assert( CORRUPT_DB || iEnd <= pPage->pBt->usableSize );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  assert( iSize>=4 );   /* Minimum cell size is 4 */
  assert( iStart<=iLast );

  /* Overwrite deleted information with zeros when the secure_delete
  ** option is enabled */
  if( pPage->pBt->btsFlags & BTS_FAST_SECURE ){
    memset(&data[iStart], 0, iSize);
  }

  /* The list of freeblocks must be in ascending order.  Find the 
  ** spot on the list where iStart should be inserted.
  */
  hdr = pPage->hdrOffset;

  u16 first;

  assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
  assert( sqlite3PagerGetData(pPage->pDbPage) == data );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pBt->btsFlags & BTS_FAST_SECURE ){
    memset(&data[hdr], 0, pBt->usableSize - hdr);
  }
  data[hdr] = (char)flags;
  first = hdr + ((flags&PTF_LEAF)==0 ? 12 : 8);
  memset(&data[hdr+1], 0, 4);
  data[hdr+7] = 0;
  put2byte(&data[hdr+5], pBt->usableSize);

    pBt->db = db;
    sqlite3PagerSetBusyhandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
    p->pBt = pBt;
  
    pBt->pCursor = 0;
    pBt->pPage1 = 0;
    if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
#if defined(SQLITE_SECURE_DELETE)
    pBt->btsFlags |= BTS_SECURE_DELETE;
#elif defined(SQLITE_FAST_SECURE_DELETE)
    pBt->btsFlags |= BTS_OVERWRITE;
#endif
    /* EVIDENCE-OF: R-51873-39618 The page size for a database file is
    ** determined by the 2-byte integer located at an offset of 16 bytes from
    ** the beginning of the database file. */
    pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){

  sqlite3BtreeEnter(p);
  n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
  sqlite3BtreeLeave(p);
  return n;
}

/*
** Change the values for the BTS_SECURE_DELETE and BTS_OVERWRITE flags:
**
**    newFlag==0       Both BTS_SECURE_DELETE and BTS_OVERWRITE are cleared
**    newFlag==1       BTS_SECURE_DELETE set and BTS_OVERWRITE is cleared
**    newFlag==2       BTS_SECURE_DELETE cleared and BTS_OVERWRITE is set
**    newFlag==(-1)    No changes
**
** This routine acts as a query if newFlag is less than zero
**
** With BTS_OVERWRITE set, deleted content is overwritten by zeros, but
** freelist leaf pages are not written back to the database.  Thus in-page
** deleted content is cleared, but freelist deleted content is not.
**
** With BTS_SECURE_DELETE, operation is like BTS_OVERWRITE with the addition
** that freelist leaf pages are written back into the database, increasing
** the amount of disk I/O.
*/
int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
  int b;
  if( p==0 ) return 0;
  sqlite3BtreeEnter(p);
  assert( BTS_OVERWRITE==BTS_SECURE_DELETE*2 );
  assert( BTS_FAST_SECURE==(BTS_OVERWRITE|BTS_SECURE_DELETE) );
  if( newFlag>=0 ){
    p->pBt->btsFlags &= ~BTS_FAST_SECURE;
    p->pBt->btsFlags |= BTS_SECURE_DELETE*newFlag;
  }
  b = (p->pBt->btsFlags & BTS_FAST_SECURE)/BTS_SECURE_DELETE;
  sqlite3BtreeLeave(p);
  return b;
}

/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it

      ** later on.  
      **
      ** But not if we are in secure-delete mode. In secure-delete mode,
      ** the dropCell() routine will overwrite the entire cell with zeroes.
      ** In this case, temporarily copy the cell into the aOvflSpace[]
      ** buffer. It will be copied out again as soon as the aSpace[] buffer
      ** is allocated.  */
      if( pBt->btsFlags & BTS_FAST_SECURE ){
        int iOff;

        iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
        if( (iOff+szNew[i])>(int)pBt->usableSize ){
          rc = SQLITE_CORRUPT_BKPT;
          memset(apOld, 0, (i+1)*sizeof(MemPage*));
          goto balance_cleanup;

/*
** Allowed values for BtShared.btsFlags
*/
#define BTS_READ_ONLY        0x0001   /* Underlying file is readonly */
#define BTS_PAGESIZE_FIXED   0x0002   /* Page size can no longer be changed */
#define BTS_SECURE_DELETE    0x0004   /* PRAGMA secure_delete is enabled */
#define BTS_OVERWRITE        0x0008   /* Overwrite deleted content with zeros */
#define BTS_FAST_SECURE      0x000c   /* Combination of the previous two */
#define BTS_INITIALLY_EMPTY  0x0010   /* Database was empty at trans start */
#define BTS_NO_WAL           0x0020   /* Do not open write-ahead-log files */
#define BTS_EXCLUSIVE        0x0040   /* pWriter has an exclusive lock */
#define BTS_PENDING          0x0080   /* Waiting for read-locks to clear */

/*
** An instance of the following structure is used to hold information
** about a cell.  The parseCellPtr() function fills in this structure
** based on information extract from the raw disk page.
*/
struct CellInfo {

      }
    }
    break;
  }

  /*
  **  PRAGMA [schema.]secure_delete
  **  PRAGMA [schema.]secure_delete=ON/OFF/FAST
  **
  ** The first form reports the current setting for the
  ** secure_delete flag.  The second form changes the secure_delete
  ** flag setting and reports the new value.
  */
  case PragTyp_SECURE_DELETE: {
    Btree *pBt = pDb->pBt;
    int b = -1;
    assert( pBt!=0 );
    if( zRight ){
      if( sqlite3_stricmp(zRight, "fast")==0 ){
        b = 2;
      }else{
        b = sqlite3GetBoolean(zRight, 0);
      }
    }
    if( pId2->n==0 && b>=0 ){
      int ii;
      for(ii=0; ii<db->nDb; ii++){
        sqlite3BtreeSecureDelete(db->aDb[ii].pBt, b);
      }
    }