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/*
Copyright (C) 2009 Red Hat, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _H_SHARED_CACHE
#define _H_SHARED_CACHE
#include "utils.h"
#include "threads.h"
/*class SharedCache::Treat {
T* get(T*);
void release(T*);
const char* name();
};*/
template <class T, class Treat, int HASH_SIZE, class Base = EmptyBase>
class SharedCache : public Base {
public:
SharedCache()
: _aborting (false)
{
memset(_hash, 0, sizeof(_hash));
}
~SharedCache()
{
clear();
}
void add(uint64_t id, T* data, bool is_lossy = FALSE)
{
Lock lock(_lock);
Item** item = &_hash[key(id)];
while (*item) {
if ((*item)->id == id) {
(*item)->refs++;
return;
}
item = &(*item)->next;
}
*item = new Item(id, data, is_lossy);
_new_item_cond.notify_all();
}
T* get(uint64_t id)
{
Lock lock(_lock);
Item* item = _hash[key(id)];
for (;;) {
if (!item) {
if (_aborting) {
THROW("%s aborting", Treat::name());
}
_new_item_cond.wait(lock);
item = _hash[key(id)];
continue;
}
if (item->id != id) {
item = item->next;
continue;
}
return Treat::get(item->data);
}
}
T* get_lossless(uint64_t id)
{
Lock lock(_lock);
Item* item = _hash[key(id)];
for (;;) {
if (!item) {
if (_aborting) {
THROW("%s aborting", Treat::name());
}
_new_item_cond.wait(lock);
item = _hash[key(id)];
continue;
}
if (item->id != id) {
item = item->next;
continue;
}
break;
}
// item has been retreived. Now checking if lossless
for (;;) {
if (item->lossy) {
if (_aborting) {
THROW("%s aborting", Treat::name());
}
_replace_data_cond.wait(lock);
continue;
}
return Treat::get(item->data);
}
}
void replace(uint64_t id, T* data, bool is_lossy = FALSE)
{
Lock lock(_lock);
Item* item = _hash[key(id)];
for (;;) {
if (!item) {
if (_aborting) {
THROW("%s aborting", Treat::name());
}
_new_item_cond.wait(lock);
item = _hash[key(id)];
continue;
}
if (item->id != id) {
item = item->next;
continue;
}
item->replace(data, is_lossy);
break;
}
_replace_data_cond.notify_all();
}
void remove(uint64_t id)
{
Lock lock(_lock);
Item** item = &_hash[key(id)];
while (*item) {
if ((*item)->id == id) {
if (!--(*item)->refs) {
Item *rm_item = *item;
*item = rm_item->next;
delete rm_item;
}
return;
}
item = &(*item)->next;
}
THROW("%s id %lu, not found", Treat::name(), id);
}
void clear()
{
Lock lock(_lock);
for (int i = 0; i < HASH_SIZE; i++) {
while (_hash[i]) {
Item *item = _hash[i];
_hash[i] = item->next;
delete item;
}
}
}
void abort()
{
Lock lock(_lock);
_aborting = true;
_new_item_cond.notify_all();
}
private:
inline uint32_t key(uint64_t id) {return uint32_t(id) % HASH_SIZE;}
private:
class Item {
public:
Item(uint64_t in_id, T* data, bool is_lossy = FALSE)
: id (in_id)
, refs (1)
, next (NULL)
, data (Treat::get(data))
, lossy (is_lossy) {}
~Item()
{
Treat::release(data);
}
void replace(T* new_data, bool is_lossy = FALSE)
{
Treat::release(data);
data = Treat::get(new_data);
lossy = is_lossy;
}
uint64_t id;
int refs;
Item* next;
T* data;
bool lossy;
};
Item* _hash[HASH_SIZE];
Mutex _lock;
Condition _new_item_cond;
Condition _replace_data_cond;
bool _aborting;
};
#endif
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