trunk/src/segmentsx.c

/***************************************
 $Header: /home/amb/CVS/routino/src/segmentsx.c,v 1.48 2009-12-12 11:08:50 amb Exp $

 Extended Segment data type functions.

 Part of the Routino routing software.
 ******************/ /******************
 This file Copyright 2008,2009 Andrew M. Bishop

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***************************************/


#include <assert.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "types.h"
#include "functions.h"
#include "nodesx.h"
#include "segmentsx.h"
#include "waysx.h"
#include "nodes.h"
#include "segments.h"
#include "ways.h"


/* Variables */

/*+ The command line '--slim' option. +*/
extern int option_slim;

/*+ The command line '--tmpdir' option or its default value. +*/
extern char *option_tmpdirname;

/* Local Functions */

static int sort_by_id(SegmentX *a,SegmentX *b);

static distance_t DistanceX(NodeX *nodex1,NodeX *nodex2);


/*++++++++++++++++++++++++++++++++++++++
  Allocate a new segment list.

  SegmentsX *NewSegmentList Returns the segment list.
  ++++++++++++++++++++++++++++++++++++++*/

SegmentsX *NewSegmentList(void)
{
 SegmentsX *segmentsx;

 segmentsx=(SegmentsX*)calloc(1,sizeof(SegmentsX));

 assert(segmentsx); /* Check calloc() worked */

 segmentsx->filename=(char*)malloc(strlen(option_tmpdirname)+32);
 sprintf(segmentsx->filename,"%s/segments.%p.tmp",option_tmpdirname,segmentsx);

 segmentsx->fd=OpenFile(segmentsx->filename);

 return(segmentsx);
}


/*++++++++++++++++++++++++++++++++++++++
  Free a segment list.

  SegmentsX *segmentsx The list to be freed.
  ++++++++++++++++++++++++++++++++++++++*/

void FreeSegmentList(SegmentsX *segmentsx)
{
 DeleteFile(segmentsx->filename);
 free(segmentsx->filename);

 if(segmentsx->idata)
    free(segmentsx->idata);

 if(segmentsx->firstnode)
    free(segmentsx->firstnode);

 if(segmentsx->sdata)
    free(segmentsx->sdata);

 free(segmentsx);
}


/*++++++++++++++++++++++++++++++++++++++
  Append a single segment to a segment list.

  SegmentsX* segmentsx The set of segments to process.

  way_t way The way that the segment belongs to.

  node_t node1 The first node in the segment.

  node_t node2 The second node in the segment.

  distance_t distance The distance between the nodes (or just the flags).
  ++++++++++++++++++++++++++++++++++++++*/

void AppendSegment(SegmentsX* segmentsx,way_t way,node_t node1,node_t node2,distance_t distance)
{
 SegmentX segmentx;

 assert(!segmentsx->idata);    /* Must not have idata filled in => unsorted */

 segmentx.node1=node1;
 segmentx.node2=node2;
 segmentx.way=way;
 segmentx.distance=distance;

 WriteFile(segmentsx->fd,&segmentx,sizeof(SegmentX));

 segmentsx->xnumber++;
}


/*++++++++++++++++++++++++++++++++++++++
  Sort the segment list.

  SegmentsX* segmentsx The set of segments to process.
  ++++++++++++++++++++++++++++++++++++++*/

void SortSegmentList(SegmentsX* segmentsx)
{
 int fd;

 /* Check the start conditions */

 assert(!segmentsx->idata);    /* Must not have idata filled in => unsorted */

 /* Print the start message */

 printf("Sorting Segments");
 fflush(stdout);

 /* Close the files and re-open them (finished appending) */

 CloseFile(segmentsx->fd);
 segmentsx->fd=ReOpenFile(segmentsx->filename);

 DeleteFile(segmentsx->filename);

 fd=OpenFile(segmentsx->filename);

 /* Sort by node indexes */

 filesort_fixed(segmentsx->fd,fd,sizeof(SegmentX),(int (*)(const void*,const void*))sort_by_id,NULL);

 segmentsx->number=segmentsx->xnumber;

 /* Close the files and re-open them */

 CloseFile(segmentsx->fd);
 CloseFile(fd);

 segmentsx->fd=ReOpenFile(segmentsx->filename);

 /* Print the final message */

 printf("\rSorted Segments: Segments=%d\n",segmentsx->xnumber);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Sort the segments into id order (node1 then node2).

  int sort_by_id Returns the comparison of the node fields.

  SegmentX *a The first segment.

  SegmentX *b The second segment.
  ++++++++++++++++++++++++++++++++++++++*/

static int sort_by_id(SegmentX *a,SegmentX *b)
{
 node_t a_id1=a->node1;
 node_t b_id1=b->node1;

 if(a_id1<b_id1)
    return(-1);
 else if(a_id1>b_id1)
    return(1);
 else /* if(a_id1==b_id1) */
   {
    node_t a_id2=a->node2;
    node_t b_id2=b->node2;

    if(a_id2<b_id2)
       return(-1);
    else if(a_id2>b_id2)
       return(1);
    else
      {
       distance_t a_distance=a->distance;
       distance_t b_distance=b->distance;

       if(a_distance<b_distance)
          return(-1);
       else if(a_distance>b_distance)
          return(1);
       else
          return(0);
      }
   }
}


/*++++++++++++++++++++++++++++++++++++++
  Find the first segment index with a particular starting node.
 
  index_t IndexFirstSegmentX Returns a pointer to the index of the first extended segment with the specified id.

  SegmentsX* segmentsx The set of segments to process.

  node_t node The node to look for.
  ++++++++++++++++++++++++++++++++++++++*/

index_t IndexFirstSegmentX(SegmentsX* segmentsx,node_t node)
{
 int start=0;
 int end=segmentsx->number-1;
 int mid;
 int found;

 /* Check if the first node index exists */

 if(segmentsx->firstnode)
   {
    index_t index=segmentsx->firstnode[node];

    if(segmentsx->firstnode[node+1]==index)
       return(NO_SEGMENT);

    return(index);
   }

 assert(segmentsx->idata);      /* Must have idata filled in => sorted by node 1 */

 /* Binary search - search key exact match only is required.
  *
  *  # <- start  |  Check mid and move start or end if it doesn't match
  *  #           |
  *  #           |  Since an exact match is wanted we can set end=mid-1
  *  # <- mid    |  or start=mid+1 because we know that mid doesn't match.
  *  #           |
  *  #           |  Eventually either end=start or end=start+1 and one of
  *  # <- end    |  start or end is the wanted one.
  */

 if(end<start)                         /* There are no nodes */
    return(NO_SEGMENT);
 else if(node<segmentsx->idata[start]) /* Check key is not before start */
    return(NO_SEGMENT);
 else if(node>segmentsx->idata[end])   /* Check key is not after end */
    return(NO_SEGMENT);
 else
   {
    do
      {
       mid=(start+end)/2;                  /* Choose mid point */

       if(segmentsx->idata[mid]<node)      /* Mid point is too low */
          start=mid;
       else if(segmentsx->idata[mid]>node) /* Mid point is too high */
          end=mid;
       else                                /* Mid point is correct */
         {found=mid; goto found;}
      }
    while((end-start)>1);

    if(segmentsx->idata[start]==node)      /* Start is correct */
      {found=start; goto found;}

    if(segmentsx->idata[end]==node)        /* End is correct */
      {found=end; goto found;}
   }

 return(NO_SEGMENT);

 found:

 while(found>0 && segmentsx->idata[found-1]==node)
    found--;

 return(found);
}


/*++++++++++++++++++++++++++++++++++++++
  Find the next segment index with a particular starting node.

  index_t IndexNextSegmentX Returns the index of the next segment with the same id.

  SegmentsX* segmentsx The set of segments to process.

  index_t segindex The current segment index.

  index_t nodeindex The node index.
  ++++++++++++++++++++++++++++++++++++++*/

index_t IndexNextSegmentX(SegmentsX* segmentsx,index_t segindex,index_t nodeindex)
{
 assert(segmentsx->firstnode);   /* Must have firstnode filled in => segments updated */

 if(++segindex==segmentsx->firstnode[nodeindex+1])
    return(NO_SEGMENT);
 else
    return(segindex);
}
 
 
/*++++++++++++++++++++++++++++++++++++++
  Lookup a particular segment.

  SegmentX *LookupSegmentX Returns a pointer to the extended segment with the specified id.

  SegmentsX* segmentsx The set of segments to process.

  index_t index The segment index to look for.

  int position The position in the cache to use.
  ++++++++++++++++++++++++++++++++++++++*/

SegmentX *LookupSegmentX(SegmentsX* segmentsx,index_t index,int position)
{
 assert(index!=NO_SEGMENT);     /* Must be a valid segment */

 if(option_slim)
   {
    SeekFile(segmentsx->fd,index*sizeof(SegmentX));

    ReadFile(segmentsx->fd,&segmentsx->cached[position-1],sizeof(SegmentX));

    return(&segmentsx->cached[position-1]);
   }
 else
   {
    return(&segmentsx->xdata[index]);
   }
}


/*++++++++++++++++++++++++++++++++++++++
  Remove bad segments (duplicated, zero length or missing nodes).

  NodesX *nodesx The nodes to check.

  SegmentsX *segmentsx The segments to modify.
  ++++++++++++++++++++++++++++++++++++++*/

void RemoveBadSegments(NodesX *nodesx,SegmentsX *segmentsx)
{
 int duplicate=0,loop=0,missing=0,good=0,total=0;
 SegmentX segmentx;
 int fd;
 node_t prevnode1=NO_NODE,prevnode2=NO_NODE;

 /* Print the start message */

 printf("Checking: Segments=0 Duplicate=0 Loop=0 Missing-Node=0");
 fflush(stdout);

 /* Allocate the array of indexes */

 segmentsx->idata=(node_t*)malloc(segmentsx->xnumber*sizeof(node_t));

 assert(segmentsx->idata); /* Check malloc() worked */

 /* Modify the on-disk image */

 DeleteFile(segmentsx->filename);

 fd=OpenFile(segmentsx->filename);
 SeekFile(segmentsx->fd,0);

 while(!ReadFile(segmentsx->fd,&segmentx,sizeof(SegmentX)))
   {
    if(prevnode1==segmentx.node1 && prevnode2==segmentx.node2)
       duplicate++;
    else if(segmentx.node1==segmentx.node2)
       loop++;
    else if(IndexNodeX(nodesx,segmentx.node1)==NO_NODE ||
            IndexNodeX(nodesx,segmentx.node2)==NO_NODE)
       missing++;
    else
      {
       WriteFile(fd,&segmentx,sizeof(SegmentX));

       segmentsx->idata[good]=segmentx.node1;
       good++;

       prevnode1=segmentx.node1;
       prevnode2=segmentx.node2;
      }

    total++;

    if(!(total%10000))
      {
       printf("\rChecking: Segments=%d Duplicate=%d Loop=%d Missing-Node=%d",total,duplicate,loop,missing);
       fflush(stdout);
      }
   }

 /* Close the files and re-open them */

 CloseFile(segmentsx->fd);
 CloseFile(fd);

 segmentsx->fd=ReOpenFile(segmentsx->filename);

 segmentsx->number=good;

 /* Print the final message */

 printf("\rChecked: Segments=%d Duplicate=%d Loop=%d Missing-Node=%d  \n",total,duplicate,loop,missing);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Measure the segments and replace node/way ids with indexes.

  SegmentsX* segmentsx The set of segments to process.

  NodesX *nodesx The list of nodes to use.

  WaysX *waysx The list of ways to use.
  ++++++++++++++++++++++++++++++++++++++*/

void UpdateSegments(SegmentsX* segmentsx,NodesX *nodesx,WaysX *waysx)
{
 index_t index=0;
 int i,fd;
 SegmentX segmentx;

 /* Print the start message */

 printf("Measuring Segments: Segments=0");
 fflush(stdout);

 /* Map into memory */

 if(!option_slim)
    nodesx->xdata=MapFile(nodesx->filename);

 /* Free the now-unneeded index */

 free(segmentsx->idata);
 segmentsx->idata=NULL;

 /* Allocate the array of indexes */

 segmentsx->firstnode=(index_t*)malloc((nodesx->number+1)*sizeof(index_t));

 assert(segmentsx->firstnode); /* Check malloc() worked */

 for(i=0;i<nodesx->number;i++)
    segmentsx->firstnode[i]=NO_SEGMENT;

 segmentsx->firstnode[nodesx->number]=segmentsx->number;

 /* Modify the on-disk image */

 DeleteFile(segmentsx->filename);

 fd=OpenFile(segmentsx->filename);
 SeekFile(segmentsx->fd,0);

 while(!ReadFile(segmentsx->fd,&segmentx,sizeof(SegmentX)))
   {
    index_t node1=IndexNodeX(nodesx,segmentx.node1);
    index_t node2=IndexNodeX(nodesx,segmentx.node2);
    index_t way  =IndexWayX (waysx ,segmentx.way);

    NodeX *nodex1=LookupNodeX(nodesx,node1,1);
    NodeX *nodex2=LookupNodeX(nodesx,node2,2);

    /* Replace the node and way ids with their indexes */

    segmentx.node1=node1;
    segmentx.node2=node2;
    segmentx.way  =way;

    /* Set the distance but preserve the ONEWAY_* flags */

    segmentx.distance|=DISTANCE(DistanceX(nodex1,nodex2));

    /* Set the first segment index in the nodes */

    if(index<segmentsx->firstnode[node1])
       segmentsx->firstnode[node1]=index;

    /* Write the modified segment */

    WriteFile(fd,&segmentx,sizeof(SegmentX));

    index++;

    if(!(index%10000))
      {
       printf("\rMeasuring Segments: Segments=%d",index);
       fflush(stdout);
      }
   }

 /* Close the files and re-open them */

 CloseFile(segmentsx->fd);
 CloseFile(fd);

 segmentsx->fd=ReOpenFile(segmentsx->filename);

 /* Free the other now-unneeded indexes */

 free(nodesx->idata);
 nodesx->idata=NULL;

 free(waysx->idata);
 waysx->idata=NULL;

 /* Unmap from memory */

 if(!option_slim)
    nodesx->xdata=UnmapFile(nodesx->filename);

 /* Print the final message */

 printf("\rMeasured Segments: Segments=%d \n",segmentsx->number);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Make the segments all point the same way (node1<node2).

  SegmentsX* segmentsx The set of segments to process.
  ++++++++++++++++++++++++++++++++++++++*/

void RotateSegments(SegmentsX* segmentsx)
{
 int index=0,rotated=0;
 int fd;
 SegmentX segmentx;

 /* Check the start conditions */

 assert(!segmentsx->idata);    /* Must not have idata filled in => not sorted by node 1 */

 /* Print the start message */

 printf("Rotating Segments: Segments=0 Rotated=0");
 fflush(stdout);

 /* Close the files and re-open them (finished appending) */

 CloseFile(segmentsx->fd);
 segmentsx->fd=ReOpenFile(segmentsx->filename);

 DeleteFile(segmentsx->filename);

 fd=OpenFile(segmentsx->filename);

 /* Modify the file contents */

 while(!ReadFile(segmentsx->fd,&segmentx,sizeof(SegmentX)))
   {
    if(segmentx.node1>segmentx.node2)
      {
       node_t temp;

       temp=segmentx.node1;
       segmentx.node1=segmentx.node2;
       segmentx.node2=temp;

       if(segmentx.distance&(ONEWAY_2TO1|ONEWAY_1TO2))
          segmentx.distance^=ONEWAY_2TO1|ONEWAY_1TO2;

       rotated++;
      }

    WriteFile(fd,&segmentx,sizeof(SegmentX));

    index++;

    if(!(index%10000))
      {
       printf("\rRotating Segments: Segments=%d Rotated=%d",index,rotated);
       fflush(stdout);
      }
   }

 /* Close the files and re-open them */

 CloseFile(segmentsx->fd);
 CloseFile(fd);

 segmentsx->fd=ReOpenFile(segmentsx->filename);

 /* Print the final message */

 printf("\rRotated Segments: Segments=%d Rotated=%d \n",index,rotated);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Remove the duplicate segments.

  SegmentsX* segmentsx The set of segments to process.

  NodesX *nodesx The list of nodes to use.

  WaysX *waysx The list of ways to use.
  ++++++++++++++++++++++++++++++++++++++*/

void DeduplicateSegments(SegmentsX* segmentsx,NodesX *nodesx,WaysX *waysx)
{
 int duplicate=0,good=0;
 index_t firstindex=0,index=0;
 int i,fd;
 SegmentX prevsegmentx[16],segmentx;

 /* Print the start message */

 printf("Deduplicating Segments: Segments=0 Duplicate=0");
 fflush(stdout);

 /* Map into memory */

 if(!option_slim)
    waysx->xdata=MapFile(waysx->filename);

 /* Allocate the array of indexes */

 segmentsx->firstnode=(index_t*)malloc((nodesx->number+1)*sizeof(index_t));

 assert(segmentsx->firstnode); /* Check malloc() worked */

 for(i=0;i<nodesx->number;i++)
    segmentsx->firstnode[i]=NO_SEGMENT;

 segmentsx->firstnode[nodesx->number]=segmentsx->number;

 /* Modify the on-disk image */

 DeleteFile(segmentsx->filename);

 fd=OpenFile(segmentsx->filename);
 SeekFile(segmentsx->fd,0);

 while(!ReadFile(segmentsx->fd,&segmentx,sizeof(SegmentX)))
   {
    int isduplicate=0;

    if(index && segmentx.node1==prevsegmentx[0].node1 &&
                segmentx.node2==prevsegmentx[0].node2)
      {
       index_t previndex=firstindex;

       while(previndex<index)
         {
          int offset=previndex-firstindex;

          if(DISTFLAG(segmentx.distance)==DISTFLAG(prevsegmentx[offset].distance))
            {
             WayX *wayx1=LookupWayX(waysx,prevsegmentx[offset].way,1);
             WayX *wayx2=LookupWayX(waysx,    segmentx        .way,2);

             if(!WaysCompare(&wayx1->way,&wayx2->way))
               {
                isduplicate=1;
                duplicate++;
                break;
               }
            }

          previndex++;
         }

       assert((index-firstindex)<(sizeof(prevsegmentx)/sizeof(prevsegmentx[0])));

       prevsegmentx[index-firstindex]=segmentx;
      }
    else
      {
       firstindex=index;
       prevsegmentx[0]=segmentx;
      }

    if(!isduplicate)
      {
       WriteFile(fd,&segmentx,sizeof(SegmentX));

       if(good<segmentsx->firstnode[segmentx.node1])
          segmentsx->firstnode[segmentx.node1]=good;

       good++;
      }

    index++;

    if(!(index%10000))
      {
       printf("\rDeduplicating Segments: Segments=%d Duplicate=%d",index,duplicate);
       fflush(stdout);
      }
   }

 /* Close the files and re-open them */

 CloseFile(segmentsx->fd);
 CloseFile(fd);

 segmentsx->fd=ReOpenFile(segmentsx->filename);

 segmentsx->number=good;

 /* Fix-up the firstnode index for the missing nodes */

 for(i=nodesx->number-1;i>=0;i--)
    if(segmentsx->firstnode[i]==NO_SEGMENT)
       segmentsx->firstnode[i]=segmentsx->firstnode[i+1];

 /* Unmap from memory */

 if(!option_slim)
    waysx->xdata=UnmapFile(waysx->filename);

 /* Print the final message */

 printf("\rDeduplicated Segments: Segments=%d Duplicate=%d Unique=%d\n",index,duplicate,index-duplicate);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Create the real segments data.

  SegmentsX* segmentsx The set of segments to use.

  WaysX* waysx The set of ways to use.
  ++++++++++++++++++++++++++++++++++++++*/

void CreateRealSegments(SegmentsX *segmentsx,WaysX *waysx)
{
 index_t i;

 /* Check the start conditions */

 assert(!segmentsx->sdata);     /* Must not have sdata filled in => no real segments */

 /* Print the start message */

 printf("Creating Real Segments: Segments=0");
 fflush(stdout);

 /* Map into memory */

 if(!option_slim)
   {
    segmentsx->xdata=MapFile(segmentsx->filename);
    waysx->xdata=MapFile(waysx->filename);
   }

 /* Free the unneeded memory */

 free(segmentsx->firstnode);
 segmentsx->firstnode=NULL;

 /* Allocate the memory */

 segmentsx->sdata=(Segment*)malloc(segmentsx->number*sizeof(Segment));

 assert(segmentsx->sdata); /* Check malloc() worked */

 /* Loop through and fill */

 for(i=0;i<segmentsx->number;i++)
   {
    SegmentX *segmentx=LookupSegmentX(segmentsx,i,1);
    WayX *wayx=LookupWayX(waysx,segmentx->way,1);

    segmentsx->sdata[i].node1=0;
    segmentsx->sdata[i].node2=0;
    segmentsx->sdata[i].next2=NO_NODE;
    segmentsx->sdata[i].way=wayx->prop;
    segmentsx->sdata[i].distance=segmentx->distance;

    if(!((i+1)%10000))
      {
       printf("\rCreating Real Segments: Segments=%d",i+1);
       fflush(stdout);
      }
   }

 /* Unmap from memory */

 if(!option_slim)
   {
    segmentsx->xdata=UnmapFile(segmentsx->filename);
    waysx->xdata=UnmapFile(waysx->filename);
   }

 /* Print the final message */

 printf("\rCreating Real Segments: Segments=%d \n",segmentsx->number);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Assign the nodes indexes to the segments.

  SegmentsX* segmentsx The set of segments to process.

  NodesX *nodesx The list of nodes to use.
  ++++++++++++++++++++++++++++++++++++++*/

void IndexSegments(SegmentsX* segmentsx,NodesX *nodesx)
{
 index_t i;

 /* Check the start conditions */

 assert(nodesx->ndata);         /* Must have ndata filled in => real nodes exist */
 assert(segmentsx->sdata);      /* Must have sdata filled in => real segments exist */

 /* Print the start message */

 printf("Indexing Nodes: Nodes=0");
 fflush(stdout);

 /* Map into memory */

 if(!option_slim)
   {
    nodesx->xdata=MapFile(nodesx->filename);
    segmentsx->xdata=MapFile(segmentsx->filename);
   }

 /* Index the segments */

 for(i=0;i<nodesx->number;i++)
   {
    NodeX  *nodex=LookupNodeX(nodesx,i,1);
    Node   *node =&nodesx->ndata[nodex->id];
    index_t index=SEGMENT(node->firstseg);

    do
      {
       SegmentX *segmentx=LookupSegmentX(segmentsx,index,1);

       if(segmentx->node1==nodex->id)
         {
          segmentsx->sdata[index].node1=i;

          index++;

          if(index>=segmentsx->number)
             break;

          segmentx=LookupSegmentX(segmentsx,index,1);

          if(segmentx->node1!=nodex->id)
             break;
         }
       else
         {
          segmentsx->sdata[index].node2=i;

          if(segmentsx->sdata[index].next2==NO_NODE)
             break;
          else
             index=segmentsx->sdata[index].next2;
         }
      }
    while(1);

    if(!((i+1)%10000))
      {
       printf("\rIndexing Nodes: Nodes=%d",i+1);
       fflush(stdout);
      }
   }

 /* Unmap from memory */

 if(!option_slim)
   {
    nodesx->xdata=UnmapFile(nodesx->filename);
    segmentsx->xdata=UnmapFile(segmentsx->filename);
   }

 /* Print the final message */

 printf("\rIndexed Nodes: Nodes=%d \n",nodesx->number);
 fflush(stdout);
}


/*++++++++++++++++++++++++++++++++++++++
  Save the segment list to a file.

  SegmentsX* segmentsx The set of segments to save.

  const char *filename The name of the file to save.
  ++++++++++++++++++++++++++++++++++++++*/

void SaveSegmentList(SegmentsX* segmentsx,const char *filename)
{
 index_t i;
 int fd;
 Segments *segments;
 int super_number=0,normal_number=0;

 /* Check the start conditions */

 assert(segmentsx->sdata);      /* Must have sdata filled in => real segments */

 /* Print the start message */

 printf("Writing Segments: Segments=0");
 fflush(stdout);

 /* Count the number of super-segments and normal segments */

 for(i=0;i<segmentsx->number;i++)
   {
    if(IsSuperSegment(&segmentsx->sdata[i]))
       super_number++;
    if(IsNormalSegment(&segmentsx->sdata[i]))
       normal_number++;
   }

 /* Fill in a Segments structure with the offset of the real data in the file after
    the Segment structure itself. */

 segments=calloc(1,sizeof(Segments));

 assert(segments); /* Check calloc() worked */

 segments->number=segmentsx->number;
 segments->snumber=super_number;
 segments->nnumber=normal_number;

 segments->data=NULL;

 segments->segments=(void*)sizeof(Segments);

 /* Write out the Segments structure and then the real data. */

 fd=OpenFile(filename);

 WriteFile(fd,segments,sizeof(Segments));

 for(i=0;i<segments->number;i++)
   {
    WriteFile(fd,&segmentsx->sdata[i],sizeof(Segment));

    if(!((i+1)%10000))
      {
       printf("\rWriting Segments: Segments=%d",i+1);
       fflush(stdout);
      }
   }

 CloseFile(fd);

 /* Print the final message */

 printf("\rWrote Segments: Segments=%d  \n",segments->number);
 fflush(stdout);

 /* Free the fake Segments */

 free(segments);
}


/*++++++++++++++++++++++++++++++++++++++
  Calculate the distance between two nodes.

  distance_t DistanceX Returns the distance between the extended nodes.

  NodeX *nodex1 The starting node.

  NodeX *nodex2 The end node.
  ++++++++++++++++++++++++++++++++++++++*/

static distance_t DistanceX(NodeX *nodex1,NodeX *nodex2)
{
 double dlon = latlong_to_radians(nodex1->longitude) - latlong_to_radians(nodex2->longitude);
 double dlat = latlong_to_radians(nodex1->latitude)  - latlong_to_radians(nodex2->latitude);
 double lat1 = latlong_to_radians(nodex1->latitude);
 double lat2 = latlong_to_radians(nodex2->latitude);

 double a1,a2,a,sa,c,d;

 if(dlon==0 && dlat==0)
   return 0;

 a1 = sin (dlat / 2);
 a2 = sin (dlon / 2);
 a = (a1 * a1) + cos (lat1) * cos (lat2) * a2 * a2;
 sa = sqrt (a);
 if (sa <= 1.0)
   {c = 2 * asin (sa);}
 else
   {c = 2 * asin (1.0);}
 d = 6378.137 * c;

 return km_to_distance(d);
}