strtok实现

char* my_strtok(char *s, const char *delim)
{
    static int flags[256];
    static char *orig_s = NULL;
    static const char *orig_delim = NULL;

    char *p;

    if (NULL == delim)
        return s ? s : orig_s;

    if (delim != orig_delim)
    {
        orig_delim = delim;
        memset(flags, 0, sizeof(flags));
        while (*delim)
            flags[(int)*delim++] = 1;
    }

    if (s)
        orig_s = s;

    if ((!orig_s) || (!*orig_s))
        return NULL;

    while (flags[(int)*orig_s])
        ++orig_s;
    p = orig_s;
    while (!flags[(int)*orig_s])
        ++orig_s;
    *orig_s++ = 0;

    return p;
}