/*
 * call-seq:
 *    res.fieldname( index )
 *
 * Returns the name of the field (column) corresponding to the index.
 *
 *   res=conn.exec("SELECT foo,bar AS biggles,jim,jam FROM mytable;")
 *   puts res.fieldname(2) => 'jim'
 *   puts res.fieldname(1) => 'biggles'
 *
 * Equivalent to <tt>res.fields[_index_]</tt>.
 */
static VALUE
pgresult_fieldname(obj, index)
  VALUE obj, index;
{
  PGresult *result;
  int i = NUM2INT(index);
  char *name;

  result = get_pgresult(obj);
  if (i < 0 || i >= PQnfields(result)) {
  rb_raise(rb_eArgError,"invalid field number %d", i);
  }
  name = PQfname(result, i);
  return rb_tainted_str_new2(name);
}