Question

How to swap two bits of a byte in C++

Answer 1

#include <iostream>

void showBits(const unsigned char ch) {
    for (int i = 1 << 8 - 1; i > 0; i = i / 2) {
        (ch & i) ? std::cout << "1" : std::cout << "0";
    }
}
 
int swap2Bits(unsigned char num, const unsigned char firstPos, const unsigned char secondPos) {
    unsigned int firstBit = (num >> firstPos) & 1;
    unsigned int secondBit = (num >> secondPos) & 1;
   
    unsigned int xorBit = (firstBit ^ secondBit);
 
    xorBit = (xorBit << firstPos) | (xorBit << secondPos);
 
    return num ^ xorBit;
}
    
int main()
{
    unsigned char ch = 29;
       
    showBits(ch);
   
    unsigned char result = swap2Bits(ch, 1, 2);
       
    std::cout << "\n";
       
    showBits(result);
}
  
 
 
/*
run:
    
00011101
00011011
             
*/

 

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