** 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 1.116 2004/05/08 20:07:40 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.
................................................................................
  u8 isInit;                     /* True if previously initialized */
  u8 idxShift;                   /* True if Cell indices have changed */
  u8 isOverfull;                 /* Some aCell[] do not fit on page */
  u8 intKey;                     /* True if intkey flag is set */
  u8 leaf;                       /* True if leaf flag is set */
  u8 zeroData;                   /* True if zero data flag is set */
  u8 hdrOffset;                  /* 100 for page 1.  0 otherwise */

  int idxParent;                 /* Index in pParent->aCell[] of this node */
  int nFree;                     /* Number of free bytes on the page */
  int nCell;                     /* Number of entries on this page */
  int nCellAlloc;                /* Number of slots allocated in aCell[] */
  unsigned char **aCell;         /* Pointer to start of each cell */
  struct Btree *pBt;             /* Pointer back to BTree structure */

................................................................................
  maxPayload = pPage->pBt->maxLocal;
  if( nPayload>maxPayload ){
    nPayload = maxPayload + 4;
  }
  return n + nPayload;
}









































































/*
** Defragment the page given.  All Cells are moved to the
** beginning of the page and all free space is collected 
** into one big FreeBlk at the end of the page.
*/
static void defragmentPage(MemPage *pPage){
  int pc, i, n, addr;
................................................................................
  int leftover;
  unsigned char *oldPage;
  unsigned char newPage[MX_PAGE_SIZE];

  assert( sqlite3pager_iswriteable(pPage->aData) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->pageSize <= MX_PAGE_SIZE );


  oldPage = pPage->aData;
  hdr = pPage->hdrOffset;
  addr = 3+hdr;
  n = 6+hdr;
  if( !pPage->leaf ){
    n += 4;
  }
................................................................................
  pc = get2byte(&oldPage[addr]);
  i = 0;
  while( pc>0 ){
    assert( n<pPage->pBt->pageSize );
    size = cellSize(pPage, &oldPage[pc]);
    memcpy(&newPage[n], &oldPage[pc], size);
    put2byte(&newPage[addr],n);

    pPage->aCell[i++] = &oldPage[n];

    n += size;
    addr = pc;
    pc = get2byte(&oldPage[pc]);
  }
  assert( i==pPage->nCell );
  leftover = pPage->pBt->pageSize - n;
  assert( leftover>=0 );
  assert( pPage->nFree==leftover );
  if( leftover<4 ){
................................................................................
  hdr = pPage->hdrOffset;
  data = pPage->aData;
  c = data[hdr];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_LEAF)!=0;
  pPage->isOverfull = 0;

  pPage->idxShift = 0;
  pageSize = pPage->pBt->pageSize;

  /* Initialize the cell count and cell pointers */
  pc = get2byte(&data[hdr+3]);
  while( pc>0 ){
    if( pc>=pageSize ) return SQLITE_CORRUPT;
................................................................................
  /* Sanity check:  Cells and freespace and header must sum to the size
  ** a page. */
  if( sumCell+pPage->nFree+hdr+10-pPage->leaf*4 != pageSize ){
    return SQLITE_CORRUPT;
  }

  pPage->isInit = 1;

  return SQLITE_OK;
}

/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
................................................................................
  pPage->nCellAlloc = 0;
  pPage->nFree = pBt->pageSize - first;
  pPage->intKey = (flags & PTF_INTKEY)!=0;
  pPage->leaf = (flags & PTF_LEAF)!=0;
  pPage->zeroData = (flags & PTF_ZERODATA)!=0;
  pPage->hdrOffset = hdr;
  pPage->isOverfull = 0;

  pPage->idxShift = 0;
  pPage->isInit = 1;

}

/*
** Get a page from the pager.  Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(Btree *pBt, Pgno pgno, MemPage **ppPage){
................................................................................
/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){
  MemPage *pPage = (MemPage*)&((char*)pData)[SQLITE_PAGE_SIZE];

  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    pPage->pParent = 0;
    releasePage(pParent);
  }
  sqliteFree(pPage->aCell);
  pPage->aCell = 0;
................................................................................
/*
** Invalidate all cursors
*/
static void invalidateCursors(Btree *pBt){
  BtCursor *pCur;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    if( pPage && !pPage->isInit ){

      releasePage(pPage);
      pCur->pPage = 0;
      pCur->isValid = 0;
      pCur->status = SQLITE_ABORT;
    }
  }
}
................................................................................
  MemPage *pPage;
  unsigned char *cell;

  if( !pCur->isValid ){
    *pSize = 0;
  }else{
    pPage = pCur->pPage;

    assert( pPage!=0 );
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( !pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
................................................................................
  u64 nData, nKey;
  int maxLocal, ovflSize;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->isValid );
  pBt = pCur->pBt;
  pPage = pCur->pPage;

  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( !pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
  if( pPage->zeroData ){
................................................................................
  if( !pCur->isValid ){
    return 0;
  }
  assert( pCur->pPage!=0 );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  pBt = pCur->pBt;
  pPage = pCur->pPage;

  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  assert( pPage->intKey==0 );
  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( !pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
................................................................................

  if( !pCur->isValid ){
    return pCur->status ? pCur->status : SQLITE_INTERNAL;
  }
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( pPage->isInit );

  if( pPage->zeroData ){
    *pSize = 0;
  }else{
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( !pPage->leaf ){
................................................................................
  MemPage *pNewPage;
  MemPage *pOldPage;
  Btree *pBt = pCur->pBt;

  assert( pCur->isValid );
  rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
  if( rc ) return rc;

  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;
  releasePage(pOldPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  if( pNewPage->nCell<1 ){
................................................................................
  MemPage *pPage;
  int idxParent;

  assert( pCur->isValid );
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( !isRootPage(pPage) );

  pParent = pPage->pParent;
  assert( pParent!=0 );

  idxParent = pPage->idxParent;
  sqlite3pager_ref(pParent->aData);
  oldPgno = pPage->pgno;
  releasePage(pPage);
  pCur->pPage = pParent;
  assert( pParent->idxShift==0 );
  if( pParent->idxShift==0 ){
................................................................................

  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0);
  if( rc ){
    pCur->isValid = 0;
    return rc;
  }
  releasePage(pCur->pPage);

  pCur->pPage = pRoot;
  pCur->idx = 0;
  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    assert( pRoot->pgno==1 );
    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+6]);
    assert( subpage>0 );
................................................................................
  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 ){
      void *pCellKey;
      u64 nCellKey;
      pCur->idx = (lwr+upr)/2;
      sqlite3BtreeKeySize(pCur, &nCellKey);
      if( pPage->intKey ){
        if( nCellKey<nKey ){
................................................................................
static void reparentPage(Btree *pBt, Pgno pgno, MemPage *pNewParent, int idx){
  MemPage *pThis;
  unsigned char *aData;

  if( pgno==0 ) return;
  assert( pBt->pPager!=0 );
  aData = sqlite3pager_lookup(pBt->pPager, pgno);

  pThis = (MemPage*)&aData[pBt->pageSize];
  if( pThis && pThis->isInit ){
    if( pThis->pParent!=pNewParent ){
      if( pThis->pParent ) sqlite3pager_unref(pThis->pParent->aData);
      pThis->pParent = pNewParent;
      if( pNewParent ) sqlite3pager_ref(pNewParent->aData);
    }
    pThis->idxParent = idx;

    sqlite3pager_unref(aData);
  }
}

/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
................................................................................
** Remove the i-th cell from pPage.  This routine effects pPage only.
** The cell content is not freed or deallocated.  It is assumed that
** the cell content has been copied someplace else.  This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
**
** Do not bother maintaining the integrity of the linked list of Cells.
** Only the pPage->aCell[] array is important.  The relinkCellList() 
** routine will be called soon after this routine in order to rebuild 

** the linked list.
*/
static void dropCell(MemPage *pPage, int idx, int sz){
  int j, pc;

  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, pPage->aCell[idx]) );
  assert( sqlite3pager_iswriteable(pPage->aData) );
  assert( pPage->aCell[idx]>=pPage->aData );
  assert( pPage->aCell[idx]<&pPage->aData[pPage->pBt->pageSize-sz] );

  pc = Addr(pPage->aCell[idx]) - Addr(pPage->aData);
  assert( pc>pPage->hdrOffset && pc+sz<=pPage->pBt->pageSize );
  freeSpace(pPage, pc, sz);
  for(j=idx; j<pPage->nCell-1; j++){
    pPage->aCell[j] = pPage->aCell[j+1];
  }
  pPage->nCell--;

















  pPage->idxShift = 1;
}

/*
** Insert a new cell on pPage at cell index "i".  pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there.  If it
** will not fit, then just make pPage->aCell[i] point to the content
** and set pPage->isOverfull.  
**
** Do not bother maintaining the integrity of the linked list of Cells.
** Only the pPage->aCell[] array is important.  The relinkCellList() 
** routine will be called soon after this routine in order to rebuild 

** the linked list.
*/
static void insertCell(MemPage *pPage, int i, unsigned char *pCell, int sz){
  int idx, j;
  assert( i>=0 && i<=pPage->nCell );
  assert( sz==cellSize(pPage, pCell) );
  assert( sqlite3pager_iswriteable(pPage->aData) );
  idx = allocateSpace(pPage, sz);
  resizeCellArray(pPage, pPage->nCell+1);
  for(j=pPage->nCell; j>i; j--){
    pPage->aCell[j] = pPage->aCell[j-1];
  }
  pPage->nCell++;
  if( idx<=0 ){
    pPage->isOverfull = 1;
    pPage->aCell[i] = pCell;
  }else{

    memcpy(&pPage->aData[idx], pCell, sz);
    pPage->aCell[i] = &pPage->aData[idx];















  }
  pPage->idxShift = 1;
}

/*
** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->aCell[] array.  
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
*/
static void relinkCellList(MemPage *pPage){
  int i, idxFrom;
  assert( sqlite3pager_iswriteable(pPage->aData) );

  idxFrom = pPage->hdrOffset+3;
  for(i=0; i<pPage->nCell; i++){
    int idx = Addr(pPage->aCell[i]) - Addr(pPage->aData);
    assert( idx>pPage->hdrOffset && idx<pPage->pBt->pageSize );
    put2byte(&pPage->aData[idxFrom], idx);
    idxFrom = idx;
  }
  put2byte(&pPage->aData[idxFrom], 0);

}

/*
** GCC does not define the offsetof() macro so we'll have to do it
** ourselves.
*/
#ifndef offsetof
................................................................................
    uptr x = Addr(pTo->aCell[i]);
    if( x>from && x<from+pageSize-ofst ){
      *((uptr*)&pTo->aCell[i]) = x + to - from;
    }
  }
}










/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation.  NN is the number of neighbors on either side
** of the page that participate in the balancing operation.  NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
................................................................................
  }

  /*
  ** Find the parent of the page to be balanced.  If there is no parent,
  ** it means this page is the root page and special rules apply.
  */
  pParent = pPage->pParent;

  if( pParent==0 ){
    Pgno pgnoChild;
    MemPage *pChild;
    assert( pPage->isInit );
    if( pPage->nCell==0 ){
      if( pPage->leaf ){
        /* The table is completely empty */
        relinkCellList(pPage);

      }else{
        /* The root page is empty but has one child.  Transfer the
        ** information from that one child into the root page if it 
        ** will fit.  This reduces the depth of the BTree by one.
        **
        ** If the root page is page 1, it has less space available than
        ** its child (due to the 100 byte header that occurs at the beginning
................................................................................
            zeroPage(pPage, pChild->aData[0]);
            resizeCellArray(pPage, pChild->nCell);
            for(i=0; i<pChild->nCell; i++){
              insertCell(pPage, i, pChild->aCell[i], 
                        cellSize(pChild, pChild->aCell[i]));
            }
            freePage(pChild);

          }else{
            /* The child has more information that will fit on the root.
            ** The tree is already balanced.  Do nothing. */

          }
        }else{
          memcpy(pPage, pChild, pBt->pageSize);
          pPage->isInit = 0;
          pPage->pParent = 0;
          rc = initPage(pPage, 0);
          assert( rc==SQLITE_OK );
          freePage(pChild);

        }
        reparentChildPages(pPage);
        releasePage(pChild);
      }
      return SQLITE_OK;
    }
    if( !pPage->isOverfull ){
      /* It is OK for the root page to be less than half full.
      */
      relinkCellList(pPage);

      return SQLITE_OK;
    }
    /*
    ** If we get to here, it means the root page is overfull.
    ** When this happens, Create a new child page and copy the
    ** contents of the root into the child.  Then make the root
    ** page an empty page with rightChild pointing to the new
................................................................................
    pChild->idxParent = 0;
    pChild->isOverfull = 1;
    zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
    put4byte(&pPage->aData[pPage->hdrOffset+6], pChild->pgno);
    pParent = pPage;
    pPage = pChild;
    extraUnref = pChild;

  }
  rc = sqlite3pager_write(pParent->aData);
  if( rc ) return rc;
  assert( pParent->isInit );
  
  /*
  ** Find the cell in the parent page whose left child points back
................................................................................
  reparentChildPages(pParent);

  /*
  ** balance the parent page.
  */
  assert( pPage->isInit );
  assert( pParent->isInit );

  rc = balance(pParent);
  

  /*
  ** Cleanup before returning.
  */
balance_cleanup:
................................................................................
    }
  }
  for(i=0; i<nNew; i++){
    releasePage(apNew[i]);
  }
  releasePage(pParent);
  releasePage(extraUnref);

  return rc;
}

/*
** This routine checks all cursors that point to the same table
** as pCur points to.  If any of those cursors were opened with
** wrFlag==0 then this routine returns SQLITE_LOCKED.  If all
................................................................................
  }
  hdr = pPage->hdrOffset;
  data = pPage->aData;
  c = data[hdr];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_LEAF)!=0;
  printf("PAGE %d:  flags=0x%02x  frag=%d\n", pgno,
    data[hdr], data[hdr+5]);

  i = 0;
  assert( hdr == (pgno==1 ? 100 : 0) );
  idx = get2byte(&data[hdr+3]);
  while( idx>0 && idx<=pBt->pageSize ){
    u64 nData, nKey;
    int nHeader;
    Pgno child;
................................................................................
**   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.
*/
int sqlite3BtreeCursorDump(BtCursor *pCur, int *aResult){
  int cnt, idx;
  MemPage *pPage = pCur->pPage;


  assert( pPage->isInit );
  aResult[0] = sqlite3pager_pagenumber(pPage->aData);
  assert( aResult[0]==pPage->pgno );
  aResult[1] = pCur->idx;
  aResult[2] = pPage->nCell;
  if( pCur->idx>=0 && pCur->idx<pPage->nCell ){
    aResult[3] = cellSize(pPage, pPage->aCell[pCur->idx]);

** 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 1.117 2004/05/09 00:40:52 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.
................................................................................
  u8 isInit;                     /* True if previously initialized */
  u8 idxShift;                   /* True if Cell indices have changed */
  u8 isOverfull;                 /* Some aCell[] do not fit on page */
  u8 intKey;                     /* True if intkey flag is set */
  u8 leaf;                       /* True if leaf flag is set */
  u8 zeroData;                   /* True if zero data flag is set */
  u8 hdrOffset;                  /* 100 for page 1.  0 otherwise */
  u8 needRelink;                 /* True if need to run relinkCellList() */
  int idxParent;                 /* Index in pParent->aCell[] of this node */
  int nFree;                     /* Number of free bytes on the page */
  int nCell;                     /* Number of entries on this page */
  int nCellAlloc;                /* Number of slots allocated in aCell[] */
  unsigned char **aCell;         /* Pointer to start of each cell */
  struct Btree *pBt;             /* Pointer back to BTree structure */

................................................................................
  maxPayload = pPage->pBt->maxLocal;
  if( nPayload>maxPayload ){
    nPayload = maxPayload + 4;
  }
  return n + nPayload;
}

/*
** Do sanity checking on a page.  Throw an exception if anything is
** not right.
**
** This routine is used for internal error checking only.  It is omitted
** from most builds.
*/
#if defined(BTREE_DEBUG) && !defined(NDEBUG) && 0
static void _pageIntegrity(MemPage *pPage){
  int pageSize;
  u8 *data;
  int i, idx, c, pc, hdr, nFree;
  u8 used[MX_PAGE_SIZE];

  pageSize = pPage->pBt->pageSize;
  assert( pPage->aData==&((unsigned char*)pPage)[-pageSize] );
  hdr = pPage->hdrOffset;
  assert( hdr==(pPage->pgno==1 ? 100 : 0) );
  assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
  c = pPage->aData[hdr];
  if( pPage->isInit ){
    assert( pPage->leaf == ((c & PTF_LEAF)!=0) );
    assert( pPage->zeroData == ((c & PTF_ZERODATA)!=0) );
    assert( pPage->intKey == ((c & PTF_INTKEY)!=0) );
  }
  data = pPage->aData;
  memset(used, 0, pageSize);
  for(i=0; i<hdr+10-pPage->leaf*4; i++) used[i] = 1;
  nFree = 0;
  pc = get2byte(&data[hdr+1]);
  while( pc ){
    int size;
    assert( pc>0 && pc<pageSize-4 );
    size = get2byte(&data[pc+2]);
    assert( pc+size<=pageSize );
    nFree += size;
    for(i=pc; i<pc+size; i++){
      assert( used[i]==0 );
      used[i] = 1;
    }
    pc = get2byte(&data[pc]);
  }
  assert( pPage->isInit==0 || pPage->nFree==nFree+data[hdr+5] );
  idx = 0;
  pc = get2byte(&data[hdr+3]);
  while( pc ){
    int size;
    assert( pPage->isInit==0 || idx<pPage->nCell );
    assert( pc>0 && pc<pageSize-4 );
    assert( pPage->isInit==0 || pPage->aCell[idx]==&data[pc] );
    size = cellSize(pPage, &data[pc]);
    assert( pc+size<=pageSize );
    for(i=pc; i<pc+size; i++){
      assert( used[i]==0 );
      used[i] = 1;
    }
    pc = get2byte(&data[pc]);
    idx++;
  }
  assert( idx==pPage->nCell );
  nFree = 0;
  for(i=0; i<pageSize; i++){
    assert( used[i]<=1 );
    if( used[i]==0 ) nFree++;
  }
  assert( nFree==data[hdr+5] );
}
#define pageIntegrity(X) _pageIntegrity(X)
#else
# define pageIntegrity(X)
#endif

/*
** Defragment the page given.  All Cells are moved to the
** beginning of the page and all free space is collected 
** into one big FreeBlk at the end of the page.
*/
static void defragmentPage(MemPage *pPage){
  int pc, i, n, addr;
................................................................................
  int leftover;
  unsigned char *oldPage;
  unsigned char newPage[MX_PAGE_SIZE];

  assert( sqlite3pager_iswriteable(pPage->aData) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->pageSize <= MX_PAGE_SIZE );
  assert( !pPage->needRelink );
  assert( !pPage->isOverfull );
  oldPage = pPage->aData;
  hdr = pPage->hdrOffset;
  addr = 3+hdr;
  n = 6+hdr;
  if( !pPage->leaf ){
    n += 4;
  }
................................................................................
  pc = get2byte(&oldPage[addr]);
  i = 0;
  while( pc>0 ){
    assert( n<pPage->pBt->pageSize );
    size = cellSize(pPage, &oldPage[pc]);
    memcpy(&newPage[n], &oldPage[pc], size);
    put2byte(&newPage[addr],n);
    assert( pPage->aCell[i]==&oldPage[pc] );
    pPage->aCell[i++] = &oldPage[n];
    addr = n;
    n += size;

    pc = get2byte(&oldPage[pc]);
  }
  assert( i==pPage->nCell );
  leftover = pPage->pBt->pageSize - n;
  assert( leftover>=0 );
  assert( pPage->nFree==leftover );
  if( leftover<4 ){
................................................................................
  hdr = pPage->hdrOffset;
  data = pPage->aData;
  c = data[hdr];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_LEAF)!=0;
  pPage->isOverfull = 0;
  pPage->needRelink = 0;
  pPage->idxShift = 0;
  pageSize = pPage->pBt->pageSize;

  /* Initialize the cell count and cell pointers */
  pc = get2byte(&data[hdr+3]);
  while( pc>0 ){
    if( pc>=pageSize ) return SQLITE_CORRUPT;
................................................................................
  /* Sanity check:  Cells and freespace and header must sum to the size
  ** a page. */
  if( sumCell+pPage->nFree+hdr+10-pPage->leaf*4 != pageSize ){
    return SQLITE_CORRUPT;
  }

  pPage->isInit = 1;
  pageIntegrity(pPage);
  return SQLITE_OK;
}

/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
................................................................................
  pPage->nCellAlloc = 0;
  pPage->nFree = pBt->pageSize - first;
  pPage->intKey = (flags & PTF_INTKEY)!=0;
  pPage->leaf = (flags & PTF_LEAF)!=0;
  pPage->zeroData = (flags & PTF_ZERODATA)!=0;
  pPage->hdrOffset = hdr;
  pPage->isOverfull = 0;
  pPage->needRelink = 0;
  pPage->idxShift = 0;
  pPage->isInit = 1;
  pageIntegrity(pPage);
}

/*
** Get a page from the pager.  Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(Btree *pBt, Pgno pgno, MemPage **ppPage){
................................................................................
/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){
  MemPage *pPage = (MemPage*)&((char*)pData)[SQLITE_PAGE_SIZE];
  assert( pPage->isInit==0 || pPage->needRelink==0 );
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    pPage->pParent = 0;
    releasePage(pParent);
  }
  sqliteFree(pPage->aCell);
  pPage->aCell = 0;
................................................................................
/*
** Invalidate all cursors
*/
static void invalidateCursors(Btree *pBt){
  BtCursor *pCur;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    if( pPage /* && !pPage->isInit */ ){
      pageIntegrity(pPage);
      releasePage(pPage);
      pCur->pPage = 0;
      pCur->isValid = 0;
      pCur->status = SQLITE_ABORT;
    }
  }
}
................................................................................
  MemPage *pPage;
  unsigned char *cell;

  if( !pCur->isValid ){
    *pSize = 0;
  }else{
    pPage = pCur->pPage;
    pageIntegrity(pPage);
    assert( pPage!=0 );
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( !pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
................................................................................
  u64 nData, nKey;
  int maxLocal, ovflSize;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->isValid );
  pBt = pCur->pBt;
  pPage = pCur->pPage;
  pageIntegrity(pPage);
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( !pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
  if( pPage->zeroData ){
................................................................................
  if( !pCur->isValid ){
    return 0;
  }
  assert( pCur->pPage!=0 );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  pBt = pCur->pBt;
  pPage = pCur->pPage;
  pageIntegrity(pPage);
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  assert( pPage->intKey==0 );
  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( !pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
................................................................................

  if( !pCur->isValid ){
    return pCur->status ? pCur->status : SQLITE_INTERNAL;
  }
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( pPage->isInit );
  pageIntegrity(pPage);
  if( pPage->zeroData ){
    *pSize = 0;
  }else{
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( !pPage->leaf ){
................................................................................
  MemPage *pNewPage;
  MemPage *pOldPage;
  Btree *pBt = pCur->pBt;

  assert( pCur->isValid );
  rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
  if( rc ) return rc;
  pageIntegrity(pNewPage);
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;
  releasePage(pOldPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  if( pNewPage->nCell<1 ){
................................................................................
  MemPage *pPage;
  int idxParent;

  assert( pCur->isValid );
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( !isRootPage(pPage) );
  pageIntegrity(pPage);
  pParent = pPage->pParent;
  assert( pParent!=0 );
  pageIntegrity(pParent);
  idxParent = pPage->idxParent;
  sqlite3pager_ref(pParent->aData);
  oldPgno = pPage->pgno;
  releasePage(pPage);
  pCur->pPage = pParent;
  assert( pParent->idxShift==0 );
  if( pParent->idxShift==0 ){
................................................................................

  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0);
  if( rc ){
    pCur->isValid = 0;
    return rc;
  }
  releasePage(pCur->pPage);
  pageIntegrity(pRoot);
  pCur->pPage = pRoot;
  pCur->idx = 0;
  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    assert( pRoot->pgno==1 );
    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+6]);
    assert( subpage>0 );
................................................................................
  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;
    pageIntegrity(pPage);
    while( lwr<=upr ){
      void *pCellKey;
      u64 nCellKey;
      pCur->idx = (lwr+upr)/2;
      sqlite3BtreeKeySize(pCur, &nCellKey);
      if( pPage->intKey ){
        if( nCellKey<nKey ){
................................................................................
static void reparentPage(Btree *pBt, Pgno pgno, MemPage *pNewParent, int idx){
  MemPage *pThis;
  unsigned char *aData;

  if( pgno==0 ) return;
  assert( pBt->pPager!=0 );
  aData = sqlite3pager_lookup(pBt->pPager, pgno);
  if( aData ){
    pThis = (MemPage*)&aData[pBt->pageSize];
    if( pThis->isInit ){
      if( pThis->pParent!=pNewParent ){
        if( pThis->pParent ) sqlite3pager_unref(pThis->pParent->aData);
        pThis->pParent = pNewParent;
        if( pNewParent ) sqlite3pager_ref(pNewParent->aData);
      }
      pThis->idxParent = idx;
    }
    sqlite3pager_unref(aData);
  }
}

/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
................................................................................
** Remove the i-th cell from pPage.  This routine effects pPage only.
** The cell content is not freed or deallocated.  It is assumed that
** the cell content has been copied someplace else.  This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
**
** Try to maintain the integrity of the linked list of cells.  But if
** the cell being inserted does not fit on the page, this will not be
** possible.  If the linked list is not maintained, then just update
** pPage->aCell[] and set the pPage->needRelink flag so that we will
** know to rebuild the linked list later.
*/
static void dropCell(MemPage *pPage, int idx, int sz){
  int j, pc;
  u8 *data;
  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, pPage->aCell[idx]) );
  assert( sqlite3pager_iswriteable(pPage->aData) );
  assert( pPage->aCell[idx]>=pPage->aData );
  assert( pPage->aCell[idx]<&pPage->aData[pPage->pBt->pageSize-sz] );
  data = pPage->aData;
  pc = Addr(pPage->aCell[idx]) - Addr(data);
  assert( pc>pPage->hdrOffset && pc+sz<=pPage->pBt->pageSize );
  freeSpace(pPage, pc, sz);
  for(j=idx; j<pPage->nCell-1; j++){
    pPage->aCell[j] = pPage->aCell[j+1];
  }
  pPage->nCell--;
  if( !pPage->isOverfull && !pPage->needRelink ){
    u8 *pPrev;
    if( idx==0 ){
      pPrev = &data[pPage->hdrOffset+3];
    }else{
      pPrev = pPage->aCell[idx-1];
    }
    if( idx<pPage->nCell ){
      pc = Addr(pPage->aCell[idx]) - Addr(data);
    }else{
      pc = 0;
    }
    put2byte(pPrev, pc);
    pageIntegrity(pPage);
  }else{
    pPage->needRelink = 1;
  }
  pPage->idxShift = 1;
}

/*
** Insert a new cell on pPage at cell index "i".  pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there.  If it
** will not fit, then just make pPage->aCell[i] point to the content
** and set pPage->isOverfull.  
**
** Try to maintain the integrity of the linked list of cells.  But if
** the cell being inserted does not fit on the page, this will not be
** possible.  If the linked list is not maintained, then just update
** pPage->aCell[] and set the pPage->needRelink flag so that we will
** know to rebuild the linked list later.
*/
static void insertCell(MemPage *pPage, int i, unsigned char *pCell, int sz){
  int idx, j;
  assert( i>=0 && i<=pPage->nCell );
  assert( sz==cellSize(pPage, pCell) );
  assert( sqlite3pager_iswriteable(pPage->aData) );
  idx = pPage->needRelink ? 0 : allocateSpace(pPage, sz);
  resizeCellArray(pPage, pPage->nCell+1);
  for(j=pPage->nCell; j>i; j--){
    pPage->aCell[j] = pPage->aCell[j-1];
  }
  pPage->nCell++;
  if( idx<=0 ){
    pPage->isOverfull = 1;
    pPage->aCell[i] = pCell;
  }else{
    u8 *data = pPage->aData;
    memcpy(&data[idx], pCell, sz);
    pPage->aCell[i] = &data[idx];
  }
  if( !pPage->isOverfull && !pPage->needRelink ){
    u8 *pPrev;
    int pc;
    if( i==0 ){
      pPrev = &pPage->aData[pPage->hdrOffset+3];
    }else{
      pPrev = pPage->aCell[i-1];
    }
    pc = get2byte(pPrev);
    put2byte(pPrev, idx);
    put2byte(pPage->aCell[i], pc);
    pageIntegrity(pPage);
  }else{
    pPage->needRelink = 1;
  }
  pPage->idxShift = 1;
}

/*
** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->aCell[] array.  
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
*/
static void relinkCellList(MemPage *pPage){
  int i, idxFrom;
  assert( sqlite3pager_iswriteable(pPage->aData) );
  if( !pPage->needRelink ) return;
  idxFrom = pPage->hdrOffset+3;
  for(i=0; i<pPage->nCell; i++){
    int idx = Addr(pPage->aCell[i]) - Addr(pPage->aData);
    assert( idx>pPage->hdrOffset && idx<pPage->pBt->pageSize );
    put2byte(&pPage->aData[idxFrom], idx);
    idxFrom = idx;
  }
  put2byte(&pPage->aData[idxFrom], 0);
  pPage->needRelink = 0;
}

/*
** GCC does not define the offsetof() macro so we'll have to do it
** ourselves.
*/
#ifndef offsetof
................................................................................
    uptr x = Addr(pTo->aCell[i]);
    if( x>from && x<from+pageSize-ofst ){
      *((uptr*)&pTo->aCell[i]) = x + to - from;
    }
  }
}

/*
** For debugging...
*/
#if 1
# define TRACE(X)   if( pager3_refinfo_enable ) printf X
#else
# define TRACE(X)
#endif

/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation.  NN is the number of neighbors on either side
** of the page that participate in the balancing operation.  NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
................................................................................
  }

  /*
  ** Find the parent of the page to be balanced.  If there is no parent,
  ** it means this page is the root page and special rules apply.
  */
  pParent = pPage->pParent;
  TRACE(("BALANCE: begin page %d\n", pPage->pgno));
  if( pParent==0 ){
    Pgno pgnoChild;
    MemPage *pChild;
    assert( pPage->isInit );
    if( pPage->nCell==0 ){
      if( pPage->leaf ){
        /* The table is completely empty */
        relinkCellList(pPage);
        TRACE(("BALANCE: empty table\n"));
      }else{
        /* The root page is empty but has one child.  Transfer the
        ** information from that one child into the root page if it 
        ** will fit.  This reduces the depth of the BTree by one.
        **
        ** If the root page is page 1, it has less space available than
        ** its child (due to the 100 byte header that occurs at the beginning
................................................................................
            zeroPage(pPage, pChild->aData[0]);
            resizeCellArray(pPage, pChild->nCell);
            for(i=0; i<pChild->nCell; i++){
              insertCell(pPage, i, pChild->aCell[i], 
                        cellSize(pChild, pChild->aCell[i]));
            }
            freePage(pChild);
            TRACE(("BALANCE: child %d transfer to page 1\n", pChild->pgno));
          }else{
            /* The child has more information that will fit on the root.
            ** The tree is already balanced.  Do nothing. */
            TRACE(("BALANCE: child %d will not fit on page 1\n", pChild->pgno));
          }
        }else{
          memcpy(pPage, pChild, pBt->pageSize);
          pPage->isInit = 0;
          pPage->pParent = 0;
          rc = initPage(pPage, 0);
          assert( rc==SQLITE_OK );
          freePage(pChild);
          TRACE(("BALANCE: transfer child %d into root\n", pChild->pgno));
        }
        reparentChildPages(pPage);
        releasePage(pChild);
      }
      return SQLITE_OK;
    }
    if( !pPage->isOverfull ){
      /* It is OK for the root page to be less than half full.
      */
      relinkCellList(pPage);
      TRACE(("BALANCE:  Root page is underfull but that is ok\n"));
      return SQLITE_OK;
    }
    /*
    ** If we get to here, it means the root page is overfull.
    ** When this happens, Create a new child page and copy the
    ** contents of the root into the child.  Then make the root
    ** page an empty page with rightChild pointing to the new
................................................................................
    pChild->idxParent = 0;
    pChild->isOverfull = 1;
    zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
    put4byte(&pPage->aData[pPage->hdrOffset+6], pChild->pgno);
    pParent = pPage;
    pPage = pChild;
    extraUnref = pChild;
    TRACE(("BALANCE: Copy root into %d and blance\n", pPage->pgno));
  }
  rc = sqlite3pager_write(pParent->aData);
  if( rc ) return rc;
  assert( pParent->isInit );
  
  /*
  ** Find the cell in the parent page whose left child points back
................................................................................
  reparentChildPages(pParent);

  /*
  ** balance the parent page.
  */
  assert( pPage->isInit );
  assert( pParent->isInit );
  pageIntegrity(pPage);
  rc = balance(pParent);
  

  /*
  ** Cleanup before returning.
  */
balance_cleanup:
................................................................................
    }
  }
  for(i=0; i<nNew; i++){
    releasePage(apNew[i]);
  }
  releasePage(pParent);
  releasePage(extraUnref);
  TRACE(("BALANCE: Finished with %d\n", pPage->pgno));
  return rc;
}

/*
** This routine checks all cursors that point to the same table
** as pCur points to.  If any of those cursors were opened with
** wrFlag==0 then this routine returns SQLITE_LOCKED.  If all
................................................................................
  }
  hdr = pPage->hdrOffset;
  data = pPage->aData;
  c = data[hdr];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_LEAF)!=0;
  printf("PAGE %d:  flags=0x%02x  frag=%d   parent=%d\n", pgno,
    data[hdr], data[hdr+5], 
    (pPage->isInit && pPage->pParent) ? pPage->pParent->pgno : 0);
  i = 0;
  assert( hdr == (pgno==1 ? 100 : 0) );
  idx = get2byte(&data[hdr+3]);
  while( idx>0 && idx<=pBt->pageSize ){
    u64 nData, nKey;
    int nHeader;
    Pgno child;
................................................................................
**   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.
*/
int sqlite3BtreeCursorInfo(BtCursor *pCur, int *aResult){
  int cnt, idx;
  MemPage *pPage = pCur->pPage;

  pageIntegrity(pPage);
  assert( pPage->isInit );
  aResult[0] = sqlite3pager_pagenumber(pPage->aData);
  assert( aResult[0]==pPage->pgno );
  aResult[1] = pCur->idx;
  aResult[2] = pPage->nCell;
  if( pCur->idx>=0 && pCur->idx<pPage->nCell ){
    aResult[3] = cellSize(pPage, pPage->aCell[pCur->idx]);

**    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 1.41 2004/05/08 20:07:40 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
................................................................................
int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);
int sqlite3BtreeKeyCompare(BtCursor *, const void *, int, int, int *);

char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot);
struct Pager *sqlite3BtreePager(Btree*);

#ifdef SQLITE_TEST
int sqlite3BtreeCursorDump(BtCursor*, int*);
void sqlite3BtreeCursorList(Btree*);
int sqlite3BtreeFlags(BtCursor*);
int sqlite3BtreePageDump(Btree*, int, int recursive);
#endif


#endif /* _BTREE_H_ */

**    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 1.42 2004/05/09 00:40:52 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
................................................................................
int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);
int sqlite3BtreeKeyCompare(BtCursor *, const void *, int, int, int *);

char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot);
struct Pager *sqlite3BtreePager(Btree*);

#ifdef SQLITE_TEST
int sqlite3BtreeCursorInfo(BtCursor*, int*);
void sqlite3BtreeCursorList(Btree*);
int sqlite3BtreeFlags(BtCursor*);
int sqlite3BtreePageDump(Btree*, int, int recursive);
#endif


#endif /* _BTREE_H_ */

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.31 2004/05/08 20:07:40 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
................................................................................
  sqlite3BtreeDataSize(pCur, &n2);
  sprintf(zBuf, "%d", (int)(n1+n2));
  Tcl_AppendResult(interp, zBuf, 0);
  return SQLITE_OK;
}

/*
** Usage:   btree_cursor_dump ID
**
** Return eight integers containing information about the entry the
** cursor is pointing to:
**
**   aResult[0] =  The page number
**   aResult[1] =  The entry number
**   aResult[2] =  Total number of entries on this page
**   aResult[3] =  Size of this entry
**   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
*/
static int btree_cursor_dump(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;
  int rc;
................................................................................

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  rc = sqlite3BtreeCursorDump(pCur, aResult);
  if( rc ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  j = 0;
  for(i=0; i<sizeof(aResult)/sizeof(aResult[0]); i++){
    sprintf(&zBuf[j]," %d", aResult[i]);
................................................................................
     { "btree_eof",                (Tcl_CmdProc*)btree_eof                },
     { "btree_keysize",            (Tcl_CmdProc*)btree_keysize            },
     { "btree_key",                (Tcl_CmdProc*)btree_key                },
     { "btree_data",               (Tcl_CmdProc*)btree_data               },
     { "btree_payload_size",       (Tcl_CmdProc*)btree_payload_size       },
     { "btree_first",              (Tcl_CmdProc*)btree_first              },
     { "btree_last",               (Tcl_CmdProc*)btree_last               },
     { "btree_cursor_dump",        (Tcl_CmdProc*)btree_cursor_dump        },
     { "btree_cursor_list",        (Tcl_CmdProc*)btree_cursor_list        },
     { "btree_integrity_check",    (Tcl_CmdProc*)btree_integrity_check    },
     { "btree_breakpoint",         (Tcl_CmdProc*)btree_breakpoint         },
  };
  int i;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "pager_refinfo_enable", (char*)&pager3_refinfo_enable,
     TCL_LINK_INT);
  return TCL_OK;
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.32 2004/05/09 00:40:52 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
................................................................................
  sqlite3BtreeDataSize(pCur, &n2);
  sprintf(zBuf, "%d", (int)(n1+n2));
  Tcl_AppendResult(interp, zBuf, 0);
  return SQLITE_OK;
}

/*
** Usage:   btree_cursor_info ID
**
** Return eight integers containing information about the entry the
** cursor is pointing to:
**
**   aResult[0] =  The page number
**   aResult[1] =  The entry number
**   aResult[2] =  Total number of entries on this page
**   aResult[3] =  Size of this entry
**   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
*/
static int btree_cursor_info(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;
  int rc;
................................................................................

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  rc = sqlite3BtreeCursorInfo(pCur, aResult);
  if( rc ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  j = 0;
  for(i=0; i<sizeof(aResult)/sizeof(aResult[0]); i++){
    sprintf(&zBuf[j]," %d", aResult[i]);
................................................................................
     { "btree_eof",                (Tcl_CmdProc*)btree_eof                },
     { "btree_keysize",            (Tcl_CmdProc*)btree_keysize            },
     { "btree_key",                (Tcl_CmdProc*)btree_key                },
     { "btree_data",               (Tcl_CmdProc*)btree_data               },
     { "btree_payload_size",       (Tcl_CmdProc*)btree_payload_size       },
     { "btree_first",              (Tcl_CmdProc*)btree_first              },
     { "btree_last",               (Tcl_CmdProc*)btree_last               },
     { "btree_cursor_info",        (Tcl_CmdProc*)btree_cursor_info        },
     { "btree_cursor_list",        (Tcl_CmdProc*)btree_cursor_list        },
     { "btree_integrity_check",    (Tcl_CmdProc*)btree_integrity_check    },
     { "btree_breakpoint",         (Tcl_CmdProc*)btree_breakpoint         },
  };
  int i;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "pager_refinfo_enable", (char*)&pager3_refinfo_enable,
     TCL_LINK_INT);
  return TCL_OK;
}

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is btree database backend
#
# $Id: btree.test,v 1.20 2004/05/08 20:07:40 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Basic functionality.  Open and close a database.
#
................................................................................
  # Totals 1016 bytes.  8 bytes left over
  # Keys are 1000 through 1090.
  for {set i 1000} {$i<1091} {incr i} {
    set key $i
    set data [format %5d $i]
    btree_insert $::c1 $key $data
  }
  lrange [btree_cursor_dump $::c1] 4 5
} {8 1}
do_test btree-7.3 {
  for {set i 1001} {$i<1091} {incr i 2} {
    btree_move_to $::c1 $i
    btree_delete $::c1
  }
  # Freed 45 blocks.  Total freespace is 458
  # Keys remaining are even numbers between 1000 and 1090, inclusive
  lrange [btree_cursor_dump $::c1] 4 5
} {458 46}
#btree_page_dump $::b1 2
do_test btree-7.4 {
  # The largest free block is 10 bytes long.  So if we insert
  # a record bigger than 10 bytes it should force a defrag
  # The record is 20 bytes long.
  btree_insert $::c1 2000 {123456789_12345}
  btree_move_to $::c1 2000
  btree_key $::c1
} {2000}
do_test btree-7.5 {
  lrange [btree_cursor_dump $::c1] 4 5
} {438 1}
#btree_page_dump $::b1 2

# Delete an entry to make a hole of a known size, then immediately recreate
# that entry.  This tests the path into allocateSpace where the hole exactly
# matches the size of the desired space.
#
# Keys are even numbers between 1000 and 1090 and one record of 2000.
# There are 47 keys total.
................................................................................
do_test btree-7.6 {
  btree_move_to $::c1 1006
  btree_delete $::c1
  btree_move_to $::c1 1010
  btree_delete $::c1
} {}
do_test btree-7.7 {
  lrange [btree_cursor_dump $::c1] 4 5
} {458 3}   ;# Create two new holes of 10 bytes each
#btree_page_dump $::b1 2
do_test btree-7.8 {
  btree_insert $::c1 1006 { 1006}
  lrange [btree_cursor_dump $::c1] 4 5
} {448 2}   ;# Filled in the first hole
#btree_page_dump $::b1 2

# Make sure the freeSpace() routine properly coaleses adjacent memory blocks
#
do_test btree-7.9 {
  btree_move_to $::c1 1012
  btree_delete $::c1
  lrange [btree_cursor_dump $::c1] 4 5
} {458 2}  ;# Coalesce with the whole before
do_test btree-7.10 {
  btree_move_to $::c1 1008
  btree_delete $::c1
  lrange [btree_cursor_dump $::c1] 4 5
} {468 2}  ;# Coalesce with whole after
do_test btree-7.11 {
  btree_move_to $::c1 1030
  btree_delete $::c1
  lrange [btree_cursor_dump $::c1] 4 5
} {478 3}   ;# Make a new hole
do_test btree-7.13 {
  btree_move_to $::c1 1034
  btree_delete $::c1
  lrange [btree_cursor_dump $::c1] 4 5
} {488 4}   ;# Make another hole
do_test btree-7.14 {
  btree_move_to $::c1 1032
  btree_delete $::c1
  lrange [btree_cursor_dump $::c1] 4 5
} {498 3}   ;# The freed space should coalesce on both ends
#btree_page_dump $::b1 2
do_test btree-7.15 {
  lindex [btree_pager_stats $::b1] 1
} {1}

# Check to see that data on overflow pages work correctly.
#

do_test btree-8.1 {
  set data "*** This is a very long key "
  while {[string length $data]<1234} {append data $data}
  set ::data $data
  btree_insert $::c1 2020 $data
} {}
#btree_page_dump $::b1 2
do_test btree-8.1.1 {
  lindex [btree_pager_stats $::b1] 1
} {1}
#btree_pager_ref_dump $::b1
do_test btree-8.2 {
  btree_move_to $::c1 2020
  string length [btree_data $::c1]
................................................................................
#btree_tree_dump $::b1 2
#btree_pager_ref_dump $::b1
#set pager_refinfo_enable 1
do_test btree-9.2 {
  btree_insert $::c1 020 {*** 020 *** 020 *** 020 *** 020 ***}
  select_keys $::c1
} {001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020}
#btree_page_dump $::b1 5
#btree_page_dump $::b1 2
#btree_page_dump $::b1 7
#btree_pager_ref_dump $::b1
#set pager_refinfo_enable 0

# The previous "select_keys" command left the cursor pointing at the root
# page.  So there should only be two pages checked out.  2 (the root) and
# page 1.
do_test btree-9.2.1 {
................................................................................
  #btree_tree_dump $::b1 2
}

# Create a tree with lots more pages
#
catch {unset ::data}
catch {unset ::key}
for {set i 31} {$i<=1000} {incr i} {
if {$i==88} {
set pager_refinfo_enable 1
btree_tree_dump $b1 2
btree_pager_ref_dump $b1
btree_cursor_list $b1
}
  do_test btree-11.1.$i.1 {
    set key [format %03d $i]
    set ::data "*** $key *** $key *** $key *** $key ***"
    btree_insert $::c1 $key $data
    btree_move_to $::c1 $key
    btree_key $::c1
  } [format %03d $i]
if {$i==88} {
btree_pager_ref_dump $b1
btree_cursor_list $b1
btree_tree_dump $b1 2
exit
}
  do_test btree-11.1.$i.2 {
    btree_data $::c1
  } $::data
  set ::key [format %03d [expr {$i/2}]]
  if {$::key=="012"} {set ::key 013}
  do_test btree-11.1.$i.3 {
    btree_move_to $::c1 $::key
................................................................................
  lindex [btree_pager_stats $::b1] 1
} {2}
#btree_page_dump $::b1 2

# Delete the dividers on the root page
#
do_test btree-11.4 {
  btree_move_to $::c1 257
  btree_delete $::c1
  btree_next $::c1
  btree_key $::c1
} {258}
do_test btree-11.4.1 {
  btree_move_to $::c1 256
  btree_key $::c1
} {256}
do_test btree-11.4.2 {
  btree_move_to $::c1 258
  btree_key $::c1
} {258}
do_test btree-11.4.3 {
  btree_move_to $::c1 259
  btree_key $::c1
} {259}
do_test btree-11.4.4 {
  btree_move_to $::c1 257
  set n [btree_key $::c1]
  expr {$n==256||$n==258}
} {1}
do_test btree-11.5 {
  btree_move_to $::c1 513
  btree_delete $::c1
  btree_next $::c1
  btree_key $::c1
} {514}
do_test btree-11.5.1 {
  btree_move_to $::c1 512
  btree_key $::c1
} {512}
do_test btree-11.5.2 {
  btree_move_to $::c1 514
  btree_key $::c1
} {514}
do_test btree-11.5.3 {
  btree_move_to $::c1 515
  btree_key $::c1
} {515}
do_test btree-11.5.4 {
  btree_move_to $::c1 513
  set n [btree_key $::c1]
  expr {$n==512||$n==514}
} {1}
do_test btree-11.6 {
  btree_move_to $::c1 769
  btree_delete $::c1

  btree_next $::c1

  btree_key $::c1
} {770}
do_test btree-11.6.1 {
  btree_move_to $::c1 768
  btree_key $::c1
} {768}
do_test btree-11.6.2 {
  btree_move_to $::c1 771
  btree_key $::c1
} {771}
do_test btree-11.6.3 {
  btree_move_to $::c1 770
  btree_key $::c1
} {770}
do_test btree-11.6.4 {
  btree_move_to $::c1 769
  set n [btree_key $::c1]
  expr {$n==768||$n==770}
} {1}
#btree_page_dump $::b1 2
#btree_page_dump $::b1 25

# Change the data on an intermediate node such that the node becomes overfull
# and has to split.  We happen to know that intermediate nodes exist on
# 337, 401 and 465 by the btree_page_dumps above
#
catch {unset ::data}
set ::data {This is going to be a very long data segment}
append ::data $::data
append ::data $::data
do_test btree-12.1 {
  btree_insert $::c1 337 $::data

  btree_data $::c1
} $::data
do_test btree-12.2 {
  btree_insert $::c1 401 $::data

  btree_data $::c1
} $::data
do_test btree-12.3 {
  btree_insert $::c1 465 $::data

  btree_data $::c1
} $::data
do_test btree-12.4 {
  btree_move_to $::c1 337
  btree_key $::c1
} {337}
do_test btree-12.5 {
................................................................................
  btree_next $::c1
  btree_data $::c1
} $::data
do_test btree-12.12 {
  btree_next $::c1
  btree_key $::c1
} {402}
do_test btree-13.1 {
  btree_integrity_check $::b1 2 3
} {}

# To Do:
#
#   1.  Do some deletes from the 3-layer tree
#   2.  Commit and reopen the database
#   3.  Read every 15th entry and make sure it works
#   4.  Implement btree_sanity and put it throughout this script

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is btree database backend
#
# $Id: btree.test,v 1.21 2004/05/09 00:40:52 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Basic functionality.  Open and close a database.
#
................................................................................
  # Totals 1016 bytes.  8 bytes left over
  # Keys are 1000 through 1090.
  for {set i 1000} {$i<1091} {incr i} {
    set key $i
    set data [format %5d $i]
    btree_insert $::c1 $key $data
  }
  lrange [btree_cursor_info $::c1] 4 5
} {8 1}
do_test btree-7.3 {
  for {set i 1001} {$i<1091} {incr i 2} {
    btree_move_to $::c1 $i
    btree_delete $::c1
  }
  # Freed 45 blocks.  Total freespace is 458
  # Keys remaining are even numbers between 1000 and 1090, inclusive
  lrange [btree_cursor_info $::c1] 4 5
} {458 46}
#btree_tree_dump $::b1 1
do_test btree-7.4 {
  # The largest free block is 10 bytes long.  So if we insert
  # a record bigger than 10 bytes it should force a defrag
  # The record is 20 bytes long.
  btree_insert $::c1 2000 {123456789_12345}
  btree_move_to $::c1 2000
  btree_key $::c1
} {2000}
do_test btree-7.5 {
  lrange [btree_cursor_info $::c1] 4 5
} {438 1}
#btree_tree_dump $::b1 1

# Delete an entry to make a hole of a known size, then immediately recreate
# that entry.  This tests the path into allocateSpace where the hole exactly
# matches the size of the desired space.
#
# Keys are even numbers between 1000 and 1090 and one record of 2000.
# There are 47 keys total.
................................................................................
do_test btree-7.6 {
  btree_move_to $::c1 1006
  btree_delete $::c1
  btree_move_to $::c1 1010
  btree_delete $::c1
} {}
do_test btree-7.7 {
  lrange [btree_cursor_info $::c1] 4 5
} {458 3}   ;# Create two new holes of 10 bytes each
#btree_page_dump $::b1 2
do_test btree-7.8 {
  btree_insert $::c1 1006 { 1006}
  lrange [btree_cursor_info $::c1] 4 5
} {448 2}   ;# Filled in the first hole
#btree_page_dump $::b1 2

# Make sure the freeSpace() routine properly coaleses adjacent memory blocks
#
do_test btree-7.9 {
  btree_move_to $::c1 1012
  btree_delete $::c1
  lrange [btree_cursor_info $::c1] 4 5
} {458 2}  ;# Coalesce with the whole before
do_test btree-7.10 {
  btree_move_to $::c1 1008
  btree_delete $::c1
  lrange [btree_cursor_info $::c1] 4 5
} {468 2}  ;# Coalesce with whole after
do_test btree-7.11 {
  btree_move_to $::c1 1030
  btree_delete $::c1
  lrange [btree_cursor_info $::c1] 4 5
} {478 3}   ;# Make a new hole
do_test btree-7.13 {
  btree_move_to $::c1 1034
  btree_delete $::c1
  lrange [btree_cursor_info $::c1] 4 5
} {488 4}   ;# Make another hole
do_test btree-7.14 {
  btree_move_to $::c1 1032
  btree_delete $::c1
  lrange [btree_cursor_info $::c1] 4 5
} {498 3}   ;# The freed space should coalesce on both ends
#btree_page_dump $::b1 2
do_test btree-7.15 {
  lindex [btree_pager_stats $::b1] 1
} {1}

# Check to see that data on overflow pages work correctly.
#
#btree_page_dump $::b1 1
do_test btree-8.1 {
  set data "*** This is a very long key "
  while {[string length $data]<1234} {append data $data}
  set ::data $data
  btree_insert $::c1 2020 $data
} {}
#btree_page_dump $::b1 1
do_test btree-8.1.1 {
  lindex [btree_pager_stats $::b1] 1
} {1}
#btree_pager_ref_dump $::b1
do_test btree-8.2 {
  btree_move_to $::c1 2020
  string length [btree_data $::c1]
................................................................................
#btree_tree_dump $::b1 2
#btree_pager_ref_dump $::b1
#set pager_refinfo_enable 1
do_test btree-9.2 {
  btree_insert $::c1 020 {*** 020 *** 020 *** 020 *** 020 ***}
  select_keys $::c1
} {001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020}

#btree_page_dump $::b1 2

#btree_pager_ref_dump $::b1
#set pager_refinfo_enable 0

# The previous "select_keys" command left the cursor pointing at the root
# page.  So there should only be two pages checked out.  2 (the root) and
# page 1.
do_test btree-9.2.1 {
................................................................................
  #btree_tree_dump $::b1 2
}

# Create a tree with lots more pages
#
catch {unset ::data}
catch {unset ::key}
for {set i 31} {$i<=999} {incr i} {






  do_test btree-11.1.$i.1 {
    set key [format %03d $i]
    set ::data "*** $key *** $key *** $key *** $key ***"
    btree_insert $::c1 $key $data
    btree_move_to $::c1 $key
    btree_key $::c1
  } [format %03d $i]






  do_test btree-11.1.$i.2 {
    btree_data $::c1
  } $::data
  set ::key [format %03d [expr {$i/2}]]
  if {$::key=="012"} {set ::key 013}
  do_test btree-11.1.$i.3 {
    btree_move_to $::c1 $::key
................................................................................
  lindex [btree_pager_stats $::b1] 1
} {2}
#btree_page_dump $::b1 2

# Delete the dividers on the root page
#
do_test btree-11.4 {























  btree_move_to $::c1 551
  btree_delete $::c1




  btree_move_to $::c1 551
  set k [btree_key $::c1]

















  if {$k==550} {
    set k [btree_next $::c1]
  }
  btree_key $::c1

















} {552}



# Change the data on an intermediate node such that the node becomes overfull
# and has to split.  We happen to know that intermediate nodes exist on
# 337, 401 and 465 by the btree_page_dumps above
#
catch {unset ::data}
set ::data {This is going to be a very long data segment}
append ::data $::data
append ::data $::data
do_test btree-12.1 {
  btree_insert $::c1 337 $::data
  btree_move_to $::c1 337
  btree_data $::c1
} $::data
do_test btree-12.2 {
  btree_insert $::c1 401 $::data
  btree_move_to $::c1 401
  btree_data $::c1
} $::data
do_test btree-12.3 {
  btree_insert $::c1 465 $::data
  btree_move_to $::c1 465
  btree_data $::c1
} $::data
do_test btree-12.4 {
  btree_move_to $::c1 337
  btree_key $::c1
} {337}
do_test btree-12.5 {
................................................................................
  btree_next $::c1
  btree_data $::c1
} $::data
do_test btree-12.12 {
  btree_next $::c1
  btree_key $::c1
} {402}
#do_test btree-13.1 {
#  btree_integrity_check $::b1 1 2
#} {}

# To Do:
#
#   1.  Do some deletes from the 3-layer tree
#   2.  Commit and reopen the database
#   3.  Read every 15th entry and make sure it works
#   4.  Implement btree_sanity and put it throughout this script

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is btree database backend
#
# $Id: btree2.test,v 1.10 2002/02/19 13:39:23 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info commands btree_open]!=""} {

................................................................................
      set ::c4 [btree_cursor $::b 4 1]
      set ::c5 [btree_cursor $::b 5 1]
      set ::c6 [btree_cursor $::b 6 1]
      check_invariants
    } {}
    set cnt 6
    for {set i 2} {$i<=6} {incr i} {
      if {[lindex [btree_cursor_dump [set ::c$i]] 0]!=$i} {incr cnt}
    }
    do_test $testid.1 {
      btree_begin_transaction $::b
      lindex [btree_pager_stats $::b] 1
    } $cnt
    # exec cp test2.bt test2.bt.bu1
    do_test $testid.2 [subst {

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is btree database backend
#
# $Id: btree2.test,v 1.11 2004/05/09 00:40:52 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info commands btree_open]!=""} {

................................................................................
      set ::c4 [btree_cursor $::b 4 1]
      set ::c5 [btree_cursor $::b 5 1]
      set ::c6 [btree_cursor $::b 6 1]
      check_invariants
    } {}
    set cnt 6
    for {set i 2} {$i<=6} {incr i} {
      if {[lindex [btree_cursor_info [set ::c$i]] 0]!=$i} {incr cnt}
    }
    do_test $testid.1 {
      btree_begin_transaction $::b
      lindex [btree_pager_stats $::b] 1
    } $cnt
    # exec cp test2.bt test2.bt.bu1
    do_test $testid.2 [subst {