/*** 2001 September 15**** The author disclaims copyright to this source code.  In place of** a legal notice, here is a blessing:****    May you do good and not evil.**    May you find forgiveness for yourself and forgive others.**    May you share freely, never taking more than you give.***************************************************************************** This header file defines the interface that the sqlite page cache** subsystem.  The page cache subsystem reads and writes a file a page** at a time and provides a journal for rollback.**** @(#) $Id: pager.h,v 1.26 2004/02/11 02:18:07 drh Exp $*//*** The size of one page**** You can change this value to another (reasonable) value you want.** It need not be a power of two, though the interface to the disk** will likely be faster if it is.**** Experiments show that a page size of 1024 gives the best speed** for common usages.  The speed differences for different sizes** such as 512, 2048, 4096, an so forth, is minimal.  Note, however,** that changing the page size results in a completely imcompatible** file format.*/#ifndef SQLITE_PAGE_SIZE#define SQLITE_PAGE_SIZE 1024#endif/*** Number of extra bytes of data allocated at the end of each page and** stored on disk but not used by the higher level btree layer.  Changing** this value results in a completely incompatible file format.*/#ifndef SQLITE_PAGE_RESERVE#define SQLITE_PAGE_RESERVE 0#endif/*** The total number of usable bytes stored on disk for each page.** The usable bytes come at the beginning of the page and the reserve** bytes come at the end.*/#define SQLITE_USABLE_SIZE (SQLITE_PAGE_SIZE-SQLITE_PAGE_RESERVE)/*** Maximum number of pages in one database.  (This is a limitation of** imposed by 4GB files size limits.)*/#define SQLITE_MAX_PAGE 1073741823/*** The type used to represent a page number.  The first page in a file** is called page 1.  0 is used to represent "not a page".*/typedef unsigned int Pgno;/*** Each open file is managed by a separate instance of the "Pager" structure.*/typedef struct Pager Pager;/*** See source code comments for a detailed description of the following** routines:*/int sqlitepager_open(Pager **ppPager, const char *zFilename,                     int nPage, int nExtra, int useJournal);void sqlitepager_set_destructor(Pager*, void(*)(void*));void sqlitepager_set_cachesize(Pager*, int);int sqlitepager_close(Pager *pPager);int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage);void *sqlitepager_lookup(Pager *pPager, Pgno pgno);int sqlitepager_ref(void*);int sqlitepager_unref(void*);Pgno sqlitepager_pagenumber(void*);int sqlitepager_write(void*);int sqlitepager_iswriteable(void*);int sqlitepager_overwrite(Pager *pPager, Pgno pgno, void*);int sqlitepager_pagecount(Pager*);int sqlitepager_truncate(Pager*,Pgno);int sqlitepager_begin(void*);int sqlitepager_commit(Pager*);int sqlitepager_rollback(Pager*);int sqlitepager_isreadonly(Pager*);int sqlitepager_ckpt_begin(Pager*);int sqlitepager_ckpt_commit(Pager*);int sqlitepager_ckpt_rollback(Pager*);void sqlitepager_dont_rollback(void*);void sqlitepager_dont_write(Pager*, Pgno);int *sqlitepager_stats(Pager*);void sqlitepager_set_safety_level(Pager*,int);const char *sqlitepager_filename(Pager*);int sqlitepager_rename(Pager*, const char *zNewName);void sqlitepager_set_codec(Pager*,void(*)(void*,void*,Pgno,int),void*);#ifdef SQLITE_TESTvoid sqlitepager_refdump(Pager*);int pager_refinfo_enable;int journal_format;#endif