56 lines
1.8 KiB
Python
56 lines
1.8 KiB
Python
#!/usr/bin/env python3
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"""Validate the bounded Phase 3A datagram header and fixture corpus."""
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from __future__ import annotations
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import binascii
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import pathlib
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ROOT = pathlib.Path(__file__).resolve().parents[1]
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HEADER_BYTES = 21
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MAX_FRAME_BYTES = 65536
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CHANNEL_LIMITS = {1: 1024, 2: 2048, 3: 65515}
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def classify(raw: bytes) -> str:
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if len(raw) < HEADER_BYTES:
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return "invalid:truncated"
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if raw[:2] != b"VD":
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return "invalid:magic"
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if raw[2] != 1:
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return "invalid:unsupported_version"
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if raw[3] not in CHANNEL_LIMITS:
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return "invalid:unknown_channel"
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if raw[4] != 0:
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return "invalid:flags"
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fragment_index, fragment_count = raw[17], raw[18]
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if fragment_count == 0 or fragment_index >= fragment_count:
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return "invalid:fragment"
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payload_length = int.from_bytes(raw[19:21], "big")
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if payload_length > CHANNEL_LIMITS[raw[3]]:
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return "invalid:payload_limit"
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if len(raw) != HEADER_BYTES + payload_length:
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return "invalid:length_mismatch"
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if len(raw) > MAX_FRAME_BYTES:
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return "invalid:frame_limit"
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return "valid"
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def main() -> None:
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lines = (ROOT / "fixtures/conformance/datagram-v1.tsv").read_text(encoding="utf-8").splitlines()
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assert lines[0] == "id\tversion\tkind\tinput\texpected"
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for line in lines[1:]:
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identifier, version, kind, input_value, expected = line.split("\t")
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assert kind == "datagram" and version == "1"
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encoded = input_value.removeprefix("hex=")
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try:
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actual = classify(binascii.unhexlify(encoded))
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except binascii.Error:
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actual = "invalid:hex"
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assert actual == expected, f"{identifier}: {actual} != {expected}"
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print("Datagram frame validation passed")
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if __name__ == "__main__":
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main()
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