SQLite

** Interchange to search points in a cursor.
*/
static void rtreeSearchPointSwap(RtreeCursor *p, int i, int j){
  RtreeSearchPoint t = p->aPoint[i];
  assert( i<j );
  p->aPoint[i] = p->aPoint[j];
  p->aPoint[j] = t;
  i++; j++;
  if( i<RTREE_CACHE_SZ ){
    if( j>=RTREE_CACHE_SZ ){
      nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
      p->aNode[i] = 0;
    }else{
      RtreeNode *pTemp = p->aNode[i];
      p->aNode[i] = p->aNode[j];
      p->aNode[j] = pTemp;
    }
  }
}

/*
** Return the search point with the lowest current score.
*/

  RtreeSearchPoint *pNew, *pFirst;
  pFirst = rtreeSearchPointFirst(pCur);
  if( pFirst==0
   || pFirst->rScore>rScore 
   || (pFirst->rScore==rScore && pFirst->iLevel>iLevel)
  ){
    if( pCur->bPoint ){
      int ii;
      pNew = rtreeEnqueue(pCur, rScore, iLevel);
      if( pNew==0 ) return 0;
      ii = (int)(pNew - pCur->aPoint) + 1;
      if( ii<RTREE_CACHE_SZ ){
        assert( pCur->aNode[ii]==0 );
        pCur->aNode[ii] = pCur->aNode[0];
       }else{
        nodeRelease(RTREE_OF_CURSOR(pCur), pCur->aNode[0]);
      }
      pCur->aNode[0] = 0;
      *pNew = pCur->sPoint;
    }
    pCur->sPoint.rScore = rScore;
    pCur->sPoint.iLevel = iLevel;
    pCur->bPoint = 1;
    return &pCur->sPoint;
  }else{
    return rtreeEnqueue(pCur, rScore, iLevel);
  }
}

#if 0
/* Tracing routines for the RtreeSearchPoint queue */
static void tracePoint(RtreeSearchPoint *p, int idx, RtreeCursor *pCur){
  if( idx<0 ){ printf(" s"); }else{ printf("%2d", idx); }
  printf(" %d.%05lld.%02d %g %d",
    p->iLevel, p->id, p->iCell, p->rScore, p->eWithin
  );
  idx++;
  if( idx<RTREE_CACHE_SZ ){
    printf(" %p\n", pCur->aNode[idx]);
  }else{
    printf("\n");
  }
}
static void traceQueue(RtreeCursor *pCur, const char *zPrefix){
  int ii;
  printf("=== %9s ", zPrefix);
  if( pCur->bPoint ){
    tracePoint(&pCur->sPoint, -1, pCur);
  }
  for(ii=0; ii<pCur->nPoint; ii++){
    if( ii>0 || pCur->bPoint ) printf("              ");

    tracePoint(&pCur->aPoint[ii], ii, pCur);
  }
}
#else
# define RTREE_QUEUE_TRACE(A,B)   /* no-op */
#endif

/* Remove the search point with the lowest current score.
*/
static void rtreeSearchPointPop(RtreeCursor *p){
  int i, j, k, n;
  i = p->bPoint;
  assert( i==0 || i==1 );
  if( p->aNode[i] ){
    nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
    p->aNode[i] = 0;
  }
  if( p->bPoint ){
    p->bPoint = 0;
  }else if( p->nPoint ){
    n = --p->nPoint;
    p->aPoint[0] = p->aPoint[n];
    if( n<RTREE_CACHE_SZ-1 ){
      p->aNode[1] = p->aNode[n+1];
      p->aNode[n+1] = 0;
    }
    i = 0;
    while( (j = i*2+1)<n ){
      k = j+1;
      if( k<n && rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[j])<0 ){
        if( rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[i])<0 ){
          rtreeSearchPointSwap(p, i, k);
          i = k;

        rc = rtreeTestEntry(pCur, &cell, &eWithin);
      }else{
        rc = rtreeTestCell(pCur, &cell, &eWithin);
      }
      if( rc ) return rc;
      x = *p;
      p->iCell++;
      if( eWithin==NOT_WITHIN ) continue;
      if( p->iCell>=nCell ){
        RTREE_QUEUE_TRACE(pCur, "POP-S:");
        rtreeSearchPointPop(pCur);
      }

      pNew = rtreeSearchPointNew(pCur, /*rScore*/0.0, x.iLevel-1);
      if( pNew==0 ) return SQLITE_NOMEM;
      pNew->eWithin = eWithin;
      if( pNew->iLevel ){
        pNew->id = cell.iRowid;
        pNew->iCell = 0;
      }else{
        pNew->id = x.id;
        pNew->iCell = x.iCell;
      }
      p = pNew;
      RTREE_QUEUE_TRACE(pCur, "PUSH-S:");
      break;
    }
    if( p->iCell>=nCell ){
      RTREE_QUEUE_TRACE(pCur, "POP-Se:");
      rtreeSearchPointPop(pCur);
    }
  }
  pCur->atEOF = p==0;
  return SQLITE_OK;
}

/* 
** Rtree virtual table module xNext method.
*/
static int rtreeNext(sqlite3_vtab_cursor *pVtabCursor){
  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
  int rc = SQLITE_OK;

  /* Move to the next entry that matches the configured constraints. */
  RTREE_QUEUE_TRACE(pCsr, "POP-Nx:");
  rtreeSearchPointPop(pCsr);
  rtreeStepToLeaf(pCsr);
  return rc;
}

/* 
** Rtree virtual table module xRowid method.

    p = rtreeSearchPointNew(pCsr, 0.0, 0);
    if( p==0 ) return SQLITE_NOMEM;
    rc = findLeafNode(pRtree, iRowid, &pLeaf, &p->id);
    pCsr->aNode[0] = pLeaf;
    p->eWithin = PARTLY_WITHIN;
    if( rc ) rc = nodeRowidIndex(pRtree, pLeaf, iRowid, &iCell);
    p->iCell = iCell;
    RTREE_QUEUE_TRACE(pCsr, "PUSH-F1:");
  }else{
    /* Normal case - r-tree scan. Set up the RtreeCursor.aConstraint array 
    ** with the configured constraints. 
    */
    if( argc>0 ){
      pCsr->aConstraint = sqlite3_malloc(sizeof(RtreeConstraint)*argc);
      pCsr->nConstraint = argc;

      RtreeSearchPoint *pNew = rtreeSearchPointNew(pCsr, 0.0, pRtree->iDepth+1);
      if( pNew==0 ) return SQLITE_NOMEM;
      pNew->id = 1;
      pNew->iCell = 0;
      pNew->eWithin = PARTLY_WITHIN;
      assert( pCsr->bPoint==1 );
      pCsr->aNode[0] = pRoot;
      RTREE_QUEUE_TRACE(pCsr, "PUSH-Fm:");
      rc = rtreeStepToLeaf(pCsr);
    }
  }

  rtreeRelease(pRtree);
  return rc;
}

    int jj;

    nodeGetCell(&tree, &node, ii, &cell);
    sqlite3_snprintf(512-nCell,&zCell[nCell],"%lld", cell.iRowid);
    nCell = (int)strlen(zCell);
    for(jj=0; jj<tree.nDim*2; jj++){
#ifndef SQLITE_RTREE_INT_ONLY
      sqlite3_snprintf(512-nCell,&zCell[nCell], " %g",
                       (double)cell.aCoord[jj].f);
#else
      sqlite3_snprintf(512-nCell,&zCell[nCell], " %d",
                       cell.aCoord[jj].i);
#endif
      nCell = (int)strlen(zCell);
    }