A strnstr() function in C. I was going to use this: https://stackoverflow.com/a/25705264/25416550, but its "n" start with "needle". So I implemented my own version

strnstr.c

// This is free and unencumbered software released into the public domain.

/*
    Search "needle" in "haystack", limited to the first "len" chars of haystack
 */
char *strnstr(char haystack[const restrict static 1], char needle[const restrict static 1], int len)
{
    if (len <= 0)
        return NULL;

    char *temp_str;
    int needle_len = strlen(needle);
    while (true) {
        temp_str = strchr(haystack, needle[0]);
        if (temp_str == NULL)
            return NULL;

        if ((temp_str - haystack) + needle_len > len)
            return NULL;
        if (strncmp(temp_str, needle, needle_len) == 0)
            return temp_str;
    }
}