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/* Copyright (C) 2021 Nicolas Peugnet <n.peugnet@free.fr>
This file is part of dna-backup.
dna-backup is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
dna-backup is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with dna-backup. If not, see <https://www.gnu.org/licenses/>. */
package cache
import "sync"
type Cacher interface {
Get(key interface{}) (value []byte, exists bool)
Set(key interface{}, value []byte)
Len() int
}
type FifoCache struct {
head, tail *fifoCacheEntry
data map[interface{}][]byte
capacity int
mutex sync.RWMutex
}
type fifoCacheEntry struct {
Key interface{}
Next *fifoCacheEntry
}
func NewFifoCache(capacity int) *FifoCache {
return &FifoCache{data: make(map[interface{}][]byte, capacity), capacity: capacity}
}
func (c *FifoCache) Get(key interface{}) (value []byte, exists bool) {
c.mutex.RLock()
defer c.mutex.RUnlock()
value, exists = c.data[key]
return
}
func (c *FifoCache) Set(key interface{}, value []byte) {
c.mutex.Lock()
defer c.mutex.Unlock()
if len(c.data) == c.capacity {
// Evict first entry
evicted := c.head
c.head = evicted.Next
delete(c.data, evicted.Key)
}
entry := &fifoCacheEntry{Key: key}
if c.head == nil {
c.head = entry
}
if c.tail == nil {
c.tail = entry
} else {
c.tail.Next = entry
c.tail = entry
}
c.data[key] = value
}
func (c *FifoCache) Len() int {
return len(c.data)
}
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