524 lines
18 KiB
Python
524 lines
18 KiB
Python
# MIT License
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#
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# Copyright (c) 2016-2023 Mark Qvist / unsigned.io and contributors.
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in all
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# copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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from __future__ import annotations
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import collections
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import enum
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import threading
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import time
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from types import TracebackType
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from typing import Type, Callable, TypeVar, Generic, NewType
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import abc
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import contextlib
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import struct
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import RNS
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from abc import ABC, abstractmethod
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TPacket = TypeVar("TPacket")
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class SystemMessageTypes(enum.IntEnum):
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SMT_STREAM_DATA = 0xff00
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class ChannelOutletBase(ABC, Generic[TPacket]):
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"""
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An abstract transport layer interface used by Channel.
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DEPRECATED: This was created for testing; eventually
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Channel will use Link or a LinkBase interface
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directly.
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"""
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@abstractmethod
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def send(self, raw: bytes) -> TPacket:
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raise NotImplemented()
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@abstractmethod
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def resend(self, packet: TPacket) -> TPacket:
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raise NotImplemented()
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@property
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@abstractmethod
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def mdu(self):
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raise NotImplemented()
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@property
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@abstractmethod
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def rtt(self):
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raise NotImplemented()
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@property
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@abstractmethod
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def is_usable(self):
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raise NotImplemented()
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@abstractmethod
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def get_packet_state(self, packet: TPacket) -> MessageState:
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raise NotImplemented()
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@abstractmethod
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def timed_out(self):
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raise NotImplemented()
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@abstractmethod
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def __str__(self):
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raise NotImplemented()
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@abstractmethod
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def set_packet_timeout_callback(self, packet: TPacket, callback: Callable[[TPacket], None] | None,
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timeout: float | None = None):
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raise NotImplemented()
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@abstractmethod
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def set_packet_delivered_callback(self, packet: TPacket, callback: Callable[[TPacket], None] | None):
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raise NotImplemented()
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@abstractmethod
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def get_packet_id(self, packet: TPacket) -> any:
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raise NotImplemented()
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class CEType(enum.IntEnum):
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"""
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ChannelException type codes
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"""
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ME_NO_MSG_TYPE = 0
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ME_INVALID_MSG_TYPE = 1
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ME_NOT_REGISTERED = 2
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ME_LINK_NOT_READY = 3
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ME_ALREADY_SENT = 4
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ME_TOO_BIG = 5
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class ChannelException(Exception):
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"""
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An exception thrown by Channel, with a type code.
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"""
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def __init__(self, ce_type: CEType, *args):
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super().__init__(args)
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self.type = ce_type
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class MessageState(enum.IntEnum):
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"""
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Set of possible states for a Message
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"""
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MSGSTATE_NEW = 0
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MSGSTATE_SENT = 1
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MSGSTATE_DELIVERED = 2
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MSGSTATE_FAILED = 3
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class MessageBase(abc.ABC):
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"""
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Base type for any messages sent or received on a Channel.
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Subclasses must define the two abstract methods as well as
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the ``MSGTYPE`` class variable.
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"""
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# MSGTYPE must be unique within all classes sent over a
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# channel. Additionally, MSGTYPE > 0xf000 are reserved.
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MSGTYPE = None
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"""
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Defines a unique identifier for a message class.
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* Must be unique within all classes registered with a ``Channel``
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* Must be less than ``0xf000``. Values greater than or equal to ``0xf000`` are reserved.
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"""
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@abstractmethod
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def pack(self) -> bytes:
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"""
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Create and return the binary representation of the message
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:return: binary representation of message
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"""
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raise NotImplemented()
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@abstractmethod
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def unpack(self, raw: bytes):
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"""
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Populate message from binary representation
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:param raw: binary representation
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"""
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raise NotImplemented()
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MessageCallbackType = NewType("MessageCallbackType", Callable[[MessageBase], bool])
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class Envelope:
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"""
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Internal wrapper used to transport messages over a channel and
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track its state within the channel framework.
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"""
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def unpack(self, message_factories: dict[int, Type]) -> MessageBase:
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msgtype, self.sequence, length = struct.unpack(">HHH", self.raw[:6])
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raw = self.raw[6:]
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ctor = message_factories.get(msgtype, None)
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if ctor is None:
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raise ChannelException(CEType.ME_NOT_REGISTERED, f"Unable to find constructor for Channel MSGTYPE {hex(msgtype)}")
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message = ctor()
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message.unpack(raw)
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return message
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def pack(self) -> bytes:
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if self.message.__class__.MSGTYPE is None:
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raise ChannelException(CEType.ME_NO_MSG_TYPE, f"{self.message.__class__} lacks MSGTYPE")
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data = self.message.pack()
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self.raw = struct.pack(">HHH", self.message.MSGTYPE, self.sequence, len(data)) + data
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return self.raw
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def __init__(self, outlet: ChannelOutletBase, message: MessageBase = None, raw: bytes = None, sequence: int = None):
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self.ts = time.time()
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self.id = id(self)
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self.message = message
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self.raw = raw
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self.packet: TPacket = None
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self.sequence = sequence
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self.outlet = outlet
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self.tries = 0
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self.tracked = False
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class Channel(contextlib.AbstractContextManager):
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"""
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Provides reliable delivery of messages over
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a link.
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``Channel`` differs from ``Request`` and
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``Resource`` in some important ways:
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**Continuous**
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Messages can be sent or received as long as
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the ``Link`` is open.
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**Bi-directional**
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Messages can be sent in either direction on
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the ``Link``; neither end is the client or
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server.
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**Size-constrained**
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Messages must be encoded into a single packet.
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``Channel`` is similar to ``Packet``, except that it
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provides reliable delivery (automatic retries) as well
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as a structure for exchanging several types of
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messages over the ``Link``.
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``Channel`` is not instantiated directly, but rather
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obtained from a ``Link`` with ``get_channel()``.
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"""
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def __init__(self, outlet: ChannelOutletBase):
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"""
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@param outlet:
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"""
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self._outlet = outlet
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self._lock = threading.RLock()
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self._tx_ring: collections.deque[Envelope] = collections.deque()
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self._rx_ring: collections.deque[Envelope] = collections.deque()
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self._message_callbacks: [MessageCallbackType] = []
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self._next_sequence = 0
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self._message_factories: dict[int, Type[MessageBase]] = {}
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self._max_tries = 5
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def __enter__(self) -> Channel:
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return self
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def __exit__(self, __exc_type: Type[BaseException] | None, __exc_value: BaseException | None,
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__traceback: TracebackType | None) -> bool | None:
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self._shutdown()
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return False
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def register_message_type(self, message_class: Type[MessageBase]):
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"""
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Register a message class for reception over a ``Channel``.
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Message classes must extend ``MessageBase``.
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:param message_class: Class to register
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"""
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self._register_message_type(message_class, is_system_type=False)
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def _register_message_type(self, message_class: Type[MessageBase], *, is_system_type: bool = False):
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with self._lock:
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if not issubclass(message_class, MessageBase):
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raise ChannelException(CEType.ME_INVALID_MSG_TYPE,
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f"{message_class} is not a subclass of {MessageBase}.")
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if message_class.MSGTYPE is None:
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raise ChannelException(CEType.ME_INVALID_MSG_TYPE,
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f"{message_class} has invalid MSGTYPE class attribute.")
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if message_class.MSGTYPE >= 0xf000 and not is_system_type:
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raise ChannelException(CEType.ME_INVALID_MSG_TYPE,
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f"{message_class} has system-reserved message type.")
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try:
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message_class()
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except Exception as ex:
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raise ChannelException(CEType.ME_INVALID_MSG_TYPE,
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f"{message_class} raised an exception when constructed with no arguments: {ex}")
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self._message_factories[message_class.MSGTYPE] = message_class
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def add_message_handler(self, callback: MessageCallbackType):
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"""
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Add a handler for incoming messages. A handler
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has the following signature:
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``(message: MessageBase) -> bool``
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Handlers are processed in the order they are
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added. If any handler returns True, processing
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of the message stops; handlers after the
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returning handler will not be called.
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:param callback: Function to call
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"""
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with self._lock:
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if callback not in self._message_callbacks:
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self._message_callbacks.append(callback)
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def remove_message_handler(self, callback: MessageCallbackType):
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"""
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Remove a handler added with ``add_message_handler``.
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:param callback: handler to remove
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"""
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with self._lock:
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self._message_callbacks.remove(callback)
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def _shutdown(self):
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with self._lock:
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self._message_callbacks.clear()
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self._clear_rings()
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def _clear_rings(self):
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with self._lock:
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for envelope in self._tx_ring:
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if envelope.packet is not None:
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self._outlet.set_packet_timeout_callback(envelope.packet, None)
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self._outlet.set_packet_delivered_callback(envelope.packet, None)
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self._tx_ring.clear()
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self._rx_ring.clear()
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def _emplace_envelope(self, envelope: Envelope, ring: collections.deque[Envelope]) -> bool:
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with self._lock:
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i = 0
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for existing in ring:
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if existing.sequence > envelope.sequence \
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and not existing.sequence // 2 > envelope.sequence: # account for overflow
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ring.insert(i, envelope)
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return True
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if existing.sequence == envelope.sequence:
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RNS.log(f"Envelope: Emplacement of duplicate envelope sequence.", RNS.LOG_EXTREME)
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return False
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i += 1
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envelope.tracked = True
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ring.append(envelope)
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return True
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def _prune_rx_ring(self):
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with self._lock:
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# Implementation for fixed window = 1
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stale = list(sorted(self._rx_ring, key=lambda env: env.sequence, reverse=True))[1:]
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for env in stale:
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env.tracked = False
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self._rx_ring.remove(env)
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def _run_callbacks(self, message: MessageBase):
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with self._lock:
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cbs = self._message_callbacks.copy()
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for cb in cbs:
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try:
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if cb(message):
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return
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except Exception as ex:
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RNS.log(f"Channel: Error running message callback: {ex}", RNS.LOG_ERROR)
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def _receive(self, raw: bytes):
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try:
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envelope = Envelope(outlet=self._outlet, raw=raw)
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with self._lock:
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message = envelope.unpack(self._message_factories)
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is_new = self._emplace_envelope(envelope, self._rx_ring)
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self._prune_rx_ring()
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if not is_new:
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RNS.log("Channel: Duplicate message received", RNS.LOG_DEBUG)
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return
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RNS.log(f"Message received: {message}", RNS.LOG_DEBUG)
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threading.Thread(target=self._run_callbacks, name="Message Callback", args=[message], daemon=True).start()
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except Exception as ex:
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RNS.log(f"Channel: Error receiving data: {ex}")
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def is_ready_to_send(self) -> bool:
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"""
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Check if ``Channel`` is ready to send.
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:return: True if ready
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"""
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if not self._outlet.is_usable:
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RNS.log("Channel: Link is not usable.", RNS.LOG_EXTREME)
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return False
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with self._lock:
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for envelope in self._tx_ring:
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if envelope.outlet == self._outlet and (not envelope.packet
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or self._outlet.get_packet_state(envelope.packet) == MessageState.MSGSTATE_SENT):
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RNS.log("Channel: Link has a pending message.", RNS.LOG_EXTREME)
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return False
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return True
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def _packet_tx_op(self, packet: TPacket, op: Callable[[TPacket], bool]):
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with self._lock:
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envelope = next(filter(lambda e: self._outlet.get_packet_id(e.packet) == self._outlet.get_packet_id(packet),
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self._tx_ring), None)
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if envelope and op(envelope):
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envelope.tracked = False
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if envelope in self._tx_ring:
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self._tx_ring.remove(envelope)
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else:
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RNS.log("Channel: Envelope not found in TX ring", RNS.LOG_DEBUG)
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if not envelope:
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RNS.log("Channel: Spurious message received.", RNS.LOG_EXTREME)
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def _packet_delivered(self, packet: TPacket):
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self._packet_tx_op(packet, lambda env: True)
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def _packet_timeout(self, packet: TPacket):
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def retry_envelope(envelope: Envelope) -> bool:
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if envelope.tries >= self._max_tries:
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RNS.log("Channel: Retry count exceeded, tearing down Link.", RNS.LOG_ERROR)
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self._shutdown() # start on separate thread?
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self._outlet.timed_out()
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return True
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envelope.tries += 1
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self._outlet.resend(envelope.packet)
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return False
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self._packet_tx_op(packet, retry_envelope)
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def send(self, message: MessageBase) -> Envelope:
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"""
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Send a message. If a message send is attempted and
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``Channel`` is not ready, an exception is thrown.
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:param message: an instance of a ``MessageBase`` subclass
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"""
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envelope: Envelope | None = None
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with self._lock:
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if not self.is_ready_to_send():
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raise ChannelException(CEType.ME_LINK_NOT_READY, f"Link is not ready")
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envelope = Envelope(self._outlet, message=message, sequence=self._next_sequence)
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self._next_sequence = (self._next_sequence + 1) % 0x10000
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self._emplace_envelope(envelope, self._tx_ring)
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if envelope is None:
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raise BlockingIOError()
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envelope.pack()
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if len(envelope.raw) > self._outlet.mdu:
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raise ChannelException(CEType.ME_TOO_BIG, f"Packed message too big for packet: {len(envelope.raw)} > {self._outlet.mdu}")
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envelope.packet = self._outlet.send(envelope.raw)
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envelope.tries += 1
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self._outlet.set_packet_delivered_callback(envelope.packet, self._packet_delivered)
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self._outlet.set_packet_timeout_callback(envelope.packet, self._packet_timeout)
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return envelope
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@property
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def MDU(self):
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"""
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Maximum Data Unit: the number of bytes available
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for a message to consume in a single send. This
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value is adjusted from the ``Link`` MDU to accommodate
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message header information.
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:return: number of bytes available
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"""
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return self._outlet.mdu - 6 # sizeof(msgtype) + sizeof(length) + sizeof(sequence)
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class LinkChannelOutlet(ChannelOutletBase):
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"""
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An implementation of ChannelOutletBase for RNS.Link.
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Allows Channel to send packets over an RNS Link with
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Packets.
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:param link: RNS Link to wrap
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"""
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def __init__(self, link: RNS.Link):
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self.link = link
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def send(self, raw: bytes) -> RNS.Packet:
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packet = RNS.Packet(self.link, raw, context=RNS.Packet.CHANNEL)
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packet.send()
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return packet
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def resend(self, packet: RNS.Packet) -> RNS.Packet:
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if not packet.resend():
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RNS.log("Failed to resend packet", RNS.LOG_ERROR)
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return packet
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@property
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def mdu(self):
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return self.link.MDU
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@property
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def rtt(self):
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return self.link.rtt
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@property
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def is_usable(self):
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return True # had issues looking at Link.status
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def get_packet_state(self, packet: TPacket) -> MessageState:
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status = packet.receipt.get_status()
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if status == RNS.PacketReceipt.SENT:
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return MessageState.MSGSTATE_SENT
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if status == RNS.PacketReceipt.DELIVERED:
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return MessageState.MSGSTATE_DELIVERED
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if status == RNS.PacketReceipt.FAILED:
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return MessageState.MSGSTATE_FAILED
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else:
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raise Exception(f"Unexpected receipt state: {status}")
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def timed_out(self):
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self.link.teardown()
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def __str__(self):
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return f"{self.__class__.__name__}({self.link})"
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def set_packet_timeout_callback(self, packet: RNS.Packet, callback: Callable[[RNS.Packet], None] | None,
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timeout: float | None = None):
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if timeout:
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packet.receipt.set_timeout(timeout)
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def inner(receipt: RNS.PacketReceipt):
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callback(packet)
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if packet and packet.receipt:
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packet.receipt.set_timeout_callback(inner if callback else None)
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def set_packet_delivered_callback(self, packet: RNS.Packet, callback: Callable[[RNS.Packet], None] | None):
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def inner(receipt: RNS.PacketReceipt):
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callback(packet)
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if packet and packet.receipt:
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packet.receipt.set_delivery_callback(inner if callback else None)
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def get_packet_id(self, packet: RNS.Packet) -> any:
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return packet.get_hash()
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