"""Stream-related things.""" __all__ = ['StreamReader', 'StreamReaderProtocol', 'open_connection'] import collections from . import events from . import futures from . import protocols from . import tasks _DEFAULT_LIMIT = 2**16 @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 Transport. 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) transport, _ = yield from loop.create_connection( lambda: protocol, host, port, **kwds) return reader, transport # (reader, writer) class StreamReaderProtocol(protocols.Protocol): """Trivial 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): self.stream_reader = stream_reader def connection_made(self, transport): self.stream_reader.set_transport(transport) def connection_lost(self, exc): if exc is None: self.stream_reader.feed_eof() else: self.stream_reader.set_exception(exc) def data_received(self, data): self.stream_reader.feed_data(data) def eof_received(self): self.stream_reader.feed_eof() 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 = collections.deque() # Deque of bytes objects. self.byte_count = 0 # Bytes in buffer. 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 self.byte_count <= self.limit: self._paused = False self._transport.resume() 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): if not data: return self.buffer.append(data) self.byte_count += len(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 self.byte_count > 2*self.limit): try: self._transport.pause() 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 @tasks.coroutine def readline(self): if self._exception is not None: raise self._exception parts = [] parts_size = 0 not_enough = True while not_enough: while self.buffer and not_enough: data = self.buffer.popleft() ichar = data.find(b'\n') if ichar < 0: parts.append(data) parts_size += len(data) else: ichar += 1 head, tail = data[:ichar], data[ichar:] if tail: self.buffer.appendleft(tail) not_enough = False parts.append(head) parts_size += len(head) if parts_size > self.limit: self.byte_count -= parts_size self._maybe_resume_transport() raise ValueError('Line is too long') if self.eof: break if not_enough: assert self.waiter is None self.waiter = futures.Future(loop=self.loop) try: yield from self.waiter finally: self.waiter = None line = b''.join(parts) self.byte_count -= parts_size self._maybe_resume_transport() return 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: assert not self.waiter self.waiter = futures.Future(loop=self.loop) try: yield from self.waiter finally: self.waiter = None else: if not self.byte_count and not self.eof: assert not self.waiter self.waiter = futures.Future(loop=self.loop) try: yield from self.waiter finally: self.waiter = None if n < 0 or self.byte_count <= n: data = b''.join(self.buffer) self.buffer.clear() self.byte_count = 0 self._maybe_resume_transport() return data parts = [] parts_bytes = 0 while self.buffer and parts_bytes < n: data = self.buffer.popleft() data_bytes = len(data) if n < parts_bytes + data_bytes: data_bytes = n - parts_bytes data, rest = data[:data_bytes], data[data_bytes:] self.buffer.appendleft(rest) parts.append(data) parts_bytes += data_bytes self.byte_count -= data_bytes self._maybe_resume_transport() return b''.join(parts) @tasks.coroutine def readexactly(self, n): if self._exception is not None: raise self._exception if n <= 0: return b'' while self.byte_count < n and not self.eof: assert not self.waiter self.waiter = futures.Future(loop=self.loop) try: yield from self.waiter finally: self.waiter = None return (yield from self.read(n))