A C implementation of stdlib's itoa function

itoa.c

//
//  itoa.c
//  itoa
//
//  Created by Jacob Relkin on 14/02/2021.
//

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

void jr_itoa(int i, char *buffer) {
    if (i == 0) {
        buffer[0] = '0';
        return;
    }

    int negative = (int)(i < 0);
    int x = abs(i);
    int digitCount = (int)floor(log(x) / log(10)) + 1;
    int index = 0;

    if (negative) {
        digitCount += 1;
        index += 1;
        buffer[0] = '-';
    }

    while (x > 0) {
        int digit = x % 10;
        int offset = (digitCount - 1 - index) + negative;

        buffer[offset] = digit + '0';
        index += 1;
        x /= 10;
    }

    buffer[index] = '\0';
}

int main(int argc, const char * argv[]) {
    char itoa[20];
    jr_itoa(-5, itoa);
    printf("%s\n", itoa);
    jr_itoa(450, itoa);
    printf("%s\n", itoa);
    jr_itoa(500, itoa);
    printf("%s\n", itoa);
    jr_itoa(-122222, itoa);
    printf("%s\n", itoa);
    return 0;
}