Construct a ArraySlice of `count` uninitialized elements. |
| @inlinable |
| internal init(_uninitializedCount count: Int) { |
| _precondition(count >= 0, "Can't construct ArraySlice with count < 0") |
| // Note: Sinking this constructor into an else branch below causes an extra |
| // Retain/Release. |
| _buffer = _Buffer() |
| if count > 0 { |
| // Creating a buffer instead of calling reserveCapacity saves doing an |
| // unnecessary uniqueness check. We disable inlining here to curb code |
| // growth. |
| _buffer = ArraySlice._allocateBufferUninitialized(minimumCapacity: count) |
| _buffer.count = count |
| } |
| // Can't store count here because the buffer might be pointing to the |
| // shared empty array. |
| } |
| |
| /// Entry point for `Array` literal construction; builds and returns |
| /// a ArraySlice of `count` uninitialized elements. |
| @inlinable |
| @_semantics("array.uninitialized") |
| internal static func _allocateUninitialized( |
| _ count: Int |
| ) -> (ArraySlice, UnsafeMutablePointer<Element>) { |
| let result = ArraySlice(_uninitializedCount: count) |
| return (result, result._buffer.firstElementAddress) |
| } |
| |
| //===--- basic mutations ------------------------------------------------===// |
| |
| /// Reserves enough space to store the specified number of elements. |
| /// |
| /// If you are adding a known number of elements to an array, use this method |
| /// to avoid multiple reallocations. This method ensures that the array has |
| /// unique, mutable, contiguous storage, with space allocated for at least |
| /// the requested number of elements. |
| /// |
| /// Calling the `reserveCapacity(_:)` method on an array with bridged storage |
| /// triggers a copy to contiguous storage even if the existing storage |
| /// has room to store `minimumCapacity` elements. |
| /// |
| /// For performance reasons, the size of the newly allocated storage might be |
| /// greater than the requested capacity. Use the array's `capacity` property |
| /// to determine the size of the new storage. |
| /// |
| /// Preserving an Array's Geometric Growth Strategy |
| /// =============================================== |
| /// |
| /// If you implement a custom data structure backed by an array that grows |
| /// dynamically, naively calling the `reserveCapacity(_:)` method can lead |
| /// to worse than expected performance. Arrays need to follow a geometric |
| /// allocation pattern for appending elements to achieve amortized |
| /// constant-time performance. The `Array` type's `append(_:)` and |
| /// `append(contentsOf:)` methods take care of this detail for you, but |
| /// `reserveCapacity(_:)` allocates only as much space as you tell it to |
| /// (padded to a round value), and no more. This avoids over-allocation, but |
| /// can result in insertion not having amortized constant-time performance. |
| /// |
| /// The following code declares `values`, an array of integers, and the |
| /// `addTenQuadratic()` function, which adds ten more values to the `values` |
| /// array on each call. |
| /// |
| /// var values: [Int] = [0, 1, 2, 3] |
| /// |
| /// // Don't use 'reserveCapacity(_:)' like this |
| /// func addTenQuadratic() { |
| /// let newCount = values.count + 10 |
| /// values.reserveCapacity(newCount) |
| /// for n in values.count..<newCount { |
| /// values.append(n) |
| /// } |
| /// } |
| /// |
| /// The call to `reserveCapacity(_:)` increases the `values` array's capacity |
| /// by exactly 10 elements on each pass through `addTenQuadratic()`, which |
| /// is linear growth. Instead of having constant time when averaged over |
| /// many calls, the function may decay to performance that is linear in |
| /// `values.count`. This is almost certainly not what you want. |
| /// |
| /// In cases like this, the simplest fix is often to simply remove the call |
| /// to `reserveCapacity(_:)`, and let the `append(_:)` method grow the array |
| /// for you. |
| /// |
| /// func addTen() { |
| /// let newCount = values.count + 10 |
| /// for n in values.count..<newCount { |
| /// values.append(n) |
| /// } |
| /// } |
| /// |
| /// If you need more control over the capacity of your array, implement your |
| /// own geometric growth strategy, passing the size you compute to |
| /// `reserveCapacity(_:)`. |
| /// |
| /// - Parameter minimumCapacity: The requested number of elements to store. |
| /// |
| /// - Complexity: O(*n*), where *n* is the number of elements in the array. |
| @inlinable |
| @_semantics("array.mutate_unknown") |
| public mutating func reserveCapacity(_ minimumCapacity: Int) { |
| if _buffer.requestUniqueMutableBackingBuffer( |
| minimumCapacity: minimumCapacity) == nil { |
| |
| let newBuffer = _ContiguousArrayBuffer<Element>( |
| _uninitializedCount: count, minimumCapacity: minimumCapacity) |
| |
| _buffer._copyContents( |
| subRange: _buffer.indices, |
| initializing: newBuffer.firstElementAddress) |
| _buffer = _Buffer( |
| _buffer: newBuffer, shiftedToStartIndex: _buffer.startIndex) |
| } |
| _internalInvariant(capacity >= minimumCapacity) |
| } |
| |
| /// Copy the contents of the current buffer to a new unique mutable buffer. |
| /// The count of the new buffer is set to `oldCount`, the capacity of the |
| /// new buffer is big enough to hold 'oldCount' + 1 elements. |
| @inline(never) |
| @inlinable // @specializable |
| internal mutating func _copyToNewBuffer(oldCount: Int) { |
| let newCount = oldCount + 1 |
| var newBuffer = _buffer._forceCreateUniqueMutableBuffer( |
| countForNewBuffer: oldCount, minNewCapacity: newCount) |
| _buffer._arrayOutOfPlaceUpdate( |
| &newBuffer, oldCount, 0) |
| } |
| |
| @inlinable |
| @_semantics("array.make_mutable") |
| internal mutating func _makeUniqueAndReserveCapacityIfNotUnique() { |
| if _slowPath(!_buffer.isMutableAndUniquelyReferenced()) { |
| _copyToNewBuffer(oldCount: _buffer.count) |
| } |
| } |
| |
| @inlinable |
| @_semantics("array.mutate_unknown") |
| internal mutating func _reserveCapacityAssumingUniqueBuffer(oldCount: Int) { |
| // This is a performance optimization. This code used to be in an || |
| // statement in the _internalInvariant below. |
| // |
| // _internalInvariant(_buffer.capacity == 0 || |
| // _buffer.isMutableAndUniquelyReferenced()) |
| // |
| // SR-6437 |
| let capacity = _buffer.capacity == 0 |
| |
| // Due to make_mutable hoisting the situation can arise where we hoist |
| // _makeMutableAndUnique out of loop and use it to replace |
| // _makeUniqueAndReserveCapacityIfNotUnique that preceeds this call. If the |
| // array was empty _makeMutableAndUnique does not replace the empty array |
| // buffer by a unique buffer (it just replaces it by the empty array |
| // singleton). |
| // This specific case is okay because we will make the buffer unique in this |
| // function because we request a capacity > 0 and therefore _copyToNewBuffer |
| // will be called creating a new buffer. |
| _internalInvariant(capacity || |
| _buffer.isMutableAndUniquelyReferenced()) |
| |
| if _slowPath(oldCount + 1 > _buffer.capacity) { |
| _copyToNewBuffer(oldCount: oldCount) |
| } |
| } |
| |
| @inlinable |
| @_semantics("array.mutate_unknown") |
| internal mutating func _appendElementAssumeUniqueAndCapacity( |
| _ oldCount: Int, |
| newElement: __owned Element |
| ) { |
| _internalInvariant(_buffer.isMutableAndUniquelyReferenced()) |
| _internalInvariant(_buffer.capacity >= _buffer.count + 1) |
| |
| _buffer.count = oldCount + 1 |
| (_buffer.firstElementAddress + oldCount).initialize(to: newElement) |
| } |
| |
| /// Adds a new element at the end of the array. |
| /// |
| /// Use this method to append a single element to the end of a mutable array. |
| /// |
| /// var numbers = [1, 2, 3, 4, 5] |
| /// numbers.append(100) |
| /// print(numbers) |
| /// // Prints "[1, 2, 3, 4, 5, 100]" |
| /// |
| /// Because arrays increase their allocated capacity using an exponential |
| /// strategy, appending a single element to an array is an O(1) operation |
| /// when averaged over many calls to the `append(_:)` method. When an array |
| /// has additional capacity and is not sharing its storage with another |
| /// instance, appending an element is O(1). When an array needs to |
| /// reallocate storage before appending or its storage is shared with |
| /// another copy, appending is O(*n*), where *n* is the length of the array. |
| /// |
| /// - Parameter newElement: The element to append to the array. |
| /// |
| /// - Complexity: O(1) on average, over many calls to `append(_:)` on the |
| /// same array. |
| @inlinable |
| @_semantics("array.append_element") |
| public mutating func append(_ newElement: __owned Element) { |
| _makeUniqueAndReserveCapacityIfNotUnique() |
| let oldCount = _getCount() |
| _reserveCapacityAssumingUniqueBuffer(oldCount: oldCount) |
| _appendElementAssumeUniqueAndCapacity(oldCount, newElement: newElement) |
| } |
| |
| /// Adds the elements of a sequence to the end of the array. |
| /// |
| /// Use this method to append the elements of a sequence to the end of this |
| /// array. This example appends the elements of a `Range<Int>` instance |
| /// to an array of integers. |
| /// |
| /// var numbers = [1, 2, 3, 4, 5] |
| /// numbers.append(contentsOf: 10...15) |
| /// print(numbers) |
| /// // Prints "[1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 15]" |
| /// |
| /// - Parameter newElements: The elements to append to the array. |
| /// |
| /// - Complexity: O(*m*) on average, where *m* is the length of |
| /// `newElements`, over many calls to `append(contentsOf:)` on the same |
| /// array. |
| @inlinable |
| @_semantics("array.append_contentsOf") |
| public mutating func append<S: Sequence>(contentsOf newElements: __owned S) |
| where S.Element == Element { |
| |
| let newElementsCount = newElements.underestimatedCount |
| reserveCapacityForAppend(newElementsCount: newElementsCount) |
| |
| let oldCount = self.count |
| let startNewElements = _buffer.firstElementAddress + oldCount |
| let buf = UnsafeMutableBufferPointer( |
| start: startNewElements, |
| count: self.capacity - oldCount) |
| |
| let (remainder,writtenUpTo) = buf.initialize(from: newElements) |
| |
| // trap on underflow from the sequence's underestimate: |
| let writtenCount = buf.distance(from: buf.startIndex, to: writtenUpTo) |
| _precondition(newElementsCount <= writtenCount, |
| "newElements.underestimatedCount was an overestimate") |
| // can't check for overflow as sequences can underestimate |
| |
| _buffer.count += writtenCount |
| |
| if writtenUpTo == buf.endIndex { |
| // there may be elements that didn't fit in the existing buffer, |
| // append them in slow sequence-only mode |
| _buffer._arrayAppendSequence(IteratorSequence(remainder)) |
| } |
| } |
| |
| @inlinable |
| @_semantics("array.reserve_capacity_for_append") |
| internal mutating func reserveCapacityForAppend(newElementsCount: Int) { |
| let oldCount = self.count |
| let oldCapacity = self.capacity |
| let newCount = oldCount + newElementsCount |
| |
| // Ensure uniqueness, mutability, and sufficient storage. Note that |
| // for consistency, we need unique self even if newElements is empty. |
| self.reserveCapacity( |
| newCount > oldCapacity ? |
| Swift.max(newCount, _growArrayCapacity(oldCapacity)) |
| : newCount) |
| } |
| |
| @inlinable |
| public mutating func _customRemoveLast() -> Element? { |
| _precondition(count > 0, "Can't removeLast from an empty ArraySlice") |
| // FIXME(performance): if `self` is uniquely referenced, we should remove |
| // the element as shown below (this will deallocate the element and |
| // decrease memory use). If `self` is not uniquely referenced, the code |
| // below will make a copy of the storage, which is wasteful. Instead, we |
| // should just shrink the view without allocating new storage. |
| let i = endIndex |
| // We don't check for overflow in `i - 1` because `i` is known to be |
| // positive. |
| let result = self[i &- 1] |
| self.replaceSubrange((i &- 1)..<i, with: EmptyCollection()) |
| return result |
| } |
| |
| /// Removes and returns the element at the specified position. |
| /// |
| /// All the elements following the specified position are moved up to |
| /// close the gap. |
| /// |
| /// var measurements: [Double] = [1.1, 1.5, 2.9, 1.2, 1.5, 1.3, 1.2] |
| /// let removed = measurements.remove(at: 2) |
| /// print(measurements) |
| /// // Prints "[1.1, 1.5, 1.2, 1.5, 1.3, 1.2]" |
| /// |
| /// - Parameter index: The position of the element to remove. `index` must |
| /// be a valid index of the array. |
| /// - Returns: The element at the specified index. |
| /// |
| /// - Complexity: O(*n*), where *n* is the length of the array. |
| @inlinable |
| @discardableResult |
| public mutating func remove(at index: Int) -> Element { |
| let result = self[index] |
| self.replaceSubrange(index..<(index + 1), with: EmptyCollection()) |
| return result |
| } |
| |
| |
| /// Inserts a new element at the specified position. |
| /// |
| /// The new element is inserted before the element currently at the specified |
| /// index. If you pass the array's `endIndex` property as the `index` |
| /// parameter, the new element is appended to the array. |
| /// |
| /// var numbers = [1, 2, 3, 4, 5] |
| /// numbers.insert(100, at: 3) |
| /// numbers.insert(200, at: numbers.endIndex) |
| /// |
| /// print(numbers) |
| /// // Prints "[1, 2, 3, 100, 4, 5, 200]" |
| /// |
| /// - Parameter newElement: The new element to insert into the array. |
| /// - Parameter i: The position at which to insert the new element. |
| /// `index` must be a valid index of the array or equal to its `endIndex` |
| /// property. |
| /// |
| /// - Complexity: O(*n*), where *n* is the length of the array. If |
| /// `i == endIndex`, this method is equivalent to `append(_:)`. |
| @inlinable |
| public mutating func insert(_ newElement: __owned Element, at i: Int) { |
| _checkIndex(i) |
| self.replaceSubrange(i..<i, with: CollectionOfOne(newElement)) |
| } |
| |
| /// Removes all elements from the array. |
| /// |
| /// - Parameter keepCapacity: Pass `true` to keep the existing capacity of |
| /// the array after removing its elements. The default value is |
| /// `false`. |
| /// |
| /// - Complexity: O(*n*), where *n* is the length of the array. |
| @inlinable |
| public mutating func removeAll(keepingCapacity keepCapacity: Bool = false) { |
| if !keepCapacity { |
| _buffer = _Buffer() |
| } |
| else { |
| self.replaceSubrange(indices, with: EmptyCollection()) |
| } |
| } |
| |
| //===--- algorithms -----------------------------------------------------===// |
| |
| @inlinable |
| public mutating func _withUnsafeMutableBufferPointerIfSupported<R>( |
| _ body: (inout UnsafeMutableBufferPointer<Element>) throws -> R |
| ) rethrows -> R? { |
| return try withUnsafeMutableBufferPointer { |
| (bufferPointer) -> R in |
| return try body(&bufferPointer) |
| } |
| } |
| |
| @inlinable |
| public mutating func withContiguousMutableStorageIfAvailable<R>( |
| _ body: (inout UnsafeMutableBufferPointer<Element>) throws -> R |
| ) rethrows -> R? { |
| return try withUnsafeMutableBufferPointer { |
| (bufferPointer) -> R in |
| return try body(&bufferPointer) |
| } |
| } |
| |
| @inlinable |
| public func withContiguousStorageIfAvailable<R>( |
| _ body: (UnsafeBufferPointer<Element>) throws -> R |
| ) rethrows -> R? { |
| return try withUnsafeBufferPointer { |
| (bufferPointer) -> R in |
| return try body(bufferPointer) |
| } |
| } |
| |
| @inlinable |
| public __consuming func _copyToContiguousArray() -> ContiguousArray<Element> { |
| if let n = _buffer.requestNativeBuffer() { |
| return ContiguousArray(_buffer: n) |
| } |
| return _copyCollectionToContiguousArray(self) |
| } |
| } |
| |
| extension ArraySlice: CustomReflectable { |
| /// A mirror that reflects the array. |
| public var customMirror: Mirror { |
| return Mirror( |
| self, |
| unlabeledChildren: self, |
| displayStyle: .collection) |
| } |
| } |
| |
| extension ArraySlice: CustomStringConvertible, CustomDebugStringConvertible { |
| /// A textual representation of the array and its elements. |
| public var description: String { |
| return _makeCollectionDescription() |
| } |
| |
| /// A textual representation of the array and its elements, suitable for |
| /// debugging. |
| public var debugDescription: String { |
| return _makeCollectionDescription(withTypeName: "ArraySlice") |
| } |
| } |
| |
| extension ArraySlice { |
| @usableFromInline @_transparent |
| internal func _cPointerArgs() -> (AnyObject?, UnsafeRawPointer?) { |
| let p = _baseAddressIfContiguous |
| if _fastPath(p != nil || isEmpty) { |
| return (_owner, UnsafeRawPointer(p)) |
| } |
| let n = ContiguousArray(self._buffer)._buffer |
| return (n.owner, UnsafeRawPointer(n.firstElementAddress)) |
| } |
| } |
| |
| extension ArraySlice { |
| /// Calls a closure with a pointer to the array's contiguous storage. |
| /// |
| /// Often, the optimizer can eliminate bounds checks within an array |
| /// algorithm, but when that fails, invoking the same algorithm on the |
| /// buffer pointer passed into your closure lets you trade safety for speed. |
| /// |
| /// The following example shows how you can iterate over the contents of the |
| /// buffer pointer: |
| /// |
| /// let numbers = [1, 2, 3, 4, 5] |
| /// let sum = numbers.withUnsafeBufferPointer { buffer -> Int in |
| /// var result = 0 |
| /// for i in stride(from: buffer.startIndex, to: buffer.endIndex, by: 2) { |
| /// result += buffer[i] |
| /// } |
| /// return result |
| /// } |
| /// // 'sum' == 9 |
| /// |
| /// The pointer passed as an argument to `body` is valid only during the |
| /// execution of `withUnsafeBufferPointer(_:)`. Do not store or return the |
| /// pointer for later use. |
| /// |
| /// - Parameter body: A closure with an `UnsafeBufferPointer` parameter that |
| /// points to the contiguous storage for the array. If |
| /// `body` has a return value, that value is also used as the return value |
| /// for the `withUnsafeBufferPointer(_:)` 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 |
| public func withUnsafeBufferPointer<R>( |
| _ body: (UnsafeBufferPointer<Element>) throws -> R |
| ) rethrows -> R { |
| return try _buffer.withUnsafeBufferPointer(body) |
| } |
| |
| /// Calls the given closure with a pointer to the array's mutable contiguous |
| /// storage. |
| /// |
| /// Often, the optimizer can eliminate bounds checks within an array |
| /// algorithm, but when that fails, invoking the same algorithm on the |
| /// buffer pointer passed into your closure lets you trade safety for speed. |
| /// |
| /// The following example shows how modifying the contents of the |
| /// `UnsafeMutableBufferPointer` argument to `body` alters the contents of |
| /// the array: |
| /// |
| /// var numbers = [1, 2, 3, 4, 5] |
| /// numbers.withUnsafeMutableBufferPointer { buffer in |
| /// for i in stride(from: buffer.startIndex, to: buffer.endIndex - 1, by: 2) { |
| /// buffer.swapAt(i, i + 1) |
| /// } |
| /// } |
| /// print(numbers) |
| /// // Prints "[2, 1, 4, 3, 5]" |
| /// |
| /// The pointer passed as an argument to `body` is valid only during the |
| /// execution of `withUnsafeMutableBufferPointer(_:)`. Do not store or |
| /// return the pointer for later use. |
| /// |
| /// - Warning: Do not rely on anything about the array that is the target of |
| /// this method during execution of the `body` closure; it might not |
| /// appear to have its correct value. Instead, use only the |
| /// `UnsafeMutableBufferPointer` argument to `body`. |
| /// |
| /// - Parameter body: A closure with an `UnsafeMutableBufferPointer` |
| /// parameter that points to the contiguous storage for the array. |
| /// If `body` has a return value, that value is also |
| /// used as the return value for the `withUnsafeMutableBufferPointer(_:)` |
| /// 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. |
| @_semantics("array.withUnsafeMutableBufferPointer") |
| @inlinable // FIXME(inline-always) |
| @inline(__always) // Performance: This method should get inlined into the |
| // caller such that we can combine the partial apply with the apply in this |
| // function saving on allocating a closure context. This becomes unnecessary |
| // once we allocate noescape closures on the stack. |
| public mutating func withUnsafeMutableBufferPointer<R>( |
| _ body: (inout UnsafeMutableBufferPointer<Element>) throws -> R |
| ) rethrows -> R { |
| let count = self.count |
| // Ensure unique storage |
| _buffer._outlinedMakeUniqueBuffer(bufferCount: count) |
| |
| // Ensure that body can't invalidate the storage or its bounds by |
| // moving self into a temporary working array. |
| // NOTE: The stack promotion optimization that keys of the |
| // "array.withUnsafeMutableBufferPointer" semantics annotation relies on the |
| // array buffer not being able to escape in the closure. It can do this |
| // because we swap the array buffer in self with an empty buffer here. Any |
| // escape via the address of self in the closure will therefore escape the |
| // empty array. |
| |
| var work = ArraySlice() |
| (work, self) = (self, work) |
| |
| // Create an UnsafeBufferPointer over work that we can pass to body |
| let pointer = work._buffer.firstElementAddress |
| var inoutBufferPointer = UnsafeMutableBufferPointer( |
| start: pointer, count: count) |
| |
| // Put the working array back before returning. |
| defer { |
| _precondition( |
| inoutBufferPointer.baseAddress == pointer && |
| inoutBufferPointer.count == count, |
| "ArraySlice withUnsafeMutableBufferPointer: replacing the buffer is not allowed") |
| |
| (work, self) = (self, work) |
| } |
| |
| // Invoke the body. |
| return try body(&inoutBufferPointer) |
| } |
| |
| @inlinable |
| public __consuming func _copyContents( |
| initializing buffer: UnsafeMutableBufferPointer<Element> |
| ) -> (Iterator,UnsafeMutableBufferPointer<Element>.Index) { |
| |
| guard !self.isEmpty else { return (makeIterator(),buffer.startIndex) } |
| |
| // It is not OK for there to be no pointer/not enough space, as this is |
| // a precondition and Array never lies about its count. |
| guard var p = buffer.baseAddress |
| else { _preconditionFailure("Attempt to copy contents into nil buffer pointer") } |
| _precondition(self.count <= buffer.count, |
| "Insufficient space allocated to copy array contents") |
| |
| if let s = _baseAddressIfContiguous { |
| p.initialize(from: s, count: self.count) |
| // Need a _fixLifetime bracketing the _baseAddressIfContiguous getter |
| // and all uses of the pointer it returns: |
| _fixLifetime(self._owner) |
| } else { |
| for x in self { |
| p.initialize(to: x) |
| p += 1 |
| } |
| } |
| |
| var it = IndexingIterator(_elements: self) |
| it._position = endIndex |
| return (it,buffer.index(buffer.startIndex, offsetBy: self.count)) |
| } |
| } |
| |
| extension ArraySlice { |
| /// Replaces a range of elements with the elements in the specified |
| /// collection. |
| /// |
| /// This method has the effect of removing the specified range of elements |
| /// from the array and inserting the new elements at the same location. The |
| /// number of new elements need not match the number of elements being |
| /// removed. |
| /// |
| /// In this example, three elements in the middle of an array of integers are |
| /// replaced by the five elements of a `Repeated<Int>` instance. |
| /// |
| /// var nums = [10, 20, 30, 40, 50] |
| /// nums.replaceSubrange(1...3, with: repeatElement(1, count: 5)) |
| /// print(nums) |
| /// // Prints "[10, 1, 1, 1, 1, 1, 50]" |
| /// |
| /// If you pass a zero-length range as the `subrange` parameter, this method |
| /// inserts the elements of `newElements` at `subrange.startIndex`. Calling |
| /// the `insert(contentsOf:at:)` method instead is preferred. |
| /// |
| /// Likewise, if you pass a zero-length collection as the `newElements` |
| /// parameter, this method removes the elements in the given subrange |
| /// without replacement. Calling the `removeSubrange(_:)` method instead is |
| /// preferred. |
| /// |
| /// - Parameters: |
| /// - subrange: The subrange of the array to replace. The start and end of |
| /// a subrange must be valid indices of the array. |
| /// - newElements: The new elements to add to the array. |
| /// |
| /// - Complexity: O(*n* + *m*), where *n* is length of the array and |
| /// *m* is the length of `newElements`. If the call to this method simply |
| /// appends the contents of `newElements` to the array, this method is |
| /// equivalent to `append(contentsOf:)`. |
| @inlinable |
| @_semantics("array.mutate_unknown") |
| public mutating func replaceSubrange<C>( |
| _ subrange: Range<Int>, |
| with newElements: __owned C |
| ) where C: Collection, C.Element == Element { |
| _precondition(subrange.lowerBound >= _buffer.startIndex, |
| "ArraySlice replace: subrange start is before the startIndex") |
| |
| _precondition(subrange.upperBound <= _buffer.endIndex, |
| "ArraySlice replace: subrange extends past the end") |
| |
| let oldCount = _buffer.count |
| let eraseCount = subrange.count |
| let insertCount = newElements.count |
| let growth = insertCount - eraseCount |
| |
| if _buffer.requestUniqueMutableBackingBuffer( |
| minimumCapacity: oldCount + growth) != nil { |
| |
| _buffer.replaceSubrange( |
| subrange, with: insertCount, elementsOf: newElements) |
| } else { |
| _buffer._arrayOutOfPlaceReplace(subrange, with: newElements, count: insertCount) |
| } |
| } |
| } |
| |
| extension ArraySlice: Equatable where Element: Equatable { |
| /// Returns a Boolean value indicating whether two arrays contain the same |
| /// elements in the same order. |
| /// |
| /// You can use the equal-to operator (`==`) to compare any two arrays |
| /// that store the same, `Equatable`-conforming element type. |
| /// |
| /// - Parameters: |
| /// - lhs: An array to compare. |
| /// - rhs: Another array to compare. |
| @inlinable |
| public static func ==(lhs: ArraySlice<Element>, rhs: ArraySlice<Element>) -> Bool { |
| let lhsCount = lhs.count |
| if lhsCount != rhs.count { |
| return false |
| } |
| |
| // Test referential equality. |
| if lhsCount == 0 || lhs._buffer.identity == rhs._buffer.identity { |
| return true |
| } |
| |
| |
| var streamLHS = lhs.makeIterator() |
| var streamRHS = rhs.makeIterator() |
| |
| var nextLHS = streamLHS.next() |
| while nextLHS != nil { |
| let nextRHS = streamRHS.next() |
| if nextLHS != nextRHS { |
| return false |
| } |
| nextLHS = streamLHS.next() |
| } |
| |
| |
| return true |
| } |
| } |
| |
| extension ArraySlice: Hashable where Element: Hashable { |
| /// Hashes the essential components of this value by feeding them into the |
| /// given hasher. |
| /// |
| /// - Parameter hasher: The hasher to use when combining the components |
| /// of this instance. |
| @inlinable |
| public func hash(into hasher: inout Hasher) { |
| hasher.combine(count) // discriminator |
| for element in self { |
| hasher.combine(element) |
| } |
| } |
| } |
| |
| extension ArraySlice { |
| /// Calls the given closure with a pointer to the underlying bytes of the |
| /// array's mutable contiguous storage. |
| /// |
| /// The array's `Element` type must be a *trivial type*, which can be copied |
| /// with just a bit-for-bit copy without any indirection or |
| /// reference-counting operations. Generally, native Swift types that do not |
| /// contain strong or weak references are trivial, as are imported C structs |
| /// and enums. |
| /// |
| /// The following example copies bytes from the `byteValues` array into |
| /// `numbers`, an array of `Int`: |
| /// |
| /// var numbers: [Int32] = [0, 0] |
| /// var byteValues: [UInt8] = [0x01, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00] |
| /// |
| /// numbers.withUnsafeMutableBytes { destBytes in |
| /// byteValues.withUnsafeBytes { srcBytes in |
| /// destBytes.copyBytes(from: srcBytes) |
| /// } |
| /// } |
| /// // numbers == [1, 2] |
| /// |
| /// The pointer passed as an argument to `body` is valid only for the |
| /// lifetime of the closure. Do not escape it from the closure for later |
| /// use. |
| /// |
| /// - Warning: Do not rely on anything about the array that is the target of |
| /// this method during execution of the `body` closure; it might not |
| /// appear to have its correct value. Instead, use only the |
| /// `UnsafeMutableRawBufferPointer` argument to `body`. |
| /// |
| /// - Parameter body: A closure with an `UnsafeMutableRawBufferPointer` |
| /// parameter that points to the contiguous storage for the array. |
| /// If no such storage exists, it is created. If `body` has a return value, that value is also |
| /// used as the return value for the `withUnsafeMutableBytes(_:)` method. |
| /// The argument is valid only for the duration of the closure's |
| /// execution. |
| /// - Returns: The return value, if any, of the `body` closure parameter. |
| @inlinable |
| public mutating func withUnsafeMutableBytes<R>( |
| _ body: (UnsafeMutableRawBufferPointer) throws -> R |
| ) rethrows -> R { |
| return try self.withUnsafeMutableBufferPointer { |
| return try body(UnsafeMutableRawBufferPointer($0)) |
| } |
| } |
| |
| /// Calls the given closure with a pointer to the underlying bytes of the |
| /// array's contiguous storage. |
| /// |
| /// The array's `Element` type must be a *trivial type*, which can be copied |
| /// with just a bit-for-bit copy without any indirection or |
| /// reference-counting operations. Generally, native Swift types that do not |
| /// contain strong or weak references are trivial, as are imported C structs |
| /// and enums. |
| /// |
| /// The following example copies the bytes of the `numbers` array into a |
| /// buffer of `UInt8`: |
| /// |
| /// var numbers = [1, 2, 3] |
| /// var byteBuffer: [UInt8] = [] |
| /// numbers.withUnsafeBytes { |
| /// byteBuffer.append(contentsOf: $0) |
| /// } |
| /// // byteBuffer == [1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, ...] |
| /// |
| /// - Parameter body: A closure with an `UnsafeRawBufferPointer` parameter |
| /// that points to the contiguous storage for the array. |
| /// If no such storage exists, it is created. If `body` has a return value, that value is also |
| /// used as the return value for the `withUnsafeBytes(_:)` method. The |
| /// argument is valid only for the duration of the closure's execution. |
| /// - Returns: The return value, if any, of the `body` closure parameter. |
| @inlinable |
| public func withUnsafeBytes<R>( |
| _ body: (UnsafeRawBufferPointer) throws -> R |
| ) rethrows -> R { |
| return try self.withUnsafeBufferPointer { |
| try body(UnsafeRawBufferPointer($0)) |
| } |
| } |
| } |
| |
| extension ArraySlice { |
| @inlinable |
| public // @testable |
| init(_startIndex: Int) { |
| self.init( |
| _buffer: _Buffer( |
| _buffer: ContiguousArray()._buffer, |
| shiftedToStartIndex: _startIndex)) |
| } |
| } |