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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Async Algorithms open source project
//
// Copyright (c) 2021 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 AsyncSequence {
/// Creates an asynchronous sequence that creates chunks of a given `RangeReplaceableCollection` of a given count.
@inlinable
public func chunks<Collected: RangeReplaceableCollection>(ofCount count: Int, into: Collected.Type) -> AsyncChunksOfCountSequence<Self, Collected> where Collected.Element == Element {
AsyncChunksOfCountSequence(self, count: count)
}
/// Creates an asynchronous sequence that creates chunks of a given count.
@inlinable
public func chunks(ofCount count: Int) -> AsyncChunksOfCountSequence<Self, [Element]> {
chunks(ofCount: count, into: [Element].self)
}
}
/// An `AsyncSequence` that chunks elements into `RangeReplaceableCollection` instances of at least a given count.
public struct AsyncChunksOfCountSequence<Base: AsyncSequence, Collected: RangeReplaceableCollection>: AsyncSequence where Collected.Element == Base.Element {
public typealias Element = Collected
/// The iterator for a `AsyncChunksOfCountSequence` instance.
@frozen
public struct Iterator: AsyncIteratorProtocol {
@usableFromInline
var base: Base.AsyncIterator
@usableFromInline
let count: Int
@usableFromInline
init(base: Base.AsyncIterator, count: Int) {
self.base = base
self.count = count
}
@inlinable
public mutating func next() async rethrows -> Collected? {
guard let first = try await base.next() else {
return nil
}
if count == 1 {
return Collected(CollectionOfOne(first))
}
var result: Collected = .init()
result.append(first)
while let next = try await base.next() {
result.append(next)
if result.count == count {
break
}
}
return result
}
}
@usableFromInline
let base : Base
@usableFromInline
let count : Int
@usableFromInline
init(_ base: Base, count: Int) {
precondition(count > 0)
self.base = base
self.count = count
}
@inlinable
public func makeAsyncIterator() -> Iterator {
Iterator(base: base.makeAsyncIterator(), count: count)
}
}
extension AsyncChunksOfCountSequence : Sendable where Base : Sendable, Base.Element : Sendable { }
extension AsyncChunksOfCountSequence.Iterator : Sendable where Base.AsyncIterator : Sendable, Base.Element : Sendable { }
@available(*, unavailable)
extension AsyncChunksOfCountSequence.Iterator: Sendable { }
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