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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 <list>
#include <map>
#include <unordered_map>
#include <utility>
#include "common/ceph_mutex.h"
template <class K, class V, class C = std::less<K>, class H = std::hash<K> >
class SimpleLRU {
ceph::mutex lock = ceph::make_mutex("SimpleLRU::lock");
size_t max_size;
size_t max_bytes = 0;
size_t total_bytes = 0;
std::unordered_map<K, typename std::list<std::pair<K, V>>::iterator, H> contents;
std::list<std::pair<K, V> > lru;
std::map<K, V, C> pinned;
void trim_cache() {
while (contents.size() > max_size) {
contents.erase(lru.back().first);
lru.pop_back();
}
}
void trim_cache_bytes() {
while(total_bytes > max_bytes) {
total_bytes -= lru.back().second.length();
contents.erase(lru.back().first);
lru.pop_back();
}
}
void _add(K key, V&& value) {
lru.emplace_front(key, std::move(value)); // can't move key because we access it below
contents[key] = lru.begin();
trim_cache();
}
void _add_bytes(K key, V&& value) {
lru.emplace_front(key, std::move(value)); // can't move key because we access it below
contents[key] = lru.begin();
trim_cache_bytes();
}
public:
SimpleLRU(size_t max_size) : max_size(max_size) {
contents.rehash(max_size);
}
void pin(K key, V val) {
std::lock_guard l(lock);
pinned.emplace(std::move(key), std::move(val));
}
void clear_pinned(K e) {
std::lock_guard l(lock);
for (auto i = pinned.begin();
i != pinned.end() && i->first <= e;
pinned.erase(i++)) {
auto iter = contents.find(i->first);
if (iter == contents.end())
_add(i->first, std::move(i->second));
else
lru.splice(lru.begin(), lru, iter->second);
}
}
void clear(K key) {
std::lock_guard l(lock);
auto i = contents.find(key);
if (i == contents.end())
return;
total_bytes -= i->second->second.length();
lru.erase(i->second);
contents.erase(i);
}
void set_size(size_t new_size) {
std::lock_guard l(lock);
max_size = new_size;
trim_cache();
}
size_t get_size() {
std::lock_guard l(lock);
return contents.size();
}
void set_bytes(size_t num_bytes) {
std::lock_guard l(lock);
max_bytes = num_bytes;
trim_cache_bytes();
}
size_t get_bytes() {
std::lock_guard l(lock);
return total_bytes;
}
bool lookup(K key, V *out) {
std::lock_guard l(lock);
auto i = contents.find(key);
if (i != contents.end()) {
*out = i->second->second;
lru.splice(lru.begin(), lru, i->second);
return true;
}
auto i_pinned = pinned.find(key);
if (i_pinned != pinned.end()) {
*out = i_pinned->second;
return true;
}
return false;
}
void add(K key, V value) {
std::lock_guard l(lock);
_add(std::move(key), std::move(value));
}
void add_bytes(K key, V value) {
std::lock_guard l(lock);
total_bytes += value.length();
_add_bytes(std::move(key), std::move(value));
}
};
#endif
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