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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
//
//===----------------------------------------------------------------------===//
extension Sequence {
/// An asynchronous sequence containing the same elements as this sequence,
/// but on which operations, such as `map` and `filter`, are
/// implemented asynchronously.
@inlinable
public var async: AsyncSyncSequence<Self> {
AsyncSyncSequence(self)
}
}
/// An asynchronous sequence composed from a synchronous sequence.
///
/// Asynchronous lazy sequences can be used to interface existing or pre-calculated
/// data to interoperate with other asynchronous sequences and algorithms based on
/// asynchronous sequences.
///
/// This functions similarly to `LazySequence` by accessing elements sequentially
/// in the iterator's `next()` method.
@frozen
public struct AsyncSyncSequence<Base: Sequence>: AsyncSequence {
public typealias Element = Base.Element
@frozen
public struct Iterator: AsyncIteratorProtocol {
@usableFromInline
var iterator: Base.Iterator?
@usableFromInline
init(_ iterator: Base.Iterator) {
self.iterator = iterator
}
@inlinable
public mutating func next() async -> Base.Element? {
if !Task.isCancelled, let value = iterator?.next() {
return value
} else {
iterator = nil
return nil
}
}
}
@usableFromInline
let base: Base
@usableFromInline
init(_ base: Base) {
self.base = base
}
@inlinable
public func makeAsyncIterator() -> Iterator {
Iterator(base.makeIterator())
}
}
extension AsyncSyncSequence: Sendable where Base: Sendable { }
@available(*, unavailable)
extension AsyncSyncSequence.Iterator: Sendable { }
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