/
turnstile.go
96 lines (79 loc) · 1.27 KB
/
turnstile.go
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package main
import (
"fmt"
"sync"
)
type Signal struct{}
type Barrier struct {
ready chan Signal
wait chan Signal
done chan struct{}
}
func (b Barrier) Join() {
b.ready <- Signal{}
<-b.wait
}
func NewBarrier(N int) Barrier {
ready := make(chan Signal)
wait := make(chan Signal)
done := make(chan struct{})
helper := func() {
for {
for i := N; i > 0; i-- {
select {
case <-ready:
case <-done:
close(ready)
close(wait)
return
}
}
for i := N; i > 0; i-- {
select {
case wait <- Signal{}:
case <-done:
close(ready)
close(wait)
return
}
}
}
}
go helper()
return Barrier{
ready: ready,
wait: wait,
done: done,
}
}
func (b Barrier) Done() {
close(b.done)
}
func worker(name string, N int, b1, b2 Barrier) {
for i := N; i > 0; i-- {
fmt.Printf("Worker %s entering: %d\n", name, N-i)
b1.Join()
fmt.Printf("Worker %s leaving: %d\n", name, N-i)
b2.Join()
}
}
func goWg(wg *sync.WaitGroup, f func()) {
wg.Add(1)
go func() {
f()
wg.Done()
}()
}
func main() {
wg := &sync.WaitGroup{}
N, M := 10, 5
b1 := NewBarrier(N)
b2 := NewBarrier(N)
for i := 0; i < N; i++ {
name := string('a' + i)
goWg(wg, func() { worker(name, M, b1, b2) })
}
wg.Wait()
b1.Done()
b2.Done()
}