| % 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]). |
| |
| -compile({parse_transform, exprecs}). |
| -export_records([mtp3_routing_label, mtp3_msg]). |
| |
| % Parse standard routing label according to Section 2.2 of ITU-T Q.704 |
| parse_mtp3_routing_label(_, LabelBin) when is_binary(LabelBin) -> |
| % we need to swap the four bytes and then parse the fields |
| <<Label32:32/little, Remain/binary>> = LabelBin, |
| LabelRev = <<Label32:32/big>>, |
| <<Sls:4/big, Dpc:14/big, Opc:14/big>> = LabelRev, |
| {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), |
| PayloadDec = decode_payload(ServiceInd, Payload), |
| #mtp3_msg{network_ind = NetInd, service_ind = ServiceInd, routing_label = RoutLbl, |
| payload = PayloadDec}. |
| |
| |
| encode_mtp3_routing_label(#mtp3_routing_label{sig_link_sel = Sls, origin_pc = OpcIn, |
| dest_pc = DpcIn}) -> |
| Opc = osmo_util:pointcode2int(OpcIn), |
| Dpc = osmo_util:pointcode2int(DpcIn), |
| % we need to swap the four bytes after encoding the fields |
| <<Label32:32/little>> = <<Sls:4/big, Dpc:14/big, Opc:14/big>>, |
| <<Label32:32/big>>. |
| |
| encode_mtp3_msg(#mtp3_msg{network_ind = NetInd, service_ind = ServiceInd, |
| routing_label = RoutLbl, payload = Payload}) -> |
| RoutLblBin = encode_mtp3_routing_label(RoutLbl), |
| PayloadBin = payload_to_binary(ServiceInd, Payload), |
| <<NetInd:2, 0:2, ServiceInd:4, RoutLblBin/binary, PayloadBin/binary>>. |
| |
| |
| decode_payload(?MTP3_SERV_MTN, Payload) -> |
| <<H1:4, H0:4, Len:4, 0:4, TP/binary>> = Payload, |
| #mtp3mg_msg{h0 = H0, h1 = H1, payload = TP}; |
| decode_payload(?MTP3_SERV_MGMT, Payload) -> |
| <<H1:4, H0:4, Remain/binary>> = Payload, |
| #mtp3mg_msg{h0 = H0, h1 = H1, payload = Payload}; |
| decode_payload(_, Payload) -> |
| Payload. |
| |
| payload_to_binary(?MTP3_SERV_MTN, #mtp3mg_msg{h0=H0, h1=H1, payload=TP}) -> |
| Len = byte_size(TP), |
| <<H1:4, H0:4, Len:4, 0:4, TP/binary>>; |
| payload_to_binary(?MTP3_SERV_MGMT, #mtp3mg_msg{h0=H0, h1=H1, payload=Payload}) -> |
| <<H1:4, H0:4, Payload/binary>>; |
| payload_to_binary(_, Whatever) -> |
| Whatever. |
| |