From 92e783d1098e99161401ab08cccd3a08356749cd Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@gnumonks.org>
Date: Sun, 1 Apr 2012 19:52:01 +0200
Subject: rename sua_codec to generic xua_codec

SUA/M3UA/M2UA/M2PA actaully all uses almost the same message format,
so it makes sense to write one generic xua_codec and derive from that.

The current SUA implementation didn't actually contain anything SUA
specific, so we can just rename it and use xua_codec directly from the
users.
---
 src/xua_codec.erl | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 src/xua_codec.erl

(limited to 'src/xua_codec.erl')

diff --git a/src/xua_codec.erl b/src/xua_codec.erl
new file mode 100644
index 0000000..8da94a2
--- /dev/null
+++ b/src/xua_codec.erl
@@ -0,0 +1,92 @@
+% 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/>.
+
+-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>>).
+
+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/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.
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