转置位矩阵

/*
* http://www-graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith64Bits *
* 0010 0100 -- 24
* 0010 0001 -- 21
* 1111 0000 -- F0
* 0111 1111 -- 7F
* 1000 0000 -- 80
* 0011 0111 -- 37
* 1111 1111 -- FF
* 0001 1111 -- 1F
* |||| ||||
* 4CFC 898A
* 546E CEEE
*
*/

uint8_t t1[ 8 ] =
{ 0x24, 0x21, 0xf0, 0x7f, 0x80, 0x37, 0xff, 0x1f };

uint8_t t2[ 8 ];

union
{
uint32_t l[ 2 ];
uint8_t c[ 8 ];
} Tmp;

void foo( void )
{
long Ll, Lh;
uint8_t i;
for ( i = 0; i < 8; i++ )
Tmp.c = t1;

i = 8;
while ( i-- )
{
Ll = ( Tmp.l[ 0 ] & 0x01010101 ) * 0x01020408;  // 0x08040201
Lh = ( Tmp.l[ 1 ] & 0x01010101 ) * 0x01020408;  // Reserved

t2 = (uint8_t) ( ( ( Lh & 0x0F000000 ) >> 20 )
| ( ( Ll & 0x0F000000 ) >> 24 ) );

Tmp.l[ 0 ] >>= 1;
Tmp.l[ 1 ] >>= 1;
}
}

// 《高效程序的奥秘》翻译 Henry S. Warren. Jr. 的“Hacher's Delight"
// 0x57 0x17 0x97 0x13 0x37 0xf6 0x32 0x2a
void transpose8( uint8_t i[ 8 ], uint8_t o[ 8 ] )
{
uint32_t x, y, t;

x = ( i[ 0 ] << 24 ) | ( i[ 1 ] << 16 ) | ( i[ 2 ] << 8 ) | i[ 3 ];
y = ( i[ 4 ] << 24 ) | ( i[ 5 ] << 16 ) | ( i[ 6 ] << 8 ) | i[ 7 ];

t = ( x & 0xf0f0f0f0 ) | ( ( y >> 4 ) & 0x0f0f0f0f );
y = ( ( x << 4 ) & 0xf0f0f0f0 ) | ( y & 0x0f0f0f0f );
x = t;

t = ( x ^ ( x >> 14 ) ) & 0x0000cccc;
x = x ^ t ^ ( t << 14 );
t = ( y ^ ( y >> 14 ) ) & 0x0000cccc;
y = y ^ t ^ ( t << 14 );

t = ( x ^ ( x >> 7 ) ) & 0x00aa00aa;
x = x ^ t ^ ( t << 7 );
t = ( y ^ ( y >> 7 ) ) & 0x00aa00aa;
y = y ^ t ^ ( t << 7 );

o[ 7 ] = x >> 24;
o[ 6 ] = x >> 16;
o[ 5 ] = x >> 8;
o[ 4 ] = x;
o[ 3 ] = y >> 24;
o[ 2 ] = y >> 16;
o[ 1 ] = y >> 8;
o[ 0 ] = y;
}

int main( void )
{
int i;
uint8_t t1[ 8 ] =
{ 0x24, 0x21, 0xf0, 0x7f, 0x80, 0x37, 0xff, 0x1f };
uint8_t t2[ 8 ];

transpose8( t1, t2 );
for ( i = 0; i < 8; i++ )
printf( "0x%x ", t2 );
}