proc_events.go

// walkEvents walks an event list applying a hook function.
// This is intended to be parallelized.  Apply only when the
// computation has no dependency on the order in which commits
// are processed.
// Source: http://esr.ibiblio.org/?p=8607#comment-2365265
func walkEvents(events []Event, hook func(int, Event)) {
	if control.flagOptions["serial"] {
		for i, e := range events {
			hook(i, e)
		}
		return
	}

	var (
		maxWorkers = runtime.GOMAXPROCS(0)
		channel    = make(chan int, maxWorkers)
		done       = make(chan bool, maxWorkers)
	)

	// Create the workers that will loop though events
  // Note: Each loop iteration we create a new worker
  // Note: The queue "channel" is populated after this loop.
	for n := 0; n < maxWorkers; n++ {
		go func() {
			// The for loop will stop when channel is closed
			for i := range channel {
				hook(i, events[i])
			}
      // Note: After finishing all events in its queue, the worker is done.
			done <- true
		}()
	}

	// Populate the channel with the events
	for i := range events {
		channel <- i
	}
	close(channel)

	// Wait for all workers to finish
	for n := 0; n < maxWorkers; n++ {
		<-done
	}
}