"""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 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)