maptree.c

/******************************************************************************
 * $Id$
 *
 * Project:  MapServer
 * Purpose:  .qix spatial index implementation.  Derived from shapelib, and
 *           relicensed with permission of Frank Warmerdam (shapelib author).
 * Author:   Steve Lime
 *
 ******************************************************************************
 * Copyright (c) 1996-2005 Regents of the University of Minnesota.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies of this Software or works derived from this Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include "mapserver.h"
#include "maptree.h"


/* -------------------------------------------------------------------- */
/*      If the following is 0.5, nodes will be split in half.  If it    */
/*      is 0.6 then each subnode will contain 60% of the parent         */
/*      node, with 20% representing overlap.  This can be help to       */
/*      prevent small objects on a boundary from shifting too high      */
/*      up the tree.                                                    */
/* -------------------------------------------------------------------- */
#define SPLITRATIO  0.55

static int treeAddShapeId(treeObj *tree, int id, rectObj rect);

static void SwapWord( int length, void * wordP )
{
  int i;
  uchar temp;

  for( i=0; i < length/2; i++ ) {
    temp = ((uchar *) wordP)[i];
    ((uchar *)wordP)[i] = ((uchar *) wordP)[length-i-1];
    ((uchar *) wordP)[length-i-1] = temp;
  }
}

static void * SfRealloc( void * pMem, int nNewSize )

{
  if( pMem == NULL )
    return( (void *) malloc(nNewSize) );
  else
    return( (void *) realloc(pMem,nNewSize) );
}

static treeNodeObj *treeNodeCreate(rectObj rect)
{
  treeNodeObj *node;

  node = (treeNodeObj *) msSmallMalloc(sizeof(treeNodeObj));

  node->numshapes = 0;
  node->ids = NULL;

  node->numsubnodes = 0;

  memcpy(&(node->rect), &(rect), sizeof(rectObj));

  return node;
}


SHPTreeHandle msSHPDiskTreeOpen(const char * pszTree, int debug)
{
  char    *pszFullname, *pszBasename;
  SHPTreeHandle psTree;

  char    pabyBuf[16];
  int     i;
  char    bBigEndian;

  /* -------------------------------------------------------------------- */
  /*  Establish the byte order on this machine.         */
  /* -------------------------------------------------------------------- */
  i = 1;
  if( *((uchar *) &i) == 1 )
    bBigEndian = MS_FALSE;
  else
    bBigEndian = MS_TRUE;

  /* -------------------------------------------------------------------- */
  /*  Initialize the info structure.              */
  /* -------------------------------------------------------------------- */
  psTree = (SHPTreeHandle) msSmallMalloc(sizeof(SHPTreeInfo));

  /* -------------------------------------------------------------------- */
  /*  Compute the base (layer) name.  If there is any extension     */
  /*  on the passed in filename we will strip it off.         */
  /* -------------------------------------------------------------------- */
  pszBasename = (char *) msSmallMalloc(strlen(pszTree)+5);
  strcpy( pszBasename, pszTree );
  for( i = strlen(pszBasename)-1;
       i > 0 && pszBasename[i] != '.' && pszBasename[i] != '/'
       && pszBasename[i] != '\\';
       i-- ) {}

  if( pszBasename[i] == '.' )
    pszBasename[i] = '\0';

  /* -------------------------------------------------------------------- */
  /*  Open the .shp and .shx files.  Note that files pulled from      */
  /*  a PC to Unix with upper case filenames won't work!        */
  /* -------------------------------------------------------------------- */
  pszFullname = (char *) msSmallMalloc(strlen(pszBasename) + 5);
  sprintf( pszFullname, "%s%s", pszBasename, MS_INDEX_EXTENSION);
  psTree->fp = fopen(pszFullname, "rb" );
  if( psTree->fp == NULL ) {
      sprintf( pszFullname, "%s.QIX", pszBasename);
      psTree->fp = fopen(pszFullname, "rb" );
  }

  msFree(pszBasename); /* don't need these any more */
  msFree(pszFullname);

  if( psTree->fp == NULL ) {
    msFree(psTree);
    return( NULL );
  }

  fread( pabyBuf, 8, 1, psTree->fp );

  memcpy( &psTree->signature, pabyBuf, 3 );
  if( strncmp(psTree->signature,"SQT",3) ) {
    /* ---------------------------------------------------------------------- */
    /*     must check if the 2 first bytes equal 0 of max depth that cannot   */
    /*     be more than 65535. If yes, we must swap all value. The problem    */
    /*     here is if there's no Depth (bytea 5,6,7,8 in the file) all bytes  */
    /*     will be set to 0. So,we will test with the number of shapes (bytes */
    /*     1,2,3,4) that cannot be more than 65535 too.                       */
    /* ---------------------------------------------------------------------- */
    if (debug) {
      msDebug("WARNING in msSHPDiskTreeOpen(): %s is in old index format "
              "which has been deprecated.  It is strongly recommended to "
              "regenerate it in new format.\n", pszTree);
    }
    if((pabyBuf[4] == 0 && pabyBuf[5] == 0 &&
        pabyBuf[6] == 0 && pabyBuf[7] == 0)) {
      psTree->LSB_order = !(pabyBuf[0] == 0 && pabyBuf[1] == 0);
    } else {
      psTree->LSB_order = !(pabyBuf[4] == 0 && pabyBuf[5] == 0);
    }
    psTree->needswap = ((psTree->LSB_order) != (!bBigEndian));

    /* ---------------------------------------------------------------------- */
    /*     poor hack to see if this quadtree was created by a computer with a */
    /*     different Endian                                                   */
    /* ---------------------------------------------------------------------- */
    psTree->version = 0;
  } else {
    psTree->needswap = (( pabyBuf[3] == MS_NEW_MSB_ORDER ) ^ ( bBigEndian ));

    psTree->LSB_order = ( pabyBuf[3] == MS_NEW_LSB_ORDER );
    memcpy( &psTree->version, pabyBuf+4, 1 );
    memcpy( &psTree->flags, pabyBuf+5, 3 );

    fread( pabyBuf, 8, 1, psTree->fp );
  }

  if( psTree->needswap ) SwapWord( 4, pabyBuf );
  memcpy( &psTree->nShapes, pabyBuf, 4 );

  if( psTree->needswap ) SwapWord( 4, pabyBuf+4 );
  memcpy( &psTree->nDepth, pabyBuf+4, 4 );

  return( psTree );
}


void msSHPDiskTreeClose(SHPTreeHandle disktree)
{
  fclose( disktree->fp );
  free( disktree );
}


treeObj *msCreateTree(shapefileObj *shapefile, int maxdepth)
{
  int i;
  treeObj *tree;
  rectObj bounds;

  if(!shapefile) return NULL;

  /* -------------------------------------------------------------------- */
  /*      Allocate the tree object                                        */
  /* -------------------------------------------------------------------- */
  tree = (treeObj *) msSmallMalloc(sizeof(treeObj));

  tree->numshapes = shapefile->numshapes;
  tree->maxdepth = maxdepth;

  /* -------------------------------------------------------------------- */
  /*      If no max depth was defined, try to select a reasonable one     */
  /*      that implies approximately 8 shapes per node.                   */
  /* -------------------------------------------------------------------- */
  if( tree->maxdepth == 0 ) {
    int numnodes = 1;

    while(numnodes*4 < shapefile->numshapes) {
      tree->maxdepth += 1;
      numnodes = numnodes * 2;
    }
  }

  /* -------------------------------------------------------------------- */
  /*      Allocate the root node.                                         */
  /* -------------------------------------------------------------------- */
  tree->root = treeNodeCreate(shapefile->bounds);

  for(i=0; i<shapefile->numshapes; i++) {
    if(msSHPReadBounds(shapefile->hSHP, i, &bounds) == MS_SUCCESS)
      treeAddShapeId(tree, i, bounds);
  }

  return tree;
}

static void destroyTreeNode(treeNodeObj *node)
{
  int i;

  for(i=0; i<node->numsubnodes; i++ ) {
    if(node->subnode[i])
      destroyTreeNode(node->subnode[i]);
  }

  if(node->ids)
    free(node->ids);

  free(node);
}

void msDestroyTree(treeObj *tree)
{
  destroyTreeNode(tree->root);
  free(tree);
}

static void treeSplitBounds( rectObj *in, rectObj *out1, rectObj *out2)
{
  double range;

  /* -------------------------------------------------------------------- */
  /*      The output bounds will be very similar to the input bounds,     */
  /*      so just copy over to start.                                     */
  /* -------------------------------------------------------------------- */
  memcpy(out1, in, sizeof(rectObj));
  memcpy(out2, in, sizeof(rectObj));

  /* -------------------------------------------------------------------- */
  /*      Split in X direction.                                           */
  /* -------------------------------------------------------------------- */
  if((in->maxx - in->minx) > (in->maxy - in->miny)) {
    range = in->maxx - in->minx;

    out1->maxx = in->minx + range * SPLITRATIO;
    out2->minx = in->maxx - range * SPLITRATIO;
  }

  /* -------------------------------------------------------------------- */
  /*      Otherwise split in Y direction.                                 */
  /* -------------------------------------------------------------------- */
  else {
    range = in->maxy - in->miny;

    out1->maxy = in->miny + range * SPLITRATIO;
    out2->miny = in->maxy - range * SPLITRATIO;
  }
}

static int treeNodeAddShapeId( treeNodeObj *node, int id, rectObj rect, int maxdepth)
{
  int i;

  /* -------------------------------------------------------------------- */
  /*      If there are subnodes, then consider whether this object        */
  /*      will fit in them.                                               */
  /* -------------------------------------------------------------------- */
  if( maxdepth > 1 && node->numsubnodes > 0 ) {
    for(i=0; i<node->numsubnodes; i++ ) {
      if( msRectContained(&rect, &node->subnode[i]->rect)) {
        return treeNodeAddShapeId( node->subnode[i], id, rect, maxdepth-1);
      }
    }
  }

  /* -------------------------------------------------------------------- */
  /*      Otherwise, consider creating four subnodes if could fit into    */
  /*      them, and adding to the appropriate subnode.                    */
  /* -------------------------------------------------------------------- */
#if MAX_SUBNODES == 4
  else if( maxdepth > 1 && node->numsubnodes == 0 ) {
    rectObj half1, half2, quad1, quad2, quad3, quad4;

    treeSplitBounds(&node->rect, &half1, &half2);
    treeSplitBounds(&half1, &quad1, &quad2);
    treeSplitBounds(&half2, &quad3, &quad4);

    if(msRectContained(&rect, &quad1) || msRectContained(&rect, &quad2) ||  msRectContained(&rect, &quad3) || msRectContained(&rect, &quad4)) {
      node->numsubnodes = 4;
      node->subnode[0] = treeNodeCreate(quad1);
      node->subnode[1] = treeNodeCreate(quad2);
      node->subnode[2] = treeNodeCreate(quad3);
      node->subnode[3] = treeNodeCreate(quad4);

      /* recurse back on this node now that it has subnodes */
      return(treeNodeAddShapeId(node, id, rect, maxdepth));
    }
  }
#endif

  /* -------------------------------------------------------------------- */
  /*      Otherwise, consider creating two subnodes if could fit into     */
  /*      them, and adding to the appropriate subnode.                    */
  /* -------------------------------------------------------------------- */
#if MAX_SUBNODE == 2
  else if( maxdepth > 1 && node->numsubnodes == 0 ) {
    rectObj half1, half2;

    treeSplitBounds(&node->rect, &half1, &half2);

    if( msRectContained(&rect, &half1)) {
      node->numsubnodes = 2;
      node->subnode[0] = treeNodeCreate(half1);
      node->subnode[1] = treeNodeCreate(half2);

      return(treeNodeAddShapeId(node->subnode[0], id, rect, maxdepth-1));
    } else if(msRectContained(&rect, &half2)) {
      node->numsubnodes = 2;
      node->subnode[0] = treeNodeCreate(&half1);
      node->subnode[1] = treeNodeCreate(&half2);

      return(treeNodeAddShapeId(node->subnode[1], id, rect, maxdepth-1));
    }
  }
#endif /* MAX_SUBNODE == 2 */

  /* -------------------------------------------------------------------- */
  /*      If none of that worked, just add it to this nodes list.         */
  /* -------------------------------------------------------------------- */
  node->numshapes++;

  node->ids = SfRealloc( node->ids, sizeof(ms_int32) * node->numshapes );
  node->ids[node->numshapes-1] = id;

  return MS_TRUE;
}

static int treeAddShapeId(treeObj *tree, int id, rectObj rect)
{
  return(treeNodeAddShapeId(tree->root, id, rect, tree->maxdepth));
}

static void treeCollectShapeIds(treeNodeObj *node, rectObj aoi, ms_bitarray status)
{
  int i;

  /* -------------------------------------------------------------------- */
  /*      Does this node overlap the area of interest at all?  If not,    */
  /*      return without adding to the list at all.                       */
  /* -------------------------------------------------------------------- */
  if(!msRectOverlap(&node->rect, &aoi))
    return;

  /* -------------------------------------------------------------------- */
  /*      Add the local nodes shapeids to the list.                       */
  /* -------------------------------------------------------------------- */
  for(i=0; i<node->numshapes; i++)
    msSetBit(status, node->ids[i], 1);

  /* -------------------------------------------------------------------- */
  /*      Recurse to subnodes if they exist.                              */
  /* -------------------------------------------------------------------- */
  for(i=0; i<node->numsubnodes; i++) {
    if(node->subnode[i])
      treeCollectShapeIds(node->subnode[i], aoi, status);
  }
}

ms_bitarray msSearchTree(treeObj *tree, rectObj aoi)
{
  ms_bitarray status=NULL;

  status = msAllocBitArray(tree->numshapes);
  if(!status) {
    msSetError(MS_MEMERR, NULL, "msSearchTree()");
    return(NULL);
  }

  treeCollectShapeIds(tree->root, aoi, status);

  return(status);
}

static int treeNodeTrim( treeNodeObj *node )
{
  int i;

  /* -------------------------------------------------------------------- */
  /*      Trim subtrees, and free subnodes that come back empty.          */
  /* -------------------------------------------------------------------- */
  for(i=0; i<node->numsubnodes; i++ ) {
    if(treeNodeTrim(node->subnode[i])) {
      destroyTreeNode(node->subnode[i]);
      node->subnode[i] = node->subnode[node->numsubnodes-1];
      node->numsubnodes--;
      i--; /* process the new occupant of this subnode entry */
    }
  }

  /* -------------------------------------------------------------------- */
  /*      If the current node has 1 subnode and no shapes, promote that   */
  /*      subnode to the current node position.                           */
  /* -------------------------------------------------------------------- */
  if( node->numsubnodes == 1 && node->numshapes == 0) {
    treeNodeObj* psSubNode = node->subnode[0];

    memcpy(&node->rect, &psSubNode->rect,
           sizeof(psSubNode->rect));
    node->numshapes = psSubNode->numshapes;
    assert(node->ids == NULL);
    node->ids = psSubNode->ids;
    node->numsubnodes = psSubNode->numsubnodes;
    for( i = 0; i < psSubNode->numsubnodes; i++ )
      node->subnode[i] = psSubNode->subnode[i];
    free(psSubNode);
  }

  /* -------------------------------------------------------------------- */
  /*      We should be trimmed if we have no subnodes, and no shapes.     */
  /* -------------------------------------------------------------------- */

  return(node->numsubnodes == 0 && node->numshapes == 0);
}

void msTreeTrim(treeObj *tree)
{
  treeNodeTrim(tree->root);
}

static void searchDiskTreeNode(SHPTreeHandle disktree, rectObj aoi, ms_bitarray status)
{
  int i;
  ms_int32 offset;
  ms_int32 numshapes, numsubnodes;
  rectObj rect;

  int *ids=NULL;

  fread( &offset, 4, 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 4, &offset );

  fread( &rect, sizeof(rectObj), 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 8, &rect.minx );
  if ( disktree->needswap ) SwapWord ( 8, &rect.miny );
  if ( disktree->needswap ) SwapWord ( 8, &rect.maxx );
  if ( disktree->needswap ) SwapWord ( 8, &rect.maxy );

  fread( &numshapes, 4, 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 4, &numshapes );

  if(!msRectOverlap(&rect, &aoi)) { /* skip rest of this node and sub-nodes */
    offset += numshapes*sizeof(ms_int32) + sizeof(ms_int32);
    fseek(disktree->fp, offset, SEEK_CUR);
    return;
  }
  if(numshapes > 0) {
    ids = (int *)msSmallMalloc(numshapes*sizeof(ms_int32));

    fread( ids, numshapes*sizeof(ms_int32), 1, disktree->fp );
    if (disktree->needswap ) {
      for( i=0; i<numshapes; i++ ) {
        SwapWord( 4, &ids[i] );
        msSetBit(status, ids[i], 1);
      }
    } else {
      for(i=0; i<numshapes; i++)
        msSetBit(status, ids[i], 1);
    }
    free(ids);
  }

  fread( &numsubnodes, 4, 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 4, &numsubnodes );

  for(i=0; i<numsubnodes; i++)
    searchDiskTreeNode(disktree, aoi, status);

  return;
}

ms_bitarray msSearchDiskTree(char *filename, rectObj aoi, int debug)
{
  SHPTreeHandle disktree;
  ms_bitarray status=NULL;

  disktree = msSHPDiskTreeOpen (filename, debug);
  if(!disktree) {

    /* only set this error IF debugging is turned on, gets annoying otherwise */
    if(debug) msSetError(MS_NOTFOUND, "Unable to open spatial index for %s. In most cases you can safely ignore this message, otherwise check file names and permissions.", "msSearchDiskTree()", filename);

    return(NULL);
  }

  status = msAllocBitArray(disktree->nShapes);
  if(!status) {
    msSetError(MS_MEMERR, NULL, "msSearchDiskTree()");
    msSHPDiskTreeClose( disktree );
    return(NULL);
  }

  searchDiskTreeNode(disktree, aoi, status);

  msSHPDiskTreeClose( disktree );
  return(status);
}

treeNodeObj *readTreeNode( SHPTreeHandle disktree )
{
  int i,res;
  ms_int32 offset;
  treeNodeObj *node;

  node = (treeNodeObj *) msSmallMalloc(sizeof(treeNodeObj));
  node->ids = NULL;

  res = fread( &offset, 4, 1, disktree->fp );
  if ( !res )
    return NULL;

  if ( disktree->needswap ) SwapWord ( 4, &offset );

  fread( &node->rect, sizeof(rectObj), 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 8, &node->rect.minx );
  if ( disktree->needswap ) SwapWord ( 8, &node->rect.miny );
  if ( disktree->needswap ) SwapWord ( 8, &node->rect.maxx );
  if ( disktree->needswap ) SwapWord ( 8, &node->rect.maxy );

  fread( &node->numshapes, 4, 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 4, &node->numshapes );
  if( node->numshapes > 0 )
    node->ids = (ms_int32 *)msSmallMalloc(sizeof(ms_int32)*node->numshapes);
  fread( node->ids, node->numshapes*4, 1, disktree->fp );
  for( i=0; i < node->numshapes; i++ ) {
    if ( disktree->needswap ) SwapWord ( 4, &node->ids[i] );
  }

  fread( &node->numsubnodes, 4, 1, disktree->fp );
  if ( disktree->needswap ) SwapWord ( 4, &node->numsubnodes );

  return node;
}

treeObj *msReadTree(char *filename, int debug)
{
  treeObj *tree=NULL;
  SHPTreeHandle disktree;

  disktree = msSHPDiskTreeOpen( filename, debug );
  if(!disktree) {
    msSetError(MS_IOERR, NULL, "msReadTree()");
    return(NULL);
  }

  tree = (treeObj *) malloc(sizeof(treeObj));
  MS_CHECK_ALLOC(tree, sizeof(treeObj), NULL);

  tree->numshapes = disktree->nShapes;
  tree->maxdepth = disktree->nDepth;

  tree->root = readTreeNode( disktree );

  return(tree);
}

static ms_int32 getSubNodeOffset(treeNodeObj *node)
{
  int i;
  ms_int32 offset=0;

  for(i=0; i<node->numsubnodes; i++ ) {
    if(node->subnode[i]) {
      offset += sizeof(rectObj) + (node->subnode[i]->numshapes+3)*sizeof(int);
      offset += getSubNodeOffset(node->subnode[i]);
    }
  }

  /* offset is the disk offset in the index file on disk       */
  /*   that format is (per node)                               */
  /*      int       offset      4 bytes           */
  /*      rectObj   rect      4 * 8 bytes         */
  /*    int   numShapes   4 bytes           */
  /*    int   ids[numShapes]  4 * numShapes bytes     */
  /*    int   numSubNodes   4 bytes           */
  /*                                               */

  return(offset);
}


static void writeTreeNode(SHPTreeHandle disktree, treeNodeObj *node)
{
  int i,j;
  ms_int32 offset;
  char *pabyRec = NULL;

  offset = getSubNodeOffset(node);

  pabyRec = msSmallMalloc(sizeof(rectObj) + (3 * sizeof(ms_int32)) + (node->numshapes * sizeof(ms_int32)) );

  memcpy( pabyRec, &offset, 4);
  if( disktree->needswap ) SwapWord( 4, pabyRec );

  memcpy( pabyRec+4, &node->rect, sizeof(rectObj));
  for (i=0; i < 4; i++)
    if( disktree->needswap ) SwapWord( 8, pabyRec+4+(8*i) );

  memcpy( pabyRec+36, &node->numshapes, 4);
  if( disktree->needswap ) SwapWord( 4, pabyRec+36 );

  j = node->numshapes*sizeof(ms_int32);
  memcpy( pabyRec+40, node->ids, j);
  for (i=0; i<node->numshapes; i++)
    if( disktree->needswap ) SwapWord( 4, pabyRec+40+(4*i));

  memcpy( pabyRec+j+40, &node->numsubnodes, 4);
  if( disktree->needswap ) SwapWord( 4, pabyRec+40+j );

  fwrite( pabyRec, 44+j, 1, disktree->fp);
  free (pabyRec);

  for(i=0; i<node->numsubnodes; i++ ) {
    if(node->subnode[i])
      writeTreeNode(disktree, node->subnode[i]);
  }


  return;

}

int msWriteTree(treeObj *tree, char *filename, int B_order)
{
  char    signature[3] = "SQT";
  char    version = 1;
  char    reserved[3] = {0,0,0};
  SHPTreeHandle disktree;
  int   i;
  char    mtBigEndian;
  char    pabyBuf[32];
  char    *pszBasename, *pszFullname;


  disktree = (SHPTreeHandle) malloc(sizeof(SHPTreeInfo));
  MS_CHECK_ALLOC(disktree, sizeof(SHPTreeInfo), MS_FALSE);

  /* -------------------------------------------------------------------- */
  /*  Compute the base (layer) name.  If there is any extension     */
  /*  on the passed in filename we will strip it off.         */
  /* -------------------------------------------------------------------- */
  pszBasename = (char *) msSmallMalloc(strlen(filename)+5);
  strcpy( pszBasename, filename );
  for( i = strlen(pszBasename)-1;
       i > 0 && pszBasename[i] != '.' && pszBasename[i] != '/'
       && pszBasename[i] != '\\';
       i-- ) {}

  if( pszBasename[i] == '.' )
    pszBasename[i] = '\0';

  /* -------------------------------------------------------------------- */
  /*  Open the .shp and .shx files.  Note that files pulled from      */
  /*  a PC to Unix with upper case filenames won't work!        */
  /* -------------------------------------------------------------------- */
  pszFullname = (char *) msSmallMalloc(strlen(pszBasename) + 5);
  sprintf( pszFullname, "%s%s", pszBasename, MS_INDEX_EXTENSION);
  disktree->fp = fopen(pszFullname, "wb");

  msFree(pszBasename); /* not needed */
  msFree(pszFullname);

  if(!disktree->fp) {
    msFree(disktree);
    msSetError(MS_IOERR, NULL, "msWriteTree()");
    return(MS_FALSE);
  }


  /* for efficiency, trim the tree */
  msTreeTrim(tree);

  /* -------------------------------------------------------------------- */
  /*  Establish the byte order on this machine.         */
  /* -------------------------------------------------------------------- */
  i = 1;
  if( *((uchar *) &i) == 1 )
    mtBigEndian = MS_FALSE;
  else
    mtBigEndian = MS_TRUE;

  if( !(mtBigEndian ^ ( B_order == MS_LSB_ORDER || B_order == MS_NEW_LSB_ORDER )) )
    disktree->needswap = 1;
  else
    disktree->needswap = 0;

  if( B_order == MS_NATIVE_ORDER )
    disktree->needswap = 0;

  /* write the header */
  if ( B_order > 0 ) {
    memcpy( pabyBuf, &signature, 3 );
    memcpy (&disktree->signature, &signature, 3);
    pabyBuf[3] = B_order;

    memcpy( pabyBuf+4, &version, 1);
    memcpy( pabyBuf+5, &reserved, 3);

    memcpy( &disktree->version, &version, 1);
    memcpy( &disktree->flags, &reserved, 3);

    fwrite( pabyBuf, 8, 1, disktree->fp );
  }

  memcpy( pabyBuf, &tree->numshapes, 4 );
  if( disktree->needswap ) SwapWord( 4, pabyBuf );

  memcpy( pabyBuf+4, &tree->maxdepth, 4 );
  if( disktree->needswap ) SwapWord( 4, pabyBuf+4 );

  i = fwrite( pabyBuf, 8, 1, disktree->fp );
  if( !i ) {
    fprintf (stderr, "unable to write to index file ... exiting \n");
    msSHPDiskTreeClose( disktree );
    return (MS_FALSE);
  }

  writeTreeNode(disktree, tree->root);

  msSHPDiskTreeClose( disktree );

  return(MS_TRUE);
}

/* Function to filter search results further against feature bboxes */
void msFilterTreeSearch(shapefileObj *shp, ms_bitarray status, rectObj search_rect)
{
  int i;
  rectObj shape_rect;

  i = msGetNextBit(status, 0, shp->numshapes);
  while(i >= 0) {
    if(msSHPReadBounds(shp->hSHP, i, &shape_rect) == MS_SUCCESS) {
      if(msRectOverlap(&shape_rect, &search_rect) != MS_TRUE) {
        msSetBit(status, i, 0);
      }
    }
    i = msGetNextBit(status, i+1, shp->numshapes);
  }

}