concurrency.swift

//: Playground - noun: a place where people can play

import Foundation

let sleepMilliSecond = 1
var initialSleepSec: UInt32? = 1000

func _sleep() {
    if let s = initialSleepSec {
        initialSleepSec = nil
        sleep(s)
    } else {
        let ms: UInt32 = 1000
        usleep(UInt32(sleepMilliSecond) * ms)
    }
}

class Object: NSObject {
    private(set) var value: [Int] = []
    private func objc_locked(_ block: (() -> ())) {
        objc_sync_enter(self); defer { objc_sync_exit(self) }
        block(); _sleep()
    }
    private let lock = NSLock()
    private func nslocked(_ block: (() -> ())) {
        lock.lock(); defer { lock.unlock() }
        block(); _sleep()
    }
    private let queue = DispatchQueue(label: "jp.toshi0383.CuncurrencyPlayground.SerialQueue")
    private func serial_queue_locked(_ block: (() -> ())) {
        queue.sync {
            block(); _sleep()
        }
    }
    func mutateValue(_ number: Int) {
//        nslocked {
        serial_queue_locked {
//        objc_locked {
            self.value.append(number)
        }
    }
}

let object = Object()
let max = 100
for i in (1...max) {
    DispatchQueue.global().asyncAfter(deadline: DispatchTime.now() + 0.1 * Double(i)) {
        object.mutateValue(i % 2 != 0 ? 1 : -1)
    }
}
let waitSecond = Double(max) * Double(sleepMilliSecond) / 10 + 1 + 1
print("waiting for \(waitSecond) seconds...")
RunLoop.main.run(until: Date(timeIntervalSince1970: Date().timeIntervalSince1970 + waitSecond))
let result = object.value.map { $0.description }.joined()
let expected = (0...max/2).map { $0 > 0 && $0 < max/2 ? 11 : 1 }.map { $0.description }.joined(separator: "-")
print("result: \(result)")
print("expected: \(expected)")
print(result == expected)