mirror of https://github.com/perkeep/perkeep.git
44 lines
1.1 KiB
Go
44 lines
1.1 KiB
Go
|
/*
|
||
|
|
Copyright 2013 Google Inc.
|
||
|
|
|
||
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
you may not use this file except in compliance with the License.
|
||
|
|
You may obtain a copy of the License at
|
||
|
|
|
||
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
|
||
|
|
Unless required by applicable law or agreed to in writing, software
|
||
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
See the License for the specific language governing permissions and
|
||
|
|
limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
// Package gate provides a mechanism to control a maximum number of
|
||
|
|
// operations happening at once.
|
||
|
|
package gate
|
||
|
|
|
||
|
|
// A Gate limits concurrency.
|
||
|
|
type Gate struct {
|
||
|
|
c chan struct{}
|
||
|
|
}
|
||
|
|
|
||
|
|
// New returns a new gate that will only permit max operations at once.
|
||
|
|
func New(max int) *Gate {
|
||
|
|
return &Gate{make(chan struct{}, max)}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Start starts an operation, blocking until the gate has room.
|
||
|
|
func (g *Gate) Start() {
|
||
|
|
g.c <- struct{}{}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Done finishes an operation.
|
||
|
|
func (g *Gate) Done() {
|
||
|
|
select {
|
||
|
|
case <-g.c:
|
||
|
|
default:
|
||
|
|
panic("Done called more than Start")
|
||
|
|
}
|
||
|
|
}
|