"""
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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 typing import Optional, Tuple, Union
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from .frame_protocol import CloseReason, FrameDecoder, FrameProtocol, Opcode, RsvBits
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class Extension:
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name: str
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def enabled(self) -> bool:
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return False
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def offer(self) -> Union[bool, str]:
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pass
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def accept(self, offer: str) -> Optional[Union[bool, str]]:
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pass
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def finalize(self, offer: str) -> None:
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pass
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def frame_inbound_header(
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self,
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proto: Union[FrameDecoder, FrameProtocol],
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opcode: Opcode,
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rsv: RsvBits,
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payload_length: int,
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) -> Union[CloseReason, RsvBits]:
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return RsvBits(False, False, False)
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def frame_inbound_payload_data(
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self, proto: Union[FrameDecoder, FrameProtocol], data: bytes
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) -> Union[bytes, CloseReason]:
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return data
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def frame_inbound_complete(
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self, proto: Union[FrameDecoder, FrameProtocol], fin: bool
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) -> Union[bytes, CloseReason, None]:
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pass
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def frame_outbound(
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self,
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proto: Union[FrameDecoder, FrameProtocol],
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opcode: Opcode,
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rsv: RsvBits,
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data: bytes,
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fin: bool,
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) -> Tuple[RsvBits, bytes]:
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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: bool = False,
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client_max_window_bits: Optional[int] = None,
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server_no_context_takeover: bool = False,
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server_max_window_bits: Optional[int] = None,
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) -> None:
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self.client_no_context_takeover = client_no_context_takeover
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self.server_no_context_takeover = server_no_context_takeover
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self._client_max_window_bits = self.DEFAULT_CLIENT_MAX_WINDOW_BITS
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self._server_max_window_bits = self.DEFAULT_SERVER_MAX_WINDOW_BITS
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if client_max_window_bits is not None:
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self.client_max_window_bits = client_max_window_bits
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if server_max_window_bits is not None:
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self.server_max_window_bits = server_max_window_bits
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self._compressor: Optional[zlib._Compress] = None # noqa
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self._decompressor: Optional[zlib._Decompress] = None # noqa
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# This refers to the current frame
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self._inbound_is_compressible: Optional[bool] = 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: Optional[bool] = None
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self._enabled = False
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@property
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def client_max_window_bits(self) -> int:
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return self._client_max_window_bits
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@client_max_window_bits.setter
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def client_max_window_bits(self, value: int) -> None:
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if value < 9 or value > 15:
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raise ValueError("Window size must be between 9 and 15 inclusive")
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self._client_max_window_bits = value
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@property
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def server_max_window_bits(self) -> int:
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return self._server_max_window_bits
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@server_max_window_bits.setter
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def server_max_window_bits(self, value: int) -> None:
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if value < 9 or value > 15:
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raise ValueError("Window size must be between 9 and 15 inclusive")
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self._server_max_window_bits = value
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def _compressible_opcode(self, opcode: Opcode) -> bool:
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return opcode in (Opcode.TEXT, Opcode.BINARY, Opcode.CONTINUATION)
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def enabled(self) -> bool:
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return self._enabled
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def offer(self) -> Union[bool, str]:
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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: str) -> None:
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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: str) -> Tuple[Optional[int], Optional[int]]:
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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: str) -> Union[bool, None, str]:
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client_max_window_bits, server_max_window_bits = self._parse_params(offer)
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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 self.server_no_context_takeover:
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parameters.append("server_no_context_takeover")
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try:
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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 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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except ValueError:
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return None
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else:
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self._enabled = True
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return "; ".join(parameters)
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def frame_inbound_header(
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self,
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proto: Union[FrameDecoder, FrameProtocol],
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opcode: Opcode,
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rsv: RsvBits,
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payload_length: int,
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) -> Union[CloseReason, RsvBits]:
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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(
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self, proto: Union[FrameDecoder, FrameProtocol], data: bytes
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) -> Union[bytes, CloseReason]:
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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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assert self._decompressor is not None
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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(
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self, proto: Union[FrameDecoder, FrameProtocol], fin: bool
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) -> Union[bytes, CloseReason, None]:
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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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assert self._decompressor is not 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(
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self,
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proto: Union[FrameDecoder, FrameProtocol],
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opcode: Opcode,
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rsv: RsvBits,
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data: bytes,
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fin: bool,
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) -> Tuple[RsvBits, bytes]:
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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) -> str:
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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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return "<{} {}>".format(self.__class__.__name__, "; ".join(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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