Method write_headers

tornado/http1connection.py:386–471

Implements `.HTTPConnection.write_headers`.

(
        self,
        start_line: Union[httputil.RequestStartLine, httputil.ResponseStartLine],
        headers: httputil.HTTPHeaders,
        chunk: Optional[bytes] = None,
    )

        self._max_body_size = max_body_size

    def write_headers(
        self,
        start_line: Union[httputil.RequestStartLine, httputil.ResponseStartLine],
        headers: httputil.HTTPHeaders,
        chunk: Optional[bytes] = None,
    ) -> "Future[None]":
        """Implements `.HTTPConnection.write_headers`."""
        lines = []
        if self.is_client:
            assert isinstance(start_line, httputil.RequestStartLine)
            self._request_start_line = start_line
            lines.append(utf8(f"{start_line[0]} {start_line[1]} HTTP/1.1"))
            # Client requests with a non-empty body must have either a
            # Content-Length or a Transfer-Encoding. If Content-Length is not
            # present we'll add our Transfer-Encoding below.
            self._chunking_output = (
                start_line.method in ("POST", "PUT", "PATCH")
                and "Content-Length" not in headers
            )
        else:
            assert isinstance(start_line, httputil.ResponseStartLine)
            assert self._request_start_line is not None
            assert self._request_headers is not None
            self._response_start_line = start_line
            lines.append(utf8("HTTP/1.1 %d %s" % (start_line[1], start_line[2])))
            self._chunking_output = (
                # TODO: should this use
                # self._request_start_line.version or
                # start_line.version?
                self._request_start_line.version == "HTTP/1.1"
                # Omit payload header field for HEAD request.
                and self._request_start_line.method != "HEAD"
                # 1xx, 204 and 304 responses have no body (not even a zero-length
                # body), and so should not have either Content-Length or
                # Transfer-Encoding headers.
                and start_line.code not in (204, 304)
                and (start_line.code < 100 or start_line.code >= 200)
                # No need to chunk the output if a Content-Length is specified.
                and "Content-Length" not in headers
            )
            # If connection to a 1.1 client will be closed, inform client
            if (
                self._request_start_line.version == "HTTP/1.1"
                and self._disconnect_on_finish
            ):
                headers["Connection"] = "close"
            # If a 1.0 client asked for keep-alive, add the header.
            if (
                self._request_start_line.version == "HTTP/1.0"
                and self._request_headers.get("Connection", "").lower() == "keep-alive"
            ):
                headers["Connection"] = "Keep-Alive"
        if self._chunking_output:
            headers["Transfer-Encoding"] = "chunked"
        if not self.is_client and (
            self._request_start_line.method == "HEAD"
            or cast(httputil.ResponseStartLine, start_line).code == 304
        ):