Searches the string haystack for the first occurrence of the string needle, limiting the length of the search to haystack_len.
a string
the maximum length of haystack. Note that -1 is a valid length, if haystack is nul-terminated, meaning it will search through the whole string.
the string to search for
a pointer to the found occurrence, or NULL if not found.
Searches the string haystack for the first occurrence of the string needle, limiting the length of the search to haystack_len.