
///	DDS file support, does decoding, _not_ direct uploading
///	(use SOIL for that ;-)

///	A bunch of DirectDraw Surface structures and flags
typedef struct {
    unsigned int    dwMagic;
    unsigned int    dwSize;
    unsigned int    dwFlags;
    unsigned int    dwHeight;
    unsigned int    dwWidth;
    unsigned int    dwPitchOrLinearSize;
    unsigned int    dwDepth;
    unsigned int    dwMipMapCount;
    unsigned int    dwReserved1[ 11 ];

    //  DDPIXELFORMAT
    struct {
      unsigned int    dwSize;
      unsigned int    dwFlags;
      unsigned int    dwFourCC;
      unsigned int    dwRGBBitCount;
      unsigned int    dwRBitMask;
      unsigned int    dwGBitMask;
      unsigned int    dwBBitMask;
      unsigned int    dwAlphaBitMask;
    }               sPixelFormat;

    //  DDCAPS2
    struct {
      unsigned int    dwCaps1;
      unsigned int    dwCaps2;
      unsigned int    dwDDSX;
      unsigned int    dwReserved;
    }               sCaps;
    unsigned int    dwReserved2;
} DDS_header ;

//	the following constants were copied directly off the MSDN website

//	The dwFlags member of the original DDSURFACEDESC2 structure
//	can be set to one or more of the following values.
#define DDSD_CAPS	0x00000001
#define DDSD_HEIGHT	0x00000002
#define DDSD_WIDTH	0x00000004
#define DDSD_PITCH	0x00000008
#define DDSD_PIXELFORMAT	0x00001000
#define DDSD_MIPMAPCOUNT	0x00020000
#define DDSD_LINEARSIZE	0x00080000
#define DDSD_DEPTH	0x00800000

//	DirectDraw Pixel Format
#define DDPF_ALPHAPIXELS	0x00000001
#define DDPF_FOURCC	0x00000004
#define DDPF_RGB	0x00000040

//	The dwCaps1 member of the DDSCAPS2 structure can be
//	set to one or more of the following values.
#define DDSCAPS_COMPLEX	0x00000008
#define DDSCAPS_TEXTURE	0x00001000
#define DDSCAPS_MIPMAP	0x00400000

//	The dwCaps2 member of the DDSCAPS2 structure can be
//	set to one or more of the following values.
#define DDSCAPS2_CUBEMAP	0x00000200
#define DDSCAPS2_CUBEMAP_POSITIVEX	0x00000400
#define DDSCAPS2_CUBEMAP_NEGATIVEX	0x00000800
#define DDSCAPS2_CUBEMAP_POSITIVEY	0x00001000
#define DDSCAPS2_CUBEMAP_NEGATIVEY	0x00002000
#define DDSCAPS2_CUBEMAP_POSITIVEZ	0x00004000
#define DDSCAPS2_CUBEMAP_NEGATIVEZ	0x00008000
#define DDSCAPS2_VOLUME	0x00200000

static int dds_test(void)
{
	//	check the magic number
	if (get8() != 'D') return 0;
	if (get8() != 'D') return 0;
	if (get8() != 'S') return 0;
	if (get8() != ' ') return 0;
	//	check header size
	if (get32le() != 124) return 0;
	return 1;
}
#ifndef STBI_NO_STDIO
int      stbi_dds_test_file        (FILE *f)
{
   int r,n = ftell(f);
   start_file(f);
   r = dds_test();
   fseek(f,n,SEEK_SET);
   return r;
}
#endif

int      stbi_dds_test_memory      (stbi_uc *buffer, int len)
{
   start_mem(buffer, len);
   return dds_test();
}

//	helper functions
int stbi_convert_bit_range( int c, int from_bits, int to_bits )
{
	int b = (1 << (from_bits - 1)) + c * ((1 << to_bits) - 1);
	return (b + (b >> from_bits)) >> from_bits;
}
void stbi_rgb_888_from_565( unsigned int c, int *r, int *g, int *b )
{
	*r = stbi_convert_bit_range( (c >> 11) & 31, 5, 8 );
	*g = stbi_convert_bit_range( (c >> 05) & 63, 6, 8 );
	*b = stbi_convert_bit_range( (c >> 00) & 31, 5, 8 );
}
void stbi_decode_DXT1_block(
			unsigned char uncompressed[16*4],
			unsigned char compressed[8] )
{
	int next_bit = 4*8;
	int i, r, g, b;
	int c0, c1;
	unsigned char decode_colors[4*4];
	//	find the 2 primary colors
	c0 = compressed[0] + (compressed[1] << 8);
	c1 = compressed[2] + (compressed[3] << 8);
	stbi_rgb_888_from_565( c0, &r, &g, &b );
	decode_colors[0] = r;
	decode_colors[1] = g;
	decode_colors[2] = b;
	decode_colors[3] = 255;
	stbi_rgb_888_from_565( c1, &r, &g, &b );
	decode_colors[4] = r;
	decode_colors[5] = g;
	decode_colors[6] = b;
	decode_colors[7] = 255;
	if( c0 > c1 )
	{
		//	no alpha, 2 interpolated colors
		decode_colors[8] = (2*decode_colors[0] + decode_colors[4]) / 3;
		decode_colors[9] = (2*decode_colors[1] + decode_colors[5]) / 3;
		decode_colors[10] = (2*decode_colors[2] + decode_colors[6]) / 3;
		decode_colors[11] = 255;
		decode_colors[12] = (decode_colors[0] + 2*decode_colors[4]) / 3;
		decode_colors[13] = (decode_colors[1] + 2*decode_colors[5]) / 3;
		decode_colors[14] = (decode_colors[2] + 2*decode_colors[6]) / 3;
		decode_colors[15] = 255;
	} else
	{
		//	1 interpolated color, alpha
		decode_colors[8] = (decode_colors[0] + decode_colors[4]) / 2;
		decode_colors[9] = (decode_colors[1] + decode_colors[5]) / 2;
		decode_colors[10] = (decode_colors[2] + decode_colors[6]) / 2;
		decode_colors[11] = 255;
		decode_colors[12] = 0;
		decode_colors[13] = 0;
		decode_colors[14] = 0;
		decode_colors[15] = 0;
	}
	//	decode the block
	for( i = 0; i < 16*4; i += 4 )
	{
		int idx = ((compressed[next_bit>>3] >> (next_bit & 7)) & 3) * 4;
		next_bit += 2;
		uncompressed[i+0] = decode_colors[idx+0];
		uncompressed[i+1] = decode_colors[idx+1];
		uncompressed[i+2] = decode_colors[idx+2];
		uncompressed[i+3] = decode_colors[idx+3];
	}
	//	done
}
void stbi_decode_DXT23_alpha_block(
			unsigned char uncompressed[16*4],
			unsigned char compressed[8] )
{
	int i, next_bit = 0;
	//	each alpha value gets 4 bits
	for( i = 3; i < 16*4; i += 4 )
	{
		uncompressed[i] = stbi_convert_bit_range(
				(compressed[next_bit>>3] >> (next_bit&7)) & 15,
				4, 8 );
		next_bit += 4;
	}
}
void stbi_decode_DXT45_alpha_block(
			unsigned char uncompressed[16*4],
			unsigned char compressed[8] )
{
	int i, next_bit = 8*2;
	unsigned char decode_alpha[8];
	//	each alpha value gets 3 bits, and the 1st 2 bytes are the range
	decode_alpha[0] = compressed[0];
	decode_alpha[1] = compressed[1];
	if( decode_alpha[0] > decode_alpha[1] )
	{
		//	6 step intermediate
		decode_alpha[2] = (6*decode_alpha[0] + 1*decode_alpha[1]) / 7;
		decode_alpha[3] = (5*decode_alpha[0] + 2*decode_alpha[1]) / 7;
		decode_alpha[4] = (4*decode_alpha[0] + 3*decode_alpha[1]) / 7;
		decode_alpha[5] = (3*decode_alpha[0] + 4*decode_alpha[1]) / 7;
		decode_alpha[6] = (2*decode_alpha[0] + 5*decode_alpha[1]) / 7;
		decode_alpha[7] = (1*decode_alpha[0] + 6*decode_alpha[1]) / 7;
	} else
	{
		//	4 step intermediate, pluss full and none
		decode_alpha[2] = (4*decode_alpha[0] + 1*decode_alpha[1]) / 5;
		decode_alpha[3] = (3*decode_alpha[0] + 2*decode_alpha[1]) / 5;
		decode_alpha[4] = (2*decode_alpha[0] + 3*decode_alpha[1]) / 5;
		decode_alpha[5] = (1*decode_alpha[0] + 4*decode_alpha[1]) / 5;
		decode_alpha[6] = 0;
		decode_alpha[7] = 255;
	}
	for( i = 3; i < 16*4; i += 4 )
	{
		int idx = 0, bit;
		bit = (compressed[next_bit>>3] >> (next_bit&7)) & 1;
		idx += bit << 0;
		++next_bit;
		bit = (compressed[next_bit>>3] >> (next_bit&7)) & 1;
		idx += bit << 1;
		++next_bit;
		bit = (compressed[next_bit>>3] >> (next_bit&7)) & 1;
		idx += bit << 2;
		++next_bit;
		uncompressed[i] = decode_alpha[idx & 7];
	}
	//	done
}
void stbi_decode_DXT_color_block(
			unsigned char uncompressed[16*4],
			unsigned char compressed[8] )
{
	int next_bit = 4*8;
	int i, r, g, b;
	int c0, c1;
	unsigned char decode_colors[4*3];
	//	find the 2 primary colors
	c0 = compressed[0] + (compressed[1] << 8);
	c1 = compressed[2] + (compressed[3] << 8);
	stbi_rgb_888_from_565( c0, &r, &g, &b );
	decode_colors[0] = r;
	decode_colors[1] = g;
	decode_colors[2] = b;
	stbi_rgb_888_from_565( c1, &r, &g, &b );
	decode_colors[3] = r;
	decode_colors[4] = g;
	decode_colors[5] = b;
	//	Like DXT1, but no choicees:
	//	no alpha, 2 interpolated colors
	decode_colors[6] = (2*decode_colors[0] + decode_colors[3]) / 3;
	decode_colors[7] = (2*decode_colors[1] + decode_colors[4]) / 3;
	decode_colors[8] = (2*decode_colors[2] + decode_colors[5]) / 3;
	decode_colors[9] = (decode_colors[0] + 2*decode_colors[3]) / 3;
	decode_colors[10] = (decode_colors[1] + 2*decode_colors[4]) / 3;
	decode_colors[11] = (decode_colors[2] + 2*decode_colors[5]) / 3;
	//	decode the block
	for( i = 0; i < 16*4; i += 4 )
	{
		int idx = ((compressed[next_bit>>3] >> (next_bit & 7)) & 3) * 3;
		next_bit += 2;
		uncompressed[i+0] = decode_colors[idx+0];
		uncompressed[i+1] = decode_colors[idx+1];
		uncompressed[i+2] = decode_colors[idx+2];
	}
	//	done
}
static stbi_uc *dds_load(int *x, int *y, int *comp, int req_comp)
{
	//	all variables go up front
	stbi_uc *dds_data = NULL;
	stbi_uc block[16*4];
	stbi_uc compressed[8];
	int flags, DXT_family;
	int has_alpha, has_mipmap;
	int is_compressed, cubemap_faces;
	int block_pitch, num_blocks;
	DDS_header header;
	int i, sz, cf;
	//	load the header
	if( sizeof( DDS_header ) != 128 )
	{
		return NULL;
	}
	getn( (stbi_uc*)(&header), 128 );
	//	and do some checking
	if( header.dwMagic != (('D' << 0) | ('D' << 8) | ('S' << 16) | (' ' << 24)) ) return NULL;
	if( header.dwSize != 124 ) return NULL;
	flags = DDSD_CAPS | DDSD_HEIGHT | DDSD_WIDTH | DDSD_PIXELFORMAT;
	if( (header.dwFlags & flags) != flags ) return NULL;
	/*	According to the MSDN spec, the dwFlags should contain
		DDSD_LINEARSIZE if it's compressed, or DDSD_PITCH if
		uncompressed.  Some DDS writers do not conform to the
		spec, so I need to make my reader more tolerant	*/
	if( header.sPixelFormat.dwSize != 32 ) return NULL;
	flags = DDPF_FOURCC | DDPF_RGB;
	if( (header.sPixelFormat.dwFlags & flags) == 0 ) return NULL;
	if( (header.sCaps.dwCaps1 & DDSCAPS_TEXTURE) == 0 ) return NULL;
	//	get the image data
	img_x = header.dwWidth;
	img_y = header.dwHeight;
	img_n = 4;
	is_compressed = (header.sPixelFormat.dwFlags & DDPF_FOURCC) / DDPF_FOURCC;
	has_alpha = (header.sPixelFormat.dwFlags & DDPF_ALPHAPIXELS) / DDPF_ALPHAPIXELS;
	has_mipmap = (header.sCaps.dwCaps1 & DDSCAPS_MIPMAP) && (header.dwMipMapCount > 1);
	cubemap_faces = (header.sCaps.dwCaps2 & DDSCAPS2_CUBEMAP) / DDSCAPS2_CUBEMAP;
	/*	I need cubemaps to have square faces	*/
	cubemap_faces &= (img_x == img_y);
	cubemap_faces *= 5;
	cubemap_faces += 1;
	block_pitch = (img_x+3) >> 2;
	num_blocks = block_pitch * ((img_y+3) >> 2);
	/*	let the user know what's going on	*/
	*x = img_x;
	*y = img_y;
	*comp = img_n;
	/*	is this uncompressed?	*/
	if( is_compressed )
	{
		/*	compressed	*/
		//	note: header.sPixelFormat.dwFourCC is something like (('D'<<0)|('X'<<8)|('T'<<16)|('1'<<24))
		DXT_family = 1 + (header.sPixelFormat.dwFourCC >> 24) - '1';
		if( (DXT_family < 1) || (DXT_family > 5) ) return NULL;
		/*	check the expected size...oops, nevermind...
			those non-compliant writers leave
			dwPitchOrLinearSize == 0	*/
		//	passed all the tests, get the RAM for decoding
		sz = (img_x)*(img_y)*4*cubemap_faces;
		dds_data = (unsigned char*)malloc( sz );
		/*	do this once for each face	*/
		for( cf = 0; cf < cubemap_faces; ++ cf )
		{
			//	now read and decode all the blocks
			for( i = 0; i < num_blocks; ++i )
			{
				//	where are we?
				int bx, by, bw=4, bh=4;
				int ref_x = 4 * (i % block_pitch);
				int ref_y = 4 * (i / block_pitch);
				//	get the next block's worth of compressed data, and decompress it
				if( DXT_family == 1 )
				{
					//	DXT1
					getn( compressed, 8 );
					stbi_decode_DXT1_block( block, compressed );
				} else if( DXT_family < 4 )
				{
					//	DXT2/3
					getn( compressed, 8 );
					stbi_decode_DXT23_alpha_block ( block, compressed );
					getn( compressed, 8 );
					stbi_decode_DXT_color_block ( block, compressed );
				} else
				{
					//	DXT4/5
					getn( compressed, 8 );
					stbi_decode_DXT45_alpha_block ( block, compressed );
					getn( compressed, 8 );
					stbi_decode_DXT_color_block ( block, compressed );
				}
				//	is this a partial block?
				if( ref_x + 4 > img_x )
				{
					bw = img_x - ref_x;
				}
				if( ref_y + 4 > img_y )
				{
					bh = img_y - ref_y;
				}
				//	now drop our decompressed data into the buffer
				for( by = 0; by < bh; ++by )
				{
					int idx = 4*((ref_y+by+cf*img_x)*img_x + ref_x);
					for( bx = 0; bx < bw*4; ++bx )
					{

						dds_data[idx+bx] = block[by*16+bx];
					}
				}
			}
			/*	done reading and decoding the main image...
				skip MIPmaps if present	*/
			if( has_mipmap )
			{
				int block_size = 16;
				if( DXT_family == 1 )
				{
					block_size = 8;
				}
				for( i = 1; i < header.dwMipMapCount; ++i )
				{
					int mx = img_x >> (i + 2);
					int my = img_y >> (i + 2);
					if( mx < 1 )
					{
						mx = 1;
					}
					if( my < 1 )
					{
						my = 1;
					}
					skip( mx*my*block_size );
				}
			}
		}/* per cubemap face */
	} else
	{
		/*	uncompressed	*/
		DXT_family = 0;
		img_n = 3;
		if( has_alpha )
		{
			img_n = 4;
		}
		*comp = img_n;
		sz = img_x*img_y*img_n*cubemap_faces;
		dds_data = (unsigned char*)malloc( sz );
		/*	do this once for each face	*/
		for( cf = 0; cf < cubemap_faces; ++ cf )
		{
			/*	read the main image for this face	*/
			getn( &dds_data[cf*img_x*img_y*img_n], img_x*img_y*img_n );
			/*	done reading and decoding the main image...
				skip MIPmaps if present	*/
			if( has_mipmap )
			{
				for( i = 1; i < header.dwMipMapCount; ++i )
				{
					int mx = img_x >> i;
					int my = img_y >> i;
					if( mx < 1 )
					{
						mx = 1;
					}
					if( my < 1 )
					{
						my = 1;
					}
					skip( mx*my*img_n );
				}
			}
		}
		/*	data was BGR, I need it RGB	*/
		for( i = 0; i < sz; i += img_n )
		{
			unsigned char temp = dds_data[i];
			dds_data[i] = dds_data[i+2];
			dds_data[i+2] = temp;
		}
	}
	/*	finished decompressing into RGBA,
		adjust the y size if we have a cubemap
		note: sz is already up to date	*/
	img_y *= cubemap_faces;
	*y = img_y;
	//	did the user want something else, or
	//	see if all the alpha values are 255 (i.e. no transparency)
	has_alpha = 0;
	if( img_n == 4)
	{
		for( i = 3; (i < sz) && (has_alpha == 0); i += 4 )
		{
			has_alpha |= (dds_data[i] < 255);
		}
	}
	if( (req_comp <= 4) && (req_comp >= 1) && (req_comp != img_n) )
	{
		//	user has some requirements, meet them
		dds_data = convert_format( dds_data, img_n, req_comp );
		*comp = req_comp;
	} else
	{
		//	user had no requirements, only drop to RGB is no alpha
		if( (has_alpha == 0) && (img_n == 4) )
		{
			dds_data = convert_format( dds_data, 4, 3 );
			*comp = 3;
		}
	}
	//	OK, done
	return dds_data;
}

#ifndef STBI_NO_STDIO
stbi_uc *stbi_dds_load             (char *filename,           int *x, int *y, int *comp, int req_comp)
{
   stbi_uc *data;
   FILE *f = fopen(filename, "rb");
   if (!f) return NULL;
   data = dds_load(x,y,comp,req_comp);
   fclose(f);
   return data;
}

stbi_uc *stbi_dds_load_from_file   (FILE *f,                  int *x, int *y, int *comp, int req_comp)
{
   start_file(f);
   return dds_load(x,y,comp,req_comp);
}
#endif

stbi_uc *stbi_dds_load_from_memory (stbi_uc *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
   start_mem(buffer, len);
   return dds_load(x,y,comp,req_comp);
}
