Fastest INT to ASCII string conversion

fast_itoa.c

void uintToCStr(unsigned int val, char* c)
{
    static const char digitPairs[201] = {
        "00010203040506070809"
        "10111213141516171819"
        "20212223242526272829"
        "30313233343536373839"
        "40414243444546474849"
        "50515253545556575859"
        "60616263646566676869"
        "70717273747576777879"
        "80818283848586878889"
        "90919293949596979899"
    };

    int size;

    if(val >= 10000) {
        if(val >= 10000000) {
            if(val >= 1000000000)
                size = 10;
            else if(val >= 100000000)
                size = 9;
            else
                size = 8;
        } else {
            if(val >= 1000000)
                size = 7;
            else if(val >= 100000)
                size = 6;
            else
                size = 5;
        }
    } else {
        if(val >= 100) {
            if(val >= 1000)
                size = 4;
            else
                size = 3;
        } else {
            if(val >= 10)
                size = 2;
            else
                size = 1;
        }
    }

    c += size - 1;
    c[1] = 0;

    while(val >= 100) {
        int pos = (val % 100) * 2;
        val /= 100;
        c[-1] = digitPairs[pos];
        c[0] = digitPairs[pos + 1];
        c -= 2;
    }

    if (val < 10)
        c[0] = '0' + val;
    else {
        c[-1] = digitPairs[val * 2];
        c[0] = digitPairs[val * 2 + 1];
    }
}

void intToCStr(int n, char* c)
{
    int sign = -(n < 0);
    unsigned int val = (n ^ sign) - sign;

    if(sign)
        *c++ = '-';

    uintToCStr(val, c);
}