Bitsets in C++ are a convenient way to store and manipulate sets of bits. However, sometimes we may need to extend the size of a bitset dynamically. One possible way to achieve this is by padding the extended bits with ones. In this blog post, we will explore how to do this in C++.

The problem

Let’s say we have a std::bitset with a fixed size and we want to dynamically increase its size by adding extra bits at the end, all initialized to one.

std::bitset<8> bits("10101010");

In the above example, we have a bitset of size 8 initialized with the value 10101010. Now, we want to extend this bitset to a size of 10 by adding two extra bits, which should be set to ones.

The solution

To extend the size of the bitset, we will create a new bitset with the desired size and copy the existing bits into it. Then, we will set the newly added bits to ones. Here’s the code to do this:

#include <bitset>
#include <iostream>

std::bitset<10> extendBitset(const std::bitset<8>& bits, int newSize) {
    std::bitset<10> extendedBits;
    
    for (int i = 0; i < bits.size(); ++i) {
        extendedBits[i] = bits[i];
    }
    
    for (int i = bits.size(); i < newSize; ++i) {
        extendedBits[i] = 1;
    }
    
    return extendedBits;
}

int main() {
    std::bitset<8> bits("10101010");
    int newSize = 10;
    
    std::bitset<10> extendedBits = extendBitset(bits, newSize);
    
    std::cout << "Original bitset: " << bits << std::endl;
    std::cout << "Extended bitset: " << extendedBits << std::endl;
    
    return 0;
}

In the above code, we define a function extendBitset that takes the original bitset and the new desired size as input. We create a new bitset of the desired size and copy the bits of the original bitset into it using a for loop. Then, we set the remaining bits (from the original size to the new size) to ones.

In the main function, we create a bitset bits of size 8 with the value 10101010. We specify the new desired size as 10. We call the extendBitset function with these parameters and store the result in extendedBits. Finally, we print out the original bitset and the extended bitset.

Conclusion

In this blog post, we have learned how to extend the size of a C++ bitset by padding it with ones. By creating a new bitset of the desired size and copying the original bits into it, we can easily achieve the desired result. This technique can be useful in situations where dynamic resizing of bitsets is required.

#programming #C++