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Merged
merged 2 commits into from
Mar 18, 2022
Merged

Add a no-separator variant of joined() to match the stdlib #87

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8fa9e71
Add a no-separator variant of joined() to match the stdlib
kperryua Mar 17, 2022
3ce0c38
@inlinable and @frozen
kperryua Mar 17, 2022
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147 changes: 147 additions & 0 deletions Sources/AsyncAlgorithms/AsyncJoinedBySeparatorSequence.swift
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Original file line number Diff line number Diff line change
@@ -0,0 +1,147 @@
//===----------------------------------------------------------------------===//
//
// 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 AsyncSequence where Element: AsyncSequence {
@inlinable
public func joined<Separator: AsyncSequence>(separator: Separator) -> AsyncJoinedBySeparatorSequence<Self, Separator> {
return AsyncJoinedBySeparatorSequence(self, separator: separator)
}
}

public struct AsyncJoinedBySeparatorSequence<Base: AsyncSequence, Separator: AsyncSequence>: AsyncSequence where Base.Element: AsyncSequence, Separator.Element == Base.Element.Element {
public typealias Element = Base.Element.Element
public typealias AsyncIterator = Iterator

public struct Iterator: AsyncIteratorProtocol {
@usableFromInline
enum State {
@usableFromInline
enum SeparatorState {
case initial(Separator)
case partialAsync(Separator.AsyncIterator, ContiguousArray<Element>)
case cached(ContiguousArray<Element>)
case partialCached(ContiguousArray<Element>.Iterator, ContiguousArray<Element>)

@usableFromInline
func startSeparator() -> SeparatorState {
switch self {
case .initial(let separatorSequence):
return .partialAsync(separatorSequence.makeAsyncIterator(), [])
case .cached(let array):
return .partialCached(array.makeIterator(), array)
default:
fatalError("Invalid separator sequence state")
}
}

@usableFromInline
func next() async rethrows -> (Element?, SeparatorState) {
switch self {
case .partialAsync(var separatorIterator, var cache):
guard let next = try await separatorIterator.next() else {
return (nil, .cached(cache))
}
cache.append(next)
return (next, .partialAsync(separatorIterator, cache))
case .partialCached(var cacheIterator, let cache):
guard let next = cacheIterator.next() else {
return (nil, .cached(cache))
}
return (next, .partialCached(cacheIterator, cache))
default:
fatalError("Invalid separator sequence state")
}
}
}

case initial(Base.AsyncIterator, Separator)
case sequence(Base.AsyncIterator, Base.Element.AsyncIterator, SeparatorState)
case separator(Base.AsyncIterator, SeparatorState, Base.Element)
case terminal
}

@usableFromInline
var state: State

@usableFromInline
init(_ iterator: Base.AsyncIterator, separator: Separator) {
state = .initial(iterator, separator)
}

@inlinable
public mutating func next() async rethrows -> Base.Element.Element? {
do {
switch state {
case .terminal:
return nil
case .initial(var outerIterator, let separator):
guard let innerSequence = try await outerIterator.next() else {
state = .terminal
return nil
}
let innerIterator = innerSequence.makeAsyncIterator()
state = .sequence(outerIterator, innerIterator, .initial(separator))
return try await next()
case .sequence(var outerIterator, var innerIterator, let separatorState):
if let item = try await innerIterator.next() {
state = .sequence(outerIterator, innerIterator, separatorState)
return item
}

guard let nextInner = try await outerIterator.next() else {
state = .terminal
return nil
}

state = .separator(outerIterator, separatorState.startSeparator(), nextInner)
return try await next()
case .separator(let iterator, let separatorState, let nextBase):
let (itemOpt, newSepState) = try await separatorState.next()
guard let item = itemOpt else {
state = .sequence(iterator, nextBase.makeAsyncIterator(), newSepState)
return try await next()
}
state = .separator(iterator, newSepState, nextBase)
return item
}
} catch {
state = .terminal
throw error
}
}
}

@usableFromInline
let base: Base

@usableFromInline
let separator: Separator

@inlinable
init(_ base: Base, separator: Separator) {
self.base = base
self.separator = separator
}

@inlinable
public func makeAsyncIterator() -> Iterator {
return Iterator(base.makeAsyncIterator(), separator: separator)
}
}

extension AsyncJoinedBySeparatorSequence: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
extension AsyncJoinedBySeparatorSequence.Iterator: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
extension AsyncJoinedBySeparatorSequence.Iterator.State: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
extension AsyncJoinedBySeparatorSequence.Iterator.State.SeparatorState: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
122 changes: 34 additions & 88 deletions Sources/AsyncAlgorithms/AsyncJoinedSequence.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -11,137 +11,83 @@

extension AsyncSequence where Element: AsyncSequence {
@inlinable
public func joined<Separator: AsyncSequence>(separator: Separator) -> AsyncJoinedSequence<Self, Separator> {
return AsyncJoinedSequence(self, separator: separator)
public func joined() -> AsyncJoinedSequence<Self> {
return AsyncJoinedSequence(self)
}
}

public struct AsyncJoinedSequence<Base: AsyncSequence, Separator: AsyncSequence>: AsyncSequence where Base.Element: AsyncSequence, Separator.Element == Base.Element.Element {
public struct AsyncJoinedSequence<Base: AsyncSequence>: AsyncSequence where Base.Element: AsyncSequence {
public typealias Element = Base.Element.Element
public typealias AsyncIterator = Iterator

public struct Iterator: AsyncIteratorProtocol {
@usableFromInline
enum State {
@usableFromInline
enum SeparatorState {
case initial(Separator)
case partialAsync(Separator.AsyncIterator, ContiguousArray<Element>)
case cached(ContiguousArray<Element>)
case partialCached(ContiguousArray<Element>.Iterator, ContiguousArray<Element>)

@usableFromInline
func startSeparator() -> SeparatorState {
switch self {
case .initial(let separatorSequence):
return .partialAsync(separatorSequence.makeAsyncIterator(), [])
case .cached(let array):
return .partialCached(array.makeIterator(), array)
default:
fatalError("Invalid separator sequence state")
}
}

@usableFromInline
func next() async rethrows -> (Element?, SeparatorState) {
switch self {
case .partialAsync(var separatorIterator, var cache):
guard let next = try await separatorIterator.next() else {
return (nil, .cached(cache))
}
cache.append(next)
return (next, .partialAsync(separatorIterator, cache))
case .partialCached(var cacheIterator, let cache):
guard let next = cacheIterator.next() else {
return (nil, .cached(cache))
}
return (next, .partialCached(cacheIterator, cache))
default:
fatalError("Invalid separator sequence state")
}
}
}

case initial(Base.AsyncIterator, Separator)
case sequence(Base.AsyncIterator, Base.Element.AsyncIterator, SeparatorState)
case separator(Base.AsyncIterator, SeparatorState, Base.Element)
case initial(Base.AsyncIterator)
case sequence(Base.AsyncIterator, Base.Element.AsyncIterator)
case terminal
}

@usableFromInline
var state: State

@usableFromInline
init(_ iterator: Base.AsyncIterator, separator: Separator) {
state = .initial(iterator, separator)
init(_ iterator: Base.AsyncIterator) {
state = .initial(iterator)
}

@inlinable
public mutating func next() async rethrows -> Base.Element.Element? {
do {
switch state {
case .terminal:
return nil
case .initial(var outerIterator, let separator):
case .initial(var outerIterator):
guard let innerSequence = try await outerIterator.next() else {
state = .terminal
return nil
}
let innerIterator = innerSequence.makeAsyncIterator()
state = .sequence(outerIterator, innerIterator, .initial(separator))
state = .sequence(outerIterator, innerIterator)
return try await next()
case .sequence(var outerIterator, var innerIterator, let separatorState):
if let item = try await innerIterator.next() {
state = .sequence(outerIterator, innerIterator, separatorState)
return item
}

guard let nextInner = try await outerIterator.next() else {
state = .terminal
return nil
}

state = .separator(outerIterator, separatorState.startSeparator(), nextInner)
return try await next()
case .separator(let iterator, let separatorState, let nextBase):
let (itemOpt, newSepState) = try await separatorState.next()
guard let item = itemOpt else {
state = .sequence(iterator, nextBase.makeAsyncIterator(), newSepState)
return try await next()
case .sequence(var outerIterator, var innerIterator):
if let item = try await innerIterator.next() {
state = .sequence(outerIterator, innerIterator)
return item
}
state = .separator(iterator, newSepState, nextBase)
return item

guard let nextInner = try await outerIterator.next() else {
state = .terminal
return nil
}

state = .sequence(outerIterator, nextInner.makeAsyncIterator())
return try await next()
}
} catch {
state = .terminal
throw error
}
}
}

@usableFromInline
let base: Base

@usableFromInline
let separator: Separator

@usableFromInline
init(_ base: Base, separator: Separator) {

@inlinable
init(_ base: Base) {
self.base = base
self.separator = separator
}

@inlinable
public func makeAsyncIterator() -> Iterator {
return Iterator(base.makeAsyncIterator(), separator: separator)
return Iterator(base.makeAsyncIterator())
}
}

extension AsyncJoinedSequence: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
extension AsyncJoinedSequence.Iterator: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
extension AsyncJoinedSequence.Iterator.State: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
extension AsyncJoinedSequence.Iterator.State.SeparatorState: Sendable
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Separator: Sendable, Separator.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
where Base: Sendable, Base.Element: Sendable, Base.Element.Element: Sendable, Base.AsyncIterator: Sendable, Base.Element.AsyncIterator: Sendable { }
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