clement
44 lines
1.2 KiB
Python
44 lines
1.2 KiB
Python
"""AVLiveWire topology payload codec.
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Mirror of the Swift `TopologyPayload` (shared/AVLiveWire). Layout
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(big-endian): u16 jointCount; per joint [u8 nameLen + utf8 name];
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then per joint i16 parent (-1 = root).
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"""
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from __future__ import annotations
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import struct
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def encode_topology(names: list[str], parents: list[int]) -> bytes:
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out = bytearray()
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out += struct.pack(">H", len(names))
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for nm in names:
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b = nm.encode("utf-8")[:255]
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out.append(len(b))
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out += b
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for p in parents:
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out += struct.pack(">h", p)
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return bytes(out)
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def decode_topology(payload: bytes) -> tuple[list[str], list[int]] | None:
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"""Return (joint_names, parents) or None if malformed."""
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if len(payload) < 2:
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return None
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n = struct.unpack(">H", payload[:2])[0]
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o = 2
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names: list[str] = []
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for _ in range(n):
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if o >= len(payload):
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return None
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ln = payload[o]
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o += 1
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if o + ln > len(payload):
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return None
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names.append(payload[o:o + ln].decode("utf-8", "replace"))
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o += ln
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if o + n * 2 > len(payload):
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return None
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parents = list(struct.unpack(">" + "h" * n, payload[o:o + n * 2]))
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return names, parents
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