character encoding - Convert from UTF-8 to unicode c++

Question

How do I convert ú within a c++ application where the application receives the character as UTF-8 encoding %C3%BA and store it as the unicode equivalent %FA. I just want to know how I would go about writing code to perform this encoding process

Answer 1

I just wrote some code to do this yesterday...

I'm not saying this is the "perfect" way to do this, but it appears to work for all testcases I've run through it (I wrote both directions for that purpose).

I'll leave it to you to translate "%NN" to an integer value.

#include <iostream>
#include <deque>

std::deque<int> unicode_to_utf8(int charcode)
{
    std::deque<int> d;
    if (charcode < 128)
    {
        d.push_back(charcode);
    }
    else
    {
        int first_bits = 6; 
        const int other_bits = 6;
        int first_val = 0xC0;
        int t = 0;
        while (charcode >= (1 << first_bits))
        {
            {
                t = 128 | (charcode & ((1 << other_bits)-1));
                charcode >>= other_bits;
                first_val |= 1 << (first_bits);
                first_bits--;
            }
            d.push_front(t);
        }
        t = first_val | charcode;
        d.push_front(t);
    }
    return d;
}


int utf8_to_unicode(std::deque<int> &coded)
{
    int charcode = 0;
    int t = coded.front();
    coded.pop_front();
    if (t < 128)
    {
        return t;
    }
    int high_bit_mask = (1 << 6) -1;
    int high_bit_shift = 0;
    int total_bits = 0;
    const int other_bits = 6;
    while((t & 0xC0) == 0xC0)
    {
        t <<= 1;
        t &= 0xff;
        total_bits += 6;
        high_bit_mask >>= 1; 
        high_bit_shift++;
        charcode <<= other_bits;
        charcode |= coded.front() & ((1 << other_bits)-1);
        coded.pop_front();
    } 
    charcode |= ((t >> high_bit_shift) & high_bit_mask) << total_bits;
    return charcode;
}

int main()
{
    int charcode; 

    for(;;)
    {
        std::cout << "Enter unicode value:" << std::endl;
        std::cin >> charcode; 
        auto x = unicode_to_utf8(charcode);
        for(auto c : x)
        {
            std::cout << "\x" << std::hex << c << " ";
        }
        std::cout << std::endl;
        int c = utf8_to_unicode(x);
        std::cout << "reversed:" << std::dec << c << std::hex << " in hex:" << c << std::endl;
    }
}