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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftNIO open source project
//
// Copyright (c) 2022-2023 Apple Inc. and the SwiftNIO project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
/// The inbound message asynchronous sequence of a ``NIOAsyncChannel``.
///
/// This is a unicast async sequence that allows a single iterator to be created.
@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
public struct NIOAsyncChannelInboundStream<Inbound: Sendable>: Sendable {
@usableFromInline
typealias Producer = NIOThrowingAsyncSequenceProducer<Inbound, Error, NIOAsyncSequenceProducerBackPressureStrategies.HighLowWatermark, NIOAsyncChannelInboundStreamChannelHandlerProducerDelegate>
/// A source used for driving a ``NIOAsyncChannelInboundStream`` during tests.
public struct TestSource {
@usableFromInline
internal let continuation: AsyncThrowingStream<Inbound, Error>.Continuation
@inlinable
init(continuation: AsyncThrowingStream<Inbound, Error>.Continuation) {
self.continuation = continuation
}
/// Yields the element to the inbound stream.
///
/// - Parameter element: The element to yield to the inbound stream.
@inlinable
public func yield(_ element: Inbound) {
self.continuation.yield(element)
}
/// Finished the inbound stream.
///
/// - Parameter error: The error to throw, or nil, to finish normally.
@inlinable
public func finish(throwing error: Error? = nil) {
self.continuation.finish(throwing: error)
}
}
@usableFromInline
enum _Backing: Sendable {
case asyncStream(AsyncThrowingStream<Inbound, Error>)
case producer(Producer)
}
/// The underlying async sequence.
@usableFromInline
let _backing: _Backing
/// Creates a new stream with a source for testing.
///
/// This is useful for writing unit tests where you want to drive a ``NIOAsyncChannelInboundStream``.
///
/// - Returns: A tuple containing the input stream and a test source to drive it.
@inlinable
public static func makeTestingStream() -> (Self, TestSource) {
var continuation: AsyncThrowingStream<Inbound, Error>.Continuation!
let stream = AsyncThrowingStream<Inbound, Error> { continuation = $0 }
let source = TestSource(continuation: continuation)
let inputStream = Self(stream: stream)
return (inputStream, source)
}
@inlinable
init(stream: AsyncThrowingStream<Inbound, Error>) {
self._backing = .asyncStream(stream)
}
@inlinable
init<HandlerInbound: Sendable>(
channel: Channel,
backPressureStrategy: NIOAsyncSequenceProducerBackPressureStrategies.HighLowWatermark?,
closeOnDeinit: Bool,
handler: NIOAsyncChannelInboundStreamChannelHandler<HandlerInbound, Inbound>
) throws {
channel.eventLoop.preconditionInEventLoop()
let strategy: NIOAsyncSequenceProducerBackPressureStrategies.HighLowWatermark
if let userProvided = backPressureStrategy {
strategy = userProvided
} else {
// Default strategy. These numbers are fairly arbitrary, but they line up with the default value of
// maxMessagesPerRead.
strategy = .init(lowWatermark: 2, highWatermark: 10)
}
let sequence = Producer.makeSequence(
backPressureStrategy: strategy,
finishOnDeinit: closeOnDeinit,
delegate: NIOAsyncChannelInboundStreamChannelHandlerProducerDelegate(handler: handler)
)
handler.source = sequence.source
try channel.pipeline.syncOperations.addHandler(handler)
self._backing = .producer(sequence.sequence)
}
/// Creates a new ``NIOAsyncChannelInboundStream`` which is used when the pipeline got synchronously wrapped.
@inlinable
static func makeWrappingHandler(
channel: Channel,
backPressureStrategy: NIOAsyncSequenceProducerBackPressureStrategies.HighLowWatermark?,
closeOnDeinit: Bool
) throws -> NIOAsyncChannelInboundStream {
let handler = NIOAsyncChannelInboundStreamChannelHandler<Inbound, Inbound>.makeHandler(
eventLoop: channel.eventLoop
)
return try .init(
channel: channel,
backPressureStrategy: backPressureStrategy,
closeOnDeinit: closeOnDeinit,
handler: handler
)
}
/// Creates a new ``NIOAsyncChannelInboundStream`` which has hooks for transformations.
@inlinable
static func makeTransformationHandler(
channel: Channel,
backPressureStrategy: NIOAsyncSequenceProducerBackPressureStrategies.HighLowWatermark?,
closeOnDeinit: Bool,
channelReadTransformation: @Sendable @escaping (Channel) -> EventLoopFuture<Inbound>
) throws -> NIOAsyncChannelInboundStream {
let handler = NIOAsyncChannelInboundStreamChannelHandler<Channel, Inbound>.makeHandlerWithTransformations(
eventLoop: channel.eventLoop,
channelReadTransformation: channelReadTransformation
)
return try .init(
channel: channel,
backPressureStrategy: backPressureStrategy,
closeOnDeinit: closeOnDeinit,
handler: handler
)
}
}
@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
extension NIOAsyncChannelInboundStream: AsyncSequence {
public typealias Element = Inbound
public struct AsyncIterator: AsyncIteratorProtocol {
@usableFromInline
enum _Backing {
case asyncStream(AsyncThrowingStream<Inbound, Error>.Iterator)
case producer(Producer.AsyncIterator)
}
@usableFromInline var _backing: _Backing
@inlinable
init(_ backing: NIOAsyncChannelInboundStream<Inbound>._Backing) {
switch backing {
case .asyncStream(let asyncStream):
self._backing = .asyncStream(asyncStream.makeAsyncIterator())
case .producer(let producer):
self._backing = .producer(producer.makeAsyncIterator())
}
}
@inlinable
public mutating func next() async throws -> Element? {
switch self._backing {
case .asyncStream(var iterator):
defer {
self._backing = .asyncStream(iterator)
}
let value = try await iterator.next()
return value
case .producer(let iterator):
return try await iterator.next()
}
}
}
@inlinable
public func makeAsyncIterator() -> AsyncIterator {
return AsyncIterator(self._backing)
}
}
/// The ``NIOAsyncChannelInboundStream/AsyncIterator`` MUST NOT be shared across `Task`s. With marking this as
/// unavailable we are explicitly declaring this.
@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
@available(*, unavailable)
extension NIOAsyncChannelInboundStream.AsyncIterator: Sendable {}
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