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CommView allows you to use
two types of your own custom decoders.
Simple Decoder
If you implement this type
of decoder, the output of your decoder will be displayed in the
additional column in the Packets
tab. Your
decoder must be a 32-bit DLL file named "Custom.dll" that exports
the only procedure named "Decode". The prototype of this procedure
is shown below in C and Pascal:
extern "C" {
void __stdcall Decode(unsigned char *PacketData, int
PacketLen, char *Buffer, int BufferLen);
}
procedure Decode (PacketData: PChar; PacketLen: integer; Buffer:
PChar; BufferLen: integer); stdcall;
The DLL must be located in
the CommView application folder. When you launch CommView, it looks
for "Custom.dll" in the application folder and loads it into
memory. If the "Decode" entry point is found, CommView adds a new
column named "Custom" to the packet list.
When a new packet is
captured and is about to be displayed, CommView calls the "Decode"
procedure and passes the packet contents to the DLL. The "Decode"
procedure must process the packet data and copy the result to the
supplied buffer. The first argument is the pointer to the packet
data, the second argument is the data length, the third argument is
the pointer to the buffer where the results of your decoding must
be copied to, and the forth argument is the buffer size (currently
always 1024 bytes). The buffer is allocated and freed by CommView,
so don't attempt to reallocate or free it. The result that you
copied to the buffer will be displayed as a string in the "Custom"
column.
Your procedure must be
fast enough to handle thousands of packets per second; otherwise it
may slow down the application. Don't forget to use the STDCALL
calling convention.
Two demo DLLs are
available. They demonstrate a very simple operation: The output of
the "Decode" function is the hex code of the packet's last byte.
Your own decoder can be as complex as you wish.
·http://www.tamos.com/products/commview/cust_decoder_c.zip.
This is a Visual Studio project with C++ source code.
·http://www.tamos.com/products/commview/cust_decoder_d.zip.
This is a Delphi project with Pascal source code.
Complex Decoder
If you implement this type
of decoder, the output of your decoder will be displayed as
additional items in the packet decoder tree. For information on the
implementation of this decoder, please download the following
file:
http://www.tamos.com/products/commview/complex_decoder_c7.zip
This type of decoder can
be written in Microsoft Visual C++ only, as it is built using C++
classes.
Technical Support
Technical support for
custom decoders is provided on the "best effort" basis. We may not
be able to answer your programming-related questions.
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