111 lines
4.4 KiB
Erlang
111 lines
4.4 KiB
Erlang
% RFC 3868 SUA SCCP Adaption Layer coding / decoding
|
|
|
|
% (C) 2012 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(xua_codec).
|
|
-author('Harald Welte <laforge@gnumonks.org>').
|
|
-include("xua.hrl").
|
|
|
|
-export([parse_msg/1, encode_msg/1, parse_xua_opts/1, encode_xua_opts/1]).
|
|
|
|
parse_msg(DataBin) when is_binary(DataBin) ->
|
|
<<Version:8, _Reserved:8, MsgClass:8, MsgType:8, MsgLen:32/big, Remain/binary>> = DataBin,
|
|
RemainLen = MsgLen - 4,
|
|
OptList = parse_xua_opts(Remain),
|
|
#xua_msg{version = Version, msg_class = MsgClass, msg_type = MsgType,
|
|
payload = OptList};
|
|
parse_msg(Data) when is_list(Data) ->
|
|
parse_msg(list_to_binary(Data)).
|
|
|
|
parse_xua_opts(OptBin) when is_binary(OptBin) ->
|
|
parse_xua_opts(OptBin, []).
|
|
|
|
parse_xua_opts(<<>>, OptList) when is_list(OptList) ->
|
|
OptList;
|
|
parse_xua_opts(OptBin, OptList) when is_binary(OptBin), is_list(OptList) ->
|
|
<<Tag:16/big, LengthIncHdr:16/big, Remain/binary>> = OptBin,
|
|
Length = LengthIncHdr - 4,
|
|
PadLength = get_num_pad_bytes(Length),
|
|
%io:format("Tag ~w, LenInHdr ~w, Len ~w, PadLen ~w, Remain ~w(~p)~n",
|
|
% [Tag, LengthIncHdr, Length, PadLength, byte_size(Remain), Remain]),
|
|
<<Value:Length/binary, PadNextOpts/binary>> = Remain,
|
|
% this is ridiculous, we cannot use "<<Value:Length/binary,
|
|
% 0:PadLength, Remain/binary>>" as the last part would not match an
|
|
% empty binary <<>> anymore. Without the "0:PadLengh" this works
|
|
% perfectly fine. Now we need some complicated construct and check if
|
|
% the resulting list would be empty :((
|
|
if
|
|
byte_size(PadNextOpts) > PadLength ->
|
|
<<0:PadLength/integer-unit:8, NextOpts/binary>> = PadNextOpts;
|
|
true ->
|
|
NextOpts = <<>>
|
|
end,
|
|
NewOpt = {Tag, {Length, Value}},
|
|
parse_xua_opts(NextOpts, OptList ++ [NewOpt]).
|
|
|
|
|
|
|
|
encode_msg(#xua_msg{version = Version, msg_class = MsgClass,
|
|
msg_type = MsgType, payload = OptList}) ->
|
|
OptBin = encode_xua_opts(OptList),
|
|
MsgLen = byte_size(OptBin) + 8,
|
|
<<Version:8, 0:8, MsgClass:8, MsgType:8, MsgLen:32/big, OptBin/binary>>.
|
|
|
|
encode_xua_opts(OptList) when is_list(OptList) ->
|
|
encode_xua_opts(OptList, <<>>).
|
|
|
|
encode_xua_opts([], Bin) ->
|
|
Bin;
|
|
encode_xua_opts([{Iei, Attr}|Tail], Bin) ->
|
|
OptBin = encode_xua_opt(Iei, Attr),
|
|
encode_xua_opts(Tail, <<Bin/binary, OptBin/binary>>).
|
|
|
|
% convert integer parameters to binary before continuing
|
|
encode_xua_opt(Iei, {LenIn, Data}) when is_integer(Iei), is_integer(Data) ->
|
|
encode_xua_opt(Iei, {LenIn, <<Data:LenIn/big-integer-unit:8>>});
|
|
|
|
encode_xua_opt(Iei, {LenIn, Data}) when is_integer(Iei), is_binary(Data) ->
|
|
Length = LenIn + 4,
|
|
PadLen = get_num_pad_bytes(Length),
|
|
<<Iei:16/big, Length:16/big, Data:LenIn/binary, 0:PadLen/integer-unit:8>>;
|
|
encode_xua_opt(Iei, Data) when is_integer(Iei), is_binary(Data) ->
|
|
Length = byte_size(Data) + 4,
|
|
PadLen = get_num_pad_bytes(Length),
|
|
<<Iei:16/big, Length:16/big, Data/binary, 0:PadLen/integer-unit:8>>.
|
|
|
|
% compute the number of pad bits required after a binary parameter
|
|
get_num_pad_bytes(BinLenBytes) ->
|
|
case BinLenBytes rem 4 of
|
|
0 -> 0;
|
|
Val -> 4 - Val
|
|
end.
|