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Diffstat (limited to 'Lib/asyncio/streams.py')
| -rw-r--r-- | Lib/asyncio/streams.py | 429 |
1 files changed, 429 insertions, 0 deletions
diff --git a/Lib/asyncio/streams.py b/Lib/asyncio/streams.py new file mode 100644 index 0000000..8fc2147 --- /dev/null +++ b/Lib/asyncio/streams.py @@ -0,0 +1,429 @@ +"""Stream-related things.""" + +__all__ = ['StreamReader', 'StreamWriter', 'StreamReaderProtocol', + 'open_connection', 'start_server', 'IncompleteReadError', + ] + +from . import events +from . import futures +from . import protocols +from . import tasks + + +_DEFAULT_LIMIT = 2**16 + + +class IncompleteReadError(EOFError): + """ + Incomplete read error. Attributes: + + - partial: read bytes string before the end of stream was reached + - expected: total number of expected bytes + """ + def __init__(self, partial, expected): + EOFError.__init__(self, "%s bytes read on a total of %s expected bytes" + % (len(partial), expected)) + self.partial = partial + self.expected = expected + + +@tasks.coroutine +def open_connection(host=None, port=None, *, + loop=None, limit=_DEFAULT_LIMIT, **kwds): + """A wrapper for create_connection() returning a (reader, writer) pair. + + The reader returned is a StreamReader instance; the writer is a + StreamWriter instance. + + The arguments are all the usual arguments to create_connection() + except protocol_factory; most common are positional host and port, + with various optional keyword arguments following. + + Additional optional keyword arguments are loop (to set the event loop + instance to use) and limit (to set the buffer limit passed to the + StreamReader). + + (If you want to customize the StreamReader and/or + StreamReaderProtocol classes, just copy the code -- there's + really nothing special here except some convenience.) + """ + if loop is None: + loop = events.get_event_loop() + reader = StreamReader(limit=limit, loop=loop) + protocol = StreamReaderProtocol(reader, loop=loop) + transport, _ = yield from loop.create_connection( + lambda: protocol, host, port, **kwds) + writer = StreamWriter(transport, protocol, reader, loop) + return reader, writer + + +@tasks.coroutine +def start_server(client_connected_cb, host=None, port=None, *, + loop=None, limit=_DEFAULT_LIMIT, **kwds): + """Start a socket server, call back for each client connected. + + The first parameter, `client_connected_cb`, takes two parameters: + client_reader, client_writer. client_reader is a StreamReader + object, while client_writer is a StreamWriter object. This + parameter can either be a plain callback function or a coroutine; + if it is a coroutine, it will be automatically converted into a + Task. + + The rest of the arguments are all the usual arguments to + loop.create_server() except protocol_factory; most common are + positional host and port, with various optional keyword arguments + following. The return value is the same as loop.create_server(). + + Additional optional keyword arguments are loop (to set the event loop + instance to use) and limit (to set the buffer limit passed to the + StreamReader). + + The return value is the same as loop.create_server(), i.e. a + Server object which can be used to stop the service. + """ + if loop is None: + loop = events.get_event_loop() + + def factory(): + reader = StreamReader(limit=limit, loop=loop) + protocol = StreamReaderProtocol(reader, client_connected_cb, + loop=loop) + return protocol + + return (yield from loop.create_server(factory, host, port, **kwds)) + + +class FlowControlMixin(protocols.Protocol): + """Reusable flow control logic for StreamWriter.drain(). + + This implements the protocol methods pause_writing(), + resume_reading() and connection_lost(). If the subclass overrides + these it must call the super methods. + + StreamWriter.drain() must check for error conditions and then call + _make_drain_waiter(), which will return either () or a Future + depending on the paused state. + """ + + def __init__(self, loop=None): + self._loop = loop # May be None; we may never need it. + self._paused = False + self._drain_waiter = None + + def pause_writing(self): + assert not self._paused + self._paused = True + + def resume_writing(self): + assert self._paused + self._paused = False + waiter = self._drain_waiter + if waiter is not None: + self._drain_waiter = None + if not waiter.done(): + waiter.set_result(None) + + def connection_lost(self, exc): + # Wake up the writer if currently paused. + if not self._paused: + return + waiter = self._drain_waiter + if waiter is None: + return + self._drain_waiter = None + if waiter.done(): + return + if exc is None: + waiter.set_result(None) + else: + waiter.set_exception(exc) + + def _make_drain_waiter(self): + if not self._paused: + return () + waiter = self._drain_waiter + assert waiter is None or waiter.cancelled() + waiter = futures.Future(loop=self._loop) + self._drain_waiter = waiter + return waiter + + +class StreamReaderProtocol(FlowControlMixin, protocols.Protocol): + """Helper class to adapt between Protocol and StreamReader. + + (This is a helper class instead of making StreamReader itself a + Protocol subclass, because the StreamReader has other potential + uses, and to prevent the user of the StreamReader to accidentally + call inappropriate methods of the protocol.) + """ + + def __init__(self, stream_reader, client_connected_cb=None, loop=None): + super().__init__(loop=loop) + self._stream_reader = stream_reader + self._stream_writer = None + self._client_connected_cb = client_connected_cb + + def connection_made(self, transport): + self._stream_reader.set_transport(transport) + if self._client_connected_cb is not None: + self._stream_writer = StreamWriter(transport, self, + self._stream_reader, + self._loop) + res = self._client_connected_cb(self._stream_reader, + self._stream_writer) + if tasks.iscoroutine(res): + tasks.Task(res, loop=self._loop) + + def connection_lost(self, exc): + if exc is None: + self._stream_reader.feed_eof() + else: + self._stream_reader.set_exception(exc) + super().connection_lost(exc) + + def data_received(self, data): + self._stream_reader.feed_data(data) + + def eof_received(self): + self._stream_reader.feed_eof() + + +class StreamWriter: + """Wraps a Transport. + + This exposes write(), writelines(), [can_]write_eof(), + get_extra_info() and close(). It adds drain() which returns an + optional Future on which you can wait for flow control. It also + adds a transport property which references the Transport + directly. + """ + + def __init__(self, transport, protocol, reader, loop): + self._transport = transport + self._protocol = protocol + self._reader = reader + self._loop = loop + + @property + def transport(self): + return self._transport + + def write(self, data): + self._transport.write(data) + + def writelines(self, data): + self._transport.writelines(data) + + def write_eof(self): + return self._transport.write_eof() + + def can_write_eof(self): + return self._transport.can_write_eof() + + def close(self): + return self._transport.close() + + def get_extra_info(self, name, default=None): + return self._transport.get_extra_info(name, default) + + def drain(self): + """This method has an unusual return value. + + The intended use is to write + + w.write(data) + yield from w.drain() + + When there's nothing to wait for, drain() returns (), and the + yield-from continues immediately. When the transport buffer + is full (the protocol is paused), drain() creates and returns + a Future and the yield-from will block until that Future is + completed, which will happen when the buffer is (partially) + drained and the protocol is resumed. + """ + if self._reader is not None and self._reader._exception is not None: + raise self._reader._exception + if self._transport._conn_lost: # Uses private variable. + raise ConnectionResetError('Connection lost') + return self._protocol._make_drain_waiter() + + +class StreamReader: + + def __init__(self, limit=_DEFAULT_LIMIT, loop=None): + # The line length limit is a security feature; + # it also doubles as half the buffer limit. + self._limit = limit + if loop is None: + loop = events.get_event_loop() + self._loop = loop + self._buffer = bytearray() + self._eof = False # Whether we're done. + self._waiter = None # A future. + self._exception = None + self._transport = None + self._paused = False + + def exception(self): + return self._exception + + def set_exception(self, exc): + self._exception = exc + + waiter = self._waiter + if waiter is not None: + self._waiter = None + if not waiter.cancelled(): + waiter.set_exception(exc) + + def set_transport(self, transport): + assert self._transport is None, 'Transport already set' + self._transport = transport + + def _maybe_resume_transport(self): + if self._paused and len(self._buffer) <= self._limit: + self._paused = False + self._transport.resume_reading() + + def feed_eof(self): + self._eof = True + waiter = self._waiter + if waiter is not None: + self._waiter = None + if not waiter.cancelled(): + waiter.set_result(True) + + def at_eof(self): + """Return True if the buffer is empty and 'feed_eof' was called.""" + return self._eof and not self._buffer + + def feed_data(self, data): + assert not self._eof, 'feed_data after feed_eof' + + if not data: + return + + self._buffer.extend(data) + + waiter = self._waiter + if waiter is not None: + self._waiter = None + if not waiter.cancelled(): + waiter.set_result(False) + + if (self._transport is not None and + not self._paused and + len(self._buffer) > 2*self._limit): + try: + self._transport.pause_reading() + except NotImplementedError: + # The transport can't be paused. + # We'll just have to buffer all data. + # Forget the transport so we don't keep trying. + self._transport = None + else: + self._paused = True + + def _create_waiter(self, func_name): + # StreamReader uses a future to link the protocol feed_data() method + # to a read coroutine. Running two read coroutines at the same time + # would have an unexpected behaviour. It would not possible to know + # which coroutine would get the next data. + if self._waiter is not None: + raise RuntimeError('%s() called while another coroutine is ' + 'already waiting for incoming data' % func_name) + return futures.Future(loop=self._loop) + + @tasks.coroutine + def readline(self): + if self._exception is not None: + raise self._exception + + line = bytearray() + not_enough = True + + while not_enough: + while self._buffer and not_enough: + ichar = self._buffer.find(b'\n') + if ichar < 0: + line.extend(self._buffer) + self._buffer.clear() + else: + ichar += 1 + line.extend(self._buffer[:ichar]) + del self._buffer[:ichar] + not_enough = False + + if len(line) > self._limit: + self._maybe_resume_transport() + raise ValueError('Line is too long') + + if self._eof: + break + + if not_enough: + self._waiter = self._create_waiter('readline') + try: + yield from self._waiter + finally: + self._waiter = None + + self._maybe_resume_transport() + return bytes(line) + + @tasks.coroutine + def read(self, n=-1): + if self._exception is not None: + raise self._exception + + if not n: + return b'' + + if n < 0: + while not self._eof: + self._waiter = self._create_waiter('read') + try: + yield from self._waiter + finally: + self._waiter = None + else: + if not self._buffer and not self._eof: + self._waiter = self._create_waiter('read') + try: + yield from self._waiter + finally: + self._waiter = None + + if n < 0 or len(self._buffer) <= n: + data = bytes(self._buffer) + self._buffer.clear() + else: + # n > 0 and len(self._buffer) > n + data = bytes(self._buffer[:n]) + del self._buffer[:n] + + self._maybe_resume_transport() + return data + + @tasks.coroutine + def readexactly(self, n): + if self._exception is not None: + raise self._exception + + # There used to be "optimized" code here. It created its own + # Future and waited until self._buffer had at least the n + # bytes, then called read(n). Unfortunately, this could pause + # the transport if the argument was larger than the pause + # limit (which is twice self._limit). So now we just read() + # into a local buffer. + + blocks = [] + while n > 0: + block = yield from self.read(n) + if not block: + partial = b''.join(blocks) + raise IncompleteReadError(partial, len(partial) + n) + blocks.append(block) + n -= len(block) + + return b''.join(blocks) |