/
concurrent_limiter.go
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/
concurrent_limiter.go
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// Copyright (C) 2020-2021, IrineSistiana
//
// This file is part of mosdns.
//
// mosdns is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// mosdns is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package concurrent_limiter
import (
"fmt"
"sync/atomic"
)
// ConcurrentLimiter is a soft limiter.
type ConcurrentLimiter struct {
running int32
bucket chan struct{}
}
// NewConcurrentLimiter returns a ConcurrentLimiter, max must > 0.
func NewConcurrentLimiter(max int) *ConcurrentLimiter {
if max <= 0 {
panic(fmt.Sprintf("ConcurrentLimiter: invalid max arg: %d", max))
}
bucket := make(chan struct{}, max)
return &ConcurrentLimiter{bucket: bucket}
}
func (l *ConcurrentLimiter) Wait() chan<- struct{} {
r := atomic.AddInt32(&l.running, 1)
if r < 0 {
panic("ConcurrentLimiter: running overflow")
}
return l.bucket
}
func (l *ConcurrentLimiter) Done() {
r := atomic.AddInt32(&l.running, -1)
if r < 0 {
panic("ConcurrentLimiter: running overflow")
}
select {
case <-l.bucket:
default:
panic("ConcurrentLimiter: bucket overflow")
}
}
func (l *ConcurrentLimiter) Available() int {
return cap(l.bucket) - len(l.bucket)
}
func (l *ConcurrentLimiter) Running() int32 {
return atomic.LoadInt32(&l.running)
}