AsyncTimerSequence.swift

//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

/// An `AsyncSequence` that produces elements at regular intervals.
@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0,*)
publicstructAsyncTimerSequence<C:Clock>:AsyncSequence{
publictypealiasElement=C.Instant

 /// The iterator for an `AsyncTimerSequence` instance.
publicstructIterator:AsyncIteratorProtocol{
varclock:C?
letinterval:C.Instant.Duration
lettolerance:C.Instant.Duration?
varlast:C.Instant?

init(interval:C.Instant.Duration, tolerance:C.Instant.Duration?, clock:C){
self.clock = clock
self.interval = interval
self.tolerance = tolerance
}

publicmutatingfunc next()async->C.Instant?{
guardlet clock =self.clock else{
returnnil
}

letnext=(self.last ?? clock.now).advanced(by:self.interval)
do{
tryawait clock.sleep(until: next, tolerance:self.tolerance)
}catch{
self.clock =nil
returnnil
}
letnow= clock.now
self.last = next
return now
}
}

letclock:C
letinterval:C.Instant.Duration
lettolerance:C.Instant.Duration?

 /// Create an `AsyncTimerSequence` with a given repeating interval.
publicinit(interval:C.Instant.Duration, tolerance:C.Instant.Duration?=nil, clock:C){
self.clock = clock
self.interval = interval
self.tolerance = tolerance
}

publicfunc makeAsyncIterator()->Iterator{
Iterator(interval: interval, tolerance: tolerance, clock: clock)
}
}

@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0,*)
extensionAsyncTimerSequence{
 /// Create an `AsyncTimerSequence` with a given repeating interval.
publicstaticfunc repeating(
 every interval:C.Instant.Duration,
 tolerance:C.Instant.Duration?=nil,
 clock:C
)->AsyncTimerSequence<C>{
returnAsyncTimerSequence(interval: interval, tolerance: tolerance, clock: clock)
}
}

@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0,*)
extensionAsyncTimerSequencewhere C ==SuspendingClock{
 /// Create an `AsyncTimerSequence` with a given repeating interval.
publicstaticfunc repeating(
 every interval:Duration,
 tolerance:Duration?=nil
)->AsyncTimerSequence<SuspendingClock>{
returnAsyncTimerSequence(interval: interval, tolerance: tolerance, clock:SuspendingClock())
}
}

@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0,*)
extensionAsyncTimerSequence:Sendable{}

@available(*, unavailable)
extensionAsyncTimerSequence.Iterator:Sendable{}