This function reads a complete newline-terminated line from the stream and returns it in allocated memory.
The trailing newline (and carriage return if any) are not included in the returned string.
| this |
a StreamBuffer object |
| cancellable |
optional Cancellable object, or null |
|
the line read, which the caller must free when done with, or null on eof. If an error occurs, throws will be set. |