Appends len bytes of val to string. Because len is
provided, val may contain embedded nuls and need not
be nul-terminated.
Since this function does not stop at nul bytes, it is
the caller's responsibility to ensure that val has at
least len addressable bytes.
Appends len bytes of val to string. Because len is provided, val may contain embedded nuls and need not be nul-terminated. Since this function does not stop at nul bytes, it is the caller's responsibility to ensure that val has at least len addressable bytes.