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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.
66 lines
2.3 KiB
Swift
66 lines
2.3 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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extension Array {
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/// Returns true if `Array.withContiguousStorageIfAvailable` is broken
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/// in the stdlib we're currently running on.
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///
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/// See https://bugs.swift.org/browse/SR-14663.
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internal static func _isWCSIABroken() -> Bool {
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#if _runtime(_ObjC)
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guard _isBridgedVerbatimToObjectiveC(Element.self) else {
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// SR-14663 only triggers on array values that are verbatim bridged
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// from Objective-C, so it cannot ever trigger for element types
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// that aren't verbatim bridged.
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return false
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}
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// SR-14663 was introduced in Swift 5.1. Check if we have a broken stdlib.
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// The bug is caused by a bogus precondition inside a non-inlinable stdlib
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// method, so to determine if we're affected, we need to check the currently
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// running OS version.
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#if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
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guard #available(macOS 10.15, iOS 13, watchOS 6, tvOS 13, *) else {
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// The OS is too old to be affected by this bug.
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return false
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}
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#endif
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// FIXME: When a stdlib is released that contains a fix, add a check for it.
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return true
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#else
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// Platforms that don't have an Objective-C runtime don't have verbatim
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// bridged array values, so the bug doesn't apply to them.
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return false
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#endif
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}
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}
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extension Sequence {
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// An adjusted version of the standard `withContiguousStorageIfAvailable`
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// method that works around https://bugs.swift.org/browse/SR-14663.
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internal func _withContiguousStorageIfAvailable_SR14663<R>(
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_ body: (UnsafeBufferPointer<Element>) throws -> R
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) rethrows -> R? {
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if Self.self == Array<Element>.self && Array<Element>._isWCSIABroken() {
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return nil
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}
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return try self.withContiguousStorageIfAvailable(body)
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}
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}
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