Example db walk tree

This example is for current stable release 7.24.X. In latest release (7.26.1) the function prototype for db_walk_tree has changed, the corresponding changes to the code are: Latest db_walk_tree()

This is a simple example program that shows how to walk a geometry database while performing some operation on geometry as it is encountered. In this particular example, we iterate just over regions and simply count them:

<source lang="c">

1. include "common.h"
2. include "raytrace.h"

int incr_region(struct db_tree_state *tsp, struct db_full_path *pathp, const struct rt_comb_internal *combp, genptr_t data) {

 int *counter = (int*)data;
 bu_log("...incrementing...\n");
 (*counter)++;
 return 0;

}

int main(int argc, char *argv[]) {

 struct db_i *dbip;
 int counter = 0;
 struct db_tree_state state = rt_initial_tree_state;

 if (argc < 2) {
   bu_exit(0, "need more, db.g obj\n");
 }

 dbip = db_open(argv[1], "r");
 if (dbip == NULL) {
   bu_exit(1, "Unable to open %s\n", argv[1]);
 }

 if (db_dirbuild(dbip) < 0) {
   db_close(dbip);
   bu_exit(1, "Unable to load %s\n", argv[1]);
 }

 bu_log("Database title is:\n%s\n", dbip->dbi_title);
 bu_log("Units: %s\n", bu_units_string(dbip->dbi_local2base));

 if (db_lookup(dbip, argv[2], 1) == NULL) {
   db_close(dbip);
   bu_exit(1, "Unable to find %s\n", argv[2]);
 }

 state.ts_dbip = dbip;
 state.ts_resp = &rt_uniresource;
 rt_init_resource( &rt_uniresource, 0, NULL );

 db_walk_tree(dbip, 1, (const char **)argv+2, 1, &state, incr_region, NULL, NULL, &counter);

 bu_log("counter is %d\n", counter);

 return 0;

}

</source>

If we compile this program and run it on a sample geometry database, we get the following:

<source lang="bash"> $ gcc db_walk_tree_example.c -L/usr/brlcad/lib -lrt -lbu -I/usr/brlcad/include -I/usr/brlcad/include/brlcad $ ./a.out db/ktank.g tank Database title is: Keith's Tank Units: in ...incrementing... <... trimmed output ...> ...incrementing... counter is 80

</source>