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/*
* cache.h (C) 2008, Aurélien Croc (AP²C)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the
* Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* $Id: cache.h 141 2008-02-01 00:10:50Z ap2c $
*
*/
#ifndef _CACHE_H_
#define _CACHE_H_
class Page;
/**
* List all the different cache policy available.
*/
enum CachePolicy {
/** All pages are needed with page number increasing. */
EveryPagesIncreasing,
/** Only even pages are needed with page number decreasing. */
EvenDecreasing,
/** Only odd pages are needed with page number increasing. */
OddIncreasing,
};
/**
* Initialize the cache mechanism and load the cache controller thread.
* @return TRUE if the initialization succeed. Otherwise it returns FALSE.
*/
extern bool initializeCache();
/**
* Uninitialize the cache mechanism and unload the cache controller thread.
* @return TRUE if the uninitialization succeed. Otherwise it returns FALSE.
*/
extern bool uninitializeCache();
/**
* Extract the next page (depending on the curernt cache policy)
* @return the instance of the page. Otherwise it returns NULL if no page are
* found.
*/
extern Page* getNextPage();
/**
* Register a new page in the cache.
* @param page the page instance to register in the cache
*/
extern void registerPage(Page* page);
/**
* Set the new cache policy.
* @param policy the new cache policy
*/
extern void setCachePolicy(CachePolicy policy);
/**
* Set the number of pages in the document.
* @param nr the number of pages
*/
extern void setNumberOfPages(unsigned long nr);
/**
* @brief This class represent a cache entry to store a page.
* To preserve memory a swapping mechanism is present.
*/
class CacheEntry {
protected:
Page* _page;
CacheEntry* _previous;
CacheEntry* _next;
char* _tempFile;
public:
/**
* Initialize the cache entry instance.
* @param page the page instance associated to this entry.
*/
CacheEntry(Page* page);
/**
* Destroy the cache entry instance.
*/
virtual ~CacheEntry();
public:
/**
* Set the next cache entry.
* @param entry the next cache entry
*/
void setNext(CacheEntry *entry) {_next = entry;}
/**
* Set the previous cache entry.
* @param entry the previous cache entry
*/
void setPrevious(CacheEntry *entry)
{_previous = entry;}
/**
* Swap the page instance on the disk.
* @return TRUE if the page has been successfully swapped. Otherwise it
* returns FALSE.
*/
bool swapToDisk();
/**
* Restore a previously swapped page into memory.
* @return TRUE if the page has been successfully restored. Otherwise
* it returns FALSE.
*/
bool restoreIntoMemory();
/**
* @return the page instance.
*/
Page* page() const {return _page;}
/**
* @return the next instance.
*/
CacheEntry* next() const {return _next;}
/**
* @return the previous instance.
*/
CacheEntry* previous() const {return _previous;}
/**
* @return TRUE if the page is currently swapped on disk. Otherwise
* returns FALSE.
*/
bool isSwapped() const
{return _tempFile ? true : false;}
};
#endif /* _CACHE_H_ */
/* vim: set expandtab tabstop=4 shiftwidth=4 smarttab tw=80 cin enc=utf8: */
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