Creates a new reference counted string and copies the contents of str into it, up to len bytes.
Since this function does not stop at nul bytes, it is the caller's responsibility to ensure that str has at least len addressable bytes.
a string
length of str to use, or -1 if str is nul-terminated
the newly created reference counted string
Creates a new reference counted string and copies the contents of str into it, up to len bytes.
Since this function does not stop at nul bytes, it is the caller's responsibility to ensure that str has at least len addressable bytes.