//
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// AsyncLock.swift
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// RxSwift
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//
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// Created by Krunoslav Zaher on 3/21/15.
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// Copyright © 2015 Krunoslav Zaher. All rights reserved.
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//
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/**
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In case nobody holds this lock, the work will be queued and executed immediately
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on thread that is requesting lock.
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In case there is somebody currently holding that lock, action will be enqueued.
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When owned of the lock finishes with it's processing, it will also execute
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and pending work.
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That means that enqueued work could possibly be executed later on a different thread.
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*/
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final class AsyncLock<I: InvocableType>
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: Disposable
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, Lock
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, SynchronizedDisposeType {
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typealias Action = () -> Void
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private var _lock = SpinLock()
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private var queue: Queue<I> = Queue(capacity: 0)
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private var isExecuting: Bool = false
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private var hasFaulted: Bool = false
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// lock {
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func lock() {
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self._lock.lock()
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}
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func unlock() {
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self._lock.unlock()
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}
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// }
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private func enqueue(_ action: I) -> I? {
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self.lock(); defer { self.unlock() }
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if self.hasFaulted {
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return nil
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}
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if self.isExecuting {
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self.queue.enqueue(action)
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return nil
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}
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self.isExecuting = true
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return action
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}
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private func dequeue() -> I? {
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self.lock(); defer { self.unlock() }
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if !self.queue.isEmpty {
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return self.queue.dequeue()
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}
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else {
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self.isExecuting = false
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return nil
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}
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}
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func invoke(_ action: I) {
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let firstEnqueuedAction = self.enqueue(action)
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if let firstEnqueuedAction = firstEnqueuedAction {
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firstEnqueuedAction.invoke()
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}
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else {
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// action is enqueued, it's somebody else's concern now
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return
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}
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while true {
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let nextAction = self.dequeue()
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if let nextAction = nextAction {
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nextAction.invoke()
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}
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else {
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return
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}
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}
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}
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func dispose() {
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self.synchronizedDispose()
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}
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func synchronized_dispose() {
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self.queue = Queue(capacity: 0)
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self.hasFaulted = true
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}
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}
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