RossComputerGuy/stardustos

/**
    * StardustOS libc - (C) 2019 Tristan Ross
    */
#include <string.h>

int itoa(char* buf, int base, int d) {
    char* p = buf;
    char* p1, *p2;
    unsigned long ud = d;
    int divisor = 10;
    int wrote = 0;

    /* If %d is specified and D is minus, put `-' in the head.    */
    if (base == 'd' && d < 0) {
        *p++ = '-';
        buf++;
        wrote++;
        ud = -d;
    } else if (base == 'x') divisor = 16;

    /* Divide UD by DIVISOR until UD == 0.    */
    do {
        int remainder = ud % divisor;
        *p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
    } while (ud /= divisor);

    /* Terminate BUF.    */
    *p = 0;

    /* Reverse BUF.    */
    p1 = buf;
    p2 = p - 1;
    while (p1 < p2) {
        char tmp = *p1;
        *p1 = *p2;
        *p2 = tmp;
        p1++;
        p2--;
        wrote++;
    }
    return wrote;
}