Geografic-Information-System/doc/vector/v.example/main.c

/****************************************************************
 *
 * MODULE:     v.example
 *
 * AUTHOR(S):  GRASS Development Team, Radim Blazek, Maris Nartiss
 *
 * PURPOSE:    copies vector data from source map to destination map
 *             prints out all point coordinates and attributes
 *
 * COPYRIGHT:  (C) 2002-2009 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.
 *
 ****************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <grass/gis.h>
#include <grass/vector.h>
#include <grass/dbmi.h>
#include <grass/glocale.h>

int main(int argc, char *argv[])
{
    struct Map_info In, Out;
    static struct line_pnts *Points;
    struct line_cats *Cats;
    int i, type, cat, ncols, nrows, col, more, open3d;
    char *mapset, sql[200];
    struct GModule *module;	/* GRASS module for parsing arguments */
    struct Option *old, *new;
    dbDriver *driver;
    dbHandle handle;
    dbCursor cursor;
    dbTable *table;
    dbColumn *column;
    dbString table_name, dbsql, valstr;
    struct field_info *Fi, *Fin;

    /* initialize GIS environment */
    /* reads grass env, stores program name to G_program_name() */
    G_gisinit(argv[0]);

    /* initialize module */
    module = G_define_module();
    G_add_keyword(_("vector"));
    G_add_keyword(_("keyword2"));
    G_add_keyword(_("keyword3"));
    module->description = _("My first vector module");

    /* Define the different options as defined in gis.h */
    old = G_define_standard_option(G_OPT_V_INPUT);

    new = G_define_standard_option(G_OPT_V_OUTPUT);

    /* options and flags parser */
    if (G_parser(argc, argv))
	exit(EXIT_FAILURE);

    /* Create and initialize struct's where to store points/lines and categories */
    Points = Vect_new_line_struct();
    Cats = Vect_new_cats_struct();

    /* Check 1) output is legal vector name; 2) if can find input map; 
       3) if input was found in current mapset, check if input != output.
       lib/vector/Vlib/legal_vname.c
     */
    Vect_check_input_output_name(old->answer, new->answer, G_FATAL_EXIT);

    if ((mapset = (char *)G_find_vector2(old->answer, "")) == NULL)
	G_fatal_error(_("Vector map <%s> not found"), old->answer);

    /* Predetermine level at which a map will be opened for reading 
       lib/vector/Vlib/open.c
     */
    if (Vect_set_open_level(2))
	G_fatal_error(_("Unable to set predetermined vector open level"));

    /* Open existing vector for reading
       lib/vector/Vlib/open.c
     */
    if (1 > Vect_open_old(&In, old->answer, mapset))
	G_fatal_error(_("Unable to open vector map <%s>"), old->answer);

    /* Check if old vector is 3D. We should preserve 3D data. */
    if (Vect_is_3d(&In))
	open3d = WITH_Z;
    else
	open3d = WITHOUT_Z;

    /* Set error handler for input vector map */
    Vect_set_error_handler_io(&In, NULL);
    
    /* Open new vector for reading/writing */
    if (0 > Vect_open_new(&Out, new->answer, open3d)) {
	G_fatal_error(_("Unable to create vector map <%s>"), new->answer);
    }

    /* Set error handler for output vector map */
    Vect_set_error_handler_io(NULL, &Out);

    /* Let's get vector layers db connections information */
    Fi = Vect_get_field(&In, 1);
    if (!Fi) {
	G_fatal_error(_("Database connection not defined for layer %d"), 1);
    }

    /* Output information useful for debuging 
       include/vect/dig_structs.h
     */
    G_debug(1,
	    "Field number:%d; Name:<%s>; Driver:<%s>; Database:<%s>; Table:<%s>; Key:<%s>;\n",
	    Fi->number, Fi->name, Fi->driver, Fi->database, Fi->table,
	    Fi->key);

    /* Prepeare strings for use in db_* calls */
    db_init_string(&dbsql);
    db_init_string(&valstr);
    db_init_string(&table_name);
    db_init_handle(&handle);

    /* Prepare database for use */
    driver = db_start_driver(Fi->driver);
    if (driver == NULL) {
	G_fatal_error(_("Unable to start driver <%s>"), Fi->driver);
    }

    /* Set error handler for DB driver */
    db_set_error_handler_driver(driver);
      
    db_set_handle(&handle, Fi->database, NULL);
    if (db_open_database(driver, &handle) != DB_OK) {
	G_fatal_error(_("Unable to open database <%s> by driver <%s>"),
		      Fi->database, Fi->driver);
    }
    db_set_string(&table_name, Fi->table);
    if (db_describe_table(driver, &table_name, &table) != DB_OK) {
	G_fatal_error(_("Unable to describe table <%s>"), Fi->table);
    }
    ncols = db_get_table_number_of_columns(table);

    /* Copy header and history data from old to new map */
    Vect_copy_head_data(&In, &Out);
    Vect_hist_copy(&In, &Out);
    Vect_hist_command(&Out);

    i = 1;
    /* Let's do something with every vector feature in input map... */
    /* Read in single line and get it's type */
    while ((type = Vect_read_next_line(&In, Points, Cats)) > 0) {
	/* If Points contain line... */
	if (type == GV_LINE || type == GV_POINT || type == GV_CENTROID) {
	    if (Vect_cat_get(Cats, 1, &cat) == 0) {
		Vect_cat_set(Cats, 1, i);
		i++;
	    }
	}
	if (type == GV_POINT) {
	    /* Print out point coordinates */
	    printf("No:%d\tX:%f\tY:%f\tZ:%f\tCAT:%d\n", i, *Points->x,
		   *Points->y, *Points->z, cat);

	    /* Prepeare SQL query to get point attribute data */
	    sprintf(sql, "select * from %s where %s=%d", Fi->table, Fi->key,
		    cat);
	    G_debug(1, "SQL: \"%s\"", sql);
	    db_set_string(&dbsql, sql);
	    /* Now execute query */
	    if (db_open_select_cursor(driver, &dbsql, &cursor, DB_SEQUENTIAL)
		!= DB_OK)
		G_warning(_("Unable to get attribute data for cat %d"), cat);
	    else {
		/* Result count */
		nrows = db_get_num_rows(&cursor);
		G_debug(1, "Result count: %d", nrows);
		table = db_get_cursor_table(&cursor);
		/* Let's output every columns name and value */
		while (1) {
		    if (db_fetch(&cursor, DB_NEXT, &more) != DB_OK) {
			G_warning(_("Error while retrieving database record for cat %d"),
				  cat);
			break;
		    }
		    if (!more)
			break;
		    for (col = 0; col < ncols; col++) {
			column = db_get_table_column(table, col);
			db_convert_column_value_to_string(column, &valstr);
			printf("%s: %s\t", db_get_column_name(column),
			       db_get_string(&valstr));
		    }
		    printf("\n");
		}
		db_close_cursor(&cursor);
	    }
	}
	/* Only now we write data into new vector */
	Vect_write_line(&Out, type, Points, Cats);
    }

    /* Create database for new vector map */
    Fin = Vect_default_field_info(&Out, 1, NULL, GV_1TABLE);
    driver = db_start_driver_open_database(Fin->driver, Fin->database);
    G_debug(1,
	    "Field number:%d; Name:<%s>; Driver:<%s>; Database:<%s>; Table:<%s>; Key:<%s>;\n",
	    Fin->number, Fin->name, Fin->driver, Fin->database, Fin->table,
	    Fin->key);

    /* Let's copy attribute table data */
    if (db_copy_table(Fi->driver, Fi->database, Fi->table,
		      Fin->driver, Vect_subst_var(Fin->database, &Out),
		      Fin->table) == DB_FAILED)
	G_warning(_("Unable to copy attribute table to vector map <%s>"),
		  new->answer);
    else
	Vect_map_add_dblink(&Out, Fin->number, Fin->name, Fin->table, Fi->key,
			    Fin->database, Fin->driver);

    /* Build topology for vector map and close them */
    Vect_build(&Out);
    Vect_close(&In);
    Vect_close(&Out);
    db_close_database_shutdown_driver(driver);

    /* Don't forget to report to caller successful end of data processing :) */
    exit(EXIT_SUCCESS);
}