The same way you do in C:
short big = 0xdead;
short little = (((big & 0xff)<<8) | ((big & 0xff00)>>8));
You could also declare a vector of unsigned chars, memcpy the input value into it, reverse the bytes into another vector and memcpy the bytes out, but that'll take orders of magnitude longer than bit-twiddling, especially with 64-bit values.