107 lines
3.9 KiB
Python
107 lines
3.9 KiB
Python
# Reticulum License
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#
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# Copyright (c) 2026 Mark Qvist
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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 Software shall not be used in any kind of system which includes amongst
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# its functions the ability to purposefully do harm to human beings.
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#
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# - The Software shall not be used, directly or indirectly, in the creation of
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# an artificial intelligence, machine learning or language model training
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# dataset, including but not limited to any use that contributes to the
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# training or development of such a model or algorithm.
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#
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# - The above copyright notice and this permission notice shall be included in
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# all 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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class HDLC():
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FLAG = 0x7E
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ESC = 0x7D
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ESC_MASK = 0x20
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FLAG_B = bytes([FLAG])
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ESC_B = bytes([ESC])
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ESCPD_FLAG = bytes([ESC, FLAG ^ ESC_MASK])
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ESCPD_ESC = bytes([ESC, ESC ^ ESC_MASK])
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@staticmethod
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def escape(data):
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data = data.replace(HDLC.ESC_B, HDLC.ESCPD_ESC)
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data = data.replace(HDLC.FLAG_B, HDLC.ESCPD_FLAG)
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return data
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@staticmethod
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def unescape(frame):
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frame = frame.replace(HDLC.ESCPD_FLAG, HDLC.FLAG_B)
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frame = frame.replace(HDLC.ESCPD_ESC, HDLC.ESC_B)
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return frame
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class ReceiveBuffer():
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def __init__(self, mtu, min_frame_len, max_frame_len=None, on_frame=None, on_invalid=None):
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self._mtu = mtu
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self._min_frame_len = min_frame_len
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self._max_frame_len = max_frame_len
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self._on_frame = on_frame
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self._on_invalid = on_invalid
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self._buf = bytearray()
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self._off = 0
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def mtu(self):
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return self._mtu() if callable(self._mtu) else self._mtu
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def max(self):
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m = self._max_frame_len
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return m() if callable(m) else m
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def feed(self, data):
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if not data: return
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self._buf.extend(data)
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buf = self._buf
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while True:
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frame_start = buf.find(HDLC.FLAG, self._off)
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if frame_start == -1:
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self.reset()
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return
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frame_end = buf.find(HDLC.FLAG, frame_start+1)
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if frame_end == -1:
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if len(buf)-self._off > self.mtu()*2: self.reset()
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return
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frame = HDLC.unescape(bytes(buf[frame_start+1:frame_end]))
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frame_len = len(frame)
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if frame_len > 0:
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max_len = self.max()
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if frame_len > self._min_frame_len and (max_len is None or frame_len <= max_len):
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if self._on_frame is not None: self._on_frame(frame)
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elif self._on_invalid is not None: self._on_invalid(frame_len)
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self._off = frame_end
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if self._off > 0 and self._off >= len(buf) // 2:
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del buf[:self._off]
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self._off = 0
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# Drops any partial frames from the buffer and
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# resets assembly offset
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def reset(self):
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self._buf.clear()
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self._off = 0
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# Buffered bytes currently unconsumed
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def __len__(self): return len(self._buf)-self._off
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