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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
//
//===----------------------------------------------------------------------===//
/// Creates an asynchronous sequence that concurrently awaits values from three `AsyncSequence` types
/// and emits a tuple of the values.
public func zip<Base1: AsyncSequence, Base2: AsyncSequence, Base3: AsyncSequence>(
_ base1: Base1,
_ base2: Base2,
_ base3: Base3
) -> AsyncZip3Sequence<Base1, Base2, Base3> {
AsyncZip3Sequence(base1, base2, base3)
}
/// An asynchronous sequence that concurrently awaits values from three `AsyncSequence` types
/// and emits a tuple of the values.
public struct AsyncZip3Sequence<Base1: AsyncSequence, Base2: AsyncSequence, Base3: AsyncSequence>: AsyncSequence, Sendable
where Base1: Sendable, Base1.Element: Sendable, Base2: Sendable, Base2.Element: Sendable, Base3: Sendable, Base3.Element: Sendable {
public typealias Element = (Base1.Element, Base2.Element, Base3.Element)
public typealias AsyncIterator = Iterator
let base1: Base1
let base2: Base2
let base3: Base3
init(_ base1: Base1, _ base2: Base2, _ base3: Base3) {
self.base1 = base1
self.base2 = base2
self.base3 = base3
}
public func makeAsyncIterator() -> AsyncIterator {
Iterator(storage: .init(self.base1, self.base2, self.base3)
)
}
public struct Iterator: AsyncIteratorProtocol {
final class InternalClass {
private let storage: ZipStorage<Base1, Base2, Base3>
fileprivate init(storage: ZipStorage<Base1, Base2, Base3>) {
self.storage = storage
}
deinit {
self.storage.iteratorDeinitialized()
}
func next() async rethrows -> Element? {
guard let element = try await self.storage.next() else {
return nil
}
// This force unwrap is safe since there must be a third element.
return (element.0, element.1, element.2!)
}
}
let internalClass: InternalClass
fileprivate init(storage: ZipStorage<Base1, Base2, Base3>) {
self.internalClass = InternalClass(storage: storage)
}
public mutating func next() async rethrows -> Element? {
try await self.internalClass.next()
}
}
}
@available(*, unavailable)
extension AsyncZip3Sequence.Iterator: Sendable { }
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