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lru_cache.go
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lru_cache.go
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// Copyright 2024 chenmingyong0423
// 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 lru
import (
"container/list"
"context"
cacheError "github.com/chenmingyong0423/go-generics-cache/error"
)
type entry[K comparable, V any] struct {
key K
value V
}
func NewCache[K comparable, V any](cap int) *Cache[K, V] {
return &Cache[K, V]{
maxEntries: cap,
cache: make(map[K]*list.Element, cap),
linkedDoublyList: list.New(),
}
}
type Cache[K comparable, V any] struct {
maxEntries int
cache map[K]*list.Element
linkedDoublyList *list.List
}
func (c *Cache[K, V]) Set(_ context.Context, key K, value V) error {
if e, ok := c.cache[key]; ok {
// 元素存在
c.linkedDoublyList.MoveToFront(e)
e.Value.(*entry[K, V]).value = value
return nil
}
// 元素不存在
e := &entry[K, V]{
key: key,
value: value,
}
c.cache[key] = c.linkedDoublyList.PushFront(e)
if c.linkedDoublyList.Len() > c.maxEntries {
// 删除最后一个元素
e := c.linkedDoublyList.Back()
c.linkedDoublyList.Remove(e)
delete(c.cache, e.Value.(*entry[K, V]).key)
}
return nil
}
func (c *Cache[K, V]) Get(_ context.Context, key K) (v V, err error) {
if e, ok := c.cache[key]; ok {
c.linkedDoublyList.MoveToFront(e)
e := e.Value.(*entry[K, V])
return e.value, nil
}
return v, cacheError.ErrNoKey
}
func (c *Cache[K, V]) Delete(_ context.Context, key K) error {
if e, ok := c.cache[key]; ok {
c.linkedDoublyList.Remove(e)
delete(c.cache, key)
return nil
}
return cacheError.ErrNoKey
}
func (c *Cache[K, V]) Keys() []K {
keys := make([]K, 0)
// 根据添加顺序返回
for e := c.linkedDoublyList.Back(); e != nil; e = e.Prev() {
keys = append(keys, e.Value.(*entry[K, V]).key)
}
return keys
}