channel.swift

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

/* This test does nothing in the playground. Not sure why it does not work, but
 * I'm not that surprised it doesn't. */

import Foundation



class Channel<T> {
	var stream: Array<T>
	let queue: dispatch_queue_t
	let semaphore: dispatch_semaphore_t
	
	init() {
		self.stream = []
		self.semaphore = dispatch_semaphore_create(0)
		self.queue = dispatch_queue_create("channel.queue.", DISPATCH_QUEUE_CONCURRENT)
	}
	
	func write(value: T) {
		dispatch_sync(self.queue) {
			self.stream.append(value)
			dispatch_semaphore_signal(self.semaphore)
		}
	}
	
	func recv() -> T {
		var result:T?
		dispatch_sync(self.queue) {
			dispatch_semaphore_wait(self.semaphore, DISPATCH_TIME_FOREVER)
			result = self.stream.removeAtIndex(0)
		}
		return result!
	}
}



let chan = Channel<Int>()
let delay = 1.5 * Double(NSEC_PER_SEC)
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))

chan.write(1)
println(chan.recv())

chan.write(2)
println(chan.recv())

dispatch_after(time, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
	chan.write(5)
})

chan.write(3)
chan.write(4)
println(chan.recv())
println(chan.recv())

println(chan.recv())