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# Motivation For AsyncStream we created a custom internal Deque implementation to use for the buffering. This implementation was relatively bare-bones compared to the one in swift-collections. Furthermore, it lacked some methods that we need to implement the new `AsyncStream` APIs that support producer backpressure. # Modification This PR copies over the Deque implementation of swift-collections and makes it internal and non-inlinable. # Result We now have a fully functional Deque.
47 lines
1.3 KiB
Swift
47 lines
1.3 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) 2021 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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//
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//===----------------------------------------------------------------------===//
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/// This file is copied from swift-collections and should not be modified here.
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/// Rather all changes should be made to swift-collections and copied back.
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import Swift
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internal struct _DequeBufferHeader {
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var capacity: Int
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var count: Int
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var startSlot: _DequeSlot
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init(capacity: Int, count: Int, startSlot: _DequeSlot) {
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self.capacity = capacity
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self.count = count
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self.startSlot = startSlot
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_checkInvariants()
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}
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#if COLLECTIONS_INTERNAL_CHECKS
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internal func _checkInvariants() {
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precondition(capacity >= 0)
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precondition(count >= 0 && count <= capacity)
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precondition(startSlot.position >= 0 && startSlot.position <= capacity)
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}
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#else
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internal func _checkInvariants() {}
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#endif // COLLECTIONS_INTERNAL_CHECKS
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}
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extension _DequeBufferHeader: CustomStringConvertible {
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internal var description: String {
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"(capacity: \(capacity), count: \(count), startSlot: \(startSlot))"
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}
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}
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