Geografic-Information-System/lib/vector/Vlib/read_sfa.c

/*!
  \file lib/vector/Vlib/read_sfa.c
  
  \brief Vector library - reading features - simple feature access
  
  Higher level functions for reading/writing/manipulating vectors.
  
  See read_ogr.c (OGR interface) and read_pg.c (PostGIS interface)
  for imlementation issues.

  (C) 2011-2012 by the GRASS Development Team
  
  This program is free software under the GNU General Public License
  (>=v2). Read the file COPYING that comes with GRASS for details.
  
  \author Martin Landa <landa.martin gmail.com>
*/

#include <grass/vector.h>
#include <grass/glocale.h>

/*!
  \brief Reads feature from OGR/PostGIS layer on topological level.
 
  This function implements random access on level 2.
  
  \param Map pointer to Map_info structure
  \param[out] line_p container used to store line points within
  (pointer to line_pnts struct)
  \param[out] line_c container used to store line categories within
  (pointer to line_cats struct)
  \param line feature id (starts at 1)
  
  \return feature type
  \return -2 no more features
  \return -1 on failure 
*/
int V2_read_line_sfa(struct Map_info *Map, struct line_pnts *line_p,
		     struct line_cats *line_c, int line)
{
#if defined HAVE_OGR || defined HAVE_POSTGRES
    struct P_line *Line;
    
    G_debug(4, "V2_read_line_sfa() line = %d", line);
    
    Line = Map->plus.Line[line];
    if (Line == NULL) {
	G_warning(_("Attempt to read dead feature %d"), line);
	return -1;
    }
    
    if (Line->type == GV_CENTROID) {
	/* read centroid for topo */
	if (line_p != NULL) {
	    int i, found;
	    struct bound_box box;
	    struct boxlist list;
	    struct P_topo_c *topo = (struct P_topo_c *)Line->topo;

	    G_debug(4, "Centroid: area = %d", topo->area);
	    Vect_reset_line(line_p);
	    
	    if (topo->area > 0 && topo->area <= Map->plus.n_areas) {
		/* get area bbox */
		Vect_get_area_box(Map, topo->area, &box);
		/* search in spatial index for centroid with area bbox */
		dig_init_boxlist(&list, TRUE);
		Vect_select_lines_by_box(Map, &box, Line->type, &list);
		
		found = -1;
		for (i = 0; i < list.n_values; i++) {
		    if (list.id[i] == line) {
			found = i;
			break;
		    }
		}
		
		if (found > -1) {
		    Vect_append_point(line_p, list.box[found].E, list.box[found].N, 0.0);
		}
		else {
		    G_warning(_("Unable to construct centroid for area %d. Skipped."),
			      topo->area);
		}
	    }
	    else {
		G_warning(_("Centroid %d: invalid area %d"), line, topo->area);
	    }
	}

	if (line_c != NULL) {
	  /* cat = fid and offset = fid for centroid */
	  Vect_reset_cats(line_c);
	  Vect_cat_set(line_c, 1, (int) Line->offset);
	}
	
	return GV_CENTROID;
    }
    
    if (!line_p && !line_c)
	return Line->type;
    
    if (Map->format == GV_FORMAT_POSTGIS)
	return V1_read_line_pg(Map, line_p, line_c, Line->offset);
    
    return V1_read_line_ogr(Map, line_p, line_c, Line->offset);
#else
    G_fatal_error(_("GRASS is not compiled with OGR/PostgreSQL support"));
    return -1;
#endif
}