mirror of
https://github.com/ergochat/ergo.git
synced 2024-12-27 13:12:43 +01:00
82 lines
2.0 KiB
Go
82 lines
2.0 KiB
Go
// Copyright (c) 2018 Shivaram Lingamneni
|
|
// released under the MIT license
|
|
|
|
package utils
|
|
|
|
import (
|
|
"context"
|
|
"log"
|
|
"runtime/debug"
|
|
"time"
|
|
)
|
|
|
|
// Semaphore is a counting semaphore.
|
|
// A semaphore of capacity 1 can be used as a trylock.
|
|
type Semaphore (chan empty)
|
|
|
|
// Initialize initializes a semaphore to a given capacity.
|
|
func (semaphore *Semaphore) Initialize(capacity int) {
|
|
*semaphore = make(chan empty, capacity)
|
|
}
|
|
|
|
// Acquire acquires a semaphore, blocking if necessary.
|
|
func (semaphore *Semaphore) Acquire() {
|
|
(*semaphore) <- empty{}
|
|
}
|
|
|
|
// TryAcquire tries to acquire a semaphore, returning whether the acquire was
|
|
// successful. It never blocks.
|
|
func (semaphore *Semaphore) TryAcquire() (acquired bool) {
|
|
select {
|
|
case (*semaphore) <- empty{}:
|
|
return true
|
|
default:
|
|
return false
|
|
}
|
|
}
|
|
|
|
// AcquireWithTimeout tries to acquire a semaphore, blocking for a maximum
|
|
// of approximately `d` while waiting for it. It returns whether the acquire
|
|
// was successful.
|
|
func (semaphore *Semaphore) AcquireWithTimeout(timeout time.Duration) (acquired bool) {
|
|
if timeout < 0 {
|
|
return semaphore.TryAcquire()
|
|
}
|
|
|
|
timer := time.NewTimer(timeout)
|
|
select {
|
|
case (*semaphore) <- empty{}:
|
|
acquired = true
|
|
case <-timer.C:
|
|
acquired = false
|
|
}
|
|
timer.Stop()
|
|
return
|
|
}
|
|
|
|
// AcquireWithContext tries to acquire a semaphore, blocking at most until
|
|
// the context expires. It returns whether the acquire was successful.
|
|
// Note that if the context is already expired, the acquire may succeed anyway.
|
|
func (semaphore *Semaphore) AcquireWithContext(ctx context.Context) (acquired bool) {
|
|
select {
|
|
case (*semaphore) <- empty{}:
|
|
acquired = true
|
|
case <-ctx.Done():
|
|
acquired = false
|
|
}
|
|
return
|
|
}
|
|
|
|
// Release releases a semaphore. It never blocks. (This is not a license
|
|
// to program spurious releases.)
|
|
func (semaphore *Semaphore) Release() {
|
|
select {
|
|
case <-(*semaphore):
|
|
// good
|
|
default:
|
|
// spurious release
|
|
log.Printf("spurious semaphore release (full to capacity %d)", cap(*semaphore))
|
|
debug.PrintStack()
|
|
}
|
|
}
|