From:	Keith Hull <keithh AT zetnet DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: big endian class
Date:	Sun, 1 Jun 1997 16:28:26 +0100
Message-ID:	<1997060116282677565@zetnet.co.uk>
References:	<338F1A19 DOT 474E AT blackmagic DOT tait DOT co DOT nz> <5mpb7b$3nm$1 AT news0 DOT xs4all DOT nl>
NNTP-Posting-Host:	crescent.zetnet.co.uk
Lines:	43
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

In message <5mpb7b$3nm$1 AT news0 DOT xs4all DOT nl>
        ellman AT xs4all DOT nl () writes: 

> In article <338F1A19 DOT 474E AT blackmagic DOT tait DOT co DOT nz>,
> Bill Currie  <billc AT blackmagic DOT tait DOT co DOT nz> wrote:
> >If anyone can figure a better way of byte swapping longs (without useing
> >bswap), preferably in c, please let me know as gcc can't optimise
> >swapBytes(long) or swapBytes(ulong) when called with constants (due to
> >the assembly code).

> void swapbytes(long *the_variable)
> {
>  register char b0,b1,b2,b3;

>  b0 = *(((char *)(the_variable)));
>  b1 = *(((char *)(the_variable))+1);
>  b2 = *(((char *)(the_variable))+2);
>  b3 = *(((char *)(the_bariable))+3);

>  *(((char *)(the_variable))) = b3;
>  *(((char *)(the_variable))+1) = b2;
>  *(((char *)(the_variable))+2) = b1;
>  *(((char *)(the_variable))+3) = b0;
> }

> If you have some means of detecting wether your program will be 
comipled for a
> 486, use inline assembly with the bswap instruction.

or

      dummy = (data & 0x000000ff) << 24;
      dummy = dummy | ((data & 0x0000ff00) << 8);
      dummy = dummy | ((data & 0x00FF0000) >> 8);
      dummy = dummy | ((data & 0xFF000000) >> 24);


-- 
Keith Hull - Bournemouth
keithh AT zetnet DOT co DOT uk
keithh AT yeomanh DOT spsxch DOT p4 DOT sps DOT co DOT uk

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