code: def test_buf_feed_data(self):
      class Proto(asyncio.BufferedProtocol):
          def __init__(self, bufsize, usemv):
              self.buf = bytearray(bufsize)
              self.mv = memoryview(self.buf)
              self.data = b""
              self.usemv = usemv
  
          def get_buffer(self, sizehint):
              if self.usemv:
                  return self.mv
              else:
                  return self.buf
  
          def buffer_updated(self, nsize):
              if self.usemv:
                  self.data += self.mv[:nsize]
              else:
                  self.data += self.buf[:nsize]
  
      for usemv in [False, True]:
          proto = Proto(1, usemv)
          protocols._feed_data_to_buffered_proto(proto, b"12345")
          self.assertEqual(proto.data, b"12345")
  
          proto = Proto(2, usemv)
          protocols._feed_data_to_buffered_proto(proto, b"12345")
          self.assertEqual(proto.data, b"12345")
  
          proto = Proto(2, usemv)
          protocols._feed_data_to_buffered_proto(proto, b"1234")
          self.assertEqual(proto.data, b"1234")
  
          proto = Proto(4, usemv)
          protocols._feed_data_to_buffered_proto(proto, b"1234")
          self.assertEqual(proto.data, b"1234")
  
          proto = Proto(100, usemv)
          protocols._feed_data_to_buffered_proto(proto, b"12345")
          self.assertEqual(proto.data, b"12345")
  
          proto = Proto(0, usemv)
          with self.assertRaisesRegex(RuntimeError, "empty buffer"):
              protocols._feed_data_to_buffered_proto(proto, b"12345")
  
imports: import logging
  import socket
  import unittest
  import weakref
  from test import support
  from test.support import socket_helper
  from unittest import mock
  import asyncio
  from asyncio import log
  from asyncio import protocols
  from asyncio import sslproto
  from test.test_asyncio import utils
  from test.test_asyncio import functional
label_desc: Use image node_id 2 for calling the BaseStartTLS obj's underlying member method code with example usage: obj.test_buf_feed_data() and returns: self, self