%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2008-2010. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%

%% Test suite for erlang:decode_packet/3

-module(decode_packet_SUITE).

-include_lib("test_server/include/test_server.hrl").

-export([all/0, suite/0,groups/0,init_per_group/2,end_per_group/2,init_per_testcase/2,fin_per_testcase/2,
	 basic/1, packet_size/1, neg/1, http/1, line/1, ssl/1, otp_8536/1]).

suite() -> [{suite_callbacks,[ts_install_scb]}].

all() -> 
[basic, packet_size, neg, http, line, ssl, otp_8536].

groups() -> 
    [].

init_per_group(_GroupName, Config) ->
	Config.

end_per_group(_GroupName, Config) ->
	Config.


init_per_testcase(Func, Config) when is_atom(Func), is_list(Config) ->
    Seed = {S1,S2,S3} = now(),
    random:seed(S1,S2,S3),
    io:format("*** SEED: ~p ***\n", [Seed]),
    Dog=?t:timetrap(?t:minutes(1)),
    [{watchdog, Dog}|Config].

fin_per_testcase(_Func, Config) ->
    Dog=?config(watchdog, Config),
    ?t:timetrap_cancel(Dog).

basic(doc) -> [];
basic(suite) -> [];
basic(Config) when is_list(Config) ->
    ?line Packet = <<101,22,203,54,175>>,
    ?line Rest = <<123,34,0,250>>,
    ?line Bin = <<Packet/binary,Rest/binary>>,
    ?line {ok, Bin, <<>>} = decode_pkt(raw,Bin),

    ?line {more, 5+1} = decode_pkt(1,<<5,1,2,3,4>>),
    ?line {more, 5+2} = decode_pkt(2,<<0,5,1,2,3,4>>),
    ?line {more, 5+4} = decode_pkt(4,<<0,0,0,5,1,2,3,4>>),

    ?line {more, undefined} = decode_pkt(1,<<>>),
    ?line {more, undefined} = decode_pkt(2,<<0>>),
    ?line {more, undefined} = decode_pkt(4,<<0,0,0>>),

    Types = [1,2,4,asn1,sunrm,cdr,fcgi,tpkt,ssl_tls],

    %% Run tests for different header types and bit offsets.

    lists:foreach(fun({Type,Bits})->basic_pack(Type,Packet,Rest,Bits), 
				    more_length(Type,Packet,Bits) end,
		  [{T,B} || T<-Types, B<-lists:seq(0,32)]),
    ok.

basic_pack(Type,Body,Rest,BitOffs) ->
    ?line {Bin,Unpacked,_} = pack(Type,Body,Rest,BitOffs),
    ?line {ok, Unpacked, Rest} = decode_pkt(Type,Bin),
    case Rest of
	<<>> -> ok;
	_ -> 
	    ?line <<_:1,NRest/bits>> = Rest,
	    basic_pack(Type,Body,NRest,BitOffs)
    end.

more_length(Type,Body,BitOffs) ->
    ?line {Bin,_,_} = pack(Type,Body,<<>>,BitOffs),
    HdrSize = byte_size(Bin) - byte_size(Body),
    more_length_do(Type,HdrSize,Bin,byte_size(Bin)).

more_length_do(_,_,_,0) ->
    ok;
more_length_do(Type,HdrSize,Bin,Size) ->
    TrySize = (Size*3) div 4,
    NSize = if TrySize < HdrSize -> Size - 1;
	       true -> TrySize
	    end,
    {B1,_} = split_binary(Bin,NSize),
    ?line {more, Length} = decode_pkt(Type,B1),
    case Length of
	L when L=:=byte_size(Bin) -> ok;
	undefined when NSize<HdrSize -> ok
    end,
    more_length_do(Type,HdrSize,Bin,NSize).

   

pack(Type,Packet,Rest) ->
    {Bin,Unpacked} = pack(Type,Packet),
    {<<Bin/binary,Rest/bits>>,Unpacked}.

%pack(0,B,R,Bits) -> 
%    pack(raw,B,R,Bits);
%pack(raw,Body,Rest,BitOffs) ->
%    Orig = <<0:BitOffs,Body/binary,Rest/bits>>,
%    <<_:BitOffs,Bin/bits>> = Orig,
%    {Bin,<<Bin/binary,Rest/bits>>,Orig};
pack(Type,Body,Rest,BitOffs) ->
    {Packet,Unpacked} = pack(Type,Body),

    %% Make Bin a sub-bin with an arbitrary bitoffset within Orig
    Prefix = random:uniform(1 bsl BitOffs) - 1,
    Orig = <<Prefix:BitOffs,Packet/binary,Rest/bits>>,
    <<_:BitOffs,Bin/bits>> = Orig,
    {Bin,Unpacked,Orig}.

pack(1,Bin) ->
    Psz = byte_size(Bin),
    {<<Psz:8,Bin/binary>>, Bin};
pack(2,Bin) ->
    Psz = byte_size(Bin),
    {<<Psz:16,Bin/binary>>, Bin};
pack(4,Bin) ->
    Psz = byte_size(Bin),
    {<<Psz:32,Bin/binary>>, Bin};
pack(asn1,Bin) ->
    Ident = case random:uniform(3) of
		1 -> <<17>>;
		2 -> <<16#1f,16#81,17>>;
		3 -> <<16#1f,16#81,16#80,16#80,17>>
	    end,
    Psz = byte_size(Bin),
    Length = case random:uniform(4) of
		 1 when Psz < 128 -> 
		     <<Psz:8>>;
		 R when R=<2 andalso Psz < 16#10000 ->
		     <<16#82,Psz:16>>;
		 R when R=<3 andalso Psz < 16#1000000 -> 
		     <<16#83,Psz:24>>;
		 _ when Psz < 16#100000000 ->
		     <<16#84,Psz:32>>
	     end,
    Res = <<Ident/binary,Length/binary,Bin/binary>>,
    {Res,Res};
pack(sunrm,Bin) ->
    Psz = byte_size(Bin),
    Res = if Psz < 16#80000000 ->
		  <<Psz:32,Bin/binary>>
    end,
    {Res,Res};
pack(cdr,Bin) ->
    GIOP = <<"GIOP">>,
    Major = random:uniform(256) - 1,
    Minor = random:uniform(256) - 1,
    MType = random:uniform(256) - 1,
    Psz = byte_size(Bin),
    Res = case random:uniform(2) of 
	      1 -> <<GIOP/binary,Major:8,Minor:8,0:8,MType:8,Psz:32/big,Bin/binary>>;
	      2 -> <<GIOP/binary,Major:8,Minor:8,1:8,MType:8,Psz:32/little,Bin/binary>>
	  end,
    {Res,Res};
pack(fcgi,Bin) ->
    Ver = 1,
    Type = random:uniform(256) - 1,
    Id = random:uniform(65536) - 1,
    PaddSz = random:uniform(16) - 1,    
    Psz = byte_size(Bin),
    Reserv = random:uniform(256) - 1,
    Padd = case PaddSz of
	       0 -> <<>>;
	       _ -> list_to_binary([random:uniform(256)-1
				    || _<- lists:seq(1,PaddSz)])
	   end,
    Res = <<Ver:8,Type:8,Id:16,Psz:16/big,PaddSz:8,Reserv:8,Bin/binary>>,
    {<<Res/binary,Padd/binary>>, Res};
pack(tpkt,Bin) ->
    Ver = 3,
    Reserv = random:uniform(256) - 1,
    Size = byte_size(Bin) + 4,
    Res = <<Ver:8,Reserv:8,Size:16,Bin/binary>>,
    {Res, Res};
pack(ssl_tls,Bin) ->
    Content = case (random:uniform(256) - 1) of
		  C when C<128 -> C;
		  _ -> v2hello
	      end,
    Major = random:uniform(256) - 1,
    Minor = random:uniform(256) - 1,
    pack_ssl(Content,Major,Minor,Bin).

pack_ssl(Content, Major, Minor, Body) ->
    case Content of
	v2hello ->
	    Size = byte_size(Body),
	    Res = <<1:1,(Size+3):15, 1:8, Major:8, Minor:8, Body/binary>>,
	    C = 22,
	    Data = <<1:8, (Size+2):24, Major:8, Minor:8, Body/binary>>;
	C when is_integer(C) ->
	    Size = byte_size(Body),
	    Res = <<Content:8, Major:8, Minor:8, Size:16, Body/binary>>,
	    Data = Body			    
    end,
    {Res, {ssl_tls,[],C,{Major,Minor}, Data}}.


packet_size(doc) -> [];
packet_size(suite) -> [];
packet_size(Config) when is_list(Config) ->
    ?line Packet = <<101,22,203,54,175>>,
    ?line Rest = <<123,34,0,250>>,

    F = fun({Type,Max})->
		?line {Bin,Unpacked} = pack(Type,Packet,Rest),
		?line case decode_pkt(Type,Bin,[{packet_size,Max}]) of
			  {ok,Unpacked,Rest} when Max=:=0; Max>=byte_size(Packet) ->
			      ok;
			  {error,_} when Max<byte_size(Packet), Max=/=0 ->
			      ok;
			  {error,_} when Type=:=fcgi, Max=/=0 ->
			      %% packet includes random amount of padding
			      ok
		      end
	end,
    ?line lists:foreach(F, [{T,D} || T<-[1,2,4,asn1,sunrm,cdr,fcgi,tpkt,ssl_tls],
				     D<-lists:seq(0, byte_size(Packet)*2)]),

    %% Test OTP-8102, "negative" 4-byte sizes.
    lists:foreach(fun(Size) -> 
			  ?line {error,_} = decode_pkt(4,<<Size:32,Packet/binary>>)
		  end, 
		  lists:seq(-10,-1)),
    ok.


neg(doc) -> [];
neg(suite) -> [];
neg(Config) when is_list(Config) ->
    ?line Bin = <<"dummy">>,
    Fun = fun()->dummy end,
    
    BadargF = fun(T,B,Opts)-> {'EXIT',{badarg,_}} = (catch decode_pkt(T,B,Opts)) end,

    %% Invalid Type args
    lists:foreach(fun(T)-> BadargF(T,Bin,[]) end, 
		  [3,-1,5,2.0,{2},unknown,[],"line",Bin,Fun,self()]),

    %% Invalid Bin args
    lists:foreach(fun(B)-> BadargF(0,B,[]) end, 
		  [3,2.0,unknown,[],"Bin",[Bin],{Bin},Fun,self()]),

    %% Invalid options
    InvOpts = [2,false,self(),Bin,"Options",Fun,
	       packet_size,{packet_size},{packet_size,0,false},
	       {packet_size,-1},{packet_size,100.0},{packet_size,false},
	       {line_length,-1},{line_length,100.0},{line_length,false}],

    lists:foreach(fun(Opt)-> BadargF(0,Bin,Opt),
			     BadargF(0,Bin,[Opt]),
			     BadargF(0,Bin,[Opt,{packet_size,1000}]),
			     BadargF(0,Bin,[{packet_size,1000},Opt]) end,
		  InvOpts),
    ok.


http(doc) -> [];
http(suite) -> [];
http(Config) when is_list(Config) ->
    ?line <<"foo">> = http_do(http_request("foo")),
    ?line <<" bar">> = http_do(http_request(" bar")),
    ?line <<"Hello!">> = http_do(http_response("Hello!")),

    %% Test all known header atoms
    Val = "dummy value",
    ValB = list_to_binary(Val),
    Rest = <<"Rest">>,    
    HdrF = fun(Str,N) ->  
		   ?line StrA = list_to_atom(Str),
		   ?line StrB = list_to_binary(Str),
		   ?line Bin = <<StrB/binary,": ",ValB/binary,"\r\n",Rest/binary>>,
		   ?line {ok, {http_header,N,StrA,undefined,Val}, Rest} = decode_pkt(httph,Bin),
		   ?line {ok, {http_header,N,StrA,undefined,ValB}, Rest} = decode_pkt(httph_bin,Bin),
		   ?line N + 1
	   end,
    ?line lists:foldl(HdrF, 1, http_hdr_strings()),

    %% Test all known method atoms
    MethF = fun(Meth) ->  
		    ?line MethA = list_to_atom(Meth),
		    ?line MethB = list_to_binary(Meth),
		    ?line Bin = <<MethB/binary," /invalid/url HTTP/1.0\r\n",Rest/binary>>,
		    ?line {ok, {http_request,MethA,{abs_path,"/invalid/url"},{1,0}},
			   Rest} = decode_pkt(http,Bin),
		    ?line {ok, {http_request,MethA,{abs_path,<<"/invalid/url">>},{1,0}},
			   Rest} = decode_pkt(http_bin,Bin)
	    end,
    ?line lists:foreach(MethF, http_meth_strings()),

    %% Test all uri variants    
    UriF = fun({Str,ResL,ResB}) -> 
		   Bin = <<"GET ",(list_to_binary(Str))/binary," HTTP/1.1\r\n",Rest/binary>>,
		   {ok, {http_request, 'GET', ResL, {1,1}}, Rest} = decode_pkt(http,Bin),
		   {ok, {http_request, 'GET', ResB, {1,1}}, Rest} = decode_pkt(http_bin,Bin) 
	   end,
    lists:foreach(UriF, http_uri_variants()),

    %% Response with empty phrase
    ?line {ok,{http_response,{1,1},200,[]},<<>>} = decode_pkt(http, <<"HTTP/1.1 200\r\n">>, []),
    ?line {ok,{http_response,{1,1},200,<<>>},<<>>} = decode_pkt(http_bin, <<"HTTP/1.1 200\r\n">>, []),
    ok.
	     
http_with_bin(http) ->
    http_bin;
http_with_bin(httph) ->
    httph_bin.

http_do(Tup) ->
    http_do(Tup,http).
http_do({Bin, []}, _) ->
    Bin;
http_do({Bin,[{_Line,PL,PB}|Tail]}, Type) ->
    ?line {ok, PL, Rest} = decode_pkt(Type,Bin),
    ?line {ok, PB, Rest} = decode_pkt(http_with_bin(Type),Bin),

    %% Same tests again but as SubBin
    PreLen = random:uniform(64),
    Prefix = random:uniform(1 bsl PreLen) - 1,
    SufLen = random:uniform(64),
    Suffix = random:uniform(1 bsl SufLen) - 1,
    Orig = <<Prefix:PreLen, Bin/bits, Suffix:SufLen>>,
    BinLen = bit_size(Bin),
    <<_:PreLen, SubBin:BinLen/bits, _/bits>> = Orig, % Make SubBin
    ?line SubBin = Bin, % just to make sure

    ?line {ok, PL, Rest} = decode_pkt(Type,SubBin),
    ?line {ok, PB, Rest} = decode_pkt(http_with_bin(Type),SubBin),
    http_do({Rest, Tail}, httph).

http_request(Msg) ->
    QnA = [{"POST /invalid/url HTTP/1.1\r\n",
	  {http_request, 'POST', {abs_path,  "/invalid/url"  }, {1,1}},
	  {http_request, 'POST', {abs_path,<<"/invalid/url">>}, {1,1}}},
	 {"Connection: close\r\n",
	  {http_header,2,'Connection',undefined,  "close"},
	  {http_header,2,'Connection',undefined,<<"close">>}},	 
	 {"Host\t : localhost:8000\r\n", % white space before :
	  {http_header,14,'Host',undefined,  "localhost:8000"},
	  {http_header,14,'Host',undefined,<<"localhost:8000">>}},
	 {"User-Agent: perl post\r\n",
	  {http_header,24,'User-Agent',undefined,  "perl post"},
	  {http_header,24,'User-Agent',undefined,<<"perl post">>}},
	 {"Content-Length: 4\r\n",
	  {http_header,38,'Content-Length',undefined,  "4"},
	  {http_header,38,'Content-Length',undefined,<<"4">>}},
	 {"Content-Type: text/xml; charset=utf-8\r\n",
	  {http_header,42,'Content-Type',undefined,  "text/xml; charset=utf-8"},
	  {http_header,42,'Content-Type',undefined,<<"text/xml; charset=utf-8">>}},
	 {"Other-Field: with some text\r\n",
	  {http_header,0,  "Other-Field"  ,undefined,  "with some text"},
	  {http_header,0,<<"Other-Field">>,undefined,<<"with some text">>}},
	 {"Multi-Line: Once upon a time in a land far far away,\r\n"
	  " there lived a princess imprisoned in the highest tower\r\n"
	  " of the most haunted castle.\r\n",
	  {http_header,0,  "Multi-Line"  ,undefined,  "Once upon a time in a land far far away,\r\n there lived a princess imprisoned in the highest tower\r\n of the most haunted castle."},
	  {http_header,0,<<"Multi-Line">>,undefined,<<"Once upon a time in a land far far away,\r\n there lived a princess imprisoned in the highest tower\r\n of the most haunted castle.">>}},
	 {"\r\n",
	  http_eoh,
	  http_eoh}],
    Bin = lists:foldl(fun({Line,_,_},Acc) -> LineBin = list_to_binary(Line), 
					     <<Acc/binary,LineBin/binary>> end,
		      <<"">>, QnA),
    MsgBin = list_to_binary(Msg),
    {<<Bin/binary,MsgBin/binary>>, QnA}.


http_response(Msg) ->
    QnA = [{"HTTP/1.0 404 Object Not Found\r\n",
	    {http_response, {1,0}, 404,   "Object Not Found"},
	    {http_response, {1,0}, 404, <<"Object Not Found">>}},
	   {"Server: inets/4.7.16\r\n",
	    {http_header, 30, 'Server', undefined,   "inets/4.7.16"},
	    {http_header, 30, 'Server', undefined, <<"inets/4.7.16">>}},
	   {"Date: Fri, 04 Jul 2008 17:16:22 GMT\r\n",
	    {http_header, 3, 'Date', undefined,   "Fri, 04 Jul 2008 17:16:22 GMT"},
	    {http_header, 3, 'Date', undefined, <<"Fri, 04 Jul 2008 17:16:22 GMT">>}},
	   {"Content-Type: text/html\r\n",
	    {http_header, 42, 'Content-Type', undefined,   "text/html"},
	    {http_header, 42, 'Content-Type', undefined, <<"text/html">>}},
	   {"Content-Length: 207\r\n",
	    {http_header, 38, 'Content-Length', undefined,   "207"},
	    {http_header, 38, 'Content-Length', undefined, <<"207">>}},
	   {"\r\n",
	    http_eoh,
	    http_eoh}],



    Bin = lists:foldl(fun({Line,_,_},Acc) -> LineBin = list_to_binary(Line), 
					     <<Acc/binary,LineBin/binary>> end,
		      <<"">>, QnA),
    MsgBin = list_to_binary(Msg),
    {<<Bin/binary,MsgBin/binary>>, QnA}.

http_hdr_strings() ->
    %% Must be correct order
    ["Cache-Control","Connection","Date","Pragma","Transfer-Encoding",
     "Upgrade","Via","Accept", "Accept-Charset", "Accept-Encoding",
     "Accept-Language", "Authorization","From","Host","If-Modified-Since",
     "If-Match","If-None-Match","If-Range","If-Unmodified-Since","Max-Forwards",
     "Proxy-Authorization","Range","Referer","User-Agent","Age","Location",
     "Proxy-Authenticate","Public","Retry-After","Server","Vary","Warning",
     "Www-Authenticate","Allow","Content-Base","Content-Encoding",
     "Content-Language","Content-Length","Content-Location","Content-Md5",
     "Content-Range","Content-Type","Etag","Expires","Last-Modified",
     "Accept-Ranges","Set-Cookie","Set-Cookie2","X-Forwarded-For","Cookie",
     "Keep-Alive","Proxy-Connection"].

http_meth_strings() ->
    ["OPTIONS", "GET", "HEAD", "POST", "PUT", "DELETE", "TRACE"].

http_uri_variants() ->
    [{"*", '*', '*'},
     {"http://tools.ietf.org/html/rfc3986",
      {absoluteURI,http,  "tools.ietf.org",  undefined,  "/html/rfc3986"},
      {absoluteURI,http,<<"tools.ietf.org">>,undefined,<<"/html/rfc3986">>}},
     {"http://otp.ericsson.se:8000/product/internal/",
      {absoluteURI,http,  "otp.ericsson.se"  ,8000,  "/product/internal/"},
      {absoluteURI,http,<<"otp.ericsson.se">>,8000,<<"/product/internal/">>}},
     {"https://example.com:8042/over/there?name=ferret#nose",
      {absoluteURI,https,  "example.com",  8042,  "/over/there?name=ferret#nose"},
      {absoluteURI,https,<<"example.com">>,8042,<<"/over/there?name=ferret#nose">>}},
     {"ftp://cnn.example.com&story=breaking_news@10.0.0.1/top_story.htm",
      {scheme,  "ftp",    "//cnn.example.com&story=breaking_news@10.0.0.1/top_story.htm"},
      {scheme,<<"ftp">>,<<"//cnn.example.com&story=breaking_news@10.0.0.1/top_story.htm">>}},
     {"/some/absolute/path",
      {abs_path,  "/some/absolute/path"},
      {abs_path,<<"/some/absolute/path">>}},
     {"something_else", "something_else", <<"something_else">>}].


line(doc) -> [];
line(suite) -> [];
line(Config) when is_list(Config) ->
    Text = <<"POST /invalid/url HTTP/1.1\r\n"
	    "Connection: close\r\n"
	    "Host\t : localhost:8000\r\n"
	    "User-Agent: perl post\r\n"
	    "Content-Length: 4\r\n"
	    "Content-Type: text/xml; charset=utf-8\r\n"
	    "Other-Field: with some text\r\n"
	    "Multi-Line: Once upon a time in a land far far away,\r\n"
	    " there lived a princess imprisoned in the highest tower\r\n"
	    " of the most haunted castle.\r\n"
	    "\r\nThe residue">>,

    lists:foreach(fun(MaxLen) -> line_do(Text,MaxLen) end,
		  [0,7,19,29,37]),
    ok.

line_do(Bin,MaxLen) ->
    Res = decode_pkt(line,Bin,[{line_length,MaxLen}]),
    MyRes = decode_line(Bin,MaxLen),
    ?line MyRes = Res,
    case Res of
	{ok,_,Rest} ->
	    line_do(Rest,MaxLen);
	{more,undefined} ->
	    ok
    end.
    
% Emulates decode_packet(line,Bin,[{line_length,MaxLen}])
decode_line(Bin,MaxLen) ->
    ?line case find_in_binary($\n,Bin) of
	notfound when MaxLen>0 andalso byte_size(Bin) >= MaxLen ->
	    {LineB,Rest} = split_binary(Bin,MaxLen),
	    {ok,LineB,Rest};
	notfound ->
	    {more,undefined};
	Pos when MaxLen>0 andalso Pos > MaxLen ->
	    {LineB,Rest} = split_binary(Bin,MaxLen),
	    {ok,LineB,Rest};
	Pos ->
	    {LineB,Rest} = split_binary(Bin,Pos),
	    {ok,LineB,Rest}
    end.

find_in_binary(Byte, Bin) ->
    case string:chr(binary_to_list(Bin),Byte) of
	0 -> notfound;	    
	P -> P
    end.    

ssl(doc) -> [];
ssl(suite) -> [];
ssl(Config) when is_list(Config) ->
    Major = 34,
    Minor = 17,
    Body = <<234,189,73,199,1,32,4,0,254>>,
    Rest = <<23,123,203,12,234>>,

    F = fun(Content) ->
		{Packet,Unpacked} = pack_ssl(Content, Major, Minor, Body),
		Bin = <<Packet/binary,Rest/binary>>,
		?line {ok, Unpacked, Rest} = decode_pkt(ssl_tls, Bin)
	end,    
    F(25),
    F(v2hello),
    ok.

otp_8536(doc) -> ["Corrupt sub-binary-strings from httph_bin"];
otp_8536(Config) when is_list(Config) ->
    lists:foreach(fun otp_8536_do/1, lists:seq(1,50)),
    ok.

otp_8536_do(N) ->
    Data = <<"some data 123">>,
    Letters = <<"bcdefghijklmnopqrstuvwxyzyxwvutsrqponmlkjihgfedcba">>,
    <<HdrTail:N/binary,_/binary>> = Letters,
    Hdr = <<$A, HdrTail/binary>>,
    Bin = <<Hdr/binary, ": ", Data/binary, "\r\n\r\n">>,

    io:format("Bin='~p'\n",[Bin]),
    ?line {ok,{http_header,0,Hdr2,undefined,Data2},<<"\r\n">>} = decode_pkt(httph_bin, Bin,  []),

    %% Do something to trash the C-stack, how about another decode_packet:
    decode_pkt(httph_bin,<<Letters/binary, ": ", Data/binary, "\r\n\r\n">>, []),

    %% Now check that we got the expected binaries
    {Hdr, Data} = {Hdr2, Data2}.

decode_pkt(Type,Bin) ->
    decode_pkt(Type,Bin,[]).		       
decode_pkt(Type,Bin,Opts) ->
    %%io:format("decode_packet(~p,~p,~p)\n",[Type,Bin,Opts]),
    Res = erlang:decode_packet(Type,Bin,Opts),
    %%io:format(" -> ~p\n",[Res]),
    Res.