bpo-41279: Add StreamReaderBufferedProtocol by tontinton · Pull Request #21446 · python/cpython

This class gets better performance as BufferedProtocol uses read_into
into a buffer allocated before, instead of allocating a new buffer
each time read is called.

…pythonGH-21446)

The transport did not know how to use the proper api exported by
BufferedProtocol.

Added a new callback function that calls getbuffer() and
buffer_updated() instead of data_received() when the protocol given to
it is of type BufferedProtocol.

This is exactly the same way _SelectorSocketTransport handles a
BufferedProtocol.

…port (pythonGH-21446)

In the __init__ function if the protocol is of instance BufferedProtocol
instead of creating a buffer object, we call get_buffer on the protocol
to get its buffer.

In addition _loop_reading now calls _data_received as soon as there is
actual data instead of calling only after adding a recv_into event.

The reason for this change is because read_into could call it's callback
immediatly meaning overriding the data on the buffer before we actually
call _data_received on it, which fixes the potential issue of missed data.

…pythonGH-21446)

When calling set_protocol to change the protocol you can now change the
type of the protocol from BufferedProtocol to Protocol or vice versa.

start_tls needed this feature as it could read into a buffered protocol
at first and then change the protocol to SSLProto which is a regular
protocol.