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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Async Algorithms open source project
//
// Copyright (c) 2022 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
//
//===----------------------------------------------------------------------===//
struct ChannelStorage<Element: Sendable, Failure: Error>: Sendable {
private let stateMachine: ManagedCriticalState<ChannelStateMachine<Element, Failure>>
private let ids = ManagedCriticalState<UInt64>(0)
init() {
self.stateMachine = ManagedCriticalState(ChannelStateMachine())
}
func generateId() -> UInt64 {
self.ids.withCriticalRegion { ids in
defer { ids &+= 1 }
return ids
}
}
func send(element: Element) async {
// check if a suspension is needed
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.send()
}
switch action {
case .suspend:
break
case .resumeConsumer(let continuation):
continuation?.resume(returning: element)
return
}
let producerID = self.generateId()
await withTaskCancellationHandler {
// a suspension is needed
await withUnsafeContinuation { (continuation: UnsafeContinuation<Void, Never>) in
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.sendSuspended(continuation: continuation, element: element, producerID: producerID)
}
switch action {
case .none:
break
case .resumeProducer:
continuation.resume()
case .resumeProducerAndConsumer(let consumerContinuation):
continuation.resume()
consumerContinuation?.resume(returning: element)
}
}
} onCancel: {
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.sendCancelled(producerID: producerID)
}
switch action {
case .none:
break
case .resumeProducer(let continuation):
continuation?.resume()
}
}
}
func finish(error: Failure? = nil) {
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.finish(error: error)
}
switch action {
case .none:
break
case .resumeProducersAndConsumers(let producerContinuations, let consumerContinuations):
producerContinuations.forEach { $0?.resume() }
if let error {
consumerContinuations.forEach { $0?.resume(throwing: error) }
} else {
consumerContinuations.forEach { $0?.resume(returning: nil) }
}
}
}
func next() async throws -> Element? {
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.next()
}
switch action {
case .suspend:
break
case .resumeProducer(let producerContinuation, let result):
producerContinuation?.resume()
return try result._rethrowGet()
}
let consumerID = self.generateId()
return try await withTaskCancellationHandler {
try await withUnsafeThrowingContinuation { (continuation: UnsafeContinuation<Element?, any Error>) in
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.nextSuspended(
continuation: continuation,
consumerID: consumerID
)
}
switch action {
case .none:
break
case .resumeConsumer(let element):
continuation.resume(returning: element)
case .resumeConsumerWithError(let error):
continuation.resume(throwing: error)
case .resumeProducerAndConsumer(let producerContinuation, let element):
producerContinuation?.resume()
continuation.resume(returning: element)
}
}
} onCancel: {
let action = self.stateMachine.withCriticalRegion { stateMachine in
stateMachine.nextCancelled(consumerID: consumerID)
}
switch action {
case .none:
break
case .resumeConsumer(let continuation):
continuation?.resume(returning: nil)
}
}
}
}
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