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

[Cyril Le Guienne <cleguienne@xxxxxxxxx>]

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 is outdated?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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