Re: Question about GTK+ and timers

[Igor Korot <ikorot01 gmail com>]

Hi, guys,

On Sat, Apr 9, 2011 at 4:04 AM, Chris Vine <chris cvine freeserve co uk> wrote:
> On Sat, 9 Apr 2011 00:14:45 -0700
> Igor Korot <ikorot01 gmail com> wrote:
> [snip]
>> Is there any way to find out if the device is little- or big-endian?
>
> Which device are you referring to?  You appear to be writing some
> code for a machine receiving data sent over a wire, and that machine's
> endianness can be tested by seeing whether G_BYTE_ORDER is defined as
> G_LITTLE_ENDIAN or G_BIG_ENDIAN, and then used for conditional
> compilation purposes. glib also has some built in byte-swapping macros:
>
> http://developer.gnome.org/glib/stable/glib-Byte-Order-Macros.html
>
> However the thing that puzzles me is that there are other issues here,
> apart from the byte order of data elements whose size is greater than 1.
> As another poster has pointed out, the format of the data stream
> requires specification somewhere.  How do you know it is sent as structs
> with the potentially compiler-dependent layout that you referred to?  As
> I mentioned (and others have mentioned) earlier, what is being sent is
> serialised data.  What you need to know is how the data packet layout
> of the serialised data is specified and work from there.

This is very simple.
If I connect the device to the x86-based machine and run minicom I can see
a string of numbers which is received from the device.
By looking at the documentation I can find out that the first byte
(let's say it's chr(3))
correspond to some particular data. However minicom will dispaly it as 03.
And so forth.
Now what I want to do is read those data in the m_data, grab some pieces,
convert them to double and present them to the screen.
Some data that I need are 2 bytes, some 3 bytes and some just 1 byte.

I thought I could rely on the compiler to do the right thing in terms of
endianess, however it looks like from my testing and what you all telling
me I was wrong. And I need to take care of this by myself.
I will look if I can compile serial port software to be run on this device
to get a data dump from serial device and check if I need to do something
additional.

Thank you.

>
> Chris
>
>
>