SQLite

**             -----------
**            /     |     \
**           /      |      \
**  ---------   ---------   ---------
**  |Child-1|   |Child-2|   |Child-3|
**  ---------   ---------   ---------
**
** The order of cells is in the array is for an index btree is:
**
**       1.  All cells from Child-1 in order
**       2.  The first divider cell from Parent
**       3.  All cells from Child-2 in order
**       4.  The second divider cell from Parent
**       5.  All cells from Child-3 in order
**
** For a table-btree (with rowids) the items 2 and 4 are empty because
** content exists only in leaves and there are no divider cells.
**
** For an index btree, the apEnd[] array holds pointer to the end of page
** for Child-1, the Parent, Child-2, the Parent (again), and Child-3,
** respectively. The ixNx[] array holds the number of cells contained in
** each of these 5 stages, and all stages to the left.  Hence:
**
**    ixNx[0] = Number of cells in Child-1.
**    ixNx[1] = Number of cells in Child-1 plus 1 for first divider.
**    ixNx[2] = Number of cells in Child-1 and Child-2 + 1 for 1st divider.
**    ixNx[3] = Number of cells in Child-1 and Child-2 + both divider cells
**    ixNx[4] = Total number of cells.
**
** For a table-btree, the concept is similar, except only apEnd[0]..apEnd[2]
** are used and they point to the leaf pages only, and the ixNx value are:
**
**    ixNx[0] = Number of cells in Child-1.
**    ixNx[1] = Number of cells in Child-1 and Child-2 + 1 for 1st divider.
**    ixNx[2] = Number of cells in Child-1 and Child-2 + both divider cells
*/
typedef struct CellArray CellArray;
struct CellArray {
  int nCell;              /* Number of cells in apCell[] */
  MemPage *pRef;          /* Reference page */
  u8 **apCell;            /* All cells begin balanced */
  u16 *szCell;            /* Local size of all cells in apCell[] */

  **    szNew[i]: Spaced used on the i-th sibling page.
  **   cntNew[i]: Index in b.apCell[] and b.szCell[] for the first cell to
  **              the right of the i-th sibling page.
  ** usableSpace: Number of bytes of space available on each sibling.
  ** 
  */
  usableSpace = pBt->usableSize - 12 + leafCorrection;
  for(i=k=0; i<nOld; i++, k++){
    MemPage *p = apOld[i];
    b.apEnd[k] = p->aDataEnd;
    b.ixNx[k] = cntOld[i];
    if( !leafData ){
      k++;
      b.apEnd[k] = pParent->aDataEnd;

      b.ixNx[k] = cntOld[i]+1;
    }
    szNew[i] = usableSpace - p->nFree;
    for(j=0; j<p->nOverflow; j++){
      szNew[i] += 2 + p->xCellSize(p, p->apOvfl[j]);
    }
    cntNew[i] = cntOld[i];
  }
  k = nOld;