/*
 * call-seq:
 *   entities
 *
 * Get a hash of the elements for this DTD.
 */
static VALUE entities(VALUE self)
{
  xmlDtdPtr dtd;
  Data_Get_Struct(self, xmlDtd, dtd);

  if(!dtd->entities) return Qnil;

  VALUE hash = rb_hash_new();

  xmlHashScan((xmlHashTablePtr)dtd->entities, element_copier, (void *)hash);

  return hash;
}