Obtains an iterator pointing to @byte_index within the given line.
@byte_index must be the start of a UTF-8 character. Note bytes, not
characters; UTF-8 may encode one character as multiple bytes.
Before the 3.20 version, it was not allowed to pass an invalid location.
Since the 3.20 version, if @line_number is greater than the number of lines
in the @buffer, the end iterator is returned. And if @byte_index is off the
end of the line, the iterator at the end of the line is returned.
Obtains an iterator pointing to @byte_index within the given line. @byte_index must be the start of a UTF-8 character. Note bytes, not characters; UTF-8 may encode one character as multiple bytes.
Before the 3.20 version, it was not allowed to pass an invalid location.
Since the 3.20 version, if @line_number is greater than the number of lines in the @buffer, the end iterator is returned. And if @byte_index is off the end of the line, the iterator at the end of the line is returned.