How to swap nibbles in C?

Question

How to swap the nibble bit positions of a number?

For example: 534, convert it into binary, the rightmost 4 bits has to be interchanged with the leftmost 4 bits and

Answer 1

If swap is more like a 32 bit endiness conversion the below API must work:

uint32 decode_32le(uint8 *p)
{
return ( p[0] | (p[1] << 8) | (p[2] << 16) |(p[3]<<24));
}

*here it will swap the consecutive memory location/bytes which is allocated by malloc/calloc only, not an array.