Harald Welte | 26bdef2 | 2012-01-16 22:22:17 +0100 | [diff] [blame] | 1 | % RFC 3868 SUA SCCP Adaption Layer coding / decoding |
| 2 | |
| 3 | % (C) 2012 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(sua_codec). |
| 21 | -author('Harald Welte <laforge@gnumonks.org>'). |
| 22 | -include("sua.hrl"). |
| 23 | |
| 24 | -export([parse_msg/1, encode_msg/1]). |
| 25 | |
| 26 | parse_msg(DataBin) when is_binary(DataBin) -> |
| 27 | <<Version:8, _Reserved:8, MsgClass:8, MsgType:8, MsgLen:32/big, Remain/binary>> = DataBin, |
| 28 | OptList = parse_sua_opts(Remain), |
| 29 | #sua_msg{version = Version, msg_class = MsgClass, msg_type = MsgType, |
| 30 | msg_length = MsgLen-4, payload = OptList}; |
| 31 | parse_msg(Data) when is_list(Data) -> |
| 32 | parse_msg(list_to_binary(Data)). |
| 33 | |
| 34 | parse_sua_opts(OptBin) when is_binary(OptBin) -> |
| 35 | parse_sua_opts(OptBin, []). |
| 36 | |
| 37 | parse_sua_opts(<<>>, OptList) when is_list(OptList) -> |
| 38 | OptList; |
| 39 | parse_sua_opts(OptBin, OptList) when is_binary(OptBin), is_list(OptList) -> |
| 40 | <<Tag:16/big, LengthIncHdr:16/big, Remain/binary>> = OptBin, |
| 41 | Length = LengthIncHdr - 4, |
| 42 | PadLength = get_num_pad_bytes(Length), |
| 43 | %io:format("Tag ~w, LenInHdr ~w, Len ~w, PadLen ~w, Remain ~w(~p)~n", |
| 44 | % [Tag, LengthIncHdr, Length, PadLength, byte_size(Remain), Remain]), |
| 45 | <<Value:Length/binary, PadNextOpts/binary>> = Remain, |
| 46 | % this is ridiculous, we cannot use "<<Value:Length/binary, |
| 47 | % 0:PadLength, Remain/binary>>" as the last part would not match an |
| 48 | % empty binary <<>> anymore. Without the "0:PadLengh" this works |
| 49 | % perfectly fine. Now we need some complicated construct and check if |
| 50 | % the resulting list would be empty :(( |
| 51 | if |
| 52 | byte_size(PadNextOpts) > PadLength -> |
| 53 | <<0:PadLength/integer-unit:8, NextOpts/binary>> = PadNextOpts; |
| 54 | true -> |
| 55 | NextOpts = <<>> |
| 56 | end, |
| 57 | NewOpt = {Tag, {Length, Value}}, |
| 58 | parse_sua_opts(NextOpts, OptList ++ [NewOpt]). |
| 59 | |
| 60 | parse_sua_opt(Opt, Msg) -> |
| 61 | {Opt, Msg}. |
| 62 | |
| 63 | |
| 64 | encode_msg(#sua_msg{version = Version, msg_class = MsgClass, |
| 65 | msg_type = MsgType, payload = OptList}) -> |
| 66 | OptBin = encode_sua_opts(OptList), |
| 67 | MsgLen = byte_size(OptBin) + 8, |
| 68 | <<Version:8, 0:8, MsgClass:8, MsgType:8, MsgLen:32/big, OptBin/binary>>. |
| 69 | |
| 70 | encode_sua_opts(OptList) when is_list(OptList) -> |
| 71 | encode_sua_opts(OptList, <<>>). |
| 72 | |
| 73 | encode_sua_opts([], Bin) -> |
| 74 | Bin; |
| 75 | encode_sua_opts([{Iei, Attr}|Tail], Bin) -> |
| 76 | OptBin = encode_sua_opt(Iei, Attr), |
| 77 | encode_sua_opts(Tail, <<Bin/binary, OptBin/binary>>). |
| 78 | |
| 79 | encode_sua_opt(Iei, Data) when is_integer(Iei), is_binary(Data) -> |
| 80 | Length = byte_size(Data) + 4, |
| 81 | PadLen = get_num_pad_bytes(Length), |
| 82 | <<Iei:16/big, Length:16/big, Data/binary, 0:PadLen/integer-unit:8>>. |
| 83 | |
| 84 | % compute the number of pad bits required after a binary parameter |
| 85 | get_num_pad_bytes(BinLenBytes) -> |
| 86 | case BinLenBytes rem 4 of |
| 87 | 0 -> 0; |
| 88 | Val -> 4 - Val |
| 89 | end. |