** 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 1.447 2008/03/25 17:23:33 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"

................................................................................
  #define assertCellInfo(x)
#endif
#ifdef _MSC_VER
  /* Use a real function in MSVC to work around bugs in that compiler. */
  static void getCellInfo(BtCursor *pCur){
    if( pCur->info.nSize==0 ){
      sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info);

    }else{
      assertCellInfo(pCur);
    }
  }
#else /* if not _MSC_VER */
  /* Use a macro in all other compilers so that the function is inlined */
#define getCellInfo(pCur)                                               \
  if( pCur->info.nSize==0 ){                                            \
    sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info);         \

  }else{                                                                \
    assertCellInfo(pCur);                                               \
  }
#endif /* _MSC_VER */

/*
** Set *pSize to the size of the buffer needed to hold the value of
................................................................................
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;
  releasePage(pOldPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  pCur->info.nSize = 0;

  if( pNewPage->nCell<1 ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

/*
................................................................................
  pParent = pPage->pParent;
  assert( pParent!=0 );
  idxParent = pPage->idxParent;
  sqlite3PagerRef(pParent->pDbPage);
  releasePage(pPage);
  pCur->pPage = pParent;
  pCur->info.nSize = 0;

  assert( pParent->idxShift==0 );
  pCur->idx = idxParent;
}

/*
** Move the cursor to the root page
*/
................................................................................
      return rc;
    }
    releasePage(pCur->pPage);
    pCur->pPage = pRoot;
  }
  pCur->idx = 0;
  pCur->info.nSize = 0;


  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    assert( pRoot->pgno==1 );
    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
    assert( subpage>0 );
    pCur->eState = CURSOR_VALID;
    rc = moveToChild(pCur, subpage);
................................................................................
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    pCur->idx = pPage->nCell;
    rc = moveToChild(pCur, pgno);
  }
  if( rc==SQLITE_OK ){
    pCur->idx = pPage->nCell - 1;
    pCur->info.nSize = 0;

  }
  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.
................................................................................
    if( CURSOR_INVALID==pCur->eState ){
      assert( pCur->pPage->nCell==0 );
      *pRes = 1;
    }else{
      assert( pCur->eState==CURSOR_VALID );
      *pRes = 0;
      rc = moveToRightmost(pCur);


    }
  }
  return rc;
}

/* Move the cursor so that it points to an entry near the key 
** specified by pKey/nKey/pUnKey. Return a success code.
................................................................................
  int *pRes              /* Search result flag */
){
  int rc;
  char aSpace[200];

  assert( cursorHoldsMutex(pCur) );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );















  rc = moveToRoot(pCur);
  if( rc ){
    return rc;
  }
  assert( pCur->pPage );
  assert( pCur->pPage->isInit );
  if( pCur->eState==CURSOR_INVALID ){
................................................................................
    }else{
      pCur->idx = (upr+lwr)/2;
    }
    if( lwr<=upr ) for(;;){
      void *pCellKey;
      i64 nCellKey;
      pCur->info.nSize = 0;

      if( pPage->intKey ){
        u8 *pCell;
        pCell = findCell(pPage, pCur->idx) + pPage->childPtrSize;
        if( pPage->hasData ){
          u32 dummy;
          pCell += getVarint32(pCell, &dummy);
        }
        getVarint(pCell, (u64 *)&nCellKey);
        if( nCellKey<nKey ){
          c = -1;
        }else if( nCellKey>nKey ){
          c = +1;
        }else{
          c = 0;
        }
................................................................................
          rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
          c = sqlite3VdbeRecordCompare(nCellKey, pCellKey, pUnKey);
          sqlite3_free(pCellKey);
          if( rc ) goto moveto_finish;
        }
      }
      if( c==0 ){

        if( pPage->leafData && !pPage->leaf ){
          lwr = pCur->idx;
          upr = lwr - 1;
          break;
        }else{
          if( pRes ) *pRes = 0;
          rc = SQLITE_OK;
................................................................................
      }
      if( c<0 ){
        lwr = pCur->idx+1;
      }else{
        upr = pCur->idx-1;
      }
      if( lwr>upr ){

        break;
      }
      pCur->idx = (lwr+upr)/2;
    }
    assert( lwr==upr+1 );
    assert( pPage->isInit );
    if( pPage->leaf ){
................................................................................
      assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
      if( pRes ) *pRes = c;
      rc = SQLITE_OK;
      goto moveto_finish;
    }
    pCur->idx = lwr;
    pCur->info.nSize = 0;

    rc = moveToChild(pCur, chldPg);
    if( rc ) goto moveto_finish;
  }
moveto_finish:
  if( pKey ){
    /* If we created our own unpacked key at the top of this
    ** procedure, then destroy that key before returning. */
................................................................................
  pCur->skip = 0;

  assert( pPage->isInit );
  assert( pCur->idx<pPage->nCell );

  pCur->idx++;
  pCur->info.nSize = 0;

  if( pCur->idx>=pPage->nCell ){
    if( !pPage->leaf ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      *pRes = 0;
      return rc;
................................................................................
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  rc = restoreOrClearCursorPosition(pCur);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  if( CURSOR_INVALID==pCur->eState ){
    *pRes = 1;
    return SQLITE_OK;
  }
  if( pCur->skip<0 ){
    pCur->skip = 0;
    *pRes = 0;
................................................................................
        return SQLITE_OK;
      }
      sqlite3BtreeMoveToParent(pCur);
      pPage = pCur->pPage;
    }
    pCur->idx--;
    pCur->info.nSize = 0;

    if( pPage->leafData && !pPage->leaf ){
      rc = sqlite3BtreePrevious(pCur, pRes);
    }else{
      rc = SQLITE_OK;
    }
  }
  *pRes = 0;
................................................................................
    rc = clearCell(pPage, oldCell);
    if( rc ) goto end_insert;
    dropCell(pPage, pCur->idx, szOld);
  }else if( loc<0 && pPage->nCell>0 ){
    assert( pPage->leaf );
    pCur->idx++;
    pCur->info.nSize = 0;

  }else{
    assert( pPage->leaf );
  }
  rc = insertCell(pPage, pCur->idx, newCell, szNew, 0, 0);
  if( rc!=SQLITE_OK ) goto end_insert;
  rc = balance(pPage, 1);
  /* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */

** 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 1.448 2008/03/29 16:01:04 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"

................................................................................
  #define assertCellInfo(x)
#endif
#ifdef _MSC_VER
  /* Use a real function in MSVC to work around bugs in that compiler. */
  static void getCellInfo(BtCursor *pCur){
    if( pCur->info.nSize==0 ){
      sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info);
      pCur->validNKey = 1;
    }else{
      assertCellInfo(pCur);
    }
  }
#else /* if not _MSC_VER */
  /* Use a macro in all other compilers so that the function is inlined */
#define getCellInfo(pCur)                                               \
  if( pCur->info.nSize==0 ){                                            \
    sqlite3BtreeParseCell(pCur->pPage, pCur->idx, &pCur->info);         \
    pCur->validNKey = 1;                                                \
  }else{                                                                \
    assertCellInfo(pCur);                                               \
  }
#endif /* _MSC_VER */

/*
** Set *pSize to the size of the buffer needed to hold the value of
................................................................................
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;
  releasePage(pOldPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  if( pNewPage->nCell<1 ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

/*
................................................................................
  pParent = pPage->pParent;
  assert( pParent!=0 );
  idxParent = pPage->idxParent;
  sqlite3PagerRef(pParent->pDbPage);
  releasePage(pPage);
  pCur->pPage = pParent;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  assert( pParent->idxShift==0 );
  pCur->idx = idxParent;
}

/*
** Move the cursor to the root page
*/
................................................................................
      return rc;
    }
    releasePage(pCur->pPage);
    pCur->pPage = pRoot;
  }
  pCur->idx = 0;
  pCur->info.nSize = 0;
  pCur->atLast = 0;
  pCur->validNKey = 0;
  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    assert( pRoot->pgno==1 );
    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
    assert( subpage>0 );
    pCur->eState = CURSOR_VALID;
    rc = moveToChild(pCur, subpage);
................................................................................
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    pCur->idx = pPage->nCell;
    rc = moveToChild(pCur, pgno);
  }
  if( rc==SQLITE_OK ){
    pCur->idx = pPage->nCell - 1;
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
  }
  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.
................................................................................
    if( CURSOR_INVALID==pCur->eState ){
      assert( pCur->pPage->nCell==0 );
      *pRes = 1;
    }else{
      assert( pCur->eState==CURSOR_VALID );
      *pRes = 0;
      rc = moveToRightmost(pCur);
      getCellInfo(pCur);
      pCur->atLast = rc==SQLITE_OK;
    }
  }
  return rc;
}

/* Move the cursor so that it points to an entry near the key 
** specified by pKey/nKey/pUnKey. Return a success code.
................................................................................
  int *pRes              /* Search result flag */
){
  int rc;
  char aSpace[200];

  assert( cursorHoldsMutex(pCur) );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );

  /* If the cursor is already positioned at the point we are trying
  ** to move to, then just return without doing any work */
  if( pCur->eState==CURSOR_VALID && pCur->validNKey && pCur->pPage->intKey ){
    if( pCur->info.nKey==nKey ){
      *pRes = 0;
      return SQLITE_OK;
    }
    if( pCur->atLast && pCur->info.nKey<nKey ){
      *pRes = -1;
      return SQLITE_OK;
    }
  }


  rc = moveToRoot(pCur);
  if( rc ){
    return rc;
  }
  assert( pCur->pPage );
  assert( pCur->pPage->isInit );
  if( pCur->eState==CURSOR_INVALID ){
................................................................................
    }else{
      pCur->idx = (upr+lwr)/2;
    }
    if( lwr<=upr ) for(;;){
      void *pCellKey;
      i64 nCellKey;
      pCur->info.nSize = 0;
      pCur->validNKey = 1;
      if( pPage->intKey ){
        u8 *pCell;
        pCell = findCell(pPage, pCur->idx) + pPage->childPtrSize;
        if( pPage->hasData ){
          u32 dummy;
          pCell += getVarint32(pCell, &dummy);
        }
        getVarint(pCell, (u64*)&nCellKey);
        if( nCellKey<nKey ){
          c = -1;
        }else if( nCellKey>nKey ){
          c = +1;
        }else{
          c = 0;
        }
................................................................................
          rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
          c = sqlite3VdbeRecordCompare(nCellKey, pCellKey, pUnKey);
          sqlite3_free(pCellKey);
          if( rc ) goto moveto_finish;
        }
      }
      if( c==0 ){
        pCur->info.nKey = nCellKey;
        if( pPage->leafData && !pPage->leaf ){
          lwr = pCur->idx;
          upr = lwr - 1;
          break;
        }else{
          if( pRes ) *pRes = 0;
          rc = SQLITE_OK;
................................................................................
      }
      if( c<0 ){
        lwr = pCur->idx+1;
      }else{
        upr = pCur->idx-1;
      }
      if( lwr>upr ){
        pCur->info.nKey = nCellKey;
        break;
      }
      pCur->idx = (lwr+upr)/2;
    }
    assert( lwr==upr+1 );
    assert( pPage->isInit );
    if( pPage->leaf ){
................................................................................
      assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
      if( pRes ) *pRes = c;
      rc = SQLITE_OK;
      goto moveto_finish;
    }
    pCur->idx = lwr;
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
    rc = moveToChild(pCur, chldPg);
    if( rc ) goto moveto_finish;
  }
moveto_finish:
  if( pKey ){
    /* If we created our own unpacked key at the top of this
    ** procedure, then destroy that key before returning. */
................................................................................
  pCur->skip = 0;

  assert( pPage->isInit );
  assert( pCur->idx<pPage->nCell );

  pCur->idx++;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  if( pCur->idx>=pPage->nCell ){
    if( !pPage->leaf ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      *pRes = 0;
      return rc;
................................................................................
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  rc = restoreOrClearCursorPosition(pCur);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  pCur->atLast = 0;
  if( CURSOR_INVALID==pCur->eState ){
    *pRes = 1;
    return SQLITE_OK;
  }
  if( pCur->skip<0 ){
    pCur->skip = 0;
    *pRes = 0;
................................................................................
        return SQLITE_OK;
      }
      sqlite3BtreeMoveToParent(pCur);
      pPage = pCur->pPage;
    }
    pCur->idx--;
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
    if( pPage->leafData && !pPage->leaf ){
      rc = sqlite3BtreePrevious(pCur, pRes);
    }else{
      rc = SQLITE_OK;
    }
  }
  *pRes = 0;
................................................................................
    rc = clearCell(pPage, oldCell);
    if( rc ) goto end_insert;
    dropCell(pPage, pCur->idx, szOld);
  }else if( loc<0 && pPage->nCell>0 ){
    assert( pPage->leaf );
    pCur->idx++;
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
  }else{
    assert( pPage->leaf );
  }
  rc = insertCell(pPage, pCur->idx, newCell, szNew, 0, 0);
  if( rc!=SQLITE_OK ) goto end_insert;
  rc = balance(pPage, 1);
  /* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */

** 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: btreeInt.h,v 1.19 2008/03/25 14:24:57 danielk1977 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.
................................................................................
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
  Pgno pgnoRoot;            /* The root page of this tree */
  MemPage *pPage;           /* Page that contains the entry */
  int idx;                  /* Index of the entry in pPage->aCell[] */
  CellInfo info;            /* A parse of the cell we are pointing at */
  u8 wrFlag;                /* True if writable */


  u8 eState;                /* One of the CURSOR_XXX constants (see below) */
  void *pKey;      /* Saved key that was cursor's last known position */
  i64 nKey;        /* Size of pKey, or last integer key */
  int skip;        /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
#ifndef SQLITE_OMIT_INCRBLOB
  u8 isIncrblobHandle;      /* True if this cursor is an incr. io handle */
  Pgno *aOverflow;          /* Cache of overflow page locations */

** 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: btreeInt.h,v 1.20 2008/03/29 16:01:04 drh 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.
................................................................................
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
  Pgno pgnoRoot;            /* The root page of this tree */
  MemPage *pPage;           /* Page that contains the entry */
  int idx;                  /* Index of the entry in pPage->aCell[] */
  CellInfo info;            /* A parse of the cell we are pointing at */
  u8 wrFlag;                /* True if writable */
  u8 atLast;                /* Cursor pointing to the last entry */
  u8 validNKey;             /* True if info.nKey is valid */
  u8 eState;                /* One of the CURSOR_XXX constants (see below) */
  void *pKey;      /* Saved key that was cursor's last known position */
  i64 nKey;        /* Size of pKey, or last integer key */
  int skip;        /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
#ifndef SQLITE_OMIT_INCRBLOB
  u8 isIncrblobHandle;      /* True if this cursor is an incr. io handle */
  Pgno *aOverflow;          /* Cache of overflow page locations */