itoa microsoft 版本

附上itoa  microsoft 版本代码, 只能转换2-36进制 (36限制是因为 0-9 a-z 一共36个字符，大于36的话只能用乱码表示了)

TCHAR * __cdecl _itox (
        int val,
        TCHAR *buf,
        int radix
        )
{
        if (radix == 10 && val < 0)
            xtox((unsigned long)val, buf, radix, 1);  //如果是十进制负数另外处理显示
        else
            xtox((unsigned long)(unsigned int)val, buf, radix, 0);   //其余按内存实际存放转换
        return buf;
}

//带宏_SECURE_ITOA表示安全版本


#ifdef _SECURE_ITOA
static errno_t __stdcall xtox_s
        (
        unsigned long val,
        TCHAR *buf,
        size_t sizeInTChars,
        unsigned radix,
        int is_neg
        )
#else  /* _SECURE_ITOA */
static void __stdcall xtox
        (
        unsigned long val,
        TCHAR *buf,
        unsigned radix,
        int is_neg
        )
#endif  /* _SECURE_ITOA */
{
        TCHAR *p;                /* pointer to traverse string */
        TCHAR *firstdig;         /* pointer to first digit */
        TCHAR temp;              /* temp char */
        unsigned digval;         /* value of digit */
#ifdef _SECURE_ITOA
        size_t length;           /* current length of the string */

        /* validation section */
        _VALIDATE_RETURN_ERRCODE(buf != NULL, EINVAL);
        _VALIDATE_RETURN_ERRCODE(sizeInTChars > 0, EINVAL);
        _RESET_STRING(buf, sizeInTChars);
        _VALIDATE_RETURN_ERRCODE(sizeInTChars > (size_t)(is_neg ? 2 : 1), ERANGE);
        _VALIDATE_RETURN_ERRCODE(2 <= radix && radix <= 36, EINVAL);
        length = 0;

#endif  /* _SECURE_ITOA */
        p = buf;

        if (is_neg) {
            /* negative, so output '-' and negate */
            *p++ = _T('-');
#ifdef _SECURE_ITOA
            length++;
#endif  /* _SECURE_ITOA */
            val = (unsigned long)(-(long)val);
        }

        firstdig = p;           /* save pointer to first digit */

        do {
            digval = (unsigned) (val % radix);
            val /= radix;       /* get next digit */

            /* convert to ascii and store */
            if (digval > 9)
                *p++ = (TCHAR) (digval - 10 + _T('a'));  /* a letter */
            else
                *p++ = (TCHAR) (digval + _T('0'));       /* a digit */
#ifndef _SECURE_ITOA
        } while (val > 0);
#else  /* _SECURE_ITOA */
            length++;
        } while (val > 0 && length < sizeInTChars);

        /* Check for buffer overrun */
        if (length >= sizeInTChars)
        {
            buf[0] = '\0';
            _VALIDATE_RETURN_ERRCODE(length < sizeInTChars, ERANGE);
        }
#endif  /* _SECURE_ITOA */
        /* We now have the digit of the number in the buffer, but in reverse
           order.  Thus we reverse them now. */

        *p-- = _T('\0');            /* terminate string; p points to last digit */

        do {
            temp = *p;
            *p = *firstdig;
            *firstdig = temp;   /* swap *p and *firstdig */
            --p;
            ++firstdig;         /* advance to next two digits */
        } while (firstdig < p); /* repeat until halfway */
#ifdef _SECURE_ITOA
        return 0;
#endif  /* _SECURE_ITOA */
}