260 lines
8.8 KiB
Python
260 lines
8.8 KiB
Python
# -*- coding: utf-8 -*-
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"""
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wsproto/extensions
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~~~~~~~~~~~~~~~~~~
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WebSocket extensions.
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"""
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import zlib
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from .frame_protocol import CloseReason, Opcode, RsvBits
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class Extension(object):
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name = None
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def enabled(self):
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return False
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def offer(self):
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pass
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def accept(self, offer):
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pass
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def finalize(self, offer):
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pass
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def frame_inbound_header(self, proto, opcode, rsv, payload_length):
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return RsvBits(False, False, False)
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def frame_inbound_payload_data(self, proto, data):
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return data
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def frame_inbound_complete(self, proto, fin):
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pass
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def frame_outbound(self, proto, opcode, rsv, data, fin):
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return (rsv, data)
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class PerMessageDeflate(Extension):
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name = "permessage-deflate"
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DEFAULT_CLIENT_MAX_WINDOW_BITS = 15
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DEFAULT_SERVER_MAX_WINDOW_BITS = 15
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def __init__(
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self,
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client_no_context_takeover=False,
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client_max_window_bits=None,
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server_no_context_takeover=False,
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server_max_window_bits=None,
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):
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self.client_no_context_takeover = client_no_context_takeover
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if client_max_window_bits is None:
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client_max_window_bits = self.DEFAULT_CLIENT_MAX_WINDOW_BITS
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self.client_max_window_bits = client_max_window_bits
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self.server_no_context_takeover = server_no_context_takeover
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if server_max_window_bits is None:
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server_max_window_bits = self.DEFAULT_SERVER_MAX_WINDOW_BITS
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self.server_max_window_bits = server_max_window_bits
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self._compressor = None
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self._decompressor = None
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# This refers to the current frame
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self._inbound_is_compressible = None
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# This refers to the ongoing message (which might span multiple
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# frames). Only the first frame in a fragmented message is flagged for
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# compression, so this carries that bit forward.
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self._inbound_compressed = None
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self._enabled = False
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def _compressible_opcode(self, opcode):
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return opcode in (Opcode.TEXT, Opcode.BINARY, Opcode.CONTINUATION)
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def enabled(self):
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return self._enabled
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def offer(self):
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parameters = [
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"client_max_window_bits=%d" % self.client_max_window_bits,
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"server_max_window_bits=%d" % self.server_max_window_bits,
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]
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if self.client_no_context_takeover:
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parameters.append("client_no_context_takeover")
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if self.server_no_context_takeover:
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parameters.append("server_no_context_takeover")
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return "; ".join(parameters)
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def finalize(self, offer):
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bits = [b.strip() for b in offer.split(";")]
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for bit in bits[1:]:
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if bit.startswith("client_no_context_takeover"):
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self.client_no_context_takeover = True
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elif bit.startswith("server_no_context_takeover"):
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self.server_no_context_takeover = True
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elif bit.startswith("client_max_window_bits"):
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self.client_max_window_bits = int(bit.split("=", 1)[1].strip())
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elif bit.startswith("server_max_window_bits"):
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self.server_max_window_bits = int(bit.split("=", 1)[1].strip())
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self._enabled = True
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def _parse_params(self, params):
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client_max_window_bits = None
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server_max_window_bits = None
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bits = [b.strip() for b in params.split(";")]
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for bit in bits[1:]:
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if bit.startswith("client_no_context_takeover"):
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self.client_no_context_takeover = True
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elif bit.startswith("server_no_context_takeover"):
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self.server_no_context_takeover = True
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elif bit.startswith("client_max_window_bits"):
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if "=" in bit:
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client_max_window_bits = int(bit.split("=", 1)[1].strip())
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else:
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client_max_window_bits = self.client_max_window_bits
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elif bit.startswith("server_max_window_bits"):
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if "=" in bit:
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server_max_window_bits = int(bit.split("=", 1)[1].strip())
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else:
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server_max_window_bits = self.server_max_window_bits
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return client_max_window_bits, server_max_window_bits
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def accept(self, offer):
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client_max_window_bits, server_max_window_bits = self._parse_params(offer)
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self._enabled = True
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parameters = []
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if self.client_no_context_takeover:
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parameters.append("client_no_context_takeover")
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if client_max_window_bits is not None:
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parameters.append("client_max_window_bits=%d" % client_max_window_bits)
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self.client_max_window_bits = client_max_window_bits
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if self.server_no_context_takeover:
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parameters.append("server_no_context_takeover")
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if server_max_window_bits is not None:
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parameters.append("server_max_window_bits=%d" % server_max_window_bits)
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self.server_max_window_bits = server_max_window_bits
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return "; ".join(parameters)
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def frame_inbound_header(self, proto, opcode, rsv, payload_length):
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if rsv.rsv1 and opcode.iscontrol():
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return CloseReason.PROTOCOL_ERROR
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if rsv.rsv1 and opcode is Opcode.CONTINUATION:
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return CloseReason.PROTOCOL_ERROR
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self._inbound_is_compressible = self._compressible_opcode(opcode)
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if self._inbound_compressed is None:
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self._inbound_compressed = rsv.rsv1
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if self._inbound_compressed:
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assert self._inbound_is_compressible
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if proto.client:
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bits = self.server_max_window_bits
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else:
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bits = self.client_max_window_bits
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if self._decompressor is None:
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self._decompressor = zlib.decompressobj(-int(bits))
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return RsvBits(True, False, False)
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def frame_inbound_payload_data(self, proto, data):
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if not self._inbound_compressed or not self._inbound_is_compressible:
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return data
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try:
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return self._decompressor.decompress(bytes(data))
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except zlib.error:
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return CloseReason.INVALID_FRAME_PAYLOAD_DATA
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def frame_inbound_complete(self, proto, fin):
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if not fin:
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return None
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if not self._inbound_is_compressible:
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self._inbound_compressed = None
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return None
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if not self._inbound_compressed:
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self._inbound_compressed = None
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return None
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try:
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data = self._decompressor.decompress(b"\x00\x00\xff\xff")
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data += self._decompressor.flush()
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except zlib.error:
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return CloseReason.INVALID_FRAME_PAYLOAD_DATA
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if proto.client:
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no_context_takeover = self.server_no_context_takeover
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else:
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no_context_takeover = self.client_no_context_takeover
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if no_context_takeover:
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self._decompressor = None
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self._inbound_compressed = None
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return data
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def frame_outbound(self, proto, opcode, rsv, data, fin):
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if not self._compressible_opcode(opcode):
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return (rsv, data)
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if opcode is not Opcode.CONTINUATION:
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rsv = RsvBits(True, *rsv[1:])
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if self._compressor is None:
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assert opcode is not Opcode.CONTINUATION
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if proto.client:
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bits = self.client_max_window_bits
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else:
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bits = self.server_max_window_bits
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self._compressor = zlib.compressobj(
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zlib.Z_DEFAULT_COMPRESSION, zlib.DEFLATED, -int(bits)
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)
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data = self._compressor.compress(bytes(data))
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if fin:
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data += self._compressor.flush(zlib.Z_SYNC_FLUSH)
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data = data[:-4]
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if proto.client:
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no_context_takeover = self.client_no_context_takeover
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else:
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no_context_takeover = self.server_no_context_takeover
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if no_context_takeover:
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self._compressor = None
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return (rsv, data)
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def __repr__(self):
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descr = ["client_max_window_bits=%d" % self.client_max_window_bits]
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if self.client_no_context_takeover:
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descr.append("client_no_context_takeover")
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descr.append("server_max_window_bits=%d" % self.server_max_window_bits)
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if self.server_no_context_takeover:
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descr.append("server_no_context_takeover")
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descr = "; ".join(descr)
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return "<%s %s>" % (self.__class__.__name__, descr)
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#: SUPPORTED_EXTENSIONS maps all supported extension names to their class.
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#: This can be used to iterate all supported extensions of wsproto, instantiate
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#: new extensions based on their name, or check if a given extension is
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#: supported or not.
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SUPPORTED_EXTENSIONS = {PerMessageDeflate.name: PerMessageDeflate}
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