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Wireshark-dev: Re: [Wireshark-dev] Lua Tvb and escape caracter

From: Cyril Le Guienne <cleguienne@xxxxxxxxx>
Date: Thu, 18 Jun 2009 08:23:37 +0200
Yes that's the way I found it too. I'll post a message later that day on that particular subject
Thanks
Perhaps you can try (I do not test):
    temparray.tvb()

I found this from epan/wslua/wslua_tvb.c by searching new_real.

Perhaps
   http://www.wireshark.org/docs/wsug_html_chunked/wsluarm_modules.html
is outdated?


On Tue, Jun 16, 2009 at 9:34 PM, cyril leguienne <cleguienne@xxxxxxxxx <mailto:cleguienne@xxxxxxxxx>> wrote:

    Hello everybody,
    I don't know if it is the right place to ask the question, let me know
    if not.
    I am currently writting a simple dissector using lua for a proprietary
    protocol.
    This protocol is quite basic ,i.e : frame start character+ data +
    frame
    stop character .
    But the problem is that the data field can contain frame start or stop
    characters that must be escaped with an escape character.
    In order to pass the data field to another dissector I have to remove
    the escape characters from the tvb before. But there are no
    function to
    remove data from a tvb nor a tvbrange nor byte array.
    I then wrote the following code:
    function netx_proto.dissector(buffer,pinfo,tree)
       pinfo.cols.protocol = "NetX"
       packetnum = pinfo.number
       local subtree_packet = tree:add(netx_proto,buffer(),"NetX Protocol
    ("..buffer:len()..")")
       local msgbufferarray = buffer(1,buffer:len()-2):bytes()--Here I get
    a byte array containing the data section from the frame
       local temparray=ByteArray.new()--allocation for a buffering
    byte array
       local offset=0
       for i=0,msgbufferarray:len()-2 do -- I go through the array
           if (msgbufferarray:get_index(i+1)==0x5C
               or msgbufferarray:get_index(i+1)==0x10
               or msgbufferarray:get_index(i+1)==0x13)
               and msgbufferarray:get_index(i)==0x5C then--here I m
    looking
    for escape sequences
               temparray.append(msgbufferarray:subset(offset,i+1))--if
    found I get a subset for the array that I append to the buffering
    array
               offset=offset+i+1
           end
       end
       msgbuffer = Tvb.new_real(temparray)--Here I try to create a new tvb
    without escape sequence from the temporary bytearray

    I then have an runtime error telling me "attempt to call field
    'new_real'(a nil value)". I'm quite puzzled as I can't find an example
    of Tvb creation  in the documentation and in forums.
    If someone could give me a clue about how to solve my problem.
    Thanks

    Cyril

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