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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#ifndef CEPH_SIMPLECACHE_H
#define CEPH_SIMPLECACHE_H
#include <map>
#include <list>
#include <memory>
#include "common/Mutex.h"
#include "common/Cond.h"
template <class K, class V>
class SimpleLRU {
Mutex lock;
size_t max_size;
map<K, typename list<pair<K, V> >::iterator> contents;
list<pair<K, V> > lru;
map<K, V> pinned;
void trim_cache() {
while (lru.size() > max_size) {
contents.erase(lru.back().first);
lru.pop_back();
}
}
void _add(K key, V value) {
lru.push_front(make_pair(key, value));
contents[key] = lru.begin();
trim_cache();
}
public:
SimpleLRU(size_t max_size) : lock("SimpleLRU::lock"), max_size(max_size) {}
void pin(K key, V val) {
Mutex::Locker l(lock);
pinned.insert(make_pair(key, val));
}
void clear_pinned() {
Mutex::Locker l(lock);
for (typename map<K, V>::iterator i = pinned.begin();
i != pinned.end();
++i) {
if (!contents.count(i->first))
_add(i->first, i->second);
else
lru.splice(lru.begin(), lru, contents[i->first]);
}
pinned.clear();
}
void set_size(size_t new_size) {
Mutex::Locker l(lock);
max_size = new_size;
trim_cache();
}
bool lookup(K key, V *out) {
Mutex::Locker l(lock);
typename list<pair<K, V> >::iterator loc = contents.count(key) ?
contents[key] : lru.end();
if (loc != lru.end()) {
*out = loc->second;
lru.splice(lru.begin(), lru, loc);
return true;
}
if (pinned.count(key)) {
*out = pinned[key];
return true;
}
return false;
}
void add(K key, V value) {
Mutex::Locker l(lock);
_add(key, value);
}
};
#endif
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