Create a string from an integer without using std::to_string or std::printf

integer-string-literal.cpp

#include <algorithm>
#include <cstring>
#include <string>
#include <limits>

// Literal for the IEC Mebi binary prefix
static
std::string operator""_Mi( unsigned long long value ) {
    struct Generator {
        Generator( unsigned long long value ) :
            remainder(value),
            length(0)
        {
        }

        char operator()() {
            if( remainder == 0 )
                return '\0';
            char result = '0' + remainder % 10;
            remainder = remainder / 10;
            length++;
            return result;
        }

        unsigned long long remainder;
        unsigned char length;
    };

    char result[std::numeric_limits<unsigned long long>::digits10+2];

    auto first = std::begin(result);
    auto last  = std::end(result);
    Generator gen{value * 1024 * 1024};
    std::generate(first, last, gen);

    last = std::next(first, gen.length);
    std::reverse(first, last);
    return result;
}

// Type your code here, or load an example.
std::string square() {
    return 64_Mi;
}