/* * 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 0x2avoid 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 );}