/*
 * call-seq:
 *   destroy([cache_name])
 *
 * Call krb5_cc_destroy to destroy all credentials in a cachefile.  With no parameters, it destroys the credentials in the default cachefile.  With one parameter, it destroys the credentials in the named cachefile.  Returns true on success, raises Krb5Auth::Krb5::Exception on failure.
 */
static VALUE Krb5_destroy_creds(int argc, VALUE *argv, VALUE self)
{
  VALUE cache_val;
  struct ruby_krb5 *kerb;
  krb5_error_code krbret;
  char *cache_name;
  krb5_ccache cc;

  rb_scan_args(argc, argv, "01", &cache_val);

  cache_name = get_string_or_nil(cache_val);

  Data_Get_Struct(self, struct ruby_krb5, kerb);
  if (!kerb) {
    NOSTRUCT_EXCEPT();
    return Qfalse;
  }

  if (cache_name == NULL) {
    krbret = krb5_cc_default(kerb->ctx, &cc);
  }
  else {
    krbret = krb5_cc_resolve(kerb->ctx, cache_name, &cc);
  }

  if (krbret) {
    Krb5_register_error(krbret);
    return Qfalse;
  }

  krbret = krb5_cc_destroy(kerb->ctx, cc);
  if (krbret) {
    Krb5_register_error(krbret);
    return Qfalse;
  }

  // NOTE: we don't need to call krb5_cc_close here since it is freed
  // automatically by krb5_cc_destroy()

  return Qtrue;
}