Swapping Of Nibles

[chinmaya]

how can we swap two nibles in a byte

[sicarie]

how can we swap two nibles in a byte

Do you have an algorithm for this? Have you run a search of Google? What did you find?

[weaknessforcats]

Use a circular bit shift.

[rakeshnayak]

Rakesh


Rakesh


Code removed per Posting Guidelines

[JosAH]

Use a circular bit shift.

But there isn't any such thing available in C, nor C++! ;-)

kind regards,

Jos

[mac11]

I vote for a lookup table with 256 entries (An array where each entry is the nibble swapped value of it's index) - this might speed up execution if that concerns you.

(I once used a similar table to perform bitwise byte reversal)

[weaknessforcats]

But there isn't any such thing available in C, nor C++! ;-)

True. You write a function to do this using bit operations:

void SwapNybble(unsigned short& arg)
{
    unsigned char LSB  =  arg & 0x00ff;
    unsigned char MSB = (arg & 0xff00) >> 8;
    arg = 0;
    arg = LSB;
    arg |= (arg << 8) | MSB;
}
int main()
{
     unsigned short data = 0xff00;
     bitset<16> b(data);
     cout << b.to_string() << endl;
     SwapNybble(data);
     b = data;
     cout << b.to_string() << endl;
}
 

[chinmaya]

Thanks a lot for this code
with regards
chinmaya

True. You write a function to do this using bit operations:

void SwapNybble(unsigned short& arg)
{
    unsigned char LSB  =  arg & 0x00ff;
    unsigned char MSB = (arg & 0xff00) >> 8;
    arg = 0;
    arg = LSB;
    arg |= (arg << 8) | MSB;
}
int main()
{
     unsigned short data = 0xff00;
     bitset<16> b(data);
     cout << b.to_string() << endl;
     SwapNybble(data);
     b = data;
     cout << b.to_string() << endl;
}
 

[weaknessforcats]

It occurred to me last night that I should have used an unsigned char rather than an unsigned short. A nybble is 4 bits and my example uses 8 bits.

Oops.