| //===--- UnsafeBufferPointer.swift.gyb ------------------------*- swift -*-===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| |
| /// An iterator for the elements in the buffer referenced by an |
| /// `UnsafeBufferPointer` or `UnsafeMutableBufferPointer` instance. |
| @_fixed_layout |
| public struct UnsafeBufferPointerIterator<Element> |
| : IteratorProtocol, Sequence { |
| |
| /// Advances to the next element and returns it, or `nil` if no next element |
| /// exists. |
| /// |
| /// Once `nil` has been returned, all subsequent calls return `nil`. |
| @_inlineable |
| public mutating func next() -> Element? { |
| if _position == _end { return nil } |
| |
| let result = _position!.pointee |
| _position! += 1 |
| return result |
| } |
| |
| @_versioned |
| internal var _position, _end: UnsafePointer<Element>? |
| |
| @_inlineable |
| public init(_position: UnsafePointer<Element>?, _end: UnsafePointer<Element>?) { |
| self._position = _position |
| self._end = _end |
| } |
| } |
| |
| % for mutable in (True, False): |
| % Self = 'UnsafeMutableBufferPointer' if mutable else 'UnsafeBufferPointer' |
| % Mutable = 'Mutable' if mutable else '' |
| /// A non-owning collection interface to a buffer of ${Mutable.lower()} |
| /// elements stored contiguously in memory. |
| /// |
| /// You can use an `${Self}` instance in low level operations to eliminate |
| /// uniqueness checks and, in release mode, bounds checks. Bounds checks are |
| /// always performed in debug mode. |
| /// |
| /// ${Self} Semantics |
| /// ================= |
| /// |
| /// An `${Self}` instance is a view into memory and does not own the memory |
| /// that it references. Copying a value of type `${Self}` does not copy the |
| /// instances stored in the underlying memory. However, initializing another |
| /// collection with an `${Self}` instance copies the instances out of the |
| /// referenced memory and into the new collection. |
| @_fixed_layout |
| public struct Unsafe${Mutable}BufferPointer<Element> |
| : ${Mutable}Collection, RandomAccessCollection { |
| // FIXME: rdar://18157434 - until this is fixed, this has to be fixed layout |
| // to avoid a hang in Foundation, which has the following setup: |
| // struct A { struct B { let x: UnsafeMutableBufferPointer<...> } let b: B } |
| |
| public typealias Index = Int |
| public typealias IndexDistance = Int |
| public typealias Iterator = UnsafeBufferPointerIterator<Element> |
| |
| /// The index of the first element in a nonempty buffer. |
| /// |
| /// The `startIndex` property of an `Unsafe${Mutable}BufferPointer` instance |
| /// is always zero. |
| @_inlineable |
| public var startIndex: Int { |
| return 0 |
| } |
| |
| /// The "past the end" position---that is, the position one greater than the |
| /// last valid subscript argument. |
| /// |
| /// The `endIndex` property of an `Unsafe${Mutable}BufferPointer` instance is |
| /// always identical to `count`. |
| @_inlineable |
| public var endIndex: Int { |
| return count |
| } |
| |
| @_inlineable |
| public func index(after i: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for UnsafeBufferPointer 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 |
| } |
| |
| @_inlineable |
| public func formIndex(after i: inout Int) { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for UnsafeBufferPointer 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 |
| } |
| |
| @_inlineable |
| public func index(before i: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for UnsafeBufferPointer 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 |
| } |
| |
| @_inlineable |
| public func formIndex(before i: inout Int) { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for UnsafeBufferPointer 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 |
| } |
| |
| @_inlineable |
| public func index(_ i: Int, offsetBy n: Int) -> Int { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for UnsafeBufferPointer 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 + n |
| } |
| |
| @_inlineable |
| public func index( |
| _ i: Int, offsetBy n: Int, limitedBy limit: Int |
| ) -> Int? { |
| // NOTE: this is a manual specialization of index movement for a Strideable |
| // index that is required for UnsafeBufferPointer 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 n > 0 ? l >= 0 && l < n : l <= 0 && n < l { |
| return nil |
| } |
| return i + n |
| } |
| |
| @_inlineable |
| 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 UnsafeBufferPointer 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 |
| } |
| |
| @_inlineable |
| public func _failEarlyRangeCheck(_ index: Int, bounds: Range<Int>) { |
| // NOTE: This method is a no-op for performance reasons. |
| } |
| |
| @_inlineable |
| public func _failEarlyRangeCheck(_ range: Range<Int>, bounds: Range<Int>) { |
| // NOTE: This method is a no-op for performance reasons. |
| } |
| |
| public typealias Indices = CountableRange<Int> |
| |
| @_inlineable |
| public var indices: Indices { |
| return startIndex..<endIndex |
| } |
| |
| /// Initializes the memory at `destination.baseAddress` with elements of `self`, |
| /// stopping when either `self` or `destination` is exhausted. |
| /// |
| /// - Returns: an iterator over any remaining elements of `self` and the |
| /// number of elements initialized. |
| @_inlineable // FIXME(sil-serialize-all) |
| public func _copyContents( |
| initializing destination: UnsafeMutableBufferPointer<Element> |
| ) -> (Iterator, UnsafeMutableBufferPointer<Element>.Index) { |
| guard !isEmpty && !destination.isEmpty else { return (makeIterator(), 0) } |
| let s = self.baseAddress._unsafelyUnwrappedUnchecked |
| let d = destination.baseAddress._unsafelyUnwrappedUnchecked |
| let n = Swift.min(destination.count, self.count) |
| d.initialize(from: s, count: n) |
| return (Iterator(_position: s + n, _end: _end), n) |
| } |
| |
| /// Accesses the element at the specified position. |
| /// |
| %if Mutable: |
| /// The following example uses the buffer pointer's subscript to access and |
| /// modify the elements of a mutable buffer pointing to the contiguous |
| /// contents of an 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) { |
| /// let x = buffer[i] |
| /// buffer[i + 1] = buffer[i] |
| /// buffer[i] = x |
| /// } |
| /// } |
| /// print(numbers) |
| /// // Prints "[2, 1, 4, 3, 5]" |
| %else: |
| /// The following example uses the buffer pointer's subscript to access every |
| /// other element of the buffer: |
| /// |
| /// 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 |
| %end |
| /// |
| /// - Note: Bounds checks for `i` are performed only in debug mode. |
| /// |
| /// - Parameter i: The position of the element to access. `i` must be in the |
| /// range `0..<count`. |
| @_inlineable |
| public subscript(i: Int) -> Element { |
| get { |
| _debugPrecondition(i >= 0) |
| _debugPrecondition(i < endIndex) |
| return _position![i] |
| } |
| %if Mutable: |
| nonmutating set { |
| _debugPrecondition(i >= 0) |
| _debugPrecondition(i < endIndex) |
| _position![i] = newValue |
| } |
| %end |
| } |
| |
| @_inlineable |
| public subscript(bounds: Range<Int>) |
| -> ${Mutable}RandomAccessSlice<Unsafe${Mutable}BufferPointer<Element>> |
| { |
| get { |
| _debugPrecondition(bounds.lowerBound >= startIndex) |
| _debugPrecondition(bounds.upperBound <= endIndex) |
| return ${Mutable}RandomAccessSlice( |
| base: self, bounds: bounds) |
| } |
| % if Mutable: |
| set { |
| _debugPrecondition(bounds.lowerBound >= startIndex) |
| _debugPrecondition(bounds.upperBound <= endIndex) |
| // FIXME: swift-3-indexing-model: tests. |
| _writeBackMutableSlice(&self, bounds: bounds, slice: newValue) |
| } |
| % end |
| } |
| |
| /// Creates a new buffer pointer over the specified number of contiguous |
| /// instances beginning at the given pointer. |
| /// |
| /// - Parameters: |
| /// - start: A pointer to the start of the buffer, or `nil`. If `start` is |
| /// `nil`, `count` must be zero. However, `count` may be zero even for a |
| /// non-`nil` `start`. The pointer passed as `start` must be aligned to |
| /// `MemoryLayout<Element>.alignment`. |
| /// - count: The number of instances in the buffer. `count` must not be |
| /// negative. |
| @_inlineable |
| public init(start: Unsafe${Mutable}Pointer<Element>?, count: Int) { |
| _precondition( |
| count >= 0, "Unsafe${Mutable}BufferPointer with negative count") |
| _precondition( |
| count == 0 || start != nil, |
| "Unsafe${Mutable}BufferPointer has a nil start and nonzero count") |
| _position = start |
| _end = start.map { $0 + count } |
| } |
| |
| /// Creates a buffer pointer starting at `start` and extending up to the last |
| /// addressable pointer to `Element` in the memory space |
| @_inlineable |
| public init(_unboundedStartingAt start: Unsafe${Mutable}Pointer<Element>) { |
| _position = start |
| _end = type(of: start)._max |
| } |
| |
| @_inlineable |
| public init(_empty: ()) { |
| _position = Unsafe${Mutable}Pointer._max |
| _end = _position |
| } |
| |
| % if not Mutable: |
| /// Creates a buffer over the same memory as the given buffer slice. |
| /// |
| /// The new buffer represents the same region of memory as `slice`, but is |
| /// indexed starting at zero instead of sharing indices with the original |
| /// buffer. For example: |
| /// |
| /// let buffer = returnsABuffer() |
| /// let n = 5 |
| /// let slice = buffer[n...] |
| /// let rebased = UnsafeBufferPointer(rebasing: slice) |
| /// |
| /// After rebasing `slice` as the `rebased` buffer, the following are true: |
| /// |
| /// - `rebased.startIndex == 0` |
| /// - `rebased[0] == slice[n]` |
| /// - `rebased[0] == buffer[n]` |
| /// - `rebased.count == slice.count` |
| /// |
| /// - Parameter slice: The buffer slice to rebase. |
| @_inlineable |
| public init(rebasing slice: RandomAccessSlice<UnsafeBufferPointer<Element>>) { |
| self.init(start: slice.base.baseAddress! + slice.startIndex, |
| count: slice.count) |
| } |
| % end # !mutable |
| |
| /// Creates a buffer over the same memory as the given buffer slice. |
| /// |
| /// The new buffer represents the same region of memory as `slice`, but is |
| /// indexed starting at zero instead of sharing indices with the original |
| /// buffer. For example: |
| /// |
| /// let buffer = returnsABuffer() |
| /// let n = 5 |
| /// let slice = buffer[n...] |
| /// let rebased = Unsafe${Mutable}BufferPointer(rebasing: slice) |
| /// |
| /// After rebasing `slice` as the `rebased` buffer, the following are true: |
| /// |
| /// - `rebased.startIndex == 0` |
| /// - `rebased[0] == slice[n]` |
| /// - `rebased[0] == buffer[n]` |
| /// - `rebased.count == slice.count` |
| /// |
| /// - Parameter slice: The buffer slice to rebase. |
| @_inlineable |
| public init( |
| rebasing slice: |
| MutableRandomAccessSlice<UnsafeMutableBufferPointer<Element>> |
| ) { |
| self.init(start: slice.base.baseAddress! + slice.startIndex, |
| count: slice.count) |
| } |
| |
| /// Returns an iterator over the elements of this buffer. |
| /// |
| /// - Returns: An iterator over the elements of this buffer. |
| @_inlineable |
| public func makeIterator() -> UnsafeBufferPointerIterator<Element> { |
| return UnsafeBufferPointerIterator(_position: _position, _end: _end) |
| } |
| |
| /// A pointer to the first element of the buffer. |
| /// |
| /// If the `baseAddress` of this buffer is `nil`, the count is zero. However, |
| /// a buffer can have a `count` of zero even with a non-`nil` base address. |
| @_inlineable |
| public var baseAddress: Unsafe${Mutable}Pointer<Element>? { |
| return _position |
| } |
| |
| /// The number of elements in the buffer. |
| /// |
| /// If the `baseAddress` of this buffer is `nil`, the count is zero. However, |
| /// a buffer can have a `count` of zero even with a non-`nil` base address. |
| @_inlineable |
| public var count: Int { |
| switch(_position, _end) { |
| case (.some(let pos), .some(let end)): |
| return (end - pos) |
| case _: |
| return 0 |
| } |
| } |
| |
| @_versioned |
| let _position, _end: Unsafe${Mutable}Pointer<Element>? |
| } |
| |
| extension Unsafe${Mutable}BufferPointer : CustomDebugStringConvertible { |
| /// A textual representation of the buffer, suitable for debugging. |
| @_inlineable // FIXME(sil-serialize-all) |
| public var debugDescription: String { |
| return "Unsafe${Mutable}BufferPointer" |
| + "(start: \(_position.map(String.init(describing:)) ?? "nil"), count: \(count))" |
| } |
| } |
| %end |
| |
| |
| extension UnsafeMutableBufferPointer { |
| /// Initializes the buffer's memory with the given elements. |
| /// |
| /// When calling the `initialize(from:)` method on a buffer `b`, the memory |
| /// referenced by `b` must be uninitialized or the `Element` type must be a |
| /// trivial type. After the call, the memory referenced by this buffer up |
| /// to, but not including, the returned index is initialized. The buffer |
| /// must contain sufficient memory to accommodate |
| /// `source.underestimatedCount`. |
| /// |
| /// The returned index is the position of the element in the buffer one past |
| /// the last element written. If `source` contains no elements, the returned |
| /// index is equal to the buffer's `startIndex`. If `source` contains an |
| /// equal or greater number of elements than the buffer can hold, the |
| /// returned index is equal to the buffer's `endIndex`. |
| /// |
| /// - Parameter source: A sequence of elements with which to initializer the |
| /// buffer. |
| /// - Returns: An iterator to any elements of `source` that didn't fit in the |
| /// buffer, and an index to the point in the buffer one past the last |
| /// element written. |
| @_inlineable |
| public func initialize<S: Sequence>(from source: S) -> (S.Iterator, Index) |
| where S.Element == Element { |
| return source._copyContents(initializing: self) |
| } |
| } |
| |
| // ${'Local Variables'}: |
| // eval: (read-only-mode 1) |
| // End: |