/* -----------------------------------------------------------------------------

DDS Library

Based on code from Nvidia's DDS example:
http://www.nvidia.com/object/dxtc_decompression_code.html

Copyright (c) 2003 Randy Reddig
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list
of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright notice, this
list of conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.

Neither the names of the copyright holders nor the names of its contributors may
be used to endorse or promote products derived from this software without
specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

----------------------------------------------------------------------------- */

#include "ddslib.h"

/* dependencies */
#include <stdio.h>
#include <memory.h>

/* endian tomfoolery */
typedef union
{
	float	f;
	char	c[ 4 ];
}
floatSwapUnion;


#ifndef __BIG_ENDIAN__
	#ifdef _SGI_SOURCE
		#define	__BIG_ENDIAN__
	#endif
#endif


#ifdef __BIG_ENDIAN__

int DDSLong( int src ) {
	return ((src & 0xFF000000) >> 24) |
	       ((src & 0x00FF0000) >> 8) |
	       ((src & 0x0000FF00) << 8) |
	       ((src & 0x000000FF) << 24);
}

short DDSShort( short src ) {
	return ((src & 0xFF00) >> 8) |
	       ((src & 0x00FF) << 8);
}

#else /*__BIG_ENDIAN__*/

int   DDSLong( int src ) {
	return src;
}
short DDSShort( short src ) {
	return src;
}

#endif /*__BIG_ENDIAN__*/

std::ostream& operator<< (std::ostream& os, const DDSHeader& h)
{
    os << "DDSHeader { " << (h.isValid() ? "VALID" : "INVALID")
       << " | " << h.width << "x" << h.height;

    if (h.isCompressed())
       os << " | " << h.getCompressionFormat();
    else
       os << " | " << h.getRGBBits() << " bit RGB";

    os << " | " << h.mipMapCount << " mipmaps"
       << " }";

    return os;
}

namespace
{

bool fourCCEqual(const char* l, const char* r)
{
    return *reinterpret_cast<const uint32_t*>(l)
        == *reinterpret_cast<const uint32_t*>(r);
}

}

bool DDSHeader::isValid() const
{
    return fourCCEqual(magic, "DDS ")
        && size == 124                  // fixed size structure
        && pixelFormat.size == 32
        && testFlag(DDSD_CAPS)          // required in every DDS file
        && testFlag(DDSD_HEIGHT)        // required in every DDS file
        && testFlag(DDSD_WIDTH)         // required in every DDS file
        && testFlag(DDSD_PIXELFORMAT);  // required in every DDS file
}

int DDSHeader::getWidth() const
{
    return DDSLong(width);
}

int DDSHeader::getHeight() const
{
    return DDSLong(height);
}

int DDSHeader::getMipMapCount() const
{
    if (testFlag(DDSD_MIPMAPCOUNT))
       return mipMapCount;
    else
       return 1;
}

/*
DDSDecodePixelFormat()
determines which pixel format the dds texture is in
*/

static void DDSDecodePixelFormat( const DDSHeader* header, ddsPF_t *pf ) {
	unsigned char	fourCC[4];

	/* dummy check */
	if(	header == NULL || pf == NULL )
		return;

	/* extract fourCC */
	fourCC[0] = header->pixelFormat.fourCC[0];
	fourCC[1] = header->pixelFormat.fourCC[1];
	fourCC[2] = header->pixelFormat.fourCC[2];
	fourCC[3] = header->pixelFormat.fourCC[3];

	/* test it */
	if (fourCC[0] == 0 && fourCC[1] == 0 && fourCC[2] == 0 && fourCC[3] == 0)
		*pf = DDS_PF_ARGB8888;
	else if (fourCC[0] == 'D' && fourCC[1] == 'X' && fourCC[2] == 'T' && fourCC[3] == '1')
		*pf = DDS_PF_DXT1;
	else if (fourCC[0] == 'D' && fourCC[1] == 'X' && fourCC[2] == 'T' && fourCC[3] == '2')
		*pf = DDS_PF_DXT2;
	else if (fourCC[0] == 'D' && fourCC[1] == 'X' && fourCC[2] == 'T' && fourCC[3] == '3')
		*pf = DDS_PF_DXT3;
	else if (fourCC[0] == 'D' && fourCC[1] == 'X' && fourCC[2] == 'T' && fourCC[3] == '4')
		*pf = DDS_PF_DXT4;
	else if (fourCC[0] == 'D' && fourCC[1] == 'X' && fourCC[2] == 'T' && fourCC[3] == '5')
		*pf = DDS_PF_DXT5;
	else if (fourCC[0] == 'R' && fourCC[1] == 'X' && fourCC[2] == 'G' && fourCC[3] == 'B')
		*pf = DDS_PF_DXT5_RXGB;
	else
		*pf = DDS_PF_UNKNOWN;
}



/*
DDSGetInfo()
extracts relevant info from a dds texture, returns 0 on success
*/

int DDSGetInfo(const DDSHeader* header, int *width, int *height, ddsPF_t *pf ) {
	/* dummy test */
	if( header == NULL )
		return -1;

	/* test dds header */
	if( *((int*) header->magic) != *((int*) "DDS ") )
		return -1;
	if( DDSLong( header->size ) != 124 )
		return -1;

	/* extract width and height */
	if( width != NULL )
		*width = DDSLong( header->width );
	if( height != NULL )
		*height = DDSLong( header->height );

	/* get pixel format */
	DDSDecodePixelFormat( header, pf );

	/* return ok */
	return 0;
}

/*
DDSGetColorBlockColors()
extracts colors from a dds color block
*/

static void DDSGetColorBlockColors( ddsColorBlock_t *block, ddsColor_t colors[ 4 ] ) {
	unsigned short		word;


	/* color 0 */
	word = DDSShort( block->colors[ 0 ] );
	colors[ 0 ].a = 0xff;

	/* extract rgb bits */
	colors[ 0 ].b = (unsigned char) word;
	colors[ 0 ].b <<= 3;
	colors[ 0 ].b |= (colors[ 0 ].b >> 5);
	word >>= 5;
	colors[ 0 ].g = (unsigned char) word;
	colors[ 0 ].g <<= 2;
	colors[ 0 ].g |= (colors[ 0 ].g >> 6);
	word >>= 6;
	colors[ 0 ].r = (unsigned char) word;
	colors[ 0 ].r <<= 3;
	colors[ 0 ].r |= (colors[ 0 ].r >> 5);

	/* same for color 1 */
	word = DDSShort( block->colors[ 1 ] );
	colors[ 1 ].a = 0xff;

	/* extract rgb bits */
	colors[ 1 ].b = (unsigned char) word;
	colors[ 1 ].b <<= 3;
	colors[ 1 ].b |= (colors[ 1 ].b >> 5);
	word >>= 5;
	colors[ 1 ].g = (unsigned char) word;
	colors[ 1 ].g <<= 2;
	colors[ 1 ].g |= (colors[ 1 ].g >> 6);
	word >>= 6;
	colors[ 1 ].r = (unsigned char) word;
	colors[ 1 ].r <<= 3;
	colors[ 1 ].r |= (colors[ 1 ].r >> 5);

	/* use this for all but the super-freak math method */
	if( block->colors[ 0 ] > block->colors[ 1 ] ) {
		/* four-color block: derive the other two colors.
		   00 = color 0, 01 = color 1, 10 = color 2, 11 = color 3
		   these two bit codes correspond to the 2-bit fields
		   stored in the 64-bit block. */

		word = ((unsigned short) colors[ 0 ].r * 2 + (unsigned short) colors[ 1 ].r ) / 3;
		/* no +1 for rounding */
		/* as bits have been shifted to 888 */
		colors[ 2 ].r = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].g * 2 + (unsigned short) colors[ 1 ].g) / 3;
		colors[ 2 ].g = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].b * 2 + (unsigned short) colors[ 1 ].b) / 3;
		colors[ 2 ].b = (unsigned char) word;
		colors[ 2 ].a = 0xff;

		word = ((unsigned short) colors[ 0 ].r + (unsigned short) colors[ 1 ].r * 2) / 3;
		colors[ 3 ].r = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].g + (unsigned short) colors[ 1 ].g * 2) / 3;
		colors[ 3 ].g = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].b + (unsigned short) colors[ 1 ].b * 2) / 3;
		colors[ 3 ].b = (unsigned char) word;
		colors[ 3 ].a = 0xff;
	}
	else {
		/* three-color block: derive the other color.
		   00 = color 0, 01 = color 1, 10 = color 2,
		   11 = transparent.
		   These two bit codes correspond to the 2-bit fields
		   stored in the 64-bit block */

		word = ((unsigned short) colors[ 0 ].r + (unsigned short) colors[ 1 ].r) / 2;
		colors[ 2 ].r = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].g + (unsigned short) colors[ 1 ].g) / 2;
		colors[ 2 ].g = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].b + (unsigned short) colors[ 1 ].b) / 2;
		colors[ 2 ].b = (unsigned char) word;
		colors[ 2 ].a = 0xff;

		/* random color to indicate alpha */
		colors[ 3 ].r = 0x00;
		colors[ 3 ].g = 0xff;
		colors[ 3 ].b = 0xff;
		colors[ 3 ].a = 0x00;
	}
}



/*
DDSDecodeColorBlock()
decodes a dds color block
fixme: make endian-safe
*/

static void DDSDecodeColorBlock( unsigned int *pixel, ddsColorBlock_t *block, int width, unsigned int colors[ 4 ] ) {
	int				r, n;
	unsigned int	bits;
	unsigned int	masks[] = { 3, 12, 3 << 4, 3 << 6 };	/* bit masks = 00000011, 00001100, 00110000, 11000000 */
	int				shift[] = { 0, 2, 4, 6 };

	/* r steps through lines in y */
	for( r = 0; r < 4; r++, pixel += (width - 4) )	/* no width * 4 as unsigned int ptr inc will * 4 */
	{
		/* width * 4 bytes per pixel per line, each j dxtc row is 4 lines of pixels */

		/* n steps through pixels */
		for( n = 0; n < 4; n++ ) {
			bits = block->row[ r ] & masks[ n ];
			bits >>= shift[ n ];
			*pixel = colors[bits];
			pixel++;
		}
	}
}



/*
DDSDecodeAlphaExplicit()
decodes a dds explicit alpha block
*/

static void DDSDecodeAlphaExplicit( unsigned int *pixel, ddsAlphaBlockExplicit_t *alphaBlock, int width, unsigned int alphaZero ) {
	int				row, pix;
	unsigned short	word;
	ddsColor_t		color;


	/* clear color */
	color.r = 0;
	color.g = 0;
	color.b = 0;

	/* walk rows */
	for( row = 0; row < 4; row++, pixel += (width - 4) ) {
		word = DDSShort( alphaBlock->row[ row ] );

		/* walk pixels */
		for( pix = 0; pix < 4; pix++ ) {
			/* zero the alpha bits of image pixel */
			*pixel &= alphaZero;
			color.a = word & 0x000F;
			color.a = color.a | (color.a << 4);
			*pixel |= *((unsigned int*) &color);
			word >>= 4;		/* move next bits to lowest 4 */
			pixel++;		/* move to next pixel in the row */

		}
	}
}



/*
DDSDecodeAlpha3BitLinear()
decodes interpolated alpha block
*/

static void DDSDecodeAlpha3BitLinear( unsigned int *pixel, ddsAlphaBlock3BitLinear_t *alphaBlock, int width, unsigned int alphaZero ) {

	int					row, pix;
	unsigned int		stuff;
	unsigned char		bits[ 4 ][ 4 ];
	unsigned short		alphas[ 8 ];
	ddsColor_t			aColors[ 4 ][ 4 ];


	/* get initial alphas */
	alphas[ 0 ] = alphaBlock->alpha0;
	alphas[ 1 ] = alphaBlock->alpha1;

	/* 8-alpha block */
	if( alphas[ 0 ] > alphas[ 1 ] ) {
		/* 000 = alpha_0, 001 = alpha_1, others are interpolated */
		alphas[ 2 ] = ( 6 * alphas[ 0 ] +     alphas[ 1 ]) / 7;	/* bit code 010 */
		alphas[ 3 ] = ( 5 * alphas[ 0 ] + 2 * alphas[ 1 ]) / 7;	/* bit code 011 */
		alphas[ 4 ] = ( 4 * alphas[ 0 ] + 3 * alphas[ 1 ]) / 7;	/* bit code 100 */
		alphas[ 5 ] = ( 3 * alphas[ 0 ] + 4 * alphas[ 1 ]) / 7;	/* bit code 101 */
		alphas[ 6 ] = ( 2 * alphas[ 0 ] + 5 * alphas[ 1 ]) / 7;	/* bit code 110 */
		alphas[ 7 ] = (     alphas[ 0 ] + 6 * alphas[ 1 ]) / 7;	/* bit code 111 */
	}

	/* 6-alpha block */
	else {
		/* 000 = alpha_0, 001 = alpha_1, others are interpolated */
		alphas[ 2 ] = (4 * alphas[ 0 ] +     alphas[ 1 ]) / 5;	/* bit code 010 */
		alphas[ 3 ] = (3 * alphas[ 0 ] + 2 * alphas[ 1 ]) / 5;	/* bit code 011 */
		alphas[ 4 ] = (2 * alphas[ 0 ] + 3 * alphas[ 1 ]) / 5;	/* bit code 100 */
		alphas[ 5 ] = (    alphas[ 0 ] + 4 * alphas[ 1 ]) / 5;	/* bit code 101 */
		alphas[ 6 ] = 0;										/* bit code 110 */
		alphas[ 7 ] = 255;										/* bit code 111 */
	}

	/* decode 3-bit fields into array of 16 bytes with same value */

	/* first two rows of 4 pixels each */
	stuff = *((unsigned int*) &(alphaBlock->stuff[ 0 ]));

	bits[ 0 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 0 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 0 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 0 ][ 3 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 3 ] = (unsigned char) (stuff & 0x00000007);

	/* last two rows */
	stuff = *((unsigned int*) &(alphaBlock->stuff[ 3 ])); /* last 3 bytes */

	bits[ 2 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 2 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 2 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 2 ][ 3 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 3 ] = (unsigned char) (stuff & 0x00000007);

	/* decode the codes into alpha values */
	for( row = 0; row < 4; row++ ) {
		for( pix=0; pix < 4; pix++ ) {
			aColors[ row ][ pix ].r = 0;
			aColors[ row ][ pix ].g = 0;
			aColors[ row ][ pix ].b = 0;
			aColors[ row ][ pix ].a = (unsigned char) alphas[ bits[ row ][ pix ] ];
		}
	}

	/* write out alpha values to the image bits */
	for( row = 0; row < 4; row++, pixel += width-4 ) {
		for( pix = 0; pix < 4; pix++ ) {
			/* zero the alpha bits of image pixel */
			*pixel &= alphaZero;

			/* or the bits into the prev. nulled alpha */
			*pixel |= *((unsigned int*) &(aColors[ row ][ pix ]));
			pixel++;
		}
	}
}

/** greebo: Decodes the alpha channel into the red channel for RXGB-encoded images
 */
static void DDSDecodeRXGBAlpha3BitLinear( unsigned int *pixel, ddsAlphaBlock3BitLinear_t *alphaBlock, int width, unsigned int redZero ) {

	int					row, pix;
	unsigned int		stuff;
	unsigned char		bits[ 4 ][ 4 ];
	unsigned short		alphas[ 8 ];
	ddsColor_t			aColors[ 4 ][ 4 ];


	/* get initial alphas */
	alphas[ 0 ] = alphaBlock->alpha0;
	alphas[ 1 ] = alphaBlock->alpha1;

	/* 8-alpha block */
	if( alphas[ 0 ] > alphas[ 1 ] ) {
		/* 000 = alpha_0, 001 = alpha_1, others are interpolated */
		alphas[ 2 ] = ( 6 * alphas[ 0 ] +     alphas[ 1 ]) / 7;	/* bit code 010 */
		alphas[ 3 ] = ( 5 * alphas[ 0 ] + 2 * alphas[ 1 ]) / 7;	/* bit code 011 */
		alphas[ 4 ] = ( 4 * alphas[ 0 ] + 3 * alphas[ 1 ]) / 7;	/* bit code 100 */
		alphas[ 5 ] = ( 3 * alphas[ 0 ] + 4 * alphas[ 1 ]) / 7;	/* bit code 101 */
		alphas[ 6 ] = ( 2 * alphas[ 0 ] + 5 * alphas[ 1 ]) / 7;	/* bit code 110 */
		alphas[ 7 ] = (     alphas[ 0 ] + 6 * alphas[ 1 ]) / 7;	/* bit code 111 */
	}

	/* 6-alpha block */
	else {
		/* 000 = alpha_0, 001 = alpha_1, others are interpolated */
		alphas[ 2 ] = (4 * alphas[ 0 ] +     alphas[ 1 ]) / 5;	/* bit code 010 */
		alphas[ 3 ] = (3 * alphas[ 0 ] + 2 * alphas[ 1 ]) / 5;	/* bit code 011 */
		alphas[ 4 ] = (2 * alphas[ 0 ] + 3 * alphas[ 1 ]) / 5;	/* bit code 100 */
		alphas[ 5 ] = (    alphas[ 0 ] + 4 * alphas[ 1 ]) / 5;	/* bit code 101 */
		alphas[ 6 ] = 0;										/* bit code 110 */
		alphas[ 7 ] = 255;										/* bit code 111 */
	}

	/* decode 3-bit fields into array of 16 bytes with same value */

	/* first two rows of 4 pixels each */
	stuff = *((unsigned int*) &(alphaBlock->stuff[ 0 ]));

	bits[ 0 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 0 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 0 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 0 ][ 3 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 1 ][ 3 ] = (unsigned char) (stuff & 0x00000007);

	/* last two rows */
	stuff = *((unsigned int*) &(alphaBlock->stuff[ 3 ])); /* last 3 bytes */

	bits[ 2 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 2 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 2 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 2 ][ 3 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 0 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 1 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 2 ] = (unsigned char) (stuff & 0x00000007);
	stuff >>= 3;
	bits[ 3 ][ 3 ] = (unsigned char) (stuff & 0x00000007);

	/* decode the codes into red values */
	for( row = 0; row < 4; row++ ) {
		for( pix=0; pix < 4; pix++ ) {
			aColors[ row ][ pix ].a = 0;
			aColors[ row ][ pix ].g = 0;
			aColors[ row ][ pix ].b = 0;
			aColors[ row ][ pix ].r = (unsigned char) alphas[ bits[ row ][ pix ] ];
		}
	}

	/* write out alpha values to the image bits */
	for( row = 0; row < 4; row++, pixel += width-4 ) {
		for( pix = 0; pix < 4; pix++ ) {
			/* zero the red bits of image pixel */
			*pixel &= redZero;

			/* or the bits into the prev. nulled red */
			*pixel |= *((unsigned int*) &(aColors[ row ][ pix ]));
			pixel++;
		}
	}
}


/*
DDSDecompressDXT1()
decompresses a dxt1 format texture
*/

static int DDSDecompressDXT1( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int				x, y, xBlocks, yBlocks;
	unsigned int	*pixel;
	ddsColorBlock_t	*block;
	ddsColor_t		colors[ 4 ];


	/* setup */
	xBlocks = width / 4;
	yBlocks = height / 4;

	/* walk y */
	for( y = 0; y < yBlocks; y++ ) {
		/* 8 bytes per block */
		block = (ddsColorBlock_t*) ((uintptr_t) buffer + y * xBlocks * 8);

		/* walk x */
		for( x = 0; x < xBlocks; x++, block++ ) {
			DDSGetColorBlockColors( block, colors );
			pixel = (unsigned int*) (pixels + x * 16 + (y * 4) * width * 4);
			DDSDecodeColorBlock( pixel, block, width, (unsigned int*) colors );
		}
	}

	/* return ok */
	return 0;
}



/*
DDSDecompressDXT3()
decompresses a dxt3 format texture
*/

static int DDSDecompressDXT3( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int						x, y, xBlocks, yBlocks;
	unsigned int			*pixel, alphaZero;
	ddsColorBlock_t			*block;
	ddsAlphaBlockExplicit_t	*alphaBlock;
	ddsColor_t				colors[ 4 ];


	/* setup */
	xBlocks = width / 4;
	yBlocks = height / 4;

	/* create zero alpha */
	colors[ 0 ].a = 0;
	colors[ 0 ].r = 0xFF;
	colors[ 0 ].g = 0xFF;
	colors[ 0 ].b = 0xFF;
	alphaZero = *((unsigned int*) &colors[ 0 ]);

	/* walk y */
	for( y = 0; y < yBlocks; y++ ) {
		/* 8 bytes per block, 1 block for alpha, 1 block for color */
		block = (ddsColorBlock_t*) ((uintptr_t) buffer + y * xBlocks * 16);

		/* walk x */
		for( x = 0; x < xBlocks; x++, block++ ) {
			/* get alpha block */
			alphaBlock = (ddsAlphaBlockExplicit_t*) block;

			/* get color block */
			block++;
			DDSGetColorBlockColors( block, colors );

			/* decode color block */
			pixel = (unsigned int*) (pixels + x * 16 + (y * 4) * width * 4);
			DDSDecodeColorBlock( pixel, block, width, (unsigned int*) colors );

			/* overwrite alpha bits with alpha block */
			DDSDecodeAlphaExplicit( pixel, alphaBlock, width, alphaZero );
		}
	}

	/* return ok */
	return 0;
}



/*
DDSDecompressDXT5()
decompresses a dxt5 format texture
*/

static int DDSDecompressDXT5( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int							x, y, xBlocks, yBlocks;
	unsigned int				*pixel, alphaZero;
	ddsColorBlock_t				*block;
	ddsAlphaBlock3BitLinear_t	*alphaBlock;
	ddsColor_t					colors[ 4 ];


	/* setup */
	xBlocks = width / 4;
	yBlocks = height / 4;

	/* create zero alpha */
	colors[ 0 ].a = 0;
	colors[ 0 ].r = 0xFF;
	colors[ 0 ].g = 0xFF;
	colors[ 0 ].b = 0xFF;
	alphaZero = *((unsigned int*) &colors[ 0 ]);

	/* walk y */
	for( y = 0; y < yBlocks; y++ ) {
		/* 8 bytes per block, 1 block for alpha, 1 block for color */
		block = (ddsColorBlock_t*) ((uintptr_t) buffer + y * xBlocks * 16);

		/* walk x */
		for( x = 0; x < xBlocks; x++, block++ ) {
			/* get alpha block */
			alphaBlock = (ddsAlphaBlock3BitLinear_t*) block;

			/* get color block */
			block++;
			DDSGetColorBlockColors( block, colors );

			/* decode color block */
			pixel = (unsigned int*) (pixels + x * 16 + (y * 4) * width * 4);
			DDSDecodeColorBlock( pixel, block, width, (unsigned int*) colors );

			/* overwrite alpha bits with alpha block */
			DDSDecodeAlpha3BitLinear( pixel, alphaBlock, width, alphaZero );
		}
	}

	/* return ok */
	return 0;
}



/*
DDSDecompressDXT2()
decompresses a dxt2 format texture (fixme: un-premultiply alpha)
*/

static int DDSDecompressDXT2( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int		r;


	/* decompress dxt3 first */
	r = DDSDecompressDXT3( buffer, width, height, pixels );

	/* return to sender */
	return r;
}



/*
DDSDecompressDXT4()
decompresses a dxt4 format texture (fixme: un-premultiply alpha)
*/

static int DDSDecompressDXT4( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int		r;


	/* decompress dxt5 first */
	r = DDSDecompressDXT5( buffer, width, height, pixels );

	/* return to sender */
	return r;
}



/*
DDSDecompressARGB8888()
decompresses an argb 8888 format texture
*/

static int DDSDecompressARGB8888( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int							x, y;
	const unsigned char		*in;
	unsigned char *out;


	/* setup */
	in = buffer;
	out = pixels;

	/* walk y */
	for( y = 0; y < height; y++ ) {
		/* walk x */
		for( x = 0; x < width; x++ ) {
			*out++ = *in++;
			*out++ = *in++;
			*out++ = *in++;
			*out++ = *in++;
		}
	}

	/* return ok */
	return 0;
}

/** greebo: This decompresses a DXT5 RXGB texture as used by the Doom3 engine.
 */
static int DDSDecompressRXGB( const unsigned char* buffer, int width, int height, unsigned char *pixels ) {
	int							x, y, xBlocks, yBlocks;
	unsigned int				*pixel, redZero;
	ddsColorBlock_t				*block;
	ddsAlphaBlock3BitLinear_t	*alphaBlock;
	ddsColor_t					colors[ 4 ];

	/* setup */
	xBlocks = width / 4;
	yBlocks = height / 4;

	/* create zero red */
	colors[ 0 ].r = 0;
	colors[ 0 ].a = 0xFF;
	colors[ 0 ].g = 0xFF;
	colors[ 0 ].b = 0xFF;
	redZero = *((unsigned int*) &colors[ 0 ]);

	/* walk y */
	for( y = 0; y < yBlocks; y++ ) {
		/* 8 bytes (64 bit) per block, 1 block for alpha, 1 block for color */
		block = (ddsColorBlock_t*) ((uintptr_t) buffer + y * xBlocks * 16);

		/* walk x */
		for( x = 0; x < xBlocks; x++, block++ ) {
			/* get alpha block */
			alphaBlock = (ddsAlphaBlock3BitLinear_t*) block;

			/* get color block */
			block++;
			// Decode the colour values from the 5:6:5 word and derive the c2 and c3 colours
			// The result is stored in the <colors> variable
			DDSGetColorBlockColors( block, colors );

			/* decode color block */
			pixel = (unsigned int*) (pixels + x * 16 + (y * 4) * width * 4);
			DDSDecodeColorBlock( pixel, block, width, (unsigned int*) colors );

			/* overwrite alpha bits with alpha block */
			DDSDecodeRXGBAlpha3BitLinear( pixel, alphaBlock, width, redZero );
		}
	}

	/* return ok */
	return 0;
}

/*
DDSDecompress()
decompresses a dds texture into an rgba image buffer, returns 0 on success
*/

int DDSDecompress( const DDSHeader* header, const unsigned char* buffer, unsigned char *pixels ) {
	int			width, height, r;
	ddsPF_t		pf;


	/* get dds info */
	r = DDSGetInfo( header, &width, &height, &pf );
	if( r )
		return r;

	/* decompress */
	switch( pf ) {
		case DDS_PF_ARGB8888:
			/* fixme: support other [a]rgb formats */
			r = DDSDecompressARGB8888( buffer, width, height, pixels );
			break;

		case DDS_PF_DXT1:
			r = DDSDecompressDXT1( buffer, width, height, pixels );
			break;

		case DDS_PF_DXT2:
			r = DDSDecompressDXT2( buffer, width, height, pixels );
			break;

		case DDS_PF_DXT3:
			r = DDSDecompressDXT3( buffer, width, height, pixels );
			break;

		case DDS_PF_DXT4:
			r = DDSDecompressDXT4( buffer, width, height, pixels );
			break;

		case DDS_PF_DXT5:
			r = DDSDecompressDXT5( buffer, width, height, pixels );
			break;

		case DDS_PF_DXT5_RXGB:
			r = DDSDecompressRXGB( buffer, width, height, pixels );
			break;

		default:
		case DDS_PF_UNKNOWN:
			memset( pixels, 0xFF, width * height * 4 );
			r = -1;
			break;
	}

	/* return to sender */
	return r;
}