54 lines
1.8 KiB
Python
54 lines
1.8 KiB
Python
"""Bounded fingerprints of received argument deltas, without retaining text."""
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import hashlib
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PREFIX_BYTES = 4096
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MAX_PREFIXES = 16
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MAX_TRACKED_TOOLS = 64
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class ArgumentFingerprint:
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def __init__(self):
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self.characters = 0
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self.bytes = 0
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self.deltas = 0
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self.encoding_valid = True
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self.digest = hashlib.sha256()
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self.prefixes: list[dict] = []
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def observe(self, arguments: str) -> None:
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self.characters += len(arguments)
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if not arguments:
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return
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self.deltas += 1
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if not self.encoding_valid:
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return
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try:
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encoded = arguments.encode("utf-8")
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except UnicodeEncodeError:
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# Diagnostics must not repair, reject or otherwise alter the stream.
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self.encoding_valid = False
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return
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offset = 0
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while offset < len(encoded) and len(self.prefixes) < MAX_PREFIXES:
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size = min(PREFIX_BYTES - self.bytes % PREFIX_BYTES, len(encoded) - offset)
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self.digest.update(encoded[offset : offset + size])
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self.bytes += size
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offset += size
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if self.bytes % PREFIX_BYTES == 0:
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self.prefixes.append({"bytes": self.bytes, "sha256": self.digest.hexdigest()})
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if offset < len(encoded):
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self.digest.update(encoded[offset:])
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self.bytes += len(encoded) - offset
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def snapshot(self) -> dict:
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return {
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"argument_chars": self.characters,
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"argument_bytes": self.bytes if self.encoding_valid else None,
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"argument_sha256": self.digest.hexdigest() if self.encoding_valid else None,
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"argument_deltas": self.deltas,
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"argument_prefixes": [dict(prefix) for prefix in self.prefixes],
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"argument_encoding_valid": self.encoding_valid,
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}
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