SQLite

/*
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.88 2003/04/13 18:26:51 paul Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.

**
** The first page of the file contains a magic string used to verify that
** the file really is a valid BTree database, a pointer to a list of unused
** pages in the file, and some meta information.  The root of the first
** BTree begins on page 2 of the file.  (Pages are numbered beginning with
** 1, not 0.)  Thus a minimum database contains 2 pages.
*/

/* We don't want the btree function macros as they clash with the functions
** defined in this file. This may be fixed in future by renaming the macros
** or the functions defined here, or both.
*/
#define SQLITE_NO_BTREE_DEFS

#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>

/* Forward declarations */
static BtOps sqliteBtreeOps;

*/
#define SKIP_NONE     0   /* Always step the cursor */
#define SKIP_NEXT     1   /* The next sqliteBtreeNext() is a no-op */
#define SKIP_PREV     2   /* The next sqliteBtreePrevious() is a no-op */
#define SKIP_INVALID  3   /* Calls to Next() and Previous() are invalid */

/* Forward declarations */
static int sqliteBtreeCloseCursor(BtCursor *pCur);

/*
** Routines for byte swapping.
*/
u16 swab16(u16 x){
  return ((x & 0xff)<<8) | ((x>>8)&0xff);
}

  *ppBtree = pBt;
  return SQLITE_OK;
}

/*
** Close an open database and invalidate all cursors.
*/
static int sqliteBtreeClose(Btree *pBt){
  while( pBt->pCursor ){
    sqliteBtreeCloseCursor(pBt->pCursor);
  }
  sqlitepager_close(pBt->pPager);
  sqliteFree(pBt);
  return SQLITE_OK;
}

/*

** and the database cannot be corrupted if this program
** crashes.  But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
static int sqliteBtreeSetCacheSize(Btree *pBt, int mxPage){
  sqlitepager_set_cachesize(pBt->pPager, mxPage);
  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
** probability of damage to near zero but with a write performance reduction.
*/
static int sqliteBtreeSetSafetyLevel(Btree *pBt, int level){
  sqlitepager_set_safety_level(pBt->pPager, level);
  return SQLITE_OK;
}

/*
** Get a reference to page1 of the database file.  This will
** also acquire a readlock on that file.

**      sqliteBtreeCreateIndex()
**      sqliteBtreeClearTable()
**      sqliteBtreeDropTable()
**      sqliteBtreeInsert()
**      sqliteBtreeDelete()
**      sqliteBtreeUpdateMeta()
*/
static int sqliteBtreeBeginTrans(Btree *pBt){
  int rc;
  if( pBt->inTrans ) return SQLITE_ERROR;
  if( pBt->readOnly ) return SQLITE_READONLY;
  if( pBt->page1==0 ){
    rc = lockBtree(pBt);
    if( rc!=SQLITE_OK ){
      return rc;

/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
static int sqliteBtreeCommit(Btree *pBt){
  int rc;
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_commit(pBt->pPager);
  pBt->inTrans = 0;
  pBt->inCkpt = 0;
  unlockBtreeIfUnused(pBt);
  return rc;
}

/*
** Rollback the transaction in progress.  All cursors will be
** invalided by this operation.  Any attempt to use a cursor
** that was open at the beginning of this operation will result
** in an error.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
static int sqliteBtreeRollback(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inTrans==0 ) return SQLITE_OK;
  pBt->inTrans = 0;
  pBt->inCkpt = 0;
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){

** main transaction.  You must start a transaction before starting a
** checkpoint.  The checkpoint is ended automatically if the transaction
** commits or rolls back.
**
** Only one checkpoint may be active at a time.  It is an error to try
** to start a new checkpoint if another checkpoint is already active.
*/
static int sqliteBtreeBeginCkpt(Btree *pBt){
  int rc;
  if( !pBt->inTrans || pBt->inCkpt ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_ckpt_begin(pBt->pPager);
  pBt->inCkpt = 1;
  return rc;
}


/*
** Commit a checkpoint to transaction currently in progress.  If no
** checkpoint is active, this is a no-op.
*/
static int sqliteBtreeCommitCkpt(Btree *pBt){
  int rc;
  if( pBt->inCkpt && !pBt->readOnly ){
    rc = sqlitepager_ckpt_commit(pBt->pPager);
  }else{
    rc = SQLITE_OK;
  }
  pBt->inCkpt = 0;
  return rc;
}

/*
** Rollback the checkpoint to the current transaction.  If there
** is no active checkpoint or transaction, this routine is a no-op.
**
** All cursors will be invalided by this operation.  Any attempt
** to use a cursor that was open at the beginning of this operation
** will result in an error.
*/
static int sqliteBtreeRollbackCkpt(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inCkpt==0 || pBt->readOnly ) return SQLITE_OK;
  rc = sqlitepager_ckpt_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pPage && pCur->pPage->isInit==0 ){
      sqlitepager_unref(pCur->pPage);

** should be opened with wrFlag==1 even if they never really intend
** to write.
** 
** No checking is done to make sure that page iTable really is the
** root page of a b-tree.  If it is not, then the cursor acquired
** will not work correctly.
*/
static int sqliteBtreeCursor(Btree *pBt, int iTable, int wrFlag, BtCursor **ppCur){
  int rc;
  BtCursor *pCur, *pRing;

  if( pBt->page1==0 ){
    rc = lockBtree(pBt);
    if( rc!=SQLITE_OK ){
      *ppCur = 0;

  return rc;
}

/*
** Close a cursor.  The read lock on the database file is released
** when the last cursor is closed.
*/
static int sqliteBtreeCloseCursor(BtCursor *pCur){
  Btree *pBt = pCur->pBt;
  if( pCur->pPrev ){
    pCur->pPrev->pNext = pCur->pNext;
  }else{
    pBt->pCursor = pCur->pNext;
  }
  if( pCur->pNext ){

/*
** Set *pSize to the number of bytes of key in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
static int sqliteBtreeKeySize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    *pSize = 0;

** Change:  It used to be that the amount returned will be smaller
** than the amount requested if there are not enough bytes in the key
** to satisfy the request.  But now, it must be the case that there
** is enough data available to satisfy the request.  If not, an exception
** is raised.  The change was made in an effort to boost performance
** by eliminating unneeded tests.
*/
static int sqliteBtreeKey(BtCursor *pCur, int offset, int amt, char *zBuf){
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell ){

/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
static int sqliteBtreeDataSize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    *pSize = 0;

** Read part of the data associated with cursor pCur.  A maximum
** of "amt" bytes will be transfered into zBuf[].  The transfer
** begins at "offset".  The number of bytes actually read is
** returned.  The amount returned will be smaller than the
** amount requested if there are not enough bytes in the data
** to satisfy the request.
*/
static int sqliteBtreeData(BtCursor *pCur, int offset, int amt, char *zBuf){
  Cell *pCell;
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;

**    *pRes>0    This means pCur>pKey
**
** When one key is an exact prefix of the other, the shorter key is
** considered less than the longer one.  In order to be equal the
** keys must be exactly the same length. (The length of the pCur key
** is the actual key length minus nIgnore bytes.)
*/
static int sqliteBtreeKeyCompare(
  BtCursor *pCur,       /* Pointer to entry to compare against */
  const void *pKey,     /* Key to compare against entry that pCur points to */
  int nKey,             /* Number of bytes in pKey */
  int nIgnore,          /* Ignore this many bytes at the end of pCur */
  int *pResult          /* Write the result here */
){
  Pgno nextPage;

  return SQLITE_OK;
}

/* Move the cursor to the first entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
static int sqliteBtreeFirst(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  if( pCur->pPage->nCell==0 ){
    *pRes = 1;
    return SQLITE_OK;
  }
  *pRes = 0;
  rc = moveToLeftmost(pCur);
  pCur->eSkip = SKIP_NONE;
  return rc;
}

/* Move the cursor to the last entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
static int sqliteBtreeLast(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  assert( pCur->pPage->isInit );
  if( pCur->pPage->nCell==0 ){
    *pRes = 1;

**
**     *pRes==0     The cursor is left pointing at an entry that
**                  exactly matches pKey.
**
**     *pRes>0      The cursor is left pointing at an entry that
**                  is larger than pKey.
*/

static int sqliteBtreeMoveto(BtCursor *pCur, const void *pKey, int nKey, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  pCur->eSkip = SKIP_NONE;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  for(;;){
    int lwr, upr;
    Pgno chldPg;
    MemPage *pPage = pCur->pPage;
    int c = -1;  /* pRes return if table is empty must be -1 */
    lwr = 0;
    upr = pPage->nCell-1;
    while( lwr<=upr ){
      pCur->idx = (lwr+upr)/2;
      rc = sqliteBtreeKeyCompare(pCur, pKey, nKey, 0, &c);
      if( rc ) return rc;
      if( c==0 ){
        pCur->iMatch = c;
        if( pRes ) *pRes = 0;
        return SQLITE_OK;
      }
      if( c<0 ){

/*
** Advance the cursor to the next entry in the database.  If
** successful then set *pRes=0.  If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
*/
static int sqliteBtreeNext(BtCursor *pCur, int *pRes){
  int rc;
  MemPage *pPage = pCur->pPage;
  assert( pRes!=0 );
  if( pPage==0 ){
    *pRes = 1;
    return SQLITE_ABORT;
  }

/*
** Step the cursor to the back to the previous entry in the database.  If
** successful then set *pRes=0.  If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
*/
static int sqliteBtreePrevious(BtCursor *pCur, int *pRes){
  int rc;
  Pgno pgno;
  MemPage *pPage;
  pPage = pCur->pPage;
  if( pPage==0 ){
    *pRes = 1;
    return SQLITE_ABORT;

/*
** Insert a new record into the BTree.  The key is given by (pKey,nKey)
** and the data is given by (pData,nData).  The cursor is used only to
** define what database the record should be inserted into.  The cursor
** is left pointing at the new record.
*/
static int sqliteBtreeInsert(
  BtCursor *pCur,                /* Insert data into the table of this cursor */
  const void *pKey, int nKey,    /* The key of the new record */
  const void *pData, int nData   /* The data of the new record */
){
  Cell newCell;
  int rc;
  int loc;

  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
  if( checkReadLocks(pCur) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  rc = sqliteBtreeMoveto(pCur, pKey, nKey, &loc);
  if( rc ) return rc;
  pPage = pCur->pPage;
  assert( pPage->isInit );
  rc = sqlitepager_write(pPage);
  if( rc ) return rc;
  rc = fillInCell(pBt, &newCell, pKey, nKey, pData, nData);
  if( rc ) return rc;

** sqliteBtreeNext() after a delete and the cursor will be left
** pointing to the first entry after the deleted entry.  Similarly,
** pCur->eSkip is set to SKIP_PREV is the cursor is left pointing to
** the entry prior to the deleted entry so that a subsequent call to
** sqliteBtreePrevious() will always leave the cursor pointing at the
** entry immediately before the one that was deleted.
*/
static int sqliteBtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  Cell *pCell;
  int rc;
  Pgno pgnoChild;
  Btree *pBt = pCur->pBt;

  assert( pPage->isInit );

    ** to be a leaf so we can use it.
    */
    BtCursor leafCur;
    Cell *pNext;
    int szNext;
    int notUsed;
    getTempCursor(pCur, &leafCur);
    rc = sqliteBtreeNext(&leafCur, &notUsed);
    if( rc!=SQLITE_OK ){
      return SQLITE_CORRUPT;
    }
    rc = sqlitepager_write(leafCur.pPage);
    if( rc ) return rc;
    dropCell(pBt, pPage, pCur->idx, cellSize(pBt, pCell));
    pNext = leafCur.pPage->apCell[leafCur.idx];

}

/*
** Create a new BTree table.  Write into *piTable the page
** number for the root page of the new table.
**
** In the current implementation, BTree tables and BTree indices are the 
** the same.  But in the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.

*/
static int sqliteBtreeCreateTable(Btree *pBt, int *piTable){
  MemPage *pRoot;
  Pgno pgnoRoot;
  int rc;
  if( !pBt->inTrans ){
    /* Must start a transaction first */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  if( pBt->readOnly ){
    return SQLITE_READONLY;
  }
  rc = allocatePage(pBt, &pRoot, &pgnoRoot, 0);
  if( rc ) return rc;
  assert( sqlitepager_iswriteable(pRoot) );
  zeroPage(pBt, pRoot);
  sqlitepager_unref(pRoot);
  *piTable = (int)pgnoRoot;
  return SQLITE_OK;
}

/*
** Create a new BTree index.  Write into *piTable the page
** number for the root page of the new index.
**
** In the current implementation, BTree tables and BTree indices are the 
** the same.  But in the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.
*/
static int sqliteBtreeCreateIndex(Btree *pBt, int *piIndex){
  return sqliteBtreeCreateTable(pBt, piIndex);
}

/*
** Erase the given database page and all its children.  Return
** the page to the freelist.
*/
static int clearDatabasePage(Btree *pBt, Pgno pgno, int freePageFlag){
  MemPage *pPage;
  int rc;

  sqlitepager_unref(pPage);
  return rc;
}

/*
** Delete all information from a single table in the database.
*/
static int sqliteBtreeClearTable(Btree *pBt, int iTable){
  int rc;
  BtCursor *pCur;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      if( pCur->wrFlag==0 ) return SQLITE_LOCKED;
      moveToRoot(pCur);
    }
  }
  rc = clearDatabasePage(pBt, (Pgno)iTable, 0);
  if( rc ){
    sqliteBtreeRollback(pBt);
  }
  return rc;
}

/*
** Erase all information in a table and add the root of the table to
** the freelist.  Except, the root of the principle table (the one on
** page 2) is never added to the freelist.
*/
static int sqliteBtreeDropTable(Btree *pBt, int iTable){
  int rc;
  MemPage *pPage;
  BtCursor *pCur;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      return SQLITE_LOCKED;  /* Cannot drop a table that has a cursor */
    }
  }
  rc = sqlitepager_get(pBt->pPager, (Pgno)iTable, (void**)&pPage);
  if( rc ) return rc;
  rc = sqliteBtreeClearTable(pBt, iTable);
  if( rc ) return rc;
  if( iTable>2 ){
    rc = freePage(pBt, pPage, iTable);
  }else{
    zeroPage(pBt, pPage);
  }
  sqlitepager_unref(pPage);

  return rc;
}
#endif

/*
** Read the meta-information out of a database file.
*/
static int sqliteBtreeGetMeta(Btree *pBt, int *aMeta){
  PageOne *pP1;
  int rc;
  int i;

  rc = sqlitepager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  aMeta[0] = SWAB32(pBt, pP1->nFree);
  for(i=0; i<sizeof(pP1->aMeta)/sizeof(pP1->aMeta[0]); i++){
    aMeta[i+1] = SWAB32(pBt, pP1->aMeta[i]);
  }
  sqlitepager_unref(pP1);
  return SQLITE_OK;
}

/*
** Write meta-information back into the database.
*/
static int sqliteBtreeUpdateMeta(Btree *pBt, int *aMeta){
  PageOne *pP1;
  int rc, i;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  pP1 = pBt->page1;
  rc = sqlitepager_write(pP1);

******************************************************************************/

/*
** Print a disassembly of the given page on standard output.  This routine
** is used for debugging and testing only.
*/
#ifdef SQLITE_TEST
static int sqliteBtreePageDump(Btree *pBt, int pgno, int recursive){
  int rc;
  MemPage *pPage;
  int i, j;
  int nFree;
  u16 idx;
  char range[20];
  unsigned char payload[20];

  if( idx!=0 ){
    printf("ERROR: next freeblock index out of range: %d\n", idx);
  }
  if( recursive && pPage->u.hdr.rightChild!=0 ){
    idx = SWAB16(pBt, pPage->u.hdr.firstCell);
    while( idx>0 && idx<SQLITE_PAGE_SIZE-MIN_CELL_SIZE ){
      Cell *pCell = (Cell*)&pPage->u.aDisk[idx];
      sqliteBtreePageDump(pBt, SWAB32(pBt, pCell->h.leftChild), 1);
      idx = SWAB16(pBt, pCell->h.iNext);
    }
    sqliteBtreePageDump(pBt, SWAB32(pBt, pPage->u.hdr.rightChild), 1);
  }
  sqlitepager_unref(pPage);
  return SQLITE_OK;
}
#endif

#ifdef SQLITE_TEST

**   aResult[4] =  Number of free bytes on this page
**   aResult[5] =  Number of free blocks on the page
**   aResult[6] =  Page number of the left child of this entry
**   aResult[7] =  Page number of the right child for the whole page
**
** This routine is used for testing and debugging only.
*/
static int sqliteBtreeCursorDump(BtCursor *pCur, int *aResult){
  int cnt, idx;
  MemPage *pPage = pCur->pPage;
  Btree *pBt = pCur->pBt;
  aResult[0] = sqlitepager_pagenumber(pPage);
  aResult[1] = pCur->idx;
  aResult[2] = pPage->nCell;
  if( pCur->idx>=0 && pCur->idx<pPage->nCell ){

#endif

#ifdef SQLITE_TEST
/*
** Return the pager associated with a BTree.  This routine is used for
** testing and debugging only.
*/
static Pager *sqliteBtreePager(Btree *pBt){
  return pBt->pPager;
}
#endif

/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.

** a table.  nRoot is the number of entries in aRoot.
**
** If everything checks out, this routine returns NULL.  If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned.  The calling function
** is responsible for freeing the error message when it is done.
*/
char *sqliteBtreeIntegrityCheck(Btree *pBt, int *aRoot, int nRoot){
  int i;
  int nRef;
  IntegrityCk sCheck;

  nRef = *sqlitepager_stats(pBt->pPager);
  if( lockBtree(pBt)!=SQLITE_OK ){
    return sqliteStrDup("Unable to acquire a read lock on the database");

  sqliteFree(sCheck.anRef);
  return sCheck.zErrMsg;
}

/*
** Return the full pathname of the underlying database file.
*/
static const char *sqliteBtreeGetFilename(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlitepager_filename(pBt->pPager);
}

/*
** Change the name of the underlying database file.
*/
static int sqliteBtreeChangeFilename(Btree *pBt, const char *zNew){
  return sqlitepager_rename(pBt->pPager, zNew);
}

/*
** The following tables contain pointers to all of the interface
** routines for this implementation of the B*Tree backend.  To
** substitute a different implemention of the backend, one has merely
** to provide pointers to alternative functions in similar tables.
*/
static BtOps sqliteBtreeOps = {
    sqliteBtreeClose,
    sqliteBtreeSetCacheSize,
    sqliteBtreeSetSafetyLevel,
    sqliteBtreeBeginTrans,
    sqliteBtreeCommit,
    sqliteBtreeRollback,
    sqliteBtreeBeginCkpt,
    sqliteBtreeCommitCkpt,
    sqliteBtreeRollbackCkpt,
    sqliteBtreeCreateTable,
    sqliteBtreeCreateIndex,
    sqliteBtreeDropTable,
    sqliteBtreeClearTable,
    sqliteBtreeCursor,
    sqliteBtreeGetMeta,
    sqliteBtreeUpdateMeta,
    sqliteBtreeIntegrityCheck,
    sqliteBtreeGetFilename,
    sqliteBtreeChangeFilename,
#ifdef SQLITE_TEST
    sqliteBtreePageDump,
    sqliteBtreePager
#endif
};
static BtCursorOps sqliteBtreeCursorOps = {
    sqliteBtreeMoveto,
    sqliteBtreeDelete,
    sqliteBtreeInsert,
    sqliteBtreeFirst,
    sqliteBtreeLast,
    sqliteBtreeNext,
    sqliteBtreePrevious,
    sqliteBtreeKeySize,
    sqliteBtreeKey,
    sqliteBtreeKeyCompare,
    sqliteBtreeDataSize,
    sqliteBtreeData,
    sqliteBtreeCloseCursor,
#ifdef SQLITE_TEST
    sqliteBtreeCursorDump,
#endif
};

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.30 2003/04/06 20:44:45 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/*
** Forward declarations of structure
*/

** The number of 4-byte "meta" values contained on the first page of each
** database file.
*/
#define SQLITE_N_BTREE_META 10

int sqliteBtreeOpen(const char *zFilename, int mode, int nPg, Btree **ppBtree);

#if !defined(SQLITE_NO_BTREE_DEFS)
#define btOps(pBt) (*((BtOps **)(pBt)))
#define btCOps(pCur) (*((BtCursorOps **)(pCur)))

#define sqliteBtreeClose(pBt)              (btOps(pBt)->Close(pBt))
#define sqliteBtreeSetCacheSize(pBt, sz)   (btOps(pBt)->SetCacheSize(pBt, sz))
#define sqliteBtreeSetSafetyLevel(pBt, sl) (btOps(pBt)->SetSafetyLevel(pBt, sl))
#define sqliteBtreeBeginTrans(pBt)         (btOps(pBt)->BeginTrans(pBt))

#define sqliteBtreeGetMeta(pBt, aMeta)    (btOps(pBt)->GetMeta(pBt, aMeta))
#define sqliteBtreeUpdateMeta(pBt, aMeta) (btOps(pBt)->UpdateMeta(pBt, aMeta))
#define sqliteBtreeIntegrityCheck(pBt, aRoot, nRoot)\
                (btOps(pBt)->IntegrityCheck(pBt, aRoot, nRoot))
#define sqliteBtreeGetFilename(pBt)       (btOps(pBt)->GetFilename(pBt))
#define sqliteBtreeChangeFilename(pBt, zNew)\
                (btOps(pBt)->ChangeFilename(pBt, zNew))
#endif

#ifdef SQLITE_TEST
#if !defined(SQLITE_NO_BTREE_DEFS)
#define sqliteBtreePageDump(pBt, pgno, recursive)\
                (btOps(pBt)->PageDump(pBt, pgno, recursive))
#define sqliteBtreeCursorDump(pCur, aResult)\
                (btCOps(pCur)->CursorDump(pCur, aResult))
#define sqliteBtreePager(pBt)             (btOps(pBt)->Pager(pBt))
#endif

int btree_native_byte_order;
#endif


#endif /* _BTREE_H_ */

/*
** 2003 Feb 4
**
** 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.
**
*************************************************************************
** $Id: btree_rb.c,v 1.2 2003/04/15 19:22:23 drh Exp $
**
** This file implements an in-core database using Red-Black balanced
** binary trees.
**
** It was contributed to SQLite by anonymous on 2003-Feb-04 23:24:49 UTC.
*/
#define SQLITE_NO_BTREE_DEFS
#include "btree.h"
#include "sqliteInt.h"
#include <assert.h>

/*
** Omit this whole file if the SQLITE_OMIT_INMEMORYDB macro is
** defined.  This allows a lot of code to be omitted for installations

  BtRbNode *pLeft;   /* Nodes left child, or NULL */
  BtRbNode *pRight;  /* Nodes right child, or NULL */

  int nBlackHeight;  /* Only used during the red-black integrity check */
};

/* Forward declarations */
static int sqliteBtreeMoveto(BtCursor* pCur, const void *pKey, int nKey, int *pRes);
static int sqliteBtreeClearTable(Btree* tree, int n);
static int sqliteBtreeNext(BtCursor* pCur, int *pRes);
static int sqliteBtreeLast(BtCursor* pCur, int *pRes);
static int sqliteBtreePrevious(BtCursor* pCur, int *pRes);

/*
 * The key-compare function for the red-black trees. Returns as follows:
 *
 * (key1 < key2)             -1
 * (key1 == key2)             0 
 * (key1 > key2)              1

  return SQLITE_OK;
}

/*
 * Create a new table in the supplied Btree. Set *n to the new table number.
 * Return SQLITE_OK if the operation is a success.
 */
static int sqliteBtreeCreateTable(Btree* tree, int* n)
{
  assert( tree->eTransState != TRANS_NONE );

  *n = tree->next_idx++;
  btreeCreateTable(tree, *n);

  /* Set up the rollback structure (if we are not doing this as part of a
   * rollback) */
  if( tree->eTransState != TRANS_ROLLBACK ){
    BtRollbackOp *pRollbackOp = sqliteMalloc(sizeof(BtRollbackOp));
    pRollbackOp->eOp = ROLLBACK_DROP;
    pRollbackOp->iTab = *n;
    btreeLogRollbackOp(tree, pRollbackOp);
  }

  return SQLITE_OK;
}

/*
 * This is currently an alias for sqliteBtreeCreateTable(). There is a note in
 * btree.c suggesting that one day indices and tables may be optimized
 * differently.
 */
static int sqliteBtreeCreateIndex(Btree* tree, int* n)
{
  return sqliteBtreeCreateTable(tree, n);
}

/*
 * Delete table n from the supplied Btree. 
 */
static int sqliteBtreeDropTable(Btree* tree, int n)
{
  BtRbTree *pTree;
  assert( tree->eTransState != TRANS_NONE );

  sqliteBtreeClearTable(tree, n);
  pTree = sqliteHashFind(&tree->tblHash, 0, n);
  assert(pTree);
  sqliteFree(pTree);
  sqliteHashInsert(&tree->tblHash, 0, n, 0);

  if( tree->eTransState != TRANS_ROLLBACK ){
    BtRollbackOp *pRollbackOp = sqliteMalloc(sizeof(BtRollbackOp));
    pRollbackOp->eOp = ROLLBACK_CREATE;
    pRollbackOp->iTab = n;
    btreeLogRollbackOp(tree, pRollbackOp);
  }

  return SQLITE_OK;
}

static int sqliteBtreeKeyCompare(BtCursor* pCur, const void *pKey, int nKey,
				 int nIgnore, int *pRes)
{
  assert(pCur);

  if( !pCur->pNode ) {
    *pRes = -1;
  } else {

/*
 * Get a new cursor for table iTable of the supplied Btree. The wrFlag
 * parameter is ignored, all cursors are capable of write-operations. 
 *
 * Note that BtCursor.eSkip and BtCursor.pNode both initialize to 0.
 */
static int sqliteBtreeCursor(Btree* tree, int iTable, int wrFlag, BtCursor **ppCur)
{
  assert(tree);
  *ppCur = sqliteMalloc(sizeof(BtCursor));
  (*ppCur)->pTree  = sqliteHashFind(&tree->tblHash, 0, iTable);
  (*ppCur)->pBtree = tree;
  (*ppCur)->iTree  = iTable;
  (*ppCur)->pOps = &sqliteBtreeCursorOps;

  assert( (*ppCur)->pTree );
  return SQLITE_OK;
}

/*
 * Insert a new record into the Btree.  The key is given by (pKey,nKey)
 * and the data is given by (pData,nData).  The cursor is used only to
 * define what database the record should be inserted into.  The cursor
 * is left pointing at the new record.
 *
 * If the key exists already in the tree, just replace the data. 
 */
static int sqliteBtreeInsert(BtCursor* pCur, const void *pKey, int nKey,
			     const void *pDataInput, int nData)
{
  void * pData;
  int match;

  /* It is illegal to call sqliteBtreeInsert() if we are not in a transaction */
  assert( pCur->pBtree->eTransState != TRANS_NONE );

   * If there is no exact match, then the cursor points at what would be either
   * the predecessor (match == -1) or successor (match == 1) of the
   * searched-for key, were it to be inserted. The new node becomes a child of
   * this node.
   * 
   * The new node is initially red.
   */
  sqliteBtreeMoveto( pCur, pKey, nKey, &match);
  if( match ){
    BtRbNode *pNode = sqliteMalloc(sizeof(BtRbNode));
    pNode->nKey = nKey;
    pNode->pKey = sqliteMalloc(nKey);
    memcpy(pNode->pKey, pKey, nKey);
    pNode->nData = nData;
    pNode->pData = pData; 

**
**     *pRes==0     The cursor is left pointing at an entry that
**                  exactly matches pKey.
**
**     *pRes>0      The cursor is left pointing at an entry that
**                  is larger than pKey.
*/
static int sqliteBtreeMoveto(BtCursor* pCur, const void *pKey, int nKey, int *pRes)
{
  BtRbNode *pTmp = 0;

  pCur->pNode = pCur->pTree->pHead;
  *pRes = -1;
  while( pCur->pNode && *pRes ) {
    *pRes = key_compare(pCur->pNode->pKey, pCur->pNode->nKey, pKey, nKey);

** sqliteBtreeNext() after a delete and the cursor will be left
** pointing to the first entry after the deleted entry.  Similarly,
** pCur->eSkip is set to SKIP_PREV is the cursor is left pointing to
** the entry prior to the deleted entry so that a subsequent call to
** sqliteBtreePrevious() will always leave the cursor pointing at the
** entry immediately before the one that was deleted.
*/
static int sqliteBtreeDelete(BtCursor* pCur)
{
  BtRbNode *pZ;      /* The one being deleted */
  BtRbNode *pChild;  /* The child of the spliced out node */

  /* It is illegal to call sqliteBtreeDelete() if we are not in a transaction */
  assert( pCur->pBtree->eTransState != TRANS_NONE );

   * If pZ has no children or one child, then splice out pZ.  If pZ has two
   * children, splice out the successor of pZ and replace the key and data of
   * pZ with the key and data of the spliced out successor.  */
  if( pZ->pLeft && pZ->pRight ){
    BtRbNode *pTmp;
    int dummy;
    pCur->eSkip = SKIP_NONE;
    sqliteBtreeNext(pCur, &dummy);
    assert( dummy == 0 );
    if( pCur->pBtree->eTransState == TRANS_ROLLBACK ){
      sqliteFree(pZ->pKey);
      sqliteFree(pZ->pData);
    }
    pZ->pData = pCur->pNode->pData;
    pZ->nData = pCur->pNode->nData;
    pZ->pKey = pCur->pNode->pKey;
    pZ->nKey = pCur->pNode->nKey;
    pTmp = pZ;
    pZ = pCur->pNode;
    pCur->pNode = pTmp;
    pCur->eSkip = SKIP_NEXT;
  }else{
    int res;
    pCur->eSkip = SKIP_NONE;
    sqliteBtreeNext(pCur, &res);
    pCur->eSkip = SKIP_NEXT;
    if( res ){
      sqliteBtreeLast(pCur, &res);
      sqliteBtreePrevious(pCur, &res);
      pCur->eSkip = SKIP_PREV;
    }
    if( pCur->pBtree->eTransState == TRANS_ROLLBACK ){
	sqliteFree(pZ->pKey);
	sqliteFree(pZ->pData);
    }
  }

  sqliteFree(pZ);
  return SQLITE_OK;
}

/*
 * Empty table n of the Btree.
 */
static int sqliteBtreeClearTable(Btree* tree, int n)
{
  BtRbTree *pTree;
  BtRbNode *pNode;

  pTree = sqliteHashFind(&tree->tblHash, 0, n);
  assert(pTree);

    }
  }

  pTree->pHead = 0;
  return SQLITE_OK;
}

static int sqliteBtreeFirst(BtCursor* pCur, int *pRes)
{
  if( pCur->pTree->pHead ){
    pCur->pNode = pCur->pTree->pHead;
    while( pCur->pNode->pLeft ){
      pCur->pNode = pCur->pNode->pLeft;
    }
  }
  if( pCur->pNode ){
    *pRes = 0;
  }else{
    *pRes = 1;
  }
  pCur->eSkip = SKIP_NONE;
  return SQLITE_OK;
}

static int sqliteBtreeLast(BtCursor* pCur, int *pRes)
{
  if( pCur->pTree->pHead ){
    pCur->pNode = pCur->pTree->pHead;
    while( pCur->pNode->pRight ){
      pCur->pNode = pCur->pNode->pRight;
    }
  }
  if( pCur->pNode ){
    *pRes = 0;
  }else{
    *pRes = 1;
  }
  pCur->eSkip = SKIP_NONE;
  return SQLITE_OK;
}

static int sqliteBtreeNext(BtCursor* pCur, int *pRes)
{
  if( pCur->pNode && pCur->eSkip != SKIP_NEXT ){
    if( pCur->pNode->pRight ){
      pCur->pNode = pCur->pNode->pRight;
      while( pCur->pNode->pLeft )
	pCur->pNode = pCur->pNode->pLeft;
    }else{

  }else{
    *pRes = 0;
  }

  return SQLITE_OK;
}

static int sqliteBtreePrevious(BtCursor* pCur, int *pRes)
{
  if( pCur->pNode && pCur->eSkip != SKIP_PREV ){
    if( pCur->pNode->pLeft ){
      pCur->pNode = pCur->pNode->pLeft;
      while( pCur->pNode->pRight )
	pCur->pNode = pCur->pNode->pRight;
    }else{

  }else{
    *pRes = 0;
  }

  return SQLITE_OK;
}

static int sqliteBtreeKeySize(BtCursor* pCur, int *pSize)
{
  if( pCur->pNode ){
    *pSize = pCur->pNode->nKey;
  }else{
    *pSize = 0;
  }
  return SQLITE_OK;
}

static int sqliteBtreeKey(BtCursor* pCur, int offset, int amt, char *zBuf)
{
  if( !pCur->pNode ) return 0;
  if( !pCur->pNode->pKey || ((amt + offset) <= pCur->pNode->nKey) ){
    memcpy(zBuf, pCur->pNode->pKey+offset, amt);
    return amt;
  }else{
    memcpy(zBuf, pCur->pNode->pKey+offset ,pCur->pNode->nKey-offset);
    return pCur->pNode->nKey-offset;
  }
  assert(0);
}

static int sqliteBtreeDataSize(BtCursor* pCur, int *pSize)
{
  if( pCur->pNode ){
    *pSize = pCur->pNode->nData;
  }else{
    *pSize = 0;
  }
  return SQLITE_OK;
}

static int sqliteBtreeData(BtCursor *pCur, int offset, int amt, char *zBuf)
{
  if( !pCur->pNode ) return 0;
  if( (amt + offset) <= pCur->pNode->nData ){
    memcpy(zBuf, pCur->pNode->pData+offset, amt);
    return amt;
  }else{
    memcpy(zBuf, pCur->pNode->pData+offset ,pCur->pNode->nData-offset);
    return pCur->pNode->nData-offset;
  }
  assert(0);
}

static int sqliteBtreeCloseCursor(BtCursor* pCur)
{
  sqliteFree(pCur);
  return SQLITE_OK;
}

static int sqliteBtreeGetMeta(Btree* tree, int* aMeta)
{
  memcpy( aMeta, tree->aMetaData, sizeof(int) * SQLITE_N_BTREE_META );
  return SQLITE_OK;
}

static int sqliteBtreeUpdateMeta(Btree* tree, int* aMeta)
{
  memcpy( tree->aMetaData, aMeta, sizeof(int) * SQLITE_N_BTREE_META );
  return SQLITE_OK;
}

/*
 * Check that each table in the Btree meets the requirements for a red-black
 * binary tree. If an error is found, return an explanation of the problem in 
 * memory obtained from sqliteMalloc(). Parameters aRoot and nRoot are ignored. 
 */
static char *sqliteBtreeIntegrityCheck(Btree* tree, int* aRoot, int nRoot)
{
  char * msg = 0;
  HashElem *p;

  for(p=sqliteHashFirst(&tree->tblHash); p; p=sqliteHashNext(p)){
    BtRbTree *pTree = sqliteHashData(p);
    check_redblack_tree(pTree, &msg);
  }

  return msg;
}

/*
 * Close the supplied Btree. Delete everything associated with it.
 */
static int sqliteBtreeClose(Btree* tree)
{
  HashElem *p;
  for(p=sqliteHashFirst(&tree->tblHash); p; p=sqliteHashNext(p)){
    tree->eTransState = TRANS_ROLLBACK;
    sqliteBtreeClearTable(tree, sqliteHashKeysize(p));
    sqliteFree(sqliteHashData(p));
  }
  sqliteFree(tree);
  return SQLITE_OK;
}

static int sqliteBtreeSetCacheSize(Btree* tree, int sz)
{
  return SQLITE_OK;
}

static int sqliteBtreeSetSafetyLevel(Btree *pBt, int level){
  return SQLITE_OK;
}

static int sqliteBtreeBeginTrans(Btree* tree)
{
  if( tree->eTransState != TRANS_NONE ) 
    return SQLITE_ERROR;

  assert( tree->pTransRollback == 0 );
  tree->eTransState = TRANS_INTRANSACTION;
  return SQLITE_OK;
}

static int sqliteBtreeCommit(Btree* tree)
{
  /* Just delete pTransRollback and pCheckRollback */
  BtRollbackOp *pOp, *pTmp;
  pOp = tree->pCheckRollback;
  while( pOp ){
    pTmp = pOp->pNext;
    sqliteFree(pOp->pData);

  while( pList ){
    switch( pList->eOp ){
      case ROLLBACK_INSERT:
	cur.pTree  = sqliteHashFind( &pBtree->tblHash, 0, pList->iTab );
	assert(cur.pTree);
	cur.iTree  = pList->iTab;
	cur.eSkip  = SKIP_NONE;
	sqliteBtreeInsert( &cur, pList->pKey,
	    pList->nKey, pList->pData, pList->nData );
	break;
      case ROLLBACK_DELETE:
	cur.pTree  = sqliteHashFind( &pBtree->tblHash, 0, pList->iTab );
	assert(cur.pTree);
	cur.iTree  = pList->iTab;
	cur.eSkip  = SKIP_NONE;
	sqliteBtreeMoveto(&cur, pList->pKey, pList->nKey, &res);
	assert(res == 0);
	sqliteBtreeDelete( &cur );
	break;
      case ROLLBACK_CREATE:
	btreeCreateTable(pBtree, pList->iTab);
	break;
      case ROLLBACK_DROP:
	sqliteBtreeDropTable(pBtree, pList->iTab);
	break;
      default:
	assert(0);
    }
    sqliteFree(pList->pKey);
    sqliteFree(pList->pData);
    pTmp = pList->pNext;
    sqliteFree(pList);
    pList = pTmp;
  }
}

static int sqliteBtreeRollback(Btree* tree)
{
  tree->eTransState = TRANS_ROLLBACK;
  execute_rollback_list(tree, tree->pCheckRollback);
  execute_rollback_list(tree, tree->pTransRollback);
  tree->pTransRollback = 0;
  tree->pCheckRollback = 0;
  tree->pCheckRollbackTail = 0;
  tree->eTransState = TRANS_NONE;
  return SQLITE_OK;
}

static int sqliteBtreeBeginCkpt(Btree* tree)
{
  if( tree->eTransState != TRANS_INTRANSACTION ) 
    return SQLITE_ERROR;

  assert( tree->pCheckRollback == 0 );
  assert( tree->pCheckRollbackTail == 0 );
  tree->eTransState = TRANS_INCHECKPOINT;
  return SQLITE_OK;
}

static int sqliteBtreeCommitCkpt(Btree* tree)
{
  if( tree->eTransState == TRANS_INCHECKPOINT ){ 
    if( tree->pCheckRollback ){
      tree->pCheckRollbackTail->pNext = tree->pTransRollback;
      tree->pTransRollback = tree->pCheckRollback;
      tree->pCheckRollback = 0;
      tree->pCheckRollbackTail = 0;
    }
    tree->eTransState = TRANS_INTRANSACTION;
  }
  return SQLITE_OK;
}

static int sqliteBtreeRollbackCkpt(Btree* tree)
{
  if( tree->eTransState != TRANS_INCHECKPOINT ) return SQLITE_OK;
  tree->eTransState = TRANS_ROLLBACK;
  execute_rollback_list(tree, tree->pCheckRollback);
  tree->pCheckRollback = 0;
  tree->pCheckRollbackTail = 0;
  tree->eTransState = TRANS_INTRANSACTION;
  return SQLITE_OK;
  return SQLITE_OK;
}

#ifdef SQLITE_TEST
static int sqliteBtreePageDump(Btree* tree, int pgno, int rec)
{
  assert(!"Cannot call sqliteBtreePageDump");
  return SQLITE_OK;
}

static int sqliteBtreeCursorDump(BtCursor* pCur, int* aRes)
{
  assert(!"Cannot call sqliteBtreeCursorDump");
  return SQLITE_OK;
}

static struct Pager *sqliteBtreePager(Btree* tree)
{
  assert(!"Cannot call sqliteBtreePager");
  return SQLITE_OK;
}
#endif

/*
** Return the full pathname of the underlying database file.
*/
static const char *sqliteBtreeGetFilename(Btree *pBt){
  return ":memory:";
}

/*
** Change the name of the underlying database file.
*/
static int sqliteBtreeChangeFilename(Btree *pBt, const char *zNew){
  return SQLITE_OK;
}

static BtOps sqliteBtreeOps = {
    sqliteBtreeClose,
    sqliteBtreeSetCacheSize,
    sqliteBtreeSetSafetyLevel,
    sqliteBtreeBeginTrans,
    sqliteBtreeCommit,
    sqliteBtreeRollback,
    sqliteBtreeBeginCkpt,
    sqliteBtreeCommitCkpt,
    sqliteBtreeRollbackCkpt,
    sqliteBtreeCreateTable,
    sqliteBtreeCreateIndex,
    sqliteBtreeDropTable,
    sqliteBtreeClearTable,
    sqliteBtreeCursor,
    sqliteBtreeGetMeta,
    sqliteBtreeUpdateMeta,
    sqliteBtreeIntegrityCheck,
    sqliteBtreeGetFilename,
    sqliteBtreeChangeFilename,

#ifdef SQLITE_TEST
    sqliteBtreePageDump,
    sqliteBtreePager
#endif
};

static BtCursorOps sqliteBtreeCursorOps = {
    sqliteBtreeMoveto,
    sqliteBtreeDelete,
    sqliteBtreeInsert,
    sqliteBtreeFirst,
    sqliteBtreeLast,
    sqliteBtreeNext,
    sqliteBtreePrevious,
    sqliteBtreeKeySize,
    sqliteBtreeKey,
    sqliteBtreeKeyCompare,
    sqliteBtreeDataSize,
    sqliteBtreeData,
    sqliteBtreeCloseCursor,
#ifdef SQLITE_TEST
    sqliteBtreeCursorDump,
#endif

};

#endif /* SQLITE_OMIT_INMEMORYDB */

**
*************************************************************************
** 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 1.123 2003/04/15 01:19:48 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>

/*
** A pointer to this structure is used to communicate information

    sqliteHashInit(&db->aDb[i].tblHash, SQLITE_HASH_STRING, 0);
    sqliteHashInit(&db->aDb[i].idxHash, SQLITE_HASH_STRING, 0);
    sqliteHashInit(&db->aDb[i].trigHash, SQLITE_HASH_STRING, 0);
    sqliteHashInit(&db->aDb[i].aFKey, SQLITE_HASH_STRING, 1);
  }
  
  /* Open the backend database driver */
  rc = sqliteBtreeOpen(zFilename, 0, MAX_PAGES, &db->aDb[0].pBt);
  if( rc!=SQLITE_OK ){
    switch( rc ){
      default: {
        sqliteSetString(pzErrMsg, "unable to open database: ", zFilename, 0);
      }
    }
    sqliteFree(db);

** driver.  If zFilename is the name of a file, then that file is
** opened and used.  If zFilename is the magic name ":memory:" then
** the database is stored in memory (and is thus forgotten as soon as
** the connection is closed.)  If zFilename is NULL then the database
** is for temporary use only and is deleted as soon as the connection
** is closed.
**
** 
**
** A temporary database can be either a disk file (that is automatically
** deleted when the file is closed) or a set of red-black trees held in memory,
** depending on the values of the TEMP_STORE compile-time macro and the
** db->temp_store variable, according to the following chart:
**
**       TEMP_STORE     db->temp_store     Location of temporary database
**       ----------     --------------     ------------------------------