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% 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/>.
%
% Additional Permission under GNU AGPL version 3 section 7:
%
% If you modify this Program, or any covered work, by linking or
% combining it with runtime libraries of Erlang/OTP as released by
% Ericsson on http://www.erlang.org (or a modified version of these
% libraries), containing parts covered by the terms of the Erlang Public
% License (http://www.erlang.org/EPLICENSE), the licensors of this
% Program grant you additional permission to convey the resulting work
% without the need to license the runtime libraries of Erlang/OTP under
% the GNU Affero General Public License. Corresponding Source for a
% non-source form of such a combination shall include the source code
% for the parts of the runtime libraries of Erlang/OTP used as well as
% that of the covered work.
-module(mtp3_codec).
-author('Harald Welte <laforge@gnumonks.org>').
-include("mtp3.hrl").
-export([parse_mtp3_msg/1, encode_mtp3_msg/1, invert_rout_lbl/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 = Remain};
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.
invert_rout_lbl(L = #mtp3_routing_label{origin_pc = Opc, dest_pc = Dpc}) ->
L#mtp3_routing_label{origin_pc = Dpc, dest_pc = Opc}.
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