91 lines
1.7 KiB
Go
91 lines
1.7 KiB
Go
// Copyright 2019 The Prometheus Authors
|
|
// 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.
|
|
//
|
|
// Inspired / copied / modified from https://gitlab.com/cznic/strutil/blob/master/strutil.go,
|
|
// which is MIT licensed, so:
|
|
//
|
|
// Copyright (c) 2014 The strutil Authors. All rights reserved.
|
|
|
|
package remote
|
|
|
|
import (
|
|
"sync"
|
|
"sync/atomic"
|
|
)
|
|
|
|
var interner = newPool()
|
|
|
|
type pool struct {
|
|
mtx sync.RWMutex
|
|
pool map[string]*entry
|
|
}
|
|
|
|
type entry struct {
|
|
s string
|
|
refs int64
|
|
}
|
|
|
|
func newPool() *pool {
|
|
return &pool{
|
|
pool: map[string]*entry{},
|
|
}
|
|
}
|
|
|
|
func (p *pool) intern(s string) string {
|
|
if s == "" {
|
|
return ""
|
|
}
|
|
|
|
p.mtx.RLock()
|
|
interned, ok := p.pool[s]
|
|
p.mtx.RUnlock()
|
|
if ok {
|
|
atomic.AddInt64(&interned.refs, 1)
|
|
return interned.s
|
|
}
|
|
p.mtx.Lock()
|
|
defer p.mtx.Unlock()
|
|
if interned, ok := p.pool[s]; ok {
|
|
atomic.AddInt64(&interned.refs, 1)
|
|
return interned.s
|
|
}
|
|
|
|
p.pool[s] = &entry{
|
|
s: s,
|
|
refs: 1,
|
|
}
|
|
return s
|
|
}
|
|
|
|
func (p *pool) release(s string) {
|
|
p.mtx.RLock()
|
|
interned, ok := p.pool[s]
|
|
p.mtx.RUnlock()
|
|
|
|
if !ok {
|
|
panic("released unknown string")
|
|
}
|
|
|
|
refs := atomic.AddInt64(&interned.refs, -1)
|
|
if refs > 0 {
|
|
return
|
|
}
|
|
|
|
p.mtx.Lock()
|
|
defer p.mtx.Unlock()
|
|
if atomic.LoadInt64(&interned.refs) != 0 {
|
|
return
|
|
}
|
|
delete(p.pool, s)
|
|
}
|