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Top Forums Shell Programming and Scripting Extract sequences of bytes from binary for differents blocks Post 302844111 by Ophiuchus on Friday 16th of August 2013 12:49:48 PM
Old 08-16-2013
Hello ahamed,

Thank you for your great help!

I've tested your new code and prints the sequence "03 80 ...", but is not printing the
other sequences after the 03 80, I mean the sequences that begin with 81, 83, 86, 87. I would like to extract
all the sequences of 17 bytes after 0x03 that begin with 0x80 or 0x81 or 0x83 or 0x84 or 0x86 or 0x87 if they
are present and print all sequences for each block in the same line if is not too complicated.

In summary:
- The 0x03 is the byte that says the beginning of certain kind of data.
- If 0x03 is present after 0xFF 0x34 then 0x03 could be inmediately followed by any of the sequences that begin with
0x80 or 0x81 or 0x83 or 0x84 or 0x86 or 0x87, because the sequences not always are present all of them.

Sometimes these sequences that begin with 0x80 or 0x81 or 0x83 or 0x84 or 0x86 or 0x87 could be present all, sometimes 3,
2 or only one of those sequences.

So, after the 0xFF 0x34 could happen several cases, some examples below:
0x03 0x80.... 0x86...
or
0x03 0x83.... 0x84... 0x87
or
0x03 0x87
or
0x03 0x81.... 0x87

Maybe you can explain me a little bit the logic of your code and function used, for example "memcmp" in order
to be able to modify it or add it new rules if I need to extract something else or to modify the printing order
or print the bytes without spaces separating with commas different sequences.

Thanks in advance for your time and help again.

Regards
 

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NG_UI(4)                                                   BSD Kernel Interfaces Manual                                                   NG_UI(4)

NAME
ng_UI -- UI netgraph node type SYNOPSIS
#include <netgraph/ng_UI.h> DESCRIPTION
The UI node type has two hooks, upstream and downstream. Packets received on downstream must have 0x03 (indicating unnumbered information) as their first byte; if not the packet is dropped. This byte is then stripped and the remainder of the packet sent out on upstream. Conversely, packets received on upstream will have a 0x03 byte prepended to them before being forwarded out on the downstream hook. HOOKS
This node type supports the following hooks: downstream Downstream connection. Packets on this side of the node have a 0x03 as their first byte. upstream Upstream connection. Packets on this side of the node have the initial 0x03 byte stripped off. CONTROL MESSAGES
This node type supports only the generic control messages. SHUTDOWN
This node shuts down upon receipt of a NGM_SHUTDOWN control message, or when both hooks have been disconnected. SEE ALSO
netgraph(4), ngctl(8) HISTORY
The ng_UI node type was implemented in FreeBSD 4.0. AUTHORS
Julian Elischer <julian@FreeBSD.org> BSD January 19, 1999 BSD
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