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gpx-read.c
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gpx-read.c
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/* gpx-read.c
* Written by Daniel Foote.
* Started Feb 2005.
*
* This file contains routines to read the XML GPX files,
* containing GPS data.
*/
/* Copyright 2005 Daniel Foote.
*
* This file is part of gpscorrelate.
*
* gpscorrelate is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* gpscorrelate 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with gpscorrelate; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <stdio.h>
#include <string.h>
#include <locale.h>
#include <libxml/parser.h>
#include <libxml/tree.h>
#include "i18n.h"
#include "gpx-read.h"
#include "unixtime.h"
#include "gpsstructure.h"
/* Pointers to the first and last points, used during parsing */
static struct GPSPoint* FirstPoint;
static struct GPSPoint* LastPoint;
/* Returns the number of decimal places in the given decimal number string */
static int NumDecimals(const char *Decimal)
{
const char *Dec = strchr(Decimal, '.');
if (Dec) {
return strspn(Dec+1,"0123456789");
}
return 0;
}
static void ExtractTrackPoints(xmlNodePtr Start)
{
/* The pointer passed to us should be the start
* of a heap of trkpt's. So walk though them,
* extracting what we need. */
xmlNodePtr Current = NULL;
xmlNodePtr CCurrent = NULL;
xmlAttrPtr Properties = NULL;
const char* Lat;
const char* Long;
const char* Elev;
const char* Time;
for (Current = Start; Current; Current = Current->next)
{
if ((Current->type == XML_ELEMENT_NODE) &&
(strcmp((const char *)Current->name, "trkpt") == 0))
{
/* This is indeed a trackpoint. Extract! */
/* Reset the vars... so we don't get
* the data from last run. */
Lat = NULL;
Long = NULL;
Elev = NULL;
Time = NULL;
/* To get the Lat and Long, we have to
* extract the properties... another
* linked list to walk. */
for (Properties = Current->properties;
Properties;
Properties = Properties->next)
{
if (strcmp((const char *)Properties->name, "lat") == 0)
{
Lat = (const char *)Properties->children->content;
}
if (strcmp((const char *)Properties->name, "lon") == 0)
{
Long = (const char *)Properties->children->content;
}
}
/* Now, grab the elevation and time.
* These are children of trkpt. */
/* Oh, and what's the deal with the
* Node->children->content thing? */
for (CCurrent = Current->children;
CCurrent;
CCurrent = CCurrent->next)
{
if (strcmp((const char *)CCurrent->name, "ele") == 0)
{
if (CCurrent->children)
Elev = (const char *)CCurrent->children->content;
}
if (strcmp((const char *)CCurrent->name, "time") == 0)
{
if (CCurrent->children)
Time = (const char *)CCurrent->children->content;
}
}
/* Check that we have all the data. If we're missing something,
* then skip this point... */
if (Time == NULL || Long == NULL || Lat == NULL)
{
/* Missing some data. */
/* TODO: Really should report this upstream... */
continue;
}
/* Right, now we theoretically have all the data.
* Allocate ourselves some memory and go for it... */
if (FirstPoint)
{
/* Ok, adding to the list... */
LastPoint->Next = (struct GPSPoint*) malloc(sizeof(struct GPSPoint));
LastPoint = LastPoint->Next;
LastPoint->Next = NULL;
} else {
/* This is the first one. */
FirstPoint = (struct GPSPoint*) malloc(sizeof(struct GPSPoint));
FirstPoint->Next = NULL;
LastPoint = FirstPoint;
}
/* Clear the structure first... */
LastPoint->Lat = 0;
LastPoint->LatDecimals = 0;
LastPoint->Long = 0;
LastPoint->LongDecimals = 0;
LastPoint->Elev = 0;
LastPoint->ElevDecimals = -1; // default meaning no altitude was found
LastPoint->Time = 0;
LastPoint->EndOfSegment = 0;
/* Write the data into LastPoint, which should be a new point. */
LastPoint->Lat = atof(Lat);
LastPoint->LatDecimals = NumDecimals(Lat);
LastPoint->Long = atof(Long);
LastPoint->LongDecimals = NumDecimals(Long);
if (Elev) {
LastPoint->Elev = atof(Elev);
LastPoint->ElevDecimals = NumDecimals(Elev);
}
LastPoint->Time = ConvertToUnixTime(Time, GPX_DATE_FORMAT, 0, 0);
/* Debug...
printf("TrackPoint. Lat %s (%f), Long %s (%f). Elev %s (%f), Time %d.\n",
Lat, atof(Lat), Long, atof(Long), Elev, atof(Elev),
ConvertToUnixTime(Time, GPX_DATE_FORMAT, 0, 0));
printf("Decimals %d %d %d\n", LastPoint->LatDecimals, LastPoint->LongDecimals, LastPoint->ElevDecimals);
*/
}
} /* End For. */
/* Return control to the recursive function... */
}
static void FindTrackSeg(xmlNodePtr Start)
{
/* Go recursive till we find a <trgseg> tag. */
xmlNodePtr Current = NULL;
for (Current = Start; Current; Current = Current->next)
{
if ((Current->type == XML_ELEMENT_NODE) &&
(strcmp((const char *)Current->name, "trkseg") == 0))
{
/* Found it... the children should
* all be trkpt's. */
ExtractTrackPoints(Current->children);
/* Mark the last point as being the end
* of a track segment. */
if (LastPoint) LastPoint->EndOfSegment = 1;
}
/* And again, with children of this node. */
FindTrackSeg(Current->children);
} /* End For */
}
/* Determines and stores the min and max times from the GPS track */
static void GetTrackRange(struct GPSTrack* Track)
{
if (Track->Points == NULL)
return;
/* Requires us to go through the list and keep
* the biggest and smallest. The list should,
* however, be sorted. But we do it this way anyway. */
const struct GPSPoint* Fill = NULL;
Track->MaxTime = 0;
Track->MinTime = Track->Points->Time;
for (Fill = Track->Points; Fill; Fill = Fill->Next)
{
/* Check the Min time */
if (Fill->Time < Track->MinTime)
Track->MinTime = Fill->Time;
/* Check the Max time */
if (Fill->Time > Track->MaxTime)
Track->MaxTime = Fill->Time;
}
}
int ReadGPX(const char* File, struct GPSTrack* Track)
{
/* Init the libxml library. Also checks version. */
LIBXML_TEST_VERSION
xmlDocPtr GPXData;
/* Read the GPX data from file. */
GPXData = xmlParseFile(File);
if (GPXData == NULL)
{
fprintf(stderr, _("Failed to parse GPX data from %s.\n"), File);
return 0;
}
/* Now grab the "root" node. */
xmlNodePtr GPXRoot;
GPXRoot = xmlDocGetRootElement(GPXData);
if (GPXRoot == NULL)
{
fprintf(stderr, _("GPX file has no root. Not healthy.\n"));
xmlFreeDoc(GPXData);
xmlCleanupParser();
return 0;
}
/* Check that this is indeed a GPX - the root node
* should be "gpx". */
if (strcmp((const char *)GPXRoot->name, "gpx") == 0)
{
/* Ok, it is a GPX file. */
} else {
/* Not valid. */
fprintf(stderr, _("Invalid GPX file.\n"));
xmlFreeDoc(GPXData);
xmlCleanupParser();
return 0;
}
/* Now comes the messy part... walking the tree to find
* what we want.
* I've chosen to do it with two functions, one of which
* is recursive, rather than a clever inside-this-function
* walk the tree thing.
*
* We start by calling the recursive function to look for
* <trkseg> tags, and then that function calls another
* when it has found one... this sub function then
* hauls out the <trkpt> tags with the actual data.
* Messy, convoluted, but it seems to work... */
/* As to where to store the data? Again, its messy.
* We maintain two global vars, FirstPoint and LastPoint.
* FirstPoint points to the first GPSPoint done, and
* LastPoint is the last point done, used for the next
* point... we use this to build a singly-linked list. */
/* (I think I'll just be grateful for the work that libxml
* puts in for me... imagine having to write an XML parser!
* Nasty.) */
/* Before we go into this function, we also setlocale to "C".
* The GPX def indicates that the decimal separator should be
* ".", but certain locales specify otherwise. Which has caused issues.
* So we set the locale for this function, and then revert it.
*/
FirstPoint = NULL;
LastPoint = NULL;
char* OldLocale = setlocale(LC_NUMERIC, "C");
FindTrackSeg(GPXRoot);
setlocale(LC_NUMERIC, OldLocale);
/* Clean up stuff for the XML library. */
xmlFreeDoc(GPXData);
xmlCleanupParser();
Track->Points = FirstPoint;
/* Find the time range for this track */
GetTrackRange(Track);
return 1;
}
void FreeTrack(struct GPSTrack* Track)
{
/* Free the memory associated with the
* GPSPoint list... */
struct GPSPoint* NextFree = NULL;
struct GPSPoint* CurrentFree = Track->Points;
while (1)
{
if (CurrentFree == NULL) break;
NextFree = CurrentFree->Next;
free(CurrentFree);
CurrentFree = NextFree;
}
Track->Points = NULL;
}