** 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.
**
*************************************************************************
** $Id: btree.c,v 1.687 2009/07/14 17:48:06 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
static int freeSpace(MemPage *pPage, int start, int size){
  int addr, pbegin, hdr;
  int iLast;                        /* Largest possible freeblock offset */
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
  assert( (start + size)<=pPage->pBt->usableSize );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  assert( size>=0 );   /* Minimum cell size is 4 */

#ifdef SQLITE_SECURE_DELETE
  /* Overwrite deleted information with zeros when the SECURE_DELETE 
  ** option is enabled at compile-time */
................................................................................
  ** possibilities. If the free-list is currently empty, or if the first
  ** trunk page in the free-list is full, then this page will become a
  ** new free-list trunk page. Otherwise, it will become a leaf of the
  ** first trunk page in the current free-list. This block tests if it
  ** is possible to add the page as a new free-list leaf.
  */
  if( nFree!=0 ){
    int nLeaf;                /* Initial number of leaf cells on trunk page */

    iTrunk = get4byte(&pPage1->aData[32]);
    rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
    if( rc!=SQLITE_OK ){
      goto freepage_out;
    }

    nLeaf = get4byte(&pTrunk->aData[4]);
    if( nLeaf<0 ){
      rc = SQLITE_CORRUPT_BKPT;
      goto freepage_out;
    }
    if( nLeaf<pBt->usableSize/4 - 8 ){
      /* In this case there is room on the trunk page to insert the page
      ** being freed as a new leaf.
      **
      ** Note that the trunk page is not really full until it contains
      ** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
      ** coded.  But due to a coding error in versions of SQLite prior to
      ** 3.6.0, databases with freelist trunk pages holding more than
      ** usableSize/4 - 8 entries will be reported as corrupt.  In order
      ** to maintain backwards compatibility with older versions of SQLite,
      ** we will contain to restrict the number of entries to usableSize/4 - 8
      ** for now.  At some point in the future (once everyone has upgraded
      ** to 3.6.0 or later) we should consider fixing the conditional above
      ** to read "usableSize/4-2" instead of "usableSize/4-8".
      */
      rc = sqlite3PagerWrite(pTrunk->pDbPage);
      if( rc==SQLITE_OK ){
        put4byte(&pTrunk->aData[4], nLeaf+1);
................................................................................

  /* If control flows to this point, then it was not possible to add the
  ** the page being freed as a leaf page of the first trunk in the free-list.
  ** Possibly because the free-list is empty, or possibly because the 
  ** first trunk in the free-list is full. Either way, the page being freed
  ** will become the new first trunk page in the free-list.
  */
  if(   ((!pPage) && (0 != (rc = btreeGetPage(pBt, iPage, &pPage, 0))))


     || (0 != (rc = sqlite3PagerWrite(pPage->pDbPage)))
  ){

    goto freepage_out;
  }
  put4byte(pPage->aData, iTrunk);
  put4byte(&pPage->aData[4], 0);
  put4byte(&pPage1->aData[32], iPage);
  TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));

................................................................................
  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  data = pPage->aData;
  ptr = &data[pPage->cellOffset + 2*idx];
  pc = get2byte(ptr);
  if( (pc<pPage->hdrOffset+6+(pPage->leaf?0:4))
     || (pc+sz>pPage->pBt->usableSize) ){
    return SQLITE_CORRUPT_BKPT;
  }
  rc = freeSpace(pPage, pc, sz);
  if( rc!=SQLITE_OK ){
    return rc;
  }
................................................................................
  assert( p->inTrans==TRANS_WRITE );

  /* Invalidate all incrblob cursors open on table iTable (assuming iTable
  ** is the root of a table b-tree - if it is not, the following call is
  ** a no-op).  */
  invalidateIncrblobCursors(p, iTable, 0, 1);

  if( SQLITE_OK==(rc = saveAllCursors(pBt, (Pgno)iTable, 0)) ){

    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
  }
  sqlite3BtreeLeave(p);
  return rc;
}

/*
................................................................................
  assert( p->inTrans==TRANS_WRITE );

  /* It is illegal to drop a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
  ** need to move another root-page to fill a gap left by the deleted
  ** root page. If an open cursor was using this page a problem would 
  ** occur.


  */
  if( pBt->pCursor ){
    sqlite3ConnectionBlocked(p->db, pBt->pCursor->pBtree->db);
    return SQLITE_LOCKED_SHAREDCACHE;
  }

  rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
  if( rc ) return rc;
  rc = sqlite3BtreeClearTable(p, iTable, 0);
................................................................................
      rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
    }else{
      rc = freePage(pPage);
      releasePage(pPage);
    }
#endif
  }else{
    /* If sqlite3BtreeDropTable was called on page 1. */



    zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
    releasePage(pPage);
  }
  return rc;  
}
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
  int rc;

** 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.
**
*************************************************************************
** $Id: btree.c,v 1.688 2009/07/15 11:26:44 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
static int freeSpace(MemPage *pPage, int start, int size){
  int addr, pbegin, hdr;
  int iLast;                        /* Largest possible freeblock offset */
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( start>=pPage->hdrOffset+6+pPage->childPtrSize );
  assert( (start + size)<=pPage->pBt->usableSize );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  assert( size>=0 );   /* Minimum cell size is 4 */

#ifdef SQLITE_SECURE_DELETE
  /* Overwrite deleted information with zeros when the SECURE_DELETE 
  ** option is enabled at compile-time */
................................................................................
  ** possibilities. If the free-list is currently empty, or if the first
  ** trunk page in the free-list is full, then this page will become a
  ** new free-list trunk page. Otherwise, it will become a leaf of the
  ** first trunk page in the current free-list. This block tests if it
  ** is possible to add the page as a new free-list leaf.
  */
  if( nFree!=0 ){
    u32 nLeaf;                /* Initial number of leaf cells on trunk page */

    iTrunk = get4byte(&pPage1->aData[32]);
    rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
    if( rc!=SQLITE_OK ){
      goto freepage_out;
    }

    nLeaf = get4byte(&pTrunk->aData[4]);
    if( nLeaf > pBt->usableSize/4 - 2 ){
      rc = SQLITE_CORRUPT_BKPT;
      goto freepage_out;
    }
    if( nLeaf<pBt->usableSize/4 - 8 ){
      /* In this case there is room on the trunk page to insert the page
      ** being freed as a new leaf.
      **
      ** Note that the trunk page is not really full until it contains
      ** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
      ** coded.  But due to a coding error in versions of SQLite prior to
      ** 3.6.0, databases with freelist trunk pages holding more than
      ** usableSize/4 - 8 entries will be reported as corrupt.  In order
      ** to maintain backwards compatibility with older versions of SQLite,
      ** we will continue to restrict the number of entries to usableSize/4 - 8
      ** for now.  At some point in the future (once everyone has upgraded
      ** to 3.6.0 or later) we should consider fixing the conditional above
      ** to read "usableSize/4-2" instead of "usableSize/4-8".
      */
      rc = sqlite3PagerWrite(pTrunk->pDbPage);
      if( rc==SQLITE_OK ){
        put4byte(&pTrunk->aData[4], nLeaf+1);
................................................................................

  /* If control flows to this point, then it was not possible to add the
  ** the page being freed as a leaf page of the first trunk in the free-list.
  ** Possibly because the free-list is empty, or possibly because the 
  ** first trunk in the free-list is full. Either way, the page being freed
  ** will become the new first trunk page in the free-list.
  */
  if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
    goto freepage_out;
  }
  rc = sqlite3PagerWrite(pPage->pDbPage);

  if( rc!=SQLITE_OK ){
    goto freepage_out;
  }
  put4byte(pPage->aData, iTrunk);
  put4byte(&pPage->aData[4], 0);
  put4byte(&pPage1->aData[32], iPage);
  TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));

................................................................................
  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  data = pPage->aData;
  ptr = &data[pPage->cellOffset + 2*idx];
  pc = get2byte(ptr);
  if( NEVER(pc<pPage->hdrOffset+6+pPage->childPtrSize)
     || (pc+sz>pPage->pBt->usableSize) ){
    return SQLITE_CORRUPT_BKPT;
  }
  rc = freeSpace(pPage, pc, sz);
  if( rc!=SQLITE_OK ){
    return rc;
  }
................................................................................
  assert( p->inTrans==TRANS_WRITE );

  /* Invalidate all incrblob cursors open on table iTable (assuming iTable
  ** is the root of a table b-tree - if it is not, the following call is
  ** a no-op).  */
  invalidateIncrblobCursors(p, iTable, 0, 1);

  rc = saveAllCursors(pBt, (Pgno)iTable, 0);
  if( SQLITE_OK==rc ){
    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
  }
  sqlite3BtreeLeave(p);
  return rc;
}

/*
................................................................................
  assert( p->inTrans==TRANS_WRITE );

  /* It is illegal to drop a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
  ** need to move another root-page to fill a gap left by the deleted
  ** root page. If an open cursor was using this page a problem would 
  ** occur.
  **
  ** This error is caught long before control reaches this point.
  */
  if( NEVER(pBt->pCursor) ){
    sqlite3ConnectionBlocked(p->db, pBt->pCursor->pBtree->db);
    return SQLITE_LOCKED_SHAREDCACHE;
  }

  rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
  if( rc ) return rc;
  rc = sqlite3BtreeClearTable(p, iTable, 0);
................................................................................
      rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
    }else{
      rc = freePage(pPage);
      releasePage(pPage);
    }
#endif
  }else{
    /* If sqlite3BtreeDropTable was called on page 1.
    ** This really never should happen except in a corrupt
    ** database. 
    */
    zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
    releasePage(pPage);
  }
  return rc;  
}
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
  int rc;

**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.560 2009/06/26 15:14:55 drh Exp $
*/
#include "sqliteInt.h"

#ifdef SQLITE_ENABLE_FTS3
# include "fts3.h"
#endif
#ifdef SQLITE_ENABLE_RTREE
................................................................................
    **    }
    */
    case SQLITE_TESTCTRL_ALWAYS: {
      int x = va_arg(ap,int);
      rc = ALWAYS(x);
      break;
    }















  }
  va_end(ap);
#endif /* SQLITE_OMIT_BUILTIN_TEST */
  return rc;
}

**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.561 2009/07/15 11:26:44 drh Exp $
*/
#include "sqliteInt.h"

#ifdef SQLITE_ENABLE_FTS3
# include "fts3.h"
#endif
#ifdef SQLITE_ENABLE_RTREE
................................................................................
    **    }
    */
    case SQLITE_TESTCTRL_ALWAYS: {
      int x = va_arg(ap,int);
      rc = ALWAYS(x);
      break;
    }

    /*   sqlite3_test_control(SQLITE_TESTCTRL_RESERVE, sqlite3 *db, int N)
    **
    ** Set the nReserve size to N for the main database on the database
    ** connection db.
    */
    case SQLITE_TESTCTRL_RESERVE: {
      sqlite3 *db = va_arg(ap, sqlite3*);
      int x = va_arg(ap,int);
      sqlite3_mutex_enter(db->mutex);
      sqlite3BtreeSetPageSize(db->aDb[0].pBt, 0, x, 0);
      sqlite3_mutex_leave(db->mutex);
      break;
    }

  }
  va_end(ap);
#endif /* SQLITE_OMIT_BUILTIN_TEST */
  return rc;
}

** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.458 2009/06/19 22:50:31 drh 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++.
................................................................................
#define SQLITE_TESTCTRL_PRNG_RESET               7
#define SQLITE_TESTCTRL_BITVEC_TEST              8
#define SQLITE_TESTCTRL_FAULT_INSTALL            9
#define SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS     10
#define SQLITE_TESTCTRL_PENDING_BYTE            11
#define SQLITE_TESTCTRL_ASSERT                  12
#define SQLITE_TESTCTRL_ALWAYS                  13


/*
** CAPI3REF: SQLite Runtime Status {H17200} <S60200>
** EXPERIMENTAL
**
** This interface is used to retrieve runtime status information
** about the preformance of SQLite, and optionally to reset various

** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.459 2009/07/15 11:26:44 drh 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++.
................................................................................
#define SQLITE_TESTCTRL_PRNG_RESET               7
#define SQLITE_TESTCTRL_BITVEC_TEST              8
#define SQLITE_TESTCTRL_FAULT_INSTALL            9
#define SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS     10
#define SQLITE_TESTCTRL_PENDING_BYTE            11
#define SQLITE_TESTCTRL_ASSERT                  12
#define SQLITE_TESTCTRL_ALWAYS                  13
#define SQLITE_TESTCTRL_RESERVE                 14

/*
** CAPI3REF: SQLite Runtime Status {H17200} <S60200>
** EXPERIMENTAL
**
** This interface is used to retrieve runtime status information
** about the preformance of SQLite, and optionally to reset various