CoolVLViewer/indra/llcommon/llendianswizzle.h

/**
 * @file llendianswizzle.h
 * @brief Functions for in-place bit swizzling
 *
 * $LicenseInfo:firstyear=2002&license=viewergpl$
 *
 * Copyright (c) 2002-2009, Linden Research, Inc.
 *
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreemen
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
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 * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
 *
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 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online a
 * http://secondlifegrid.net/programs/open_source/licensing/flossexception
 *
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 */

#ifndef LL_LLENDIANSWIZZLE_H
#define LL_LLENDIANSWIZZLE_H

#include "llpreprocessor.h"

/* This function is intended to be used for in-place swizzling, particularly
   after fread() of binary values from a file. Such as:

	numRead = fread(scale.mV, sizeof(float), 3, fp);
	llendianswizzle(scale.mV, sizeof(float), 3);

	It assumes that the values in the file are LITTLE endian, so it's a no-op
    on a little endian machine.

	It keys off of typesize to do the correct swizzle, so make sure tha
    typesize is the size of the native type.

	64-bit types are not yet handled.
*/

#if LL_BIG_ENDIAN
// Big endian requires a bit of work.
LL_INLINE void llendianswizzle(void* p, int typesize, int count)
{
	switch (typesize)
	{
		case 2:
		{
			for (int i = count; i != 0; --i)
			{
				U16 temp = ((U16*)p)[0];
				((U16*)p)[0] = ((temp >> 8)  & 0x000000FF) |
							   ((temp << 8)  & 0x0000FF00);
				p = (void*)(((U16*)p) + 1);
			}
			break;
		}

		case 4:
		{
			for (int i = count; i != 0; --i)
			{
				U32 temp = ((U32*)p)[0];
				((U32*)p)[0] = ((temp >> 24) & 0x000000FF) |
							   ((temp >> 8)  & 0x0000FF00) |
							   ((temp << 8)  & 0x00FF0000) |
							   ((temp << 24) & 0xFF000000);
				p = (void*)(((U32*)p) + 1);
			}
			break;
		}
	}
}
#else
// Little endian is native for most things.
LL_INLINE void llendianswizzle(void*, int, int)
{
	// Nothing to do
}
#endif

// Use this when working with a single integral value you want swizzled

#define llendianswizzleone(x) llendianswizzle(&(x), sizeof(x), 1)

#endif // LL_LLENDIANSWIZZLE_H