Re: usbmon: size of different fields?

["Maynard, Chris" <Christopher.Maynard () GTECH COM>]

Not sure why I don't see this message posted on gmane?

Anyway, I see you received a few responses already elsewhere:
-> http://lkml.org/lkml/2010/11/9/243
-> http://www.spinics.net/lists/linux-usb/msg38480.html

But I don't think those responses are technically correct.  With the C standard, there are no guarantees except for 
relative sizes, ie., char <= short <= int <= long, although if the OS is POSIX-compliant, then you can sleep well at 
night knowing CHAR_BIT is defined as 8 in <limits.h>.  But there's no guarantee that every platform is POSIX-compliant 
or that the char size is guaranteed to be 8 bits on non-POSIX-conforming platforms, although I can't imagine that 
Wireshark runs today on any platform where that isn't the case.

As for int, I suspect that most platforms have 32-bit ints, but again, there are no guarantees.

- Chris
P.S. The endian-ness is not an issue because of the libpcap header's magic number.

-----Original Message-----
From: wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Németh Márton
Sent: Tuesday, November 09, 2010 1:41 AM
To: linux-usb () vger kernel org
Cc: Developer support list for Wireshark; LKML
Subject: [Wireshark-dev] usbmon: size of different fields?

Hi,

I'm looking at the struct mon_bin_hdr and struct mon_bin_isodesc in file
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=drivers/usb/mon/mon_bin.c;h=44cb37b5a4dc1f9b27075e3db5346b9ebe307b22;hb=HEAD

As far as I understand u64, s64, u32 and s32 have always fixed bit lengths.

What about "unsigned char", "char", "unsigned int" and "int"? May their size in bits
differ in different architecture?

I'm asking this because I was dealing with the USB packet dissectors for Wireshark
and it is possible to capture the USB traffic on one computer and then transfer
the file to another computer.

        Márton Németh

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