Method _read_to_buffer

python/python3/tornado/iostream.py:853–897

Reads from the socket and appends the result to the read buffer. Returns the number of bytes read. Returns 0 if there is nothing to read (i.e. the read returns EWOULDBLOCK or equivalent). On error closes the socket and raises an exception.

(self)

            self._add_io_state(ioloop.IOLoop.READ)

    def _read_to_buffer(self) -> Optional[int]:
        """Reads from the socket and appends the result to the read buffer.

        Returns the number of bytes read.  Returns 0 if there is nothing
        to read (i.e. the read returns EWOULDBLOCK or equivalent).  On
        error closes the socket and raises an exception.
        """
        try:
            while True:
                try:
                    if self._user_read_buffer:
                        buf = memoryview(self._read_buffer)[
                            self._read_buffer_size :
                        ]  # type: Union[memoryview, bytearray]
                    else:
                        buf = bytearray(self.read_chunk_size)
                    bytes_read = self.read_from_fd(buf)
                except (socket.error, IOError, OSError) as e:
                    # ssl.SSLError is a subclass of socket.error
                    if self._is_connreset(e):
                        # Treat ECONNRESET as a connection close rather than
                        # an error to minimize log spam  (the exception will
                        # be available on self.error for apps that care).
                        self.close(exc_info=e)
                        return None
                    self.close(exc_info=e)
                    raise
                break
            if bytes_read is None:
                return 0
            elif bytes_read == 0:
                self.close()
                return 0
            if not self._user_read_buffer:
                self._read_buffer += memoryview(buf)[:bytes_read]
            self._read_buffer_size += bytes_read
        finally:
            # Break the reference to buf so we don't waste a chunk's worth of
            # memory in case an exception hangs on to our stack frame.
            del buf
        if self._read_buffer_size > self.max_buffer_size:
            gen_log.error("Reached maximum read buffer size")
            self.close()
            raise StreamBufferFullError("Reached maximum read buffer size")
        return bytes_read

    def _read_from_buffer(self, pos: int) -> None:
        """Attempts to complete the currently-pending read from the buffer.