mirror of
https://github.com/caddyserver/caddy.git
synced 2024-11-26 02:09:47 +08:00
95 lines
2.9 KiB
Go
95 lines
2.9 KiB
Go
// Copyright 2015 Matthew Holt and The Caddy 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.
|
|
|
|
package caddy
|
|
|
|
import (
|
|
"fmt"
|
|
"sync"
|
|
"sync/atomic"
|
|
)
|
|
|
|
// UsagePool is a thread-safe map that pools values
|
|
// based on usage; a LoadOrStore operation increments
|
|
// the usage, and a Delete decrements from the usage.
|
|
// If the usage count reaches 0, the value will be
|
|
// removed from the map. There is no way to overwrite
|
|
// existing keys in the pool without first deleting
|
|
// it as many times as it was stored. Deleting too
|
|
// many times will panic.
|
|
//
|
|
// An empty UsagePool is NOT safe to use; always call
|
|
// NewUsagePool() to make a new value.
|
|
type UsagePool struct {
|
|
pool *sync.Map
|
|
}
|
|
|
|
// NewUsagePool returns a new usage pool.
|
|
func NewUsagePool() *UsagePool {
|
|
return &UsagePool{pool: new(sync.Map)}
|
|
}
|
|
|
|
// Delete decrements the usage count for key and removes the
|
|
// value from the underlying map if the usage is 0. It returns
|
|
// true if the usage count reached 0 and the value was deleted.
|
|
// It panics if the usage count drops below 0; always call
|
|
// Delete precisely as many times as LoadOrStore.
|
|
func (up *UsagePool) Delete(key interface{}) (deleted bool) {
|
|
usageVal, ok := up.pool.Load(key)
|
|
if !ok {
|
|
return false
|
|
}
|
|
upv := usageVal.(*usagePoolVal)
|
|
newUsage := atomic.AddInt32(&upv.usage, -1)
|
|
if newUsage == 0 {
|
|
up.pool.Delete(key)
|
|
return true
|
|
} else if newUsage < 0 {
|
|
panic(fmt.Sprintf("deleted more than stored: %#v (usage: %d)",
|
|
upv.value, upv.usage))
|
|
}
|
|
return false
|
|
}
|
|
|
|
// LoadOrStore puts val in the pool and returns false if key does
|
|
// not already exist; otherwise if the key exists, it loads the
|
|
// existing value, increments the usage for that value, and returns
|
|
// the value along with true.
|
|
func (up *UsagePool) LoadOrStore(key, val interface{}) (actual interface{}, loaded bool) {
|
|
usageVal := &usagePoolVal{
|
|
usage: 1,
|
|
value: val,
|
|
}
|
|
actual, loaded = up.pool.LoadOrStore(key, usageVal)
|
|
if loaded {
|
|
upv := actual.(*usagePoolVal)
|
|
actual = upv.value
|
|
atomic.AddInt32(&upv.usage, 1)
|
|
}
|
|
return
|
|
}
|
|
|
|
// Range iterates the pool the same way sync.Map.Range does.
|
|
// This does not affect usage counts.
|
|
func (up *UsagePool) Range(f func(key, value interface{}) bool) {
|
|
up.pool.Range(func(key, value interface{}) bool {
|
|
return f(key, value.(*usagePoolVal).value)
|
|
})
|
|
}
|
|
|
|
type usagePoolVal struct {
|
|
usage int32 // accessed atomically; must be 64-bit aligned for 32-bit systems
|
|
value interface{}
|
|
}
|