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71cc1bb6f1
Since the unsafe iterator types are now used throughout the overlay, not just by `CxxSequence` and `CxxRandomAccessCollection`, let's move them to a separate file.
93 lines
3.2 KiB
Swift
93 lines
3.2 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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/// Use this protocol to conform custom C++ sequence types to Swift's `Sequence`
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/// protocol like this:
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///
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/// extension MyCxxSequenceType : CxxSequence {}
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///
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/// This requires the C++ sequence type to define const methods `begin()` and
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/// `end()` which return input iterators into the C++ sequence. The iterator
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/// types must conform to `UnsafeCxxInputIterator`.
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public protocol CxxSequence<Element>: CxxConvertibleToCollection, Sequence {
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override associatedtype Element
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override associatedtype RawIterator: UnsafeCxxInputIterator
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where RawIterator.Pointee == Element
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override associatedtype Iterator = CxxIterator<Self>
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// `begin()` and `end()` have to be mutating, otherwise calling
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// `self.sequence.begin()` will copy `self.sequence` into a temporary value,
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// and the result will be dangling. This does not mean that the implementing
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// methods _have_ to be mutating.
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/// Do not implement this function manually in Swift.
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mutating func __beginUnsafe() -> RawIterator
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/// Do not implement this function manually in Swift.
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mutating func __endUnsafe() -> RawIterator
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}
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/// Prevents a C++ sequence from being copied or moved implicitly. Makes sure
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/// that raw C++ iterators pointing into the sequence are not invalidated.
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@usableFromInline
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internal final class CxxSequenceBox<T> where T: CxxSequence {
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@usableFromInline
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internal var sequence: T
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@usableFromInline
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internal init(_ sequence: __shared T) {
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self.sequence = sequence
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}
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}
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@frozen
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public struct CxxIterator<T>: IteratorProtocol where T: CxxSequence {
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public typealias Element = T.RawIterator.Pointee
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@usableFromInline
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internal let sequence: CxxSequenceBox<T>
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@usableFromInline
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internal var rawIterator: T.RawIterator
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@usableFromInline
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internal let endIterator: T.RawIterator
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@inlinable
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public init(sequence: __shared T) {
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self.sequence = CxxSequenceBox<T>(sequence)
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self.rawIterator = self.sequence.sequence.__beginUnsafe()
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self.endIterator = self.sequence.sequence.__endUnsafe()
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}
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@inlinable
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public mutating func next() -> Element? {
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if self.rawIterator == self.endIterator {
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return nil
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}
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let object = self.rawIterator.pointee
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self.rawIterator = self.rawIterator.successor()
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return object
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}
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}
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extension CxxSequence {
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/// Returns an iterator over the elements of this C++ container.
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///
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/// - Complexity: O(*n*), where *n* is the number of elements in the C++
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/// container when each element is copied in O(1). Note that this might not
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/// be true for certain C++ types, e.g. those with a custom copy
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/// constructor that performs additional logic.
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@inlinable
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public func makeIterator() -> CxxIterator<Self> {
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return CxxIterator(sequence: self)
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}
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}
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