gistfile1.txt

static size_t debug_itoa(int value, char *buf, unsigned int radix, int sign) {
    int neg = 0;
    char *pbuf = buf;
    unsigned int i;
    unsigned int len;

    if (radix > 16) {
        *buf = '\0';
        return 0;
    }

    if (sign && value < 0) {
        neg = 1;
        value = -value;
    }

    do {
        int digit = value % radix;
        *(pbuf++) = (digit < 10 ? '0' + digit : 'A' + digit - 10);
        value /= radix;
    } while (value > 0);

    if (neg) {
        *(pbuf++) = '-';
    }

    *pbuf = '\0';

    len = pbuf - buf;

    for (i = 0; i < len / 2; i++) {
        char tmp = buf[i];
        buf[i] = buf[len - i - 1];
        buf[len - i - 1] = tmp;
    }

    return len;
}

static size_t debug_vprintf(const char *fmt, va_list args) {
    char buf[12]; // Big enough for "-214783647\0".
    size_t n = 0;

    while (*fmt){
        if (fmt[0] != '%' || fmt[1] == '%') {
            if (fmt[0] == '%') fmt++;

            size_t i = 0;
            while (fmt[i] && fmt[i] != '%') {
                putchar(fmt[i]);
                i++;
            }

            fmt += i;
            n += i;

            continue;
        }

        const char *start = fmt++;

        switch (*fmt) {
        case 'c': {
            fmt++;
            putchar((char)va_arg(args, int));
            n++;
            break;
        }
        case 's': {
            fmt++;
            const char *str = va_arg(args, const char *);
            size_t len = strlen(str);
            for (size_t i = 0; i < len; i++) putchar(str[i]);
            n += len;
            break;
        }
        case 'x': /* fall-thru */
        case 'i': /* fall-thru */
        case 'u': {
            fmt++;
            int val = va_arg(args, int);
            size_t len = debug_itoa(val,
                                    buf,
                                    *(fmt - 1) == 'x' ? 16 : 10,
                                    *(fmt - 1) == 'i');
            for (size_t i = 0; i < len; i++) putchar(buf[i]);
            n += len;
            break;
        }
        default: {
            fmt = start;
            size_t len = strlen(fmt);
            for (size_t i = 0; i < len; i++) putchar(fmt[i]);
            n += len;
            fmt += len;
            break;
        }
        }
    }

    return n;
}

__attribute__((format(printf, 1, 2)))
static size_t debug_printf(const char *fmt, ...) {
    va_list args;
    va_start(args, fmt);
    size_t n = debug_vprintf(fmt, args);
    va_end(args);
    return n;