Hi Rajeev, I follow similar approach. The basic logic is swap bits of a pair, then swap nibbles(2 bits) and then swap (4bits), 8bits and go on.
So for ex. 0110 1101 1100 0101 In first step, I swap bits of each pair. So this becomes, Input - 0110 1101 1100 0101 output- 1001 1110 1100 1010 In second step, I swap 2bits Input - 1001 1110 1100 1010 output-0110 1011 0011 1010 I swap 4 bits now Input - 0110 1011 0011 1010 output-1011 0110 1010 0011 Now I swap 8bits Input - 1011 0110 1010 0011 output-1010 0011 1011 0110 So, now we have the bits in reverse order. First step I do this way x = ((x | 0xAAAA) >> 2) | (x<<2) | 0xAAAA; Next step similarly x = ((x | 0xCCCC) >> 4) | (x<<4) | 0xCCCC; This is the logic. Your code does the reverse way. Regards, Mithun On Fri, Aug 5, 2011 at 6:04 PM, rShetty <[email protected]> wrote: > This is the code to reverse the bits in an unsigned integer . > Could anyone please explain the logic of this approach ? Thank You !! > > #define reverse(x) \ > (x=x>>16|(0x0000ffff&x)<<16, \ > x=(0xff00ff00&x)>>8|(0x00ff00ff&x)<<8, \ > x=(0xf0f0f0f0&x)>>4|(0x0f0f0f0f&x)<<4, \ > x=(0xcccccccc&x)>>2|(0x33333333&x)<<2, \ > x=(0xaaaaaaaa&x)>>1|(0x55555555&x)<<1) > > -- > You received this message because you are subscribed to the Google Groups > "Algorithm Geeks" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/algogeeks?hl=en. > > -- Mithun.B.S M:9916775380 -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
