diff options
Diffstat (limited to 'Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru.go')
-rw-r--r-- | Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru.go | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru.go new file mode 100644 index 000000000..d9a84cde1 --- /dev/null +++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru.go @@ -0,0 +1,195 @@ +// 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 +} |