itoa.c

/**
	 * C++ version 0.4 char* style "itoa":
	 * Written by Lukás Chmela
	 * Released under GPLv3.

	 */
char *itoa(int value, char *result, int base) {
    // check that the base if valid
    if (base < 2 || base > 36) {
        *result = '\0';
        return result;
    }

    char *ptr = result, *ptr1 = result, tmp_char;
    int tmp_value;

    do {
        tmp_value = value;
        value /= base;
        *ptr++ = "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"[35 +
                                                                                           (tmp_value - value * base)];
    } while (value);

    // Apply negative sign
    if (tmp_value < 0) *ptr++ = '-';
    *ptr-- = '\0';
    while (ptr1 < ptr) {
        tmp_char = *ptr;
        *ptr-- = *ptr1;
        *ptr1++ = tmp_char;
    }
    return result;
}