#include <string.h>

static char *global_sp = NULL;

char *strtok(char *str, const char *delim)
{
    return strtok_r(str, delim, &global_sp);
}

char *strtok_r(char *str, const char *delim, char **sp)
{
    int i   = 0;
    int len = strlen(delim);

    if (len == 0) {
        return NULL;
    }

    if (!str && !sp) {
        return NULL;
    }

    if (str) {
        *sp = str;
    }

    char *p_start = *sp;
    while (1) {
        for (i = 0; i < len; i++) {
            if (*p_start == delim[i]) {
                p_start++;
                break;
            }
        }

        if (i == len) {
            *sp = p_start;
            break;
        }
    }

    if (**sp == '\0') {
        *sp = NULL;
        return *sp;
    }

    while (**sp != '\0') {
        for (i = 0; i < len; i++) {
            if (**sp == delim[i]) {
                **sp = '\0';
                break;
            }
        }

        (*sp)++;
        if (i < len) {
            break;
        }
    }

    return p_start;
}