simple_features.c

Go to the documentation of this file.

/*!
   \file lib/vector/Vlib/simple_features.c
 
   \brief Vector library - OGC Simple Features Access
 
   Higher level functions for reading/writing/manipulating vectors.
 
   Note: <b>In progress!</b> Currently on GV_POINT, GV_LINE,
   GV_BOUNDARY are supported.
 
   \todo
   - Vect_sfa_line_is_simple()
   - Vect_sfa_line_srid()
   - Vect_sfa_line_envelope()
   - Vect_sfa_line_asbinary()
   - Vect_sfa_line_is_empty()
   - Vect_sfa_line_is_3d()
   - Vect_sfa_line_is_measured()
   - Vect_sfa_line_boundary()
 
   Reference: http://www.opengeospatial.org/standards/sfa
 
   (C) 2009, 2011-2013 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 <stdio.h>
 
#include <grass/vector.h>
#include <grass/glocale.h>
 
#ifdef HAVE_POSTGRES
#include "pg_local_proto.h"
#endif
 
#ifdef HAVE_OGR
#include <ogr_api.h>
#endif
 
static int check_sftype(const struct line_pnts *, int, SF_FeatureType, int);
static int get_sftype(const struct line_pnts *, int, int);
static void print_point(const struct line_pnts *, int, int, int, FILE *);
 
/*!
   \brief Get SF type of given vector feature
 
   List of supported feature types:
   - GV_POINT         -> SF_POINT
   - GV_LINE          -> SF_LINESTRING
   - GV_LINE (closed) -> SF_LINEARRING
   - GV_BOUNDARY      -> SF_POLYGON
 
   \param Points  pointer to line_pnts structure
   \param type    feature type (see supported types above)
   \param with_z  WITH_Z for 3D data
 
   \return SF type identificator (see list of supported types)
   \return -1 on error
 */
SF_FeatureType Vect_sfa_get_line_type(const struct line_pnts *Points, int type,
                                      int with_z)
{
    return get_sftype(Points, type, with_z);
}
 
/*!
   \brief Get relevant GV type
 
   \param Map pointer to Map_info structure
   \param type SF geometry type (SF_POINT, SF_LINESTRING, ...)
 
   \return GV type
   \return -1 on error
 */
int Vect_sfa_get_type(SF_FeatureType sftype)
{
    switch (sftype) {
    case SF_POINT:
    case SF_POINT25D:
        return GV_POINT;
    case SF_LINESTRING:
    case SF_LINESTRING25D:
    case SF_LINEARRING:
        return GV_LINE;
    case SF_POLYGON:
    case SF_POLYGON25D:
        return GV_BOUNDARY;
    default:
        break;
    }
 
    return -1;
}
 
/*!
   \brief Check SF type
 
   E.g. if <em>type</em> is GV_LINE with two or more segments and the
   start node is identical with the end node, and <em>sftype</em> is
   SF_LINEARRING, functions returns 1, otherwise 0.
 
   \param Points pointer to line_pnts structure
   \param type feature type (GV_POINT, GV_LINE, ...)
   \param sftype SF type to be checked (SF_POINT, SF_LINE, ...)
   \param with_z non-zero value for 3D data
 
   \return 1 if type is sftype
   \return 0 type differs from sftype
 */
int Vect_sfa_check_line_type(const struct line_pnts *Points, int type,
                             SF_FeatureType sftype, int with_z)
{
    return check_sftype(Points, type, sftype, with_z);
}
 
/*!
   \brief Get geometry dimension
 
   \param Points pointer to line_pnts structure
   \param type   feature type (GV_POINT, GV_LINE, ...)
 
   \return 0 for GV_POINT
   \return 1 for GV_LINE
   \return 2 for GV_BOUNDARY
   \return -1 unsupported feature type
 */
int Vect_sfa_line_dimension(int type)
{
    if (type == GV_POINT)
        return 0;
    if (type == GV_LINE)
        return 1;
    if (type == GV_BOUNDARY)
        return 2;
 
    return -1;
}
 
/*!
   \brief Get geometry type (string)
 
   Supported types:
   - GV_POINT             -> SF_POINT      -> "POINT"
   - GV_LINE              -> SF_LINESTRING -> "LINESTRING"
   - GV_LINE (closed)     -> SF_LINEARRING -> "LINEARRING"
   - GV_BOUNDARY (closed) -> SF_POLYGON -> "POLYGON"
 
   Note: Allocated string should be freed by G_free().
 
   \param Points pointer to line_pnts structure (feature geometry)
   \param type   feature type (see supported types above)
 
   \return geometry type string
   \return NULL unsupported feature type
 */
char *Vect_sfa_line_geometry_type(const struct line_pnts *Points, int type)
{
    SF_FeatureType sftype = Vect_sfa_get_line_type(Points, type, 0);
 
    if (sftype == SF_POINT)
        return G_store("POINT");
    if (sftype == SF_LINESTRING)
        return G_store("LINESTRING");
    if (sftype == SF_LINEARRING)
        return G_store("LINEARRING");
    if (sftype == SF_POLYGON)
        return G_store("POLYGON");
 
    return NULL;
}
 
/*!
   \brief Export geometry to Well-Known Text
 
   \param Points    pointer to line_pnts structure
   \param type      feature type
   \param with_z    non-zero value for 3D data
   \param precision floating number precision
   \param[out] file file where to write the output
 
   \return 0 on success
   \return -1 unsupported feature type
 */
int Vect_sfa_line_astext(const struct line_pnts *Points, int type, int with_z,
                         int precision, FILE *file)
{
    int i, sftype;
 
    sftype = Vect_sfa_get_line_type(Points, type, with_z);
 
    switch (sftype) {
    case SF_POINT: { /* point */
        fprintf(file, "POINT(");
        print_point(Points, 0, with_z, precision, file);
        fprintf(file, ")\n");
        break;
    }
    case SF_LINESTRING:
    case SF_LINEARRING: /* line */ {
        if (sftype == SF_LINESTRING)
            fprintf(file, "LINESTRING(");
        else
            fprintf(file, "LINEARRING(");
        for (i = 0; i < Points->n_points; i++) {
            print_point(Points, i, with_z, precision, file);
            if (i < Points->n_points - 1)
                fprintf(file, ", ");
        }
        fprintf(file, ")\n");
        break;
    }
    case SF_POLYGON: /* polygon */ {
        /* write only outer/inner ring */
        fprintf(file, "(");
        for (i = 0; i < Points->n_points; i++) {
            print_point(Points, i, with_z, precision, file);
            if (i < Points->n_points - 1)
                fprintf(file, ", ");
        }
        fprintf(file, ")");
        break;
    }
    default: {
        G_warning(_("Unknown Simple Features type (%d)"), sftype);
        return -1;
    }
    }
 
    fflush(file);
    return 0;
}
 
/*!
   \brief Check if feature is simple
 
   \param Points pointer to line_pnts structure
   \param type   feature type (GV_POINT, GV_LINE, ...)
 
   \return 1  feature simple
   \return 0  feature not simple
   \return -1 feature type not supported (GV_POINT, GV_CENTROID, ...)
   \note Implementation is pending, now always returns 0
 */
int Vect_sfa_is_line_simple(const struct line_pnts *Points UNUSED,
                            int type UNUSED, int with_z UNUSED)
{
    /* TODO:
       SF_FeatureType sftype;
 
       Vect_sfa_get_line_type(Points, type, with_z);
 
     */
 
    return 0;
}
 
/*!
   \brief Check if feature is closed
 
   \param Points pointer to line_pnts structure
   \param type   feature type (GV_LINE or GV_BOUNDARY)
 
   \return 1  feature closed
   \return 0  feature not closed
   \return -1 feature type not supported (GV_POINT, GV_CENTROID, ...)
 */
int Vect_sfa_is_line_closed(const struct line_pnts *Points, int type,
                            int with_z)
{
    int npoints;
 
    if (type & (GV_LINES)) {
        npoints = Vect_get_num_line_points(Points);
        if (npoints > 2 && Points->x[0] == Points->x[npoints - 1] &&
            Points->y[0] == Points->y[npoints - 1]) {
            if (!with_z)
                return 1;
            if (Points->z[0] == Points->z[npoints - 1])
                return 1;
        }
        return 0;
    }
    return -1;
}
 
/*!
   \brief Get number of simple features
 
   For native format or PostGIS Topology returns -1
 
   \param Map vector map
 
   \return number of features
   \return -1 on error
 */
int Vect_sfa_get_num_features(struct Map_info *Map)
{
    int nfeat;
 
    nfeat = 0;
    if (Map->format == GV_FORMAT_OGR || Map->format == GV_FORMAT_OGR_DIRECT) {
        /* OGR */
#ifdef HAVE_OGR
        const struct Format_info_ogr *ogr_info;
 
        ogr_info = &(Map->fInfo.ogr);
 
        if (!ogr_info->layer)
            return -1;
 
        return OGR_L_GetFeatureCount(ogr_info->layer, TRUE);
#else
        G_fatal_error(_("GRASS is not compiled with OGR support"));
        return -1;
#endif
    }
    else if (Map->format == GV_FORMAT_POSTGIS &&
             !Map->fInfo.pg.toposchema_name) {
#ifdef HAVE_POSTGRES
        /* PostGIS */
        char stmt[DB_SQL_MAX];
 
        const struct Format_info_pg *pg_info;
 
        pg_info = &(Map->fInfo.pg);
 
        if (!pg_info->conn || !pg_info->table_name) {
            G_warning(_("No connection defined"));
            return -1;
        }
 
        sprintf(stmt, "SELECT count(*) FROM \"%s\".\"%s\"",
                pg_info->schema_name, pg_info->table_name);
        nfeat = Vect__execute_get_value_pg(pg_info->conn, stmt);
        if (nfeat < 0) {
            G_warning(_("Unable to get number of simple features"));
            return -1;
        }
#else
        G_fatal_error(_("GRASS is not compiled with PostgreSQL support"));
        return -1;
#endif
    }
    else {
        G_warning(_("Unable to report simple features for vector map <%s>"),
                  Vect_get_full_name(Map));
        return -1;
    }
 
    return nfeat;
}
 
int check_sftype(const struct line_pnts *points, int type,
                 SF_FeatureType sftype, int with_z)
{
    if (type == GV_POINT && sftype == SF_POINT) {
        return 1;
    }
 
    if (type == GV_LINE) {
        if (sftype == SF_LINESTRING)
            return 1;
 
        if (sftype == SF_LINEARRING &&
            Vect_sfa_is_line_closed(points, type, with_z))
            return 1;
    }
 
    if (type == GV_BOUNDARY) {
        if (sftype == SF_POLYGON &&
            Vect_sfa_is_line_closed(points, type, 0)) /* force 2D */
            return 1;
    }
 
    return 0;
}
 
int get_sftype(const struct line_pnts *points, int type, int with_z)
{
    if (check_sftype(points, type, SF_POINT, with_z))
        return SF_POINT;
 
    if (check_sftype(points, type, SF_LINEARRING, with_z))
        return SF_LINEARRING;
 
    if (check_sftype(points, type, SF_LINESTRING, with_z))
        return SF_LINESTRING;
 
    if (check_sftype(points, type, SF_POLYGON, with_z))
        return SF_POLYGON;
 
    return -1;
}
 
void print_point(const struct line_pnts *Points, int index, int with_z,
                 int precision, FILE *file)
{
    fprintf(file, "%.*f %.*f", precision, Points->x[index], precision,
            Points->y[index]);
    if (with_z)
        fprintf(file, " %.*f", precision, Points->z[index]);
}