1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
package sync2
import (
"sync"
"sync/atomic"
"time"
)
func NewSemaphore(initialCount int) *Semaphore {
res := &Semaphore{
counter: int64(initialCount),
}
res.cond.L = &res.lock
return res
}
type Semaphore struct {
lock sync.Mutex
cond sync.Cond
counter int64
}
func (s *Semaphore) Release() {
s.lock.Lock()
s.counter += 1
if s.counter >= 0 {
s.cond.Signal()
}
s.lock.Unlock()
}
func (s *Semaphore) Acquire() {
s.lock.Lock()
for s.counter < 1 {
s.cond.Wait()
}
s.counter -= 1
s.lock.Unlock()
}
func (s *Semaphore) AcquireTimeout(timeout time.Duration) bool {
done := make(chan bool, 1)
// Gate used to communicate between the threads and decide what the result
// is. If the main thread decides, we have timed out, otherwise we succeed.
decided := new(int32)
go func() {
s.Acquire()
if atomic.SwapInt32(decided, 1) == 0 {
done <- true
} else {
// If we already decided the result, and this thread did not win
s.Release()
}
}()
select {
case <-done:
return true
case <-time.NewTimer(timeout).C:
if atomic.SwapInt32(decided, 1) == 1 {
// The other thread already decided the result
return true
}
return false
}
}
|
