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# Code to read HTTP data
#
# Strategy: each writer takes an event + a write-some-bytes function, which is
# calls.
#
# WRITERS is a dict describing how to pick a reader. It maps states to either:
# - a writer
# - or, for body writers, a dict of framin-dependent writer factories
from typing import Any, Callable, Dict, List, Tuple, Type, Union
from ._events import Data, EndOfMessage, Event, InformationalResponse, Request, Response
from ._headers import Headers
from ._state import CLIENT, IDLE, SEND_BODY, SEND_RESPONSE, SERVER
from ._util import LocalProtocolError, Sentinel
__all__ = ["WRITERS"]
Writer = Callable[[bytes], Any]
def write_headers(headers: Headers, write: Writer) -> None:
# "Since the Host field-value is critical information for handling a
# request, a user agent SHOULD generate Host as the first header field
# following the request-line." - RFC 7230
raw_items = headers._full_items
for raw_name, name, value in raw_items:
if name == b"host":
write(b"%s: %s\r\n" % (raw_name, value))
for raw_name, name, value in raw_items:
if name != b"host":
write(b"%s: %s\r\n" % (raw_name, value))
write(b"\r\n")
def write_request(request: Request, write: Writer) -> None:
if request.http_version != b"1.1":
raise LocalProtocolError("I only send HTTP/1.1")
write(b"%s %s HTTP/1.1\r\n" % (request.method, request.target))
write_headers(request.headers, write)
# Shared between InformationalResponse and Response
def write_any_response(
response: Union[InformationalResponse, Response], write: Writer
) -> None:
if response.http_version != b"1.1":
raise LocalProtocolError("I only send HTTP/1.1")
status_bytes = str(response.status_code).encode("ascii")
# We don't bother sending ascii status messages like "OK"; they're
# optional and ignored by the protocol. (But the space after the numeric
# status code is mandatory.)
#
# XX FIXME: could at least make an effort to pull out the status message
# from stdlib's http.HTTPStatus table. Or maybe just steal their enums
# (either by import or copy/paste). We already accept them as status codes
# since they're of type IntEnum < int.
write(b"HTTP/1.1 %s %s\r\n" % (status_bytes, response.reason))
write_headers(response.headers, write)
class BodyWriter:
def __call__(self, event: Event, write: Writer) -> None:
if type(event) is Data:
self.send_data(event.data, write)
elif type(event) is EndOfMessage:
self.send_eom(event.headers, write)
else: # pragma: no cover
assert False
def send_data(self, data: bytes, write: Writer) -> None:
pass
def send_eom(self, headers: Headers, write: Writer) -> None:
pass
#
# These are all careful not to do anything to 'data' except call len(data) and
# write(data). This allows us to transparently pass-through funny objects,
# like placeholder objects referring to files on disk that will be sent via
# sendfile(2).
#
class ContentLengthWriter(BodyWriter):
def __init__(self, length: int) -> None:
self._length = length
def send_data(self, data: bytes, write: Writer) -> None:
self._length -= len(data)
if self._length < 0:
raise LocalProtocolError("Too much data for declared Content-Length")
write(data)
def send_eom(self, headers: Headers, write: Writer) -> None:
if self._length != 0:
raise LocalProtocolError("Too little data for declared Content-Length")
if headers:
raise LocalProtocolError("Content-Length and trailers don't mix")
class ChunkedWriter(BodyWriter):
def send_data(self, data: bytes, write: Writer) -> None:
# if we encoded 0-length data in the naive way, it would look like an
# end-of-message.
if not data:
return
write(b"%x\r\n" % len(data))
write(data)
write(b"\r\n")
def send_eom(self, headers: Headers, write: Writer) -> None:
write(b"0\r\n")
write_headers(headers, write)
class Http10Writer(BodyWriter):
def send_data(self, data: bytes, write: Writer) -> None:
write(data)
def send_eom(self, headers: Headers, write: Writer) -> None:
if headers:
raise LocalProtocolError("can't send trailers to HTTP/1.0 client")
# no need to close the socket ourselves, that will be taken care of by
# Connection: close machinery
WritersType = Dict[
Union[Tuple[Type[Sentinel], Type[Sentinel]], Type[Sentinel]],
Union[
Dict[str, Type[BodyWriter]],
Callable[[Union[InformationalResponse, Response], Writer], None],
Callable[[Request, Writer], None],
],
]
WRITERS: WritersType = {
(CLIENT, IDLE): write_request,
(SERVER, IDLE): write_any_response,
(SERVER, SEND_RESPONSE): write_any_response,
SEND_BODY: {
"chunked": ChunkedWriter,
"content-length": ContentLengthWriter,
"http/1.0": Http10Writer,
},
}
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