How to get two bytes form a buffer?

Re: How to get two bytes form a buffer?


"cylin" <cylin@avant.co m.tw> schrieb im Newsbeitrag
news:brugos$72m ju$1@ID-154203.news.uni-berlin.de...[color=blue]
> Dear all,
>
> From now on, I just can get a byte twice.
> Then decode this two bytes.
>
> for example,
> buffer is a unsigned char array.
>
> value=(*buffer) <<8;
> value+=*(buffer +1);
>[/color]
thats how I did it.
but alternatives could be:

memcpy(&value,b uffer,2);

or some fancy casting:

value = *((unsigned int*)&(buffer[i]))
respective; value=*(unsigne d int*)(buffer);


but I'm not sure if uint has two bytes size, see it for yourself


hth psy

Re: How to get two bytes form a buffer?


"Sebastian "Psy" Messerschmidt"
<sebastian.mess erschmidt@DELET ETHISstud.tu-ilmenau.de> wrote in message
news:bruhlf$i9n $1@piggy.rz.tu-ilmenau.de...[color=blue]
>
> "cylin" <cylin@avant.co m.tw> schrieb im Newsbeitrag
> news:brugos$72m ju$1@ID-154203.news.uni-berlin.de...[color=green]
> > Dear all,
> >
> > From now on, I just can get a byte twice.
> > Then decode this two bytes.
> >
> > for example,
> > buffer is a unsigned char array.
> >
> > value=(*buffer) <<8;
> > value+=*(buffer +1);
> >[/color]
> thats how I did it.
> but alternatives could be:
>
> memcpy(&value,b uffer,2);
>
> or some fancy casting:
>
> value = *((unsigned int*)&(buffer[i]))
> respective; value=*(unsigne d int*)(buffer);
>
>
> but I'm not sure if uint has two bytes size, see it for yourself
>
>
> hth psy
>[/color]

value=*(short *) buffer;

Sean

Re: How to get two bytes form a buffer?

Sean Kenwrick wrote:[color=blue]
> "Sebastian "Psy" Messerschmidt"
> <sebastian.mess erschmidt@DELET ETHISstud.tu-ilmenau.de> wrote in message
> news:bruhlf$i9n $1@piggy.rz.tu-ilmenau.de...
>[color=green]
>>"cylin" <cylin@avant.co m.tw> schrieb im Newsbeitrag
>>news:brugos$7 2mju$1@ID-154203.news.uni-berlin.de...
>>[color=darkred]
>>>Dear all,
>>>
>>>From now on, I just can get a byte twice.
>>>Then decode this two bytes.
>>>
>>>for example,
>>>buffer is a unsigned char array.
>>>
>>>value=(*buff er)<<8;
>>>value+=*(buf fer+1);
>>>[/color]
>>
>>thats how I did it.
>>but alternatives could be:
>>
>>memcpy(&value ,buffer,2);
>>
>>or some fancy casting:
>>
>>value = *((unsigned int*)&(buffer[i]))
>>respective; value=*(unsigne d int*)(buffer);
>>
>>
>>but I'm not sure if uint has two bytes size, see it for yourself
>>
>>
>>hth psy
>>[/color]
>
>[/color]
if (sizeof(short) == 2)
{[color=blue]
> value=*(short *) buffer;[/color]
}
[color=blue]
>
> Sean
>
>[/color]


--
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Re: How to get two bytes form a buffer?

On Fri, 19 Dec 2003 17:06:00 GMT, Thomas Matthews
<Thomas_Matthew sSpitsOnSpamBot s@sbcglobal.net > wrote in comp.lang.c++:
[color=blue]
> Sean Kenwrick wrote:[color=green]
> > "Sebastian "Psy" Messerschmidt"
> > <sebastian.mess erschmidt@DELET ETHISstud.tu-ilmenau.de> wrote in message
> > news:bruhlf$i9n $1@piggy.rz.tu-ilmenau.de...
> >[color=darkred]
> >>"cylin" <cylin@avant.co m.tw> schrieb im Newsbeitrag
> >>news:brugos$7 2mju$1@ID-154203.news.uni-berlin.de...
> >>
> >>>Dear all,
> >>>
> >>>From now on, I just can get a byte twice.
> >>>Then decode this two bytes.
> >>>
> >>>for example,
> >>>buffer is a unsigned char array.
> >>>
> >>>value=(*buff er)<<8;
> >>>value+=*(buf fer+1);
> >>>
> >>
> >>thats how I did it.
> >>but alternatives could be:
> >>
> >>memcpy(&value ,buffer,2);
> >>
> >>or some fancy casting:
> >>
> >>value = *((unsigned int*)&(buffer[i]))
> >>respective; value=*(unsigne d int*)(buffer);
> >>
> >>
> >>but I'm not sure if uint has two bytes size, see it for yourself
> >>
> >>
> >>hth psy
> >>[/color]
> >
> >[/color]
> if (sizeof(short) == 2)[/color]

....and it the short is big-endian.
[color=blue]
> {[color=green]
> > value=*(short *) buffer;[/color]
> }[/color]

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
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Re: How to get two bytes form a buffer?

But my buffer is 4k bytes length,
and there are lot of such values in this buffer.
It's not only in *(buffer) and *(buffer+1) but also everywhere.

memcpy only can handle the first n bytes in the buffer.

Thanks all to reply.

Regards,
cylin.

"Jack Klein" <jackklein@spam cop.net>
???????:tkm7uvo 2d88ampri3734oh t81tqibgn9ne@4a x.com...
On Fri, 19 Dec 2003 17:06:00 GMT, Thomas Matthews
<Thomas_Matthew sSpitsOnSpamBot s@sbcglobal.net > wrote in comp.lang.c++:
[color=blue]
> Sean Kenwrick wrote:[color=green]
> > "Sebastian "Psy" Messerschmidt"
> > <sebastian.mess erschmidt@DELET ETHISstud.tu-ilmenau.de> wrote in message
> > news:bruhlf$i9n $1@piggy.rz.tu-ilmenau.de...
> >[color=darkred]
> >>"cylin" <cylin@avant.co m.tw> schrieb im Newsbeitrag
> >>news:brugos$7 2mju$1@ID-154203.news.uni-berlin.de...
> >>
> >>>Dear all,
> >>>
> >>>From now on, I just can get a byte twice.
> >>>Then decode this two bytes.
> >>>
> >>>for example,
> >>>buffer is a unsigned char array.
> >>>
> >>>value=(*buff er)<<8;
> >>>value+=*(buf fer+1);
> >>>
> >>
> >>thats how I did it.
> >>but alternatives could be:
> >>
> >>memcpy(&value ,buffer,2);
> >>
> >>or some fancy casting:
> >>
> >>value = *((unsigned int*)&(buffer[i]))
> >>respective; value=*(unsigne d int*)(buffer);
> >>
> >>
> >>but I'm not sure if uint has two bytes size, see it for yourself
> >>
> >>
> >>hth psy
> >>[/color]
> >
> >[/color]
> if (sizeof(short) == 2)[/color]

....and it the short is big-endian.
[color=blue]
> {[color=green]
> > value=*(short *) buffer;[/color]
> }[/color]

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
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