From: ellman AT xs4all DOT nl ()
Newsgroups: comp.os.msdos.djgpp
Subject: Re: big endian class
Date: 31 May 1997 14:05:30 GMT
Organization: XS4ALL
Message-ID: <5mpb7b$3nm$1@news0.xs4all.nl>
References: <338F1A19 DOT 474E AT blackmagic DOT tait DOT co DOT nz>
NNTP-Posting-Host: xs1.xs4all.nl
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To: djgpp AT delorie DOT com
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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.

AE.


Andrei Ellman -- URL: http://www.xs4all.nl/~ellman/ae-a -- ae1 AT york DOT ac DOT uk
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