Convert 0x1234 to 0x11223344

Question

How do I expand the hexadecimal number 0x1234 to 0x11223344 in a high-performance way?

unsigned int c = 0x1234, b;
b = (c & 0xff) << 4 | c & 0xf |          


        

Answer 1

Perhaps this could be more simpler & efficient.

unsigned int g = 0x1234;
unsigned int ans = 0;

ans = ( ( g & 0xf000 ) << 16) + ( (g & 0xf00 ) << 12)
    + ( ( g&0xf0 ) << 8) + ( ( g&0xf ) << 4);

ans  = ( ans | ans>>4 );

printf("%p -> %p\n", g, ans);