| Harald Welte | 1f6a035 | 2011-01-15 20:07:45 +0100 | [diff] [blame^] | 1 | % RFC 3331 MTP2 User Adaption Layer coding / decoding |
| 2 | |
| 3 | % (C) 2011 by Harald Welte <laforge@gnumonks.org> |
| 4 | % |
| 5 | % All Rights Reserved |
| 6 | % |
| 7 | % This program is free software; you can redistribute it and/or modify |
| 8 | % it under the terms of the GNU Affero General Public License as |
| 9 | % published by the Free Software Foundation; either version 3 of the |
| 10 | % License, or (at your option) any later version. |
| 11 | % |
| 12 | % This program is distributed in the hope that it will be useful, |
| 13 | % but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | % GNU General Public License for more details. |
| 16 | % |
| 17 | % You should have received a copy of the GNU Affero General Public License |
| 18 | % along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 19 | |
| 20 | -module(m2ua_codec). |
| 21 | -author('Harald Welte <laforge@gnumonks.org>'). |
| 22 | -include("m2ua.hrl"). |
| 23 | |
| 24 | -export([parse_m2ua_msg/1, encode_m2ua_msg/1]). |
| 25 | |
| 26 | % parse a binary chunk of options into an options proplist |
| 27 | parse_m2ua_opts(<<>>, OptList) -> |
| 28 | OptList; |
| 29 | parse_m2ua_opts(OptBin, OptList) -> |
| 30 | <<Tag:16/big, LengthIncHdr:16/big, Remain/binary>> = OptBin, |
| 31 | Length = LengthIncHdr - 4, |
| 32 | <<Value:Length/binary, NextOpts/binary>> = Remain, |
| 33 | NewOpt = {Tag, {Length, Value}}, |
| 34 | parse_m2ua_opts(NextOpts, [NewOpt|OptList]). |
| 35 | |
| 36 | % parse a single M2UA message |
| 37 | parse_m2ua_msgt(_, _, _, Remain) -> |
| 38 | parse_m2ua_opts(Remain, []). |
| 39 | |
| 40 | % parse a M2UA message binary into a record |
| 41 | parse_m2ua_msg(DataBin) when is_binary(DataBin) -> |
| 42 | <<1:8, 0:8, MsgClass:8, MsgType:8, MsgLen:32/big, Remain/binary>> = DataBin, |
| 43 | Parsed = parse_m2ua_msgt(MsgClass, MsgType, MsgLen, Remain), |
| 44 | {ok, #m2ua_msg{msg_class = MsgClass, msg_type = MsgType, parameters = Parsed}}. |
| 45 | |
| 46 | |
| 47 | |
| 48 | % encode a single option |
| 49 | encode_m2ua_opt({OptNum, {DataBinLen, DataBin}}) when is_integer(OptNum) -> |
| 50 | LengthIncHdr = DataBinLen + 4, |
| 51 | <<OptNum:16/big, LengthIncHdr:16/big, DataBin/binary>>. |
| 52 | |
| 53 | % encode a list of options |
| 54 | encode_m2ua_opts([], OptEnc) -> |
| 55 | list_to_binary(OptEnc); |
| 56 | encode_m2ua_opts([CurOpt|OptPropList], OptEnc) -> |
| 57 | CurOptEnc = encode_m2ua_opt(CurOpt), |
| 58 | encode_m2ua_opts(OptPropList, list_to_binary([OptEnc, CurOptEnc])). |
| 59 | |
| 60 | |
| 61 | % encode a particular message type |
| 62 | encode_m2ua_msgt(MsgClass, MsgType, Params) -> |
| 63 | OptBin = encode_m2ua_opts(Params, <<>>), |
| 64 | MsgLenIncHdr = 4 + binary:byte_size(OptBin), |
| 65 | <<1:8, 0:8, MsgClass:8, MsgType:8, MsgLenIncHdr:32/big, OptBin/binary>>. |
| 66 | |
| 67 | % encode a message from record to binary |
| 68 | encode_m2ua_msg(#m2ua_msg{msg_class = MsgClass, msg_type = MsgType, parameters = Params}) -> |
| 69 | encode_m2ua_msgt(MsgClass, MsgType, Params). |