73 lines
1.9 KiB
Go
73 lines
1.9 KiB
Go
|
// Copyright 2014, Google Inc. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
|
||
|
|
package pools
|
||
|
|
|
||
|
|
import (
|
||
|
|
"fmt"
|
||
|
|
"sync"
|
||
|
|
)
|
||
|
|
|
||
|
|
// IDPool is used to ensure that the set of IDs in use concurrently never
|
||
|
|
// contains any duplicates. The IDs start at 1 and increase without bound, but
|
||
|
|
// will never be larger than the peak number of concurrent uses.
|
||
|
|
//
|
||
|
|
// IDPool's Get() and Set() methods can be used concurrently.
|
||
|
|
type IDPool struct {
|
||
|
|
sync.Mutex
|
||
|
|
|
||
|
|
// used holds the set of values that have been returned to us with Put().
|
||
|
|
used map[uint32]bool
|
||
|
|
// maxUsed remembers the largest value we've given out.
|
||
|
|
maxUsed uint32
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewIDPool creates and initializes an IDPool.
|
||
|
|
func NewIDPool() *IDPool {
|
||
|
|
return &IDPool{
|
||
|
|
used: make(map[uint32]bool),
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Get returns an ID that is unique among currently active users of this pool.
|
||
|
|
func (pool *IDPool) Get() (id uint32) {
|
||
|
|
pool.Lock()
|
||
|
|
defer pool.Unlock()
|
||
|
|
|
||
|
|
// Pick a value that's been returned, if any.
|
||
|
|
for key, _ := range pool.used {
|
||
|
|
delete(pool.used, key)
|
||
|
|
return key
|
||
|
|
}
|
||
|
|
|
||
|
|
// No recycled IDs are available, so increase the pool size.
|
||
|
|
pool.maxUsed += 1
|
||
|
|
return pool.maxUsed
|
||
|
|
}
|
||
|
|
|
||
|
|
// Put recycles an ID back into the pool for others to use. Putting back a value
|
||
|
|
// or 0, or a value that is not currently "checked out", will result in a panic
|
||
|
|
// because that should never happen except in the case of a programming error.
|
||
|
|
func (pool *IDPool) Put(id uint32) {
|
||
|
|
pool.Lock()
|
||
|
|
defer pool.Unlock()
|
||
|
|
|
||
|
|
if id < 1 || id > pool.maxUsed {
|
||
|
|
panic(fmt.Errorf("IDPool.Put(%v): invalid value, must be in the range [1,%v]", id, pool.maxUsed))
|
||
|
|
}
|
||
|
|
|
||
|
|
if pool.used[id] {
|
||
|
|
panic(fmt.Errorf("IDPool.Put(%v): can't put value that was already recycled", id))
|
||
|
|
}
|
||
|
|
|
||
|
|
// If we're recycling maxUsed, just shrink the pool.
|
||
|
|
if id == pool.maxUsed {
|
||
|
|
pool.maxUsed = id - 1
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
// Add it to the set of recycled IDs.
|
||
|
|
pool.used[id] = true
|
||
|
|
}
|