% ITU-T Q.704 (MTP Level 3) coding / decoding

% (C) 2011 by Harald Welte <laforge@gnumonks.org>
%
% All Rights Reserved
%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU Affero General Public License as
% published by the Free Software Foundation; either version 3 of the
% License, or (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU Affero General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.

-module(mtp3_codec).
-author('Harald Welte <laforge@gnumonks.org>').
-include("mtp3.hrl").

-export([parse_mtp3_msg/1, encode_mtp3_msg/1]).

% Parse standard routing label according to Section 2.2 of ITU-T Q.704
parse_mtp3_routing_label(_, LabelBin) when is_binary(LabelBin) ->
	<<Sls:4/big, Opc:14/big, Dpc:14/big, Remain/binary>> = LabelBin,
	{ok, #mtp3_routing_label{sig_link_sel = Sls, origin_pc = Opc, dest_pc = Dpc}, Remain}.

parse_mtp3_msg(DataBin) when is_binary(DataBin) ->
	<<NetInd:2, 0:2, ServiceInd:4, Remain/binary>> = DataBin,
	{ok, RoutLbl, Payload} = parse_mtp3_routing_label(ServiceInd, Remain),
	#mtp3_msg{network_ind = NetInd, service_ind = ServiceInd, routing_label = RoutLbl,
		  payload = Payload}.


encode_mtp3_routing_label(#mtp3_routing_label{sig_link_sel = Sls, origin_pc = Opc,
					      dest_pc = Dpc}) ->
	<<Sls:4/big, Opc:14/big, Dpc:14/big>>.
					      
encode_mtp3_msg(#mtp3_msg{network_ind = NetInd, service_ind = ServiceInd,
			  routing_label = RoutLbl, payload = Payload}) ->
	RoutLblBin = encode_mtp3_routing_label(RoutLbl),
	<<NetInd:2, 0:2, ServiceInd:4, RoutLblBin/binary, Payload/binary>>.