Fast integer to decimal conversion

Question

Given an (unsigned) integer, what is the generally fastest way to convert it into a string that contains its decimal representation?

The naïve way of doing that

Answer 1

The fastest approach on all but the simplest (e.g. 8-bit) microcontrollers is to use division, but reduce the number of divisions by generating several digits at once.

You will find very highly optimized code in answers to my question here. Using it in C should be a trivial edit to eliminate std::string -- there are no C++ features used in the actual conversion. The core is

while(val>=100)
{
   int pos = val % 100;
   val /= 100;
   *(short*)(c-1)=*(short*)(digit_pairs+2*pos); // or use memcpy
   c-=2;
}
while(val>0)
{
    *c--='0' + (val % 10);
    val /= 10;
}

I also provided an optimized division-free code for 8-bit micros, similar to the idea shown in the code in the question, but without loops. It ends up with a lot of code like this:

    if (val >= 80) {
        ch |= '8';
        val -= 80;
    }
    else if (val >= 40) {
        ch |= '4';
        val -= 40;
    }
    if (val >= 20) {
        ch |= '2';
        val -= 20;
    }
    if (val >= 10) {
        ch |= '1';
        val -= 10;
    }