"""Stream-related things.""" __all__ = ['StreamReader', 'StreamWriter', 'StreamReaderProtocol', 'open_connection', 'start_server', 'IncompleteReadError', ] import socket if hasattr(socket, 'AF_UNIX'): __all__.extend(['open_unix_connection', 'start_unix_server']) from . import coroutines from . import events from . import futures from . import protocols from .coroutines import coroutine from .log import logger _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 @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 @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)) if hasattr(socket, 'AF_UNIX'): # UNIX Domain Sockets are supported on this platform @coroutine def open_unix_connection(path=None, *, loop=None, limit=_DEFAULT_LIMIT, **kwds): """Similar to `open_connection` but works with UNIX Domain Sockets.""" 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_unix_connection( lambda: protocol, path, **kwds) writer = StreamWriter(transport, protocol, reader, loop) return reader, writer @coroutine def start_unix_server(client_connected_cb, path=None, *, loop=None, limit=_DEFAULT_LIMIT, **kwds): """Similar to `start_server` but works with UNIX Domain Sockets.""" 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_unix_server(factory, path, **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 wait for _drain_helper() coroutine. """ def __init__(self, loop=None): if loop is None: self._loop = events.get_event_loop() else: self._loop = loop self._paused = False self._drain_waiter = None self._connection_lost = False def pause_writing(self): assert not self._paused self._paused = True if self._loop.get_debug(): logger.debug("%r pauses writing", self) def resume_writing(self): assert self._paused self._paused = False if self._loop.get_debug(): logger.debug("%r resumes writing", self) 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): self._connection_lost = True # 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) @coroutine def _drain_helper(self): if self._connection_lost: raise ConnectionResetError('Connection lost') 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 yield from 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 coroutines.iscoroutine(res): self._loop.create_task(res) 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 # drain() expects that the reader has a exception() method assert reader is None or isinstance(reader, StreamReader) self._reader = reader self._loop = loop def __repr__(self): info = [self.__class__.__name__, 'transport=%r' % self._transport] if self._reader is not None: info.append('reader=%r' % self._reader) return '<%s>' % ' '.join(info) @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) @coroutine def drain(self): """Flush the write buffer. The intended use is to write w.write(data) yield from w.drain() """ if self._reader is not None: exc = self._reader.exception() if exc is not None: raise exc yield from self._protocol._drain_helper() 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: self._loop = events.get_event_loop() else: self._loop = loop self._buffer = bytearray() self._eof = False # Whether we're done. self._waiter = None # A future used by _wait_for_data() 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 _wakeup_waiter(self): """Wakeup read() or readline() function waiting for data or EOF.""" waiter = self._waiter if waiter is not None: self._waiter = None if not waiter.cancelled(): waiter.set_result(None) 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 self._wakeup_waiter() 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) self._wakeup_waiter() 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 _wait_for_data(self, func_name): """Wait until feed_data() or feed_eof() is called.""" # 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) self._waiter = futures.Future(loop=self._loop) try: yield from self._waiter finally: self._waiter = None @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: yield from self._wait_for_data('readline') self._maybe_resume_transport() return bytes(line) @coroutine def read(self, n=-1): if self._exception is not None: raise self._exception if not n: return b'' if n < 0: # This used to just loop creating a new waiter hoping to # collect everything in self._buffer, but that would # deadlock if the subprocess sends more than self.limit # bytes. So just call self.read(self._limit) until EOF. blocks = [] while True: block = yield from self.read(self._limit) if not block: break blocks.append(block) return b''.join(blocks) else: if not self._buffer and not self._eof: yield from self._wait_for_data('read') 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 @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)