SQLite

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.225 2005/12/18 08:51:23 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  int nRead,nWrite;           /* Database pages read/written */
#endif
  void (*xDestructor)(void*,int); /* Call this routine when freeing pages */
  void (*xReiniter)(void*,int);   /* Call this routine when reloading pages */
  void (*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
  void *pCodecArg;            /* First argument to xCodec() */
  PgHdr *aHash[N_PG_HASH];    /* Hash table to map page number to PgHdr */
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  Pager *pNext;               /* Linked list of pagers in this thread */
#endif
};

/*
** If SQLITE_TEST is defined then increment the variable given in
** the argument
*/
#ifdef SQLITE_TEST

  int i;
  int tempFile = 0;
  int memDb = 0;
  int readOnly = 0;
  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
  char zTemp[SQLITE_TEMPNAME_SIZE];
  SqliteTsd *pTsd = sqlite3Tsd();

  *ppPager = 0;
  memset(&fd, 0, sizeof(fd));
  if( sqlite3Tsd()->mallocFailed ){
    return SQLITE_NOMEM;
  }
  if( zFilename && zFilename[0] ){

  pPager->pFirstSynced = 0;
  pPager->pLast = 0;
  pPager->nExtra = FORCE_ALIGNMENT(nExtra);
  pPager->sectorSize = PAGER_SECTOR_SIZE;
  pPager->pBusyHandler = 0;
  memset(pPager->aHash, 0, sizeof(pPager->aHash));
  *ppPager = pPager;
  pPager->pNext = pTsd->pPager;
  pTsd->pPager = pPager;
  return SQLITE_OK;
}

/*
** Set the busy handler function.
*/
void sqlite3pager_set_busyhandler(Pager *pPager, BusyHandler *pBusyHandler){

** transaction is rolled back.  All outstanding pages are invalidated
** and their memory is freed.  Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
*/
int sqlite3pager_close(Pager *pPager){
  PgHdr *pPg, *pNext;
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  SqliteTsd *pTsd = sqlite3Tsd();
#endif

  switch( pPager->state ){
    case PAGER_RESERVED:
    case PAGER_SYNCED: 
    case PAGER_EXCLUSIVE: {
      /* We ignore any IO errors that occur during the rollback
      ** operation. So disable IO error simulation so that testing
      ** works more easily.

  }
  sqlite3OsClose(&pPager->fd);
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3Os.xDelete(pPager->zFilename);
  ** }
  */

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  if( pPager==pTsd->pPager ){
    pTsd->pPager = pPager->pNext;
  }else{
    Pager *pTmp;
    for(pTmp = pTsd->pPager; pTmp->pNext!=pPager; pTmp=pTmp->pNext);
    pTmp->pNext = pPager->pNext;
  }
#endif

  sqliteFree(pPager);
  return SQLITE_OK;
}

/*
** Return the page number for the given page data.

  if( sqlite3pager_pagecount(pPager)==0 ){
    sqlite3Os.xDelete(pPager->zJournal);
    return 0;
  }else{
    return 1;
  }
}

static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
  PgHdr *pPg;
  *ppPg = 0;

  /* Find a page to recycle.  Try to locate a page that does not
  ** require us to do an fsync() on the journal.
  */
  pPg = pPager->pFirstSynced;

  /* If we could not find a page that does not require an fsync()
  ** on the journal file then fsync the journal file.  This is a
  ** very slow operation, so we work hard to avoid it.  But sometimes
  ** it can't be helped.
  */
  if( pPg==0 && syncOk ){
    int rc = syncJournal(pPager);
    if( rc!=0 ){
      sqlite3pager_rollback(pPager);
      return SQLITE_IOERR;
    }
    if( pPager->fullSync ){
      /* If in full-sync mode, write a new journal header into the
      ** journal file. This is done to avoid ever modifying a journal
      ** header that is involved in the rollback of pages that have
      ** already been written to the database (in case the header is
      ** trashed when the nRec field is updated).
      */
      pPager->nRec = 0;
      assert( pPager->journalOff > 0 );
      rc = writeJournalHdr(pPager);
      if( rc!=0 ){
        sqlite3pager_rollback(pPager);
        return SQLITE_IOERR;
      }
    }
    pPg = pPager->pFirst;
  }
  if( pPg==0 ){
    return SQLITE_OK;
  }

  assert( pPg->nRef==0 );

  /* Write the page to the database file if it is dirty.
  */
  if( pPg->dirty ){
    int rc;
    assert( pPg->needSync==0 );
    pPg->pDirty = 0;
    rc = pager_write_pagelist( pPg );
    if( rc!=SQLITE_OK ){
      sqlite3pager_rollback(pPager);
      return SQLITE_IOERR;
    }
  }
  assert( pPg->dirty==0 );

  /* If the page we are recycling is marked as alwaysRollback, then
  ** set the global alwaysRollback flag, thus disabling the
  ** sqlite_dont_rollback() optimization for the rest of this transaction.
  ** It is necessary to do this because the page marked alwaysRollback
  ** might be reloaded at a later time but at that point we won't remember
  ** that is was marked alwaysRollback.  This means that all pages must
  ** be marked as alwaysRollback from here on out.
  */
  if( pPg->alwaysRollback ){
    pPager->alwaysRollback = 1;
  }

  /* Unlink the old page from the free list and the hash table
  */
  unlinkPage(pPg);
  TEST_INCR(pPager->nOvfl);

  *ppPg = pPg;
  return SQLITE_OK;
}

/*
** This function is called to free superfluous dynamically allocated memory
** held by the pager system. Memory in use by any SQLite pager allocated
** by the current thread may be sqliteFree()ed.
**
** nReq is the number of bytes of memory required. Once this much has
** been released, the function returns. The return value is the total number 
** of bytes of memory released.
*/
int sqlite3pager_release_memory(int nReq){
  SqliteTsd *pTsd = sqlite3Tsd();
  Pager *pPager;
  int nReleased = 0;
  int i;

  /* Outermost loop runs for at most two iterations. First iteration we
  ** try to find memory that can be released without calling fsync(). Second
  ** iteration (which only runs if the first failed to free nReq bytes of
  ** memory) is permitted to call fsync(). This is of course much more 
  ** expensive.
  */
  for(i=0; i==0 || i==1; i++){

    /* Loop through all the SQLite pagers opened by the current thread. */
    for(pPager=pTsd->pPager; pPager && nReleased<nReq; pPager=pPager->pNext){
      PgHdr *pPg;
      int rc;

      /* For each pager, try to free as many pages as possible (without 
      ** calling fsync() if this is the first iteration of the outermost 
      ** loop).
      */
      while( SQLITE_OK==(rc = pager_recycle(pPager, i, &pPg)) && pPg) {
	/* We've found a page to free. At this point the page has been 
        ** removed from the page hash-table, free-list and synced-list 
	** (pFirstSynced). It is still in the all pages (pAll) list. 
        ** Remove it from this list before freeing.
        **
        ** Todo: Check the Pager.pStmt list to make sure this is Ok. It 
        ** probably is though.
        */
        PgHdr *pTmp;
        if( pPg==pPager->pAll ){
           pPager->pAll = pPg->pNextAll;
        }else{
          for( pTmp=pPager->pAll; pTmp->pNextAll!=pPg; pTmp=pTmp->pNextAll );
          pTmp->pNextAll = pPg->pNextAll;
        }
        nReleased += sqliteAllocSize(pPg);
        sqliteFree(pPg);
      }

      if( rc!=SQLITE_OK ){
        /* Assert that fsync() was enabled and the error was an io-error
        ** or a full database. Nothing else should be able to wrong in 
        ** pager_recycle.
        */
        assert( i && (rc==SQLITE_IOERR || rc==SQLITE_FULL) );

        /* TODO: Figure out what to do about this. The IO-error
        ** belongs to the connection that is executing a transaction. 
        */
        assert(0);
      }
    }
  }
  
  return nReleased;
}

/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired. 
** This read lock is dropped when the last page is released.
**

      pPager->pAll = pPg;
      pPager->nPage++;
      if( pPager->nPage>pPager->nMaxPage ){
        assert( pPager->nMaxPage==(pPager->nPage-1) );
        pPager->nMaxPage++;
      }
    }else{




      rc = pager_recycle(pPager, 1, &pPg);




































      if( rc!=SQLITE_OK ){

        return rc;
      }

      assert(pPg) ;

















    }
    pPg->pgno = pgno;
    if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
      sqlite3CheckMemory(pPager->aInJournal, pgno/8);
      assert( pPager->journalOpen );
      pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0;
      pPg->needSync = 0;

**    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 1.47 2005/12/18 08:51:24 danielk1977 Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** The default size of a database page.
*/
#ifndef SQLITE_DEFAULT_PAGE_SIZE
# define SQLITE_DEFAULT_PAGE_SIZE 1024
#endif

int sqlite3pager_lockstate(Pager*);
#endif

#ifdef SQLITE_TEST
void sqlite3pager_refdump(Pager*);
int pager3_refinfo_enable;
#endif

#endif /* _PAGER_H_ */

**    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 library
** presents to client programs.
**
** @(#) $Id: sqlite.h.in,v 1.149 2005/12/18 08:51:24 danielk1977 Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.

** one or more times to free up some space before the allocation is made.
**
** The limit is called "soft", because if sqlite3_release_memory() cannot free
** sufficient memory to prevent the limit from being exceeded, the memory is
** allocated anyway and the current operation proceeds.
**
** This function is only available if the library was compiled without the 
** SQLITE_OMIT_MEMORY_MANAGEMENT option set.
*/
void sqlite3_soft_heap_limit(int);

/*
** Register a callback function with the database connection identified by the 
** first argument to be invoked whenever a row is updated, inserted or deleted.
** Any callback set by a previous call to this function for the same 

/*
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.440 2005/12/18 08:51:24 danielk1977 Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Many people are failing to set -DNDEBUG=1 when compiling SQLite.
** Setting NDEBUG makes the code smaller and run faster.  So the following

/*
** Defer sourcing vdbe.h and btree.h until after the "u8" and 
** "BusyHandler typedefs.
*/
#include "vdbe.h"
#include "btree.h"
#include "pager.h"

/*
** This macro casts a pointer to an integer.  Useful for doing
** pointer arithmetic.
*/
#define Addr(X)  ((uptr)X)

#define sqliteMallocRaw(x)     sqlite3MallocRaw(x)
#define sqliteRealloc(x,y)     sqlite3Realloc(x,y)
#define sqliteStrDup(x)        sqlite3StrDup(x)
#define sqliteStrNDup(x,y)     sqlite3StrNDup(x,y)

#endif

#define sqliteFree(x)          sqlite3FreeX(x)
#define sqliteAllocSize(x)     sqlite3AllocSize(x)

/*
** An instance of this structure is allocated for each thread that uses SQLite.
*/
typedef struct SqliteTsd SqliteTsd;
struct SqliteTsd {
  int isInit;                     /* True if structure has been initialised */
  int mallocFailed;               /* True after a malloc() has failed */

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  unsigned int nSoftHeapLimit;    /* (uint)-1 for unlimited */
  unsigned int nAlloc;            /* Number of bytes currently allocated */
  Pager *pPager;                  /* Linked list of all pagers in this thread */
#endif

#ifndef NDEBUG
  int mallocAllowed;              /* assert() in sqlite3Malloc() if not set */
#endif
#ifdef SQLITE_MEMDEBUG
  int isFail;              /* True if all malloc() calls should fail */

void *sqlite3Realloc(void*,int);
char *sqlite3StrDup(const char*);
char *sqlite3StrNDup(const char*, int);
# define sqlite3CheckMemory(a,b)
void sqlite3ReallocOrFree(void**,int);
void sqlite3FreeX(void*);
void *sqlite3MallocX(int);
int sqlite3AllocSize(void *);

char *sqlite3MPrintf(const char*, ...);
char *sqlite3VMPrintf(const char*, va_list);
void sqlite3DebugPrintf(const char*, ...);
void *sqlite3TextToPtr(const char*);
void sqlite3SetString(char **, ...);
void sqlite3ErrorMsg(Parse*, const char*, ...);

**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.155 2005/12/18 08:51:24 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <stdarg.h>
#include <ctype.h>

/*
** MALLOC WRAPPER ARCHITECTURE
**
** The sqlite code accesses dynamic memory allocation/deallocation by invoking
** the following four APIs (which may be implemented as macros).
**
**     sqlite3Malloc()
**     sqlite3MallocRaw()
**     sqlite3Realloc()
**     sqlite3ReallocOrFree()
**     sqlite3Free()
**     sqlite3AllocSize()
**
** The function sqlite3FreeX performs the same task as sqlite3Free and is
** guaranteed to be a real function.
**
** The above APIs are implemented in terms of the functions provided at the Os
** level (not in this file). The Os level interface is never accessed directly
** by code outside of this file.

  if( p ){
    return sqlite3Os.xAllocationSize(p) - TESTALLOC_OVERHEAD;
  }
  return 0;
}

#else
/* Define macros to call the sqlite3Os.xXXX interface directly if 
** the SQLITE_MEMDEBUG macro is not defined.
*/
#define OSMALLOC(x)        sqlite3Os.xMalloc(x)
#define OSREALLOC(x,y)     sqlite3Os.xRealloc(x,y)
#define OSFREE(x)          sqlite3Os.xFree(x)
#define OSSIZEOF(x)        sqlite3Os.xAllocationSize(x)
#define OSMALLOC_FAILED()

#endif
/*
** End code for memory allocation system test layer.
**--------------------------------------------------------------------------*/

/*
** The handleSoftLimit() function is called before each call to 
** sqlite3Os.xMalloc() or xRealloc(). The parameter 'n' is the number of
** extra bytes about to be allocated (for Realloc() this means the size of the
** new allocation less the size of the old allocation). If the extra allocation
** means that the total memory allocated to SQLite in this thread would exceed
** the limit set by sqlite3_soft_heap_limit(), then sqlite3_release_memory() is
** called to try to avoid this. No indication of whether or not this is
** successful is returned to the caller.
**
** If SQLITE_OMIT_MEMORY_MANAGEMENT is defined, this function is a no-op.
*/
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
static void handleSoftLimit(int n){
  SqliteTsd *pTsd = sqlite3Tsd();
  pTsd->nAlloc += n;
  while( pTsd->nAlloc>pTsd->nSoftHeapLimit && sqlite3_release_memory(n) );
}
#else
#define handleSoftLimit()

void sqlite3ReallocOrFree(void **pp, int n){
  void *p = sqlite3Realloc(*pp, n);
  if( !p ){
    sqlite3FreeX(*pp);
  }
  *pp = p;
}

/*
** Return the number of bytes allocated at location p. p must be either 
** a NULL pointer (in which case 0 is returned) or a pointer returned by 
** sqlite3Malloc(), sqlite3Realloc() or sqlite3ReallocOrFree().
**
** The number of bytes allocated does not include any overhead inserted by 
** any malloc() wrapper functions that may be called. So the value returned
** is the number of bytes that were available to SQLite using pointer p, 
** regardless of how much memory was actually allocated.
*/
int sqlite3AllocSize(void *p){
  return OSSIZEOF(p);
}

/*
** Make a copy of a string in memory obtained from sqliteMalloc(). These 
** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
** is because when memory debugging is turned on, these two functions are 
** called via macros that record the current file and line number in the
** SqliteTsd structure.

** Clear the "mallocFailed" flag. This should be invoked before exiting any
** entry points that may have called sqliteMalloc().
*/
void sqlite3MallocClearFailed(){
  sqlite3Tsd()->mallocFailed = 0;
}

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
/*
** Set the soft heap-size limit for the current thread.
*/
void sqlite3_soft_heap_limit(int n){
  unsigned int N;
  if( n<0 ){
    /* No limit */