BtShared *pBt = p->pBt;
  assert( sqlite3_mutex_held(p->db->mutex) );
  sqlite3BtreeEnter(p);
  sqlite3PagerSetCachesize(pBt->pPager, mxPage);
  sqlite3BtreeLeave(p);
  return SQLITE_OK;
}














/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures.  Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage)  Level 2 is the default.  There
** is a very low but non-zero probability of damage.  Level 3 reduces the

  BtShared *pBt = p->pBt;
  assert( sqlite3_mutex_held(p->db->mutex) );
  sqlite3BtreeEnter(p);
  sqlite3PagerSetCachesize(pBt->pPager, mxPage);
  sqlite3BtreeLeave(p);
  return SQLITE_OK;
}

/*
** Change the limit on the amount of the database file that may be
** memory mapped.
*/
int sqlite3BtreeSetMmapSize(Btree *p, int nMap){
  BtShared *pBt = p->pBt;
  assert( sqlite3_mutex_held(p->db->mutex) );
  sqlite3BtreeEnter(p);
  sqlite3PagerSetMmapsize(pBt->pPager, nMap);
  sqlite3BtreeLeave(p);
  return SQLITE_OK;
}

/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures.  Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage)  Level 2 is the default.  There
** is a very low but non-zero probability of damage.  Level 3 reduces the

#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
#define BTREE_MEMORY        2  /* This is an in-memory DB */
#define BTREE_SINGLE        4  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED     8  /* Use of a hash implementation is OK */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);

int sqlite3BtreeSetSafetyLevel(Btree*,int,int,int);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite3BtreeGetPageSize(Btree*);
int sqlite3BtreeMaxPageCount(Btree*,int);
u32 sqlite3BtreeLastPage(Btree*);
int sqlite3BtreeSecureDelete(Btree*,int);

#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
#define BTREE_MEMORY        2  /* This is an in-memory DB */
#define BTREE_SINGLE        4  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED     8  /* Use of a hash implementation is OK */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetMmapSize(Btree*, int);
int sqlite3BtreeSetSafetyLevel(Btree*,int,int,int);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite3BtreeGetPageSize(Btree*);
int sqlite3BtreeMaxPageCount(Btree*,int);
u32 sqlite3BtreeLastPage(Btree*);
int sqlite3BtreeSecureDelete(Btree*,int);

  int iPage,
  int pgsz,
  int bExtend,                    /* True to extend file if necessary */
  void volatile **pp              /* OUT: Pointer to mapping */
){
  DO_OS_MALLOC_TEST(id);
  return id->pMethods->xShmMap(id, iPage, pgsz, bExtend, pp);



}

/*
** The next group of routines are convenience wrappers around the
** VFS methods.
*/
int sqlite3OsOpen(

  int iPage,
  int pgsz,
  int bExtend,                    /* True to extend file if necessary */
  void volatile **pp              /* OUT: Pointer to mapping */
){
  DO_OS_MALLOC_TEST(id);
  return id->pMethods->xShmMap(id, iPage, pgsz, bExtend, pp);
}
int sqlite3OsMremap(sqlite3_file *id, i64 iOff, i64 nOld, i64 nNew, void **pp){
  return id->pMethods->xMremap(id, iOff, nOld, nNew, pp);
}

/*
** The next group of routines are convenience wrappers around the
** VFS methods.
*/
int sqlite3OsOpen(

#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
int sqlite3OsSectorSize(sqlite3_file *id);
int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
void sqlite3OsShmBarrier(sqlite3_file *id);
int sqlite3OsShmUnmap(sqlite3_file *id, int);



/* 
** Functions for accessing sqlite3_vfs methods 
*/
int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
int sqlite3OsDelete(sqlite3_vfs *, const char *, int);

#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
int sqlite3OsSectorSize(sqlite3_file *id);
int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
void sqlite3OsShmBarrier(sqlite3_file *id);
int sqlite3OsShmUnmap(sqlite3_file *id, int);
int sqlite3OsMremap(sqlite3_file *id, i64, i64, i64, void **);


/* 
** Functions for accessing sqlite3_vfs methods 
*/
int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
int sqlite3OsDelete(sqlite3_vfs *, const char *, int);

#else
# define unixShmMap     0
# define unixShmLock    0
# define unixShmBarrier 0
# define unixShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */





































/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
******************************************************************************/

................................................................................
   CKLOCK,                     /* xCheckReservedLock */                      \
   unixFileControl,            /* xFileControl */                            \
   unixSectorSize,             /* xSectorSize */                             \
   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
   unixShmMap,                 /* xShmMap */                                 \
   unixShmLock,                /* xShmLock */                                \
   unixShmBarrier,             /* xShmBarrier */                             \
   unixShmUnmap                /* xShmUnmap */                               \

};                                                                           \
static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
  UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
  return &METHOD;                                                            \
}                                                                            \
static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p)    \
    = FINDER##Impl;
................................................................................
** Here are all of the sqlite3_io_methods objects for each of the
** locking strategies.  Functions that return pointers to these methods
** are also created.
*/
IOMETHODS(
  posixIoFinder,            /* Finder function name */
  posixIoMethods,           /* sqlite3_io_methods object name */
  2,                        /* shared memory is enabled */
  unixClose,                /* xClose method */
  unixLock,                 /* xLock method */
  unixUnlock,               /* xUnlock method */
  unixCheckReservedLock     /* xCheckReservedLock method */
)
IOMETHODS(
  nolockIoFinder,           /* Finder function name */

#else
# define unixShmMap     0
# define unixShmLock    0
# define unixShmBarrier 0
# define unixShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */

/*
** Map, remap or unmap part of the database file.
*/
static int unixMremap(
  sqlite3_file *fd,               /* Main database file */
  sqlite3_int64 iOff,             /* Offset to start mapping at */
  sqlite3_int64 nOld,             /* Size of old mapping, or zero */
  sqlite3_int64 nNew,             /* Size of new mapping, or zero */
  void **ppMap                    /* IN/OUT: Old/new mappings */
){
  unixFile *p = (unixFile *)fd;   /* The underlying database file */
  int rc = SQLITE_OK;             /* Return code */
  void *pNew = 0;                 /* New mapping */

  assert( iOff==0 );

  if( nOld!=0 ){
    void *pOld = *ppMap;
    munmap(pOld, nOld);
  }

  if( nNew>0 ){
    int flags = PROT_READ;
    if( (p->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
    nNew = (nNew+4095) & ~(i64)((1 << 12)-1);
    pNew = mmap(0, nNew, flags, MAP_SHARED, p->h, iOff);
    if( pNew==MAP_FAILED ){
      pNew = 0;
      rc = SQLITE_IOERR;
    }
  }

  *ppMap = pNew;
  return rc;
}

/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
******************************************************************************/

................................................................................
   CKLOCK,                     /* xCheckReservedLock */                      \
   unixFileControl,            /* xFileControl */                            \
   unixSectorSize,             /* xSectorSize */                             \
   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
   unixShmMap,                 /* xShmMap */                                 \
   unixShmLock,                /* xShmLock */                                \
   unixShmBarrier,             /* xShmBarrier */                             \
   unixShmUnmap,               /* xShmUnmap */                               \
   unixMremap,                 /* xMremap */                                 \
};                                                                           \
static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
  UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
  return &METHOD;                                                            \
}                                                                            \
static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p)    \
    = FINDER##Impl;
................................................................................
** Here are all of the sqlite3_io_methods objects for each of the
** locking strategies.  Functions that return pointers to these methods
** are also created.
*/
IOMETHODS(
  posixIoFinder,            /* Finder function name */
  posixIoMethods,           /* sqlite3_io_methods object name */
  3,                        /* shared memory and mmap are enabled */
  unixClose,                /* xClose method */
  unixLock,                 /* xLock method */
  unixUnlock,               /* xUnlock method */
  unixCheckReservedLock     /* xCheckReservedLock method */
)
IOMETHODS(
  nolockIoFinder,           /* Finder function name */

  PagerSavepoint *aSavepoint; /* Array of active savepoints */
  int nSavepoint;             /* Number of elements in aSavepoint[] */
  char dbFileVers[16];        /* Changes whenever database file changes */

  void *pMap;                 /* Memory mapped prefix of database file */
  i64 nMap;                   /* Size of mapping at pMap in bytes */ 
  i64 nMapValid;              /* Bytes at pMap known to be valid */


  int nMmapOut;               /* Number of mmap pages currently outstanding */
  PgHdr *pFree;               /* List of free mmap page headers (pDirty) */

  /*
  ** End of the routinely-changing class members
  ***************************************************************************/

  u16 nExtra;                 /* Add this many bytes to each in-memory page */
  i16 nReserve;               /* Number of unused bytes at end of each page */
  u32 vfsFlags;               /* Flags for sqlite3_vfs.xOpen() */
................................................................................

/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
}






























/*
** Free as much memory as possible from the pager.
*/
void sqlite3PagerShrink(Pager *pPager){
  sqlite3PcacheShrink(pPager->pPCache);
}
................................................................................

  *pPageSize = pPager->pageSize;
  if( rc==SQLITE_OK ){
    if( nReserve<0 ) nReserve = pPager->nReserve;
    assert( nReserve>=0 && nReserve<1000 );
    pPager->nReserve = (i16)nReserve;
    pagerReportSize(pPager);

  }
  return rc;
}

/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager.  This is a buffer that is big enough to hold the
................................................................................
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
  }
  return rc;
}

#include <sys/mman.h>

/*
** Unmap any mapping of the database file.
*/
static int pagerUnmap(Pager *pPager){
  if( pPager->pMap ){
    munmap(pPager->pMap, pPager->nMap);
    pPager->pMap = 0;
    pPager->nMap = 0;
    pPager->nMapValid = 0;
  }
  return SQLITE_OK;
}




static int pagerMap(Pager *pPager){
  int rc;
  i64 sz = 0;





  assert( pPager->pMap==0 && pPager->nMap==0 );




  rc = sqlite3OsFileSize(pPager->fd, &sz);
  sz = sz & ~(4096-1);






  if( rc==SQLITE_OK && sz>0 ){
    int fd;
    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_GETFD, (void *)&fd);


    if( rc==SQLITE_OK ){
      void *pMap = mmap(0, sz, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
      if( pMap==MAP_FAILED ){
        return SQLITE_IOERR;
      }
      pPager->pMap = pMap;
      pPager->nMapValid = pPager->nMap = sz;
    }
  }

  return rc;
}

static int pagerRemap(Pager *pPager, Pgno nPage){
  i64 sz = (i64)nPage * pPager->pageSize;
  sz = sz & ~(4096-1);

  if( pPager->nMap!=sz ){
    void *pMap = mremap(pPager->pMap, pPager->nMap, sz, MREMAP_MAYMOVE);    
    if( pMap==MAP_FAILED ){
      return SQLITE_IOERR;
    }
    pPager->pMap = pMap;
    pPager->nMapValid = pPager->nMap = sz;
  }


  return SQLITE_OK;
}











static int pagerAcquireMapPage(Pager *pPager, Pgno pgno, PgHdr **ppPage){
  int rc;
  *ppPage = 0;

  assert( pPager->pWal==0 );

  if( MEMDB==0 && pPager->tempFile==0 ){
    if( pPager->pMap==0 ){
      rc = pagerMap(pPager);
      if( rc!=SQLITE_OK ) return rc;
    }

    if( pgno!=1 && pPager->pMap 
     && pPager->nMapValid>=((i64)pgno*pPager->pageSize) 
    ){
      PgHdr *p;
      if( pPager->pFree ){
        p = pPager->pFree;
        pPager->pFree = p->pDirty;
        p->pDirty = 0;
        memset(p->pExtra, 0, pPager->nExtra);
      }else{
        p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);

        if( p==0 ) return SQLITE_NOMEM;

        p->pExtra = (void *)&p[1];
        p->flags = PGHDR_MMAP;
        p->nRef = 1;
        p->pPager = pPager;
      }

      assert( p->pExtra==(void *)&p[1] );
      assert( p->pPage==0 );
      assert( p->flags==PGHDR_MMAP );
      assert( p->pPager==pPager );
      assert( p->nRef==1 );

      p->pData = &((u8 *)pPager->pMap)[(i64)(pgno-1) * pPager->pageSize];
      p->pgno = pgno;
      pPager->nMmapOut++;
      *ppPage = p;
    }
  }

  return SQLITE_OK;
}





static void pagerReleaseMapPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  pPager->nMmapOut--;
  pPg->pDirty = pPager->pFree;
  pPager->pFree = pPg;
}




static void pagerFreeMapHdrs(Pager *pPager){
  PgHdr *p;
  PgHdr *pNext;
  for(p=pPager->pFree; p; p=pNext){
    pNext = p->pDirty;
    sqlite3_free(p);
  }
................................................................................
        ** may have truncated the database file and then extended it back
        ** to its original size while this process was not holding a lock.
        ** In this case there may exist a Pager.pMap mapping that appears
        ** to be the right size but is not actually valid. Avoid this
        ** possibility by unmapping the db here. */
        pagerUnmap(pPager);
      }else if( pPager->pMap ){
        pagerRemap(pPager, nPage);
      }
    }

    /* If there is a WAL file in the file-system, open this database in WAL
    ** mode. Otherwise, the following function call is a no-op.
    */
    rc = pagerOpenWalIfPresent(pPager);
................................................................................
  PgHdr *pPg = 0;
  const int noContent = (flags & PAGER_ACQUIRE_NOCONTENT);

  /* It is acceptable to use a read-only (mmap) page for any page except
  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
  ** flag was specified by the caller. And so long as the db is not a 
  ** temporary or in-memory database.  */
  const int bMmapOk = (
      (pgno!=1 && pPager->pWal==0 && !pPager->tempFile && !MEMDB)
   && (pPager->eState==PAGER_READER || (flags & PAGER_ACQUIRE_READONLY))
  );

  assert( pPager->eState>=PAGER_READER );
  assert( assert_pager_state(pPager) );

  if( pgno==0 ){
................................................................................
  /* If the pager is in the error state, return an error immediately. 
  ** Otherwise, request the page from the PCache layer. */
  if( pPager->errCode!=SQLITE_OK ){
    rc = pPager->errCode;
  }else{

    if( bMmapOk ){
      if( pPager->pMap==0 ){
        rc = pagerMap(pPager);
      }
      if( rc==SQLITE_OK && pPager->nMap>=((i64)pgno * pPager->pageSize) ){
        if( pPager->eState>PAGER_READER ){
          (void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg);
        }
        if( pPg==0 ){
................................................................................
  */
  if( rc==SQLITE_OK ){
    rc = sqlite3WalOpen(pPager->pVfs, 
        pPager->fd, pPager->zWal, pPager->exclusiveMode,
        pPager->journalSizeLimit, &pPager->pWal
    );
  }


  return rc;
}


/*
** The caller must be holding a SHARED lock on the database file to call
................................................................................
  */
  if( rc==SQLITE_OK && pPager->pWal ){
    rc = pagerExclusiveLock(pPager);
    if( rc==SQLITE_OK ){
      rc = sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags,
                           pPager->pageSize, (u8*)pPager->pTmpSpace);
      pPager->pWal = 0;

    }
  }
  return rc;
}

#endif /* !SQLITE_OMIT_WAL */

  PagerSavepoint *aSavepoint; /* Array of active savepoints */
  int nSavepoint;             /* Number of elements in aSavepoint[] */
  char dbFileVers[16];        /* Changes whenever database file changes */

  void *pMap;                 /* Memory mapped prefix of database file */
  i64 nMap;                   /* Size of mapping at pMap in bytes */ 
  i64 nMapValid;              /* Bytes at pMap known to be valid */
  i64 nMapLimit;              /* Maximum permitted mapping size */
  int nMapCfgLimit;           /* Configured limit value */
  int nMmapOut;               /* Number of mmap pages currently outstanding */
  PgHdr *pFree;               /* List of free mmap page headers (pDirty) */
  int bMapResize;             /* Check if the mapping should be resized */
  /*
  ** End of the routinely-changing class members
  ***************************************************************************/

  u16 nExtra;                 /* Add this many bytes to each in-memory page */
  i16 nReserve;               /* Number of unused bytes at end of each page */
  u32 vfsFlags;               /* Flags for sqlite3_vfs.xOpen() */
................................................................................

/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
}

/*
** Set Pager.nMapLimit, the maximum permitted mapping size, based on the
** current values of Pager.nMapCfgLimit and Pager.pageSize.
**
** If this connection should not use mmap at all, set nMapLimit to zero.
*/
static void pagerFixMaplimit(Pager *pPager){
  if( isOpen(pPager->fd)==0 
   || pPager->fd->pMethods->iVersion<3 
   || pPager->fd->pMethods->xMremap==0 
   || pPager->tempFile 
   || pPager->pWal 
  ){
    pPager->nMapLimit = 0;
  }else if( pPager->nMapCfgLimit<0 ){
    pPager->nMapLimit = (i64)pPager->nMapCfgLimit * -1024;
  }else{
    pPager->nMapLimit = (i64)pPager->nMapCfgLimit * pPager->pageSize;
  }
}

/*
** Change the maximum size of any memory mapping made of the database file.
*/
void sqlite3PagerSetMmapsize(Pager *pPager, int nMap){
  pPager->nMapCfgLimit = nMap;
  pagerFixMaplimit(pPager);
}

/*
** Free as much memory as possible from the pager.
*/
void sqlite3PagerShrink(Pager *pPager){
  sqlite3PcacheShrink(pPager->pPCache);
}
................................................................................

  *pPageSize = pPager->pageSize;
  if( rc==SQLITE_OK ){
    if( nReserve<0 ) nReserve = pPager->nReserve;
    assert( nReserve>=0 && nReserve<1000 );
    pPager->nReserve = (i16)nReserve;
    pagerReportSize(pPager);
    pagerFixMaplimit(pPager);
  }
  return rc;
}

/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager.  This is a buffer that is big enough to hold the
................................................................................
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
  }
  return rc;
}



/*
** Unmap any memory mapping of the database file.
*/
static int pagerUnmap(Pager *pPager){
  if( pPager->pMap ){
    sqlite3OsMremap(pPager->fd, 0, pPager->nMap, 0, &pPager->pMap);

    pPager->nMap = 0;
    pPager->nMapValid = 0;
  }
  return SQLITE_OK;
}

/*
** Create, or recreate, the memory mapping of the database file.
*/
static int pagerMap(Pager *pPager){


  int rc = SQLITE_OK;             /* Return code */
  Pgno nPg;                       /* Size of mapping to request in pages */
  i64 sz;                         /* Size of mapping to request in bytes */

  assert( pPager->pWal==0 && isOpen(pPager->fd) && pPager->tempFile==0 );
  assert( pPager->pMap==0 || pPager->nMap>0 );
  assert( pPager->eState>=1 );
  assert( pPager->nMmapOut==0 );
  assert( pPager->nMapLimit>0 );



  /* Figure out how large a mapping to request. Set variable sz to this 
  ** value in bytes. */
  nPg = (pPager->eState==1) ? pPager->dbSize : pPager->dbFileSize;
  sz = (i64)nPg * pPager->pageSize;
  if( sz>pPager->nMapLimit ) sz = pPager->nMapLimit;




  if( sz!=pPager->nMapValid ){
    rc = sqlite3OsMremap(pPager->fd, 0, pPager->nMap, sz, &pPager->pMap);
    if( rc==SQLITE_OK ){




      assert( pPager->pMap!=0 );
      pPager->nMap = sz;






    }else{
      assert( pPager->pMap==0 );


      pPager->nMap = 0;



    }

    pPager->nMapValid = pPager->nMap;
  }
  pPager->bMapResize = 0;

  return rc;
}

/*
** Obtain a reference to a memory mapped page object for page number pgno. 
** The caller must ensure that page pgno lies within the currently mapped 
** region. If successful, set *ppPage to point to the new page reference
** and return SQLITE_OK. Otherwise, return an SQLite error code and set
** *ppPage to zero.
**
** Page references obtained by calling this function should be released
** by calling pagerReleaseMapPage().
*/
static int pagerAcquireMapPage(Pager *pPager, Pgno pgno, PgHdr **ppPage){





  PgHdr *p;                       /* Memory mapped page to return */









  if( pPager->pFree ){
    *ppPage = p = pPager->pFree;
    pPager->pFree = p->pDirty;
    p->pDirty = 0;
    memset(p->pExtra, 0, pPager->nExtra);
  }else{
    *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);
    if( p==0 ){
      return SQLITE_NOMEM;
    }
    p->pExtra = (void *)&p[1];
    p->flags = PGHDR_MMAP;
    p->nRef = 1;
    p->pPager = pPager;
  }

  assert( p->pExtra==(void *)&p[1] );
  assert( p->pPage==0 );
  assert( p->flags==PGHDR_MMAP );
  assert( p->pPager==pPager );
  assert( p->nRef==1 );

  p->pData = &((u8 *)pPager->pMap)[(i64)(pgno-1) * pPager->pageSize];
  p->pgno = pgno;
  pPager->nMmapOut++;




  return SQLITE_OK;
}

/*
** Release a reference to page pPg. pPg must have been returned by an 
** earlier call to pagerAcquireMapPage().
*/
static void pagerReleaseMapPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  pPager->nMmapOut--;
  pPg->pDirty = pPager->pFree;
  pPager->pFree = pPg;
}

/*
** Free all PgHdr objects stored in the Pager.pFree list.
*/
static void pagerFreeMapHdrs(Pager *pPager){
  PgHdr *p;
  PgHdr *pNext;
  for(p=pPager->pFree; p; p=pNext){
    pNext = p->pDirty;
    sqlite3_free(p);
  }
................................................................................
        ** may have truncated the database file and then extended it back
        ** to its original size while this process was not holding a lock.
        ** In this case there may exist a Pager.pMap mapping that appears
        ** to be the right size but is not actually valid. Avoid this
        ** possibility by unmapping the db here. */
        pagerUnmap(pPager);
      }else if( pPager->pMap ){
        pPager->bMapResize = 1;
      }
    }

    /* If there is a WAL file in the file-system, open this database in WAL
    ** mode. Otherwise, the following function call is a no-op.
    */
    rc = pagerOpenWalIfPresent(pPager);
................................................................................
  PgHdr *pPg = 0;
  const int noContent = (flags & PAGER_ACQUIRE_NOCONTENT);

  /* It is acceptable to use a read-only (mmap) page for any page except
  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
  ** flag was specified by the caller. And so long as the db is not a 
  ** temporary or in-memory database.  */
  const int bMmapOk = (pPager->nMapLimit>0 && pgno!=1

   && (pPager->eState==PAGER_READER || (flags & PAGER_ACQUIRE_READONLY))
  );

  assert( pPager->eState>=PAGER_READER );
  assert( assert_pager_state(pPager) );

  if( pgno==0 ){
................................................................................
  /* If the pager is in the error state, return an error immediately. 
  ** Otherwise, request the page from the PCache layer. */
  if( pPager->errCode!=SQLITE_OK ){
    rc = pPager->errCode;
  }else{

    if( bMmapOk ){
      if( pPager->pMap==0 || (pPager->bMapResize && pPager->nMmapOut==0) ){
        rc = pagerMap(pPager);
      }
      if( rc==SQLITE_OK && pPager->nMap>=((i64)pgno * pPager->pageSize) ){
        if( pPager->eState>PAGER_READER ){
          (void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg);
        }
        if( pPg==0 ){
................................................................................
  */
  if( rc==SQLITE_OK ){
    rc = sqlite3WalOpen(pPager->pVfs, 
        pPager->fd, pPager->zWal, pPager->exclusiveMode,
        pPager->journalSizeLimit, &pPager->pWal
    );
  }
  pagerFixMaplimit(pPager);

  return rc;
}


/*
** The caller must be holding a SHARED lock on the database file to call
................................................................................
  */
  if( rc==SQLITE_OK && pPager->pWal ){
    rc = pagerExclusiveLock(pPager);
    if( rc==SQLITE_OK ){
      rc = sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags,
                           pPager->pageSize, (u8*)pPager->pTmpSpace);
      pPager->pWal = 0;
      pagerFixMaplimit(pPager);
    }
  }
  return rc;
}

#endif /* !SQLITE_OMIT_WAL */

    }else{
      int size = sqlite3Atoi(zRight);
      pDb->pSchema->cache_size = size;
      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
    }
  }else

























  /*
  **   PRAGMA temp_store
  **   PRAGMA temp_store = "default"|"memory"|"file"
  **
  ** Return or set the local value of the temp_store flag.  Changing
  ** the local value does not make changes to the disk file and the default
  ** value will be restored the next time the database is opened.

    }else{
      int size = sqlite3Atoi(zRight);
      pDb->pSchema->cache_size = size;
      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
    }
  }else

  /*
  **  PRAGMA [database.]mmap_size
  **  PRAGMA [database.]mmap_size=N
  **
  ** Used to set or query the mapping size limit. The mapping size limit is
  ** used to limit the aggregate size of all memory mapped regions of the
  ** database file. If this parameter is set to zero, then memory mapping
  ** is not used at all. If it is set to a positive value, then it is
  ** interpreted as a maximum size in pages. If set to less than zero, then
  ** the absolute value is interpreted as a size limit in KB.
  **
  ** The default value is zero (do not use memory mapped IO).
  */
  if( sqlite3StrICmp(zLeft,"mmap_size")==0 ){
    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
    if( !zRight ){
      returnSingleInt(pParse, "mmap_size", pDb->pSchema->mmap_size);
    }else{
      int size = sqlite3Atoi(zRight);
      pDb->pSchema->mmap_size = size;
      sqlite3BtreeSetMmapSize(pDb->pBt, pDb->pSchema->mmap_size);
    }
  }else

  /*
  **   PRAGMA temp_store
  **   PRAGMA temp_store = "default"|"memory"|"file"
  **
  ** Return or set the local value of the temp_store flag.  Changing
  ** the local value does not make changes to the disk file and the default
  ** value will be restored the next time the database is opened.

** to xWrite().
**
** If xRead() returns SQLITE_IOERR_SHORT_READ it must also fill
** in the unread portions of the buffer with zeros.  A VFS that
** fails to zero-fill short reads might seem to work.  However,
** failure to zero-fill short reads will eventually lead to
** database corruption.


















*/
typedef struct sqlite3_io_methods sqlite3_io_methods;
struct sqlite3_io_methods {
  int iVersion;
  int (*xClose)(sqlite3_file*);
  int (*xRead)(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
................................................................................
  int (*xDeviceCharacteristics)(sqlite3_file*);
  /* Methods above are valid for version 1 */
  int (*xShmMap)(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
  void (*xShmBarrier)(sqlite3_file*);
  int (*xShmUnmap)(sqlite3_file*, int deleteFlag);
  /* Methods above are valid for version 2 */



  /* Additional methods may be added in future releases */
};

/*
** CAPI3REF: Standard File Control Opcodes
**
** These integer constants are opcodes for the xFileControl method

** to xWrite().
**
** If xRead() returns SQLITE_IOERR_SHORT_READ it must also fill
** in the unread portions of the buffer with zeros.  A VFS that
** fails to zero-fill short reads might seem to work.  However,
** failure to zero-fill short reads will eventually lead to
** database corruption.
**
** Assuming parameter nNew is non-zero, the xMremap method should attempt
** to memory map a region nNew bytes in size starting at offset iOffset
** of the file.  If successful, it should set *ppMap to point to the
** mapping and return SQLITE_OK. If the file is opened for read-write
** access, then the mapping should also be read-write.
**
** If nOld is non-zero, then the initial value of *ppMap points to a
** mapping returned by a previous call to xMremap. The existing mapping
** is nOld bytes in size and starts at offset iOffset of the file. In
** this case the xMremap method is expected to unmap the existing mapping
** and overwrite *ppMap with the pointer to the new mapping. If nOld is
** zero, then the initial value of *ppMap is undefined.
**
** If nNew is zero, then no new mapping should be created. Any old
** mapping must still be unmapped if nOld is non-zero. If the nOld
** parameter is non-zero, then the existing mapping is always unmapped -
** even if an error occurs.
*/
typedef struct sqlite3_io_methods sqlite3_io_methods;
struct sqlite3_io_methods {
  int iVersion;
  int (*xClose)(sqlite3_file*);
  int (*xRead)(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
................................................................................
  int (*xDeviceCharacteristics)(sqlite3_file*);
  /* Methods above are valid for version 1 */
  int (*xShmMap)(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
  void (*xShmBarrier)(sqlite3_file*);
  int (*xShmUnmap)(sqlite3_file*, int deleteFlag);
  /* Methods above are valid for version 2 */
  int (*xMremap)(sqlite3_file *fd, 
      sqlite3_int64 iOff, sqlite3_int64 nOld, sqlite3_int64 nNew, void **ppMap);
  /* Methods above are valid for version 3 */
  /* Additional methods may be added in future releases */
};

/*
** CAPI3REF: Standard File Control Opcodes
**
** These integer constants are opcodes for the xFileControl method

  Hash trigHash;       /* All triggers indexed by name */
  Hash fkeyHash;       /* All foreign keys by referenced table name */
  Table *pSeqTab;      /* The sqlite_sequence table used by AUTOINCREMENT */
  u8 file_format;      /* Schema format version for this file */
  u8 enc;              /* Text encoding used by this database */
  u16 flags;           /* Flags associated with this schema */
  int cache_size;      /* Number of pages to use in the cache */

};

/*
** These macros can be used to test, set, or clear bits in the 
** Db.pSchema->flags field.
*/
#define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))

  Hash trigHash;       /* All triggers indexed by name */
  Hash fkeyHash;       /* All foreign keys by referenced table name */
  Table *pSeqTab;      /* The sqlite_sequence table used by AUTOINCREMENT */
  u8 file_format;      /* Schema format version for this file */
  u8 enc;              /* Text encoding used by this database */
  u16 flags;           /* Flags associated with this schema */
  int cache_size;      /* Number of pages to use in the cache */
  int mmap_size;       /* Number of pages to memory map */
};

/*
** These macros can be used to test, set, or clear bits in the 
** Db.pSchema->flags field.
*/
#define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))

){
  char buf[1024];
  struct rusage r;
  memset(&r, 0, sizeof(r));
  getrusage(RUSAGE_SELF, &r);

  sprintf(buf, "ru_utime=%d.%06d ru_stime=%d.%06d ru_minflt=%d ru_majflt=%d", 
    r.ru_utime.tv_sec, r.ru_utime.tv_usec, 
    r.ru_stime.tv_sec, r.ru_stime.tv_usec, 
    r.ru_minflt, r.ru_majflt
  );
  Tcl_SetObjResult(interp, Tcl_NewStringObj(buf, -1));
  return TCL_OK;
}

#if SQLITE_OS_WIN
/*

){
  char buf[1024];
  struct rusage r;
  memset(&r, 0, sizeof(r));
  getrusage(RUSAGE_SELF, &r);

  sprintf(buf, "ru_utime=%d.%06d ru_stime=%d.%06d ru_minflt=%d ru_majflt=%d", 
    (int)r.ru_utime.tv_sec, (int)r.ru_utime.tv_usec, 
    (int)r.ru_stime.tv_sec, (int)r.ru_stime.tv_usec, 
    (int)r.ru_minflt, (int)r.ru_majflt
  );
  Tcl_SetObjResult(interp, Tcl_NewStringObj(buf, -1));
  return TCL_OK;
}

#if SQLITE_OS_WIN
/*

proc db_write {db {reset 0}} {
  sqlite3_db_status $db CACHE_WRITE $reset
}

do_test 1.1 {
  db close
  sqlite3 db test.db

  expr {[file size test.db] / 1024}
} 6

do_test 1.2 {
  execsql { SELECT b FROM t1 WHERE a=2 }
  db_hit_miss db
} {{0 2 0} {0 4 0}}

proc db_write {db {reset 0}} {
  sqlite3_db_status $db CACHE_WRITE $reset
}

do_test 1.1 {
  db close
  sqlite3 db test.db
  execsql { PRAGMA mmap_size = 0 }
  expr {[file size test.db] / 1024}
} 6

do_test 1.2 {
  execsql { SELECT b FROM t1 WHERE a=2 }
  db_hit_miss db
} {{0 2 0} {0 4 0}}

#
do_not_use_codec

ifcapable {!pager_pragmas} {
  finish_test
  return
}









# This module does not work right if the cache spills at unexpected
# moments.  So disable the soft-heap-limit.
#
sqlite3_soft_heap_limit 0

proc pagerChangeCounter {filename new {fd ""}} {

#
do_not_use_codec

ifcapable {!pager_pragmas} {
  finish_test
  return
}

# Tests in this file verify that locking_mode=exclusive causes SQLite to
# use cached pages even if the database is changed on disk. This doesn't
# work with mmap.
if {[permutation]=="mmap"} {
  finish_test
  return
}

# This module does not work right if the cache spills at unexpected
# moments.  So disable the soft-heap-limit.
#
sqlite3_soft_heap_limit 0

proc pagerChangeCounter {filename new {fd ""}} {

} {1}
do_test func-29.3 {
  db close
  sqlite3 db test.db
  sqlite3_db_status db CACHE_MISS 1
  db eval {SELECT typeof(+x) FROM t29 ORDER BY id}
} {integer null real blob text}

do_test func-29.4 {
  set x [lindex [sqlite3_db_status db CACHE_MISS 1] 1]
  if {$x>100} {set x many}
  set x
} {many}

do_test func-29.5 {
  db close
  sqlite3 db test.db
  sqlite3_db_status db CACHE_MISS 1
  db eval {SELECT sum(length(x)) FROM t29}
} {1000009}
do_test func-29.6 {

} {1}
do_test func-29.3 {
  db close
  sqlite3 db test.db
  sqlite3_db_status db CACHE_MISS 1
  db eval {SELECT typeof(+x) FROM t29 ORDER BY id}
} {integer null real blob text}
if {[permutation] != "mmap"} {
  do_test func-29.4 {
    set x [lindex [sqlite3_db_status db CACHE_MISS 1] 1]
    if {$x>100} {set x many}
    set x
  } {many}
}
do_test func-29.5 {
  db close
  sqlite3 db test.db
  sqlite3_db_status db CACHE_MISS 1
  db eval {SELECT sum(length(x)) FROM t29}
} {1000009}
do_test func-29.6 {

    }
  }

  db close
  forcedelete test.db test.db-journal

  sqlite3 db test.db

  execsql "PRAGMA auto_vacuum = $AutoVacuumMode"

  do_test incrblob-2.$AutoVacuumMode.1 {
    set ::str [string repeat abcdefghij 2900]
    execsql {
      BEGIN;
      CREATE TABLE blobs(k PRIMARY KEY, v BLOB, i INTEGER);
................................................................................
    } $AutoVacuumMode
  }

  do_test incrblob-2.$AutoVacuumMode.3 {
    # Open and close the db to make sure the page cache is empty.
    db close
    sqlite3 db test.db

  
    # Read the last 20 bytes of the blob via a blob handle.
    set ::blob [db incrblob blobs v 1]
    seek $::blob -20 end
    set ::fragment [read $::blob]
    close $::blob
  
................................................................................
    string range [db one {SELECT v FROM blobs}] end-19 end
  } $::fragment

  do_test incrblob-2.$AutoVacuumMode.5 {
    # Open and close the db to make sure the page cache is empty.
    db close
    sqlite3 db test.db

  
    # Write the second-to-last 20 bytes of the blob via a blob handle.
    #
    set ::blob [db incrblob blobs v 1]
    seek $::blob -40 end
    puts -nonewline $::blob "1234567890abcdefghij"
    flush $::blob
................................................................................
    string range [db one {SELECT v FROM blobs}] end-39 end-20
  } "1234567890abcdefghij"

  do_test incrblob-2.$AutoVacuumMode.8 {
    # Open and close the db to make sure the page cache is empty.
    db close
    sqlite3 db test.db


    execsql { SELECT i FROM blobs } 
  } {45}

  do_test incrblob-2.$AutoVacuumMode.9 {
    nRead db
  } [expr $AutoVacuumMode ? 4 : 30]

    }
  }

  db close
  forcedelete test.db test.db-journal

  sqlite3 db test.db
  execsql "PRAGMA mmap_size = 0"
  execsql "PRAGMA auto_vacuum = $AutoVacuumMode"

  do_test incrblob-2.$AutoVacuumMode.1 {
    set ::str [string repeat abcdefghij 2900]
    execsql {
      BEGIN;
      CREATE TABLE blobs(k PRIMARY KEY, v BLOB, i INTEGER);
................................................................................
    } $AutoVacuumMode
  }

  do_test incrblob-2.$AutoVacuumMode.3 {
    # Open and close the db to make sure the page cache is empty.
    db close
    sqlite3 db test.db
    execsql "PRAGMA mmap_size = 0"
  
    # Read the last 20 bytes of the blob via a blob handle.
    set ::blob [db incrblob blobs v 1]
    seek $::blob -20 end
    set ::fragment [read $::blob]
    close $::blob
  
................................................................................
    string range [db one {SELECT v FROM blobs}] end-19 end
  } $::fragment

  do_test incrblob-2.$AutoVacuumMode.5 {
    # Open and close the db to make sure the page cache is empty.
    db close
    sqlite3 db test.db
    execsql "PRAGMA mmap_size = 0"
  
    # Write the second-to-last 20 bytes of the blob via a blob handle.
    #
    set ::blob [db incrblob blobs v 1]
    seek $::blob -40 end
    puts -nonewline $::blob "1234567890abcdefghij"
    flush $::blob
................................................................................
    string range [db one {SELECT v FROM blobs}] end-39 end-20
  } "1234567890abcdefghij"

  do_test incrblob-2.$AutoVacuumMode.8 {
    # Open and close the db to make sure the page cache is empty.
    db close
    sqlite3 db test.db
    execsql { PRAGMA mmap_size = 0 }

    execsql { SELECT i FROM blobs } 
  } {45}

  do_test incrblob-2.$AutoVacuumMode.9 {
    nRead db
  } [expr $AutoVacuumMode ? 4 : 30]

# must refill.
#
do_test pageropt-1.5 {
  db2 eval {CREATE TABLE t2(y)}
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 6 0 0 $blobcontent]
do_test pageropt-1.6 {
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 0 0 0 $blobcontent]

# Verify that the last page of an overflow chain is not read from

# must refill.
#
do_test pageropt-1.5 {
  db2 eval {CREATE TABLE t2(y)}
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list [expr {[permutation]=="mmap" ? 1 : 6}] 0 0 $blobcontent]
do_test pageropt-1.6 {
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 0 0 0 $blobcontent]

# Verify that the last page of an overflow chain is not read from

#
lappend ::testsuitelist xxx

test_suite "veryquick" -prefix "" -description {
  "Very" quick test suite. Runs in less than 5 minutes on a workstation. 
  This test suite is the same as the "quick" tests, except that some files
  that test malloc and IO errors are omitted.








} -files [
  test_set $allquicktests -exclude *malloc* *ioerr* *fault* \
  multiplex* server1.test shared2.test shared6.test
]

test_suite "valgrind" -prefix "" -description {
  Run the "veryquick" test suite with a couple of multi-process tests (that

#
lappend ::testsuitelist xxx

test_suite "veryquick" -prefix "" -description {
  "Very" quick test suite. Runs in less than 5 minutes on a workstation. 
  This test suite is the same as the "quick" tests, except that some files
  that test malloc and IO errors are omitted.
} -files [
  test_set $allquicktests -exclude *malloc* *ioerr* *fault*
]

test_suite "mmap" -prefix "mm-" -description {
  Similar to veryquick. Except with memory mapping enabled.
} -presql {
  pragma mmap_size = -65536;
} -files [
  test_set $allquicktests -exclude *malloc* *ioerr* *fault* \
  multiplex* server1.test shared2.test shared6.test
]

test_suite "valgrind" -prefix "" -description {
  Run the "veryquick" test suite with a couple of multi-process tests (that