vsi_l_offset GTM::findFirstTrackOffset()
{
if (firstTrackpointOffset == 0)
{
firstTrackpointOffset = findFirstTrackpointOffset();
if (firstTrackpointOffset == 0)
return 0;
}
/* First track offset is the first trackpoint offset plus number of
trackpoints time size of a trackpoint*/
return firstTrackpointOffset + static_cast<vsi_l_offset>(ntcks) * 25;
}
vsi_l_offset GTM::findFirstTrackOffset()
{
if (firstTrackpointOffset == 0)
{
firstTrackpointOffset = findFirstTrackpointOffset();
if (firstTrackpointOffset == 0)
return 0;
}
/* First track offset is the first trackpoint offset plus number of
trackpoints time size of a trackpoint*/
return (vsi_l_offset) (firstTrackpointOffset + ntcks * 25);
}
bool GTM::readHeaderNumbers()
{
if (pGTMFile == nullptr)
return false;
/* I'm supposing that the user has already checked if the file is
valid. */
/* Also, I'm ignoring some header parameters that are unnecessary
for my purpose. If you want more features, implement it. :-P */
/* Read Number of Waypoint Styles*/
/* Seek file */
if (VSIFSeekL(pGTMFile, NWPTSTYLES_OFFSET, SEEK_SET) != 0)
return false;
/* Read nwptstyles */
nwptstyles = readInt(pGTMFile);
if (nwptstyles < 0)
return false;
/* Read Number of Waypoints */
/* Seek file */
if ( VSIFSeekL(pGTMFile, NWPTS_OFFSET, SEEK_SET) != 0)
return false;
/* Read nwpts */
nwpts = readInt(pGTMFile);
if (nwpts < 0)
return false;
/* Read Number of Trackpoints */
ntcks = readInt(pGTMFile);
if (ntcks < 0)
return false;
/* Read Number of images */
/* Seek file */
if ( VSIFSeekL(pGTMFile, NMAPS_OFFSET, SEEK_SET) != 0)
return false;
/* read n_maps */
n_maps = readInt(pGTMFile);
if (n_maps < 0)
return false;
/* Read Number of Tracks */
n_tk = readInt(pGTMFile);
if (n_tk < 0)
return false;
/* Figure out the header size */
headerSize = 99; // Constant size plus size of strings
/* Read gradfont string size */
if ( VSIFSeekL(pGTMFile, 99, SEEK_SET) != 0)
return false;
unsigned short stringSize = readUShort(pGTMFile);
headerSize += stringSize + 2; // String + size field
/* Read labelfont string size */
if ( VSIFSeekL(pGTMFile, stringSize, SEEK_CUR) != 0)
return false;
stringSize = readUShort(pGTMFile);
headerSize += stringSize + 2; // String + size field
/* Read userfont string size */
if ( VSIFSeekL(pGTMFile, stringSize, SEEK_CUR) != 0)
return false;
stringSize = readUShort(pGTMFile);
headerSize += stringSize + 2; // String + size field
/* Read newdatum string size */
if ( VSIFSeekL(pGTMFile, stringSize, SEEK_CUR) != 0)
return false;
stringSize = readUShort(pGTMFile);
headerSize += stringSize + 2; // String + size field
/* -------------------------------------------------------------------- */
/* Checks if it is using WGS84 datum */
/* -------------------------------------------------------------------- */
/* Read newdatum string size */
if ( VSIFSeekL(pGTMFile, headerSize + 34, SEEK_SET) != 0)
return false;
if (readInt(pGTMFile) != 217)
{
CPLError( CE_Warning, CPLE_AppDefined,
"You are attempting to open a file that is not using "
"WGS84 datum.\n"
"Coordinates will be returned as if they were WGS84, "
"but no reprojection will be done." );
}
/* Look for the offsets */
/* Waypoints */
firstWaypointOffset = findFirstWaypointOffset();
if (firstWaypointOffset == 0)
return false;
actualWaypointOffset = firstWaypointOffset;
/* Trackpoints */
firstTrackpointOffset = findFirstTrackpointOffset();
if (firstTrackpointOffset == 0)
return false;
actualTrackpointOffset = firstTrackpointOffset;
/* Tracks */
firstTrackOffset = findFirstTrackOffset();
if (firstTrackOffset == 0)
return false;
actualTrackOffset = firstTrackOffset;
return true;
}
