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//
// AsyncOperation.swift
// MullvadVPN
//
// Created by pronebird on 01/06/2020.
// Copyright © 2020 Mullvad VPN AB. All rights reserved.
//
import Foundation
/// A base implementation of an asynchronous operation
class AsyncOperation: Operation {
/// A state lock used for manipulating the operation state flags in a thread safe fashion.
private let stateLock = NSRecursiveLock()
/// Operation state flags.
private var _isExecuting = false
private var _isFinished = false
private var _isCancelled = false
final override var isExecuting: Bool {
stateLock.lock()
defer { stateLock.unlock() }
return _isExecuting
}
final override var isFinished: Bool {
stateLock.lock()
defer { stateLock.unlock() }
return _isFinished
}
final override var isCancelled: Bool {
stateLock.lock()
defer { stateLock.unlock() }
return _isCancelled
}
final override var isAsynchronous: Bool {
return true
}
final override func start() {
stateLock.lock()
if _isCancelled {
stateLock.unlock()
finish()
} else {
setExecuting(true)
stateLock.unlock()
main()
}
}
override func main() {
// Override in subclasses
}
override func cancel() {
stateLock.lock()
if !_isCancelled {
willChangeValue(for: \.isCancelled)
_isCancelled = true
didChangeValue(for: \.isCancelled)
}
stateLock.unlock()
super.cancel()
}
func finish() {
stateLock.lock()
if _isExecuting {
setExecuting(false)
}
if !_isFinished {
willChangeValue(for: \.isFinished)
_isFinished = true
didChangeValue(for: \.isFinished)
stateLock.unlock()
} else {
stateLock.unlock()
}
}
private func setExecuting(_ value: Bool) {
willChangeValue(for: \.isExecuting)
_isExecuting = value
didChangeValue(for: \.isExecuting)
}
}
extension Operation {
func addDependencies(_ dependencies: [Operation]) {
for dependency in dependencies {
addDependency(dependency)
}
}
}
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