Hi Chris,
I am reading the 3 bytes directly from the pcap file. I have implemented my parser using the libpcap source code.
I wish I could use a function similar to
tvb_get_ntoh24 ( ). The functions provided by wireshark are marvelous.
I have written a couple of dissectors on wireshark earlier.
Regards,
Prashanth
On Fri, Mar 5, 2010 at 2:41 AM, Maynard, Chris
<Christopher.Maynard@xxxxxxxxx> wrote:
Are you really reading those 3 bytes directly from the pcap file,
or are you reading them from a tvbuff that wireshark hands your dissector?
If from a tvbuff, why not just use tvb_get_ntoh24()? And
if you’re not doing anything with that value except for adding it to your
tree, you can just use proto_tree_add_item() with the item specified as either
FT_INT24 or FT_UINT24, whichever the case may be.
- Chris
Oh, then it looks correct to write a function that reads 3 bytes int value
from pacp / wire and convert it to an int? This is what I have done: I read the
three bytes from the pcap in to an array of three bytes. And then I memcpy
these 3 bytes from array to an int variable(which has been memset with 0's) And
then I do a ntohl on this int variable and return it as an int.
Thanks Guy Harris,
Regards,
Prashanth
On Fri, Mar 5, 2010 at 2:17 AM, Guy Harris <guy@xxxxxxxxxxxx> wrote:
On Mar 4, 2010, at 12:42 PM, prashanth joshi wrote:
> thanks for the clarification.
> I was writing a function to read such 3 byte values and convert them to
int. Unaware that uint24 field is supported in C (I have seen uint24 field only
in wireshark).
> Now I am using the uint24 type.
Standard C doesn't have a uint24 data type (even C99 doesn't
have uint24_t). I suppose if you're using C on the Datacraft/Harris
machines (no relation):
http://bolt.beetlebolt.com/blog/?m=200706
you'd have a 24-bit data type, but most if not all machines capable of running
Wireshark have 8-bit bytes and 32-bit or 64-bit registers.
Wireshark supports 24-bit integral-valued fields - but you put the values into
32-bit variables.
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