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// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package cache
import (
"sync"
"unsafe"
)
type lruNode struct {
n *Node
h *Handle
ban bool
next, prev *lruNode
}
func (n *lruNode) insert(at *lruNode) {
x := at.next
at.next = n
n.prev = at
n.next = x
x.prev = n
}
func (n *lruNode) remove() {
if n.prev != nil {
n.prev.next = n.next
n.next.prev = n.prev
n.prev = nil
n.next = nil
} else {
panic("BUG: removing removed node")
}
}
type lru struct {
mu sync.Mutex
capacity int
used int
recent lruNode
}
func (r *lru) reset() {
r.recent.next = &r.recent
r.recent.prev = &r.recent
r.used = 0
}
func (r *lru) Capacity() int {
r.mu.Lock()
defer r.mu.Unlock()
return r.capacity
}
func (r *lru) SetCapacity(capacity int) {
var evicted []*lruNode
r.mu.Lock()
r.capacity = capacity
for r.used > r.capacity {
rn := r.recent.prev
if rn == nil {
panic("BUG: invalid LRU used or capacity counter")
}
rn.remove()
rn.n.CacheData = nil
r.used -= rn.n.Size()
evicted = append(evicted, rn)
}
r.mu.Unlock()
for _, rn := range evicted {
rn.h.Release()
}
}
func (r *lru) Promote(n *Node) {
var evicted []*lruNode
r.mu.Lock()
if n.CacheData == nil {
if n.Size() <= r.capacity {
rn := &lruNode{n: n, h: n.GetHandle()}
rn.insert(&r.recent)
n.CacheData = unsafe.Pointer(rn)
r.used += n.Size()
for r.used > r.capacity {
rn := r.recent.prev
if rn == nil {
panic("BUG: invalid LRU used or capacity counter")
}
rn.remove()
rn.n.CacheData = nil
r.used -= rn.n.Size()
evicted = append(evicted, rn)
}
}
} else {
rn := (*lruNode)(n.CacheData)
if !rn.ban {
rn.remove()
rn.insert(&r.recent)
}
}
r.mu.Unlock()
for _, rn := range evicted {
rn.h.Release()
}
}
func (r *lru) Ban(n *Node) {
r.mu.Lock()
if n.CacheData == nil {
n.CacheData = unsafe.Pointer(&lruNode{n: n, ban: true})
} else {
rn := (*lruNode)(n.CacheData)
if !rn.ban {
rn.remove()
rn.ban = true
r.used -= rn.n.Size()
r.mu.Unlock()
rn.h.Release()
rn.h = nil
return
}
}
r.mu.Unlock()
}
func (r *lru) Evict(n *Node) {
r.mu.Lock()
rn := (*lruNode)(n.CacheData)
if rn == nil || rn.ban {
r.mu.Unlock()
return
}
n.CacheData = nil
r.mu.Unlock()
rn.h.Release()
}
func (r *lru) EvictNS(ns uint64) {
var evicted []*lruNode
r.mu.Lock()
for e := r.recent.prev; e != &r.recent; {
rn := e
e = e.prev
if rn.n.NS() == ns {
rn.remove()
rn.n.CacheData = nil
r.used -= rn.n.Size()
evicted = append(evicted, rn)
}
}
r.mu.Unlock()
for _, rn := range evicted {
rn.h.Release()
}
}
func (r *lru) EvictAll() {
r.mu.Lock()
back := r.recent.prev
for rn := back; rn != &r.recent; rn = rn.prev {
rn.n.CacheData = nil
}
r.reset()
r.mu.Unlock()
for rn := back; rn != &r.recent; rn = rn.prev {
rn.h.Release()
}
}
func (r *lru) Close() error {
return nil
}
// NewLRU create a new LRU-cache.
func NewLRU(capacity int) Cacher {
r := &lru{capacity: capacity}
r.reset()
return r
}
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