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/*
*
* Copyright 2018 gRPC 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 grpc
import (
"container/list"
)
type linkedMapKVPair struct {
key string
value *stickyStoreEntry
}
// linkedMap is an implementation of a map that supports removing the oldest
// entry.
//
// linkedMap is NOT thread safe.
//
// It's for use of stickiness only!
type linkedMap struct {
m map[string]*list.Element
l *list.List // Head of the list is the oldest element.
}
// newLinkedMap returns a new LinkedMap.
func newLinkedMap() *linkedMap {
return &linkedMap{
m: make(map[string]*list.Element),
l: list.New(),
}
}
// put adds entry (key, value) to the map. Existing key will be overridden.
func (m *linkedMap) put(key string, value *stickyStoreEntry) {
if oldE, ok := m.m[key]; ok {
// Remove existing entry.
m.l.Remove(oldE)
}
e := m.l.PushBack(&linkedMapKVPair{key: key, value: value})
m.m[key] = e
}
// get returns the value of the given key.
func (m *linkedMap) get(key string) (*stickyStoreEntry, bool) {
e, ok := m.m[key]
if !ok {
return nil, false
}
m.l.MoveToBack(e)
return e.Value.(*linkedMapKVPair).value, true
}
// remove removes key from the map, and returns the value. The map is not
// modified if key is not in the map.
func (m *linkedMap) remove(key string) (*stickyStoreEntry, bool) {
e, ok := m.m[key]
if !ok {
return nil, false
}
delete(m.m, key)
m.l.Remove(e)
return e.Value.(*linkedMapKVPair).value, true
}
// len returns the len of the map.
func (m *linkedMap) len() int {
return len(m.m)
}
// clear removes all elements from the map.
func (m *linkedMap) clear() {
m.m = make(map[string]*list.Element)
m.l = list.New()
}
// removeOldest removes the oldest key from the map.
func (m *linkedMap) removeOldest() {
e := m.l.Front()
m.l.Remove(e)
delete(m.m, e.Value.(*linkedMapKVPair).key)
}
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