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56 lines
1.6 KiB
Python
56 lines
1.6 KiB
Python
# inspired by core/src/trezor/crypto/rlp.py
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import typing as t
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from collections.abc import Sequence
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if t.TYPE_CHECKING:
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RLPItem = t.Union[t.Sequence["RLPItem"], bytes, int]
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def _byte_size(x: int) -> int:
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if x < 0:
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raise ValueError("only unsigned ints are supported")
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return (x.bit_length() + 7) // 8
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def _int_to_bytes(n: int) -> bytes:
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"""Convert to a correctly sized bytes object."""
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return n.to_bytes(_byte_size(n), "big")
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def _encode_with_length(value: bytes, header_byte: int) -> bytes:
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length = len(value)
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if length == 1 and value[0] <= 0x7F:
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return value
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elif length <= 55:
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return (header_byte + length).to_bytes(1, "big") + value
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else:
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encoded_length = _int_to_bytes(length)
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return (
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(header_byte + 55 + len(encoded_length)).to_bytes(1, "big")
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+ encoded_length
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+ value
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)
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def encode(value: "RLPItem") -> bytes:
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"""Encode lists or objects to bytes."""
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if isinstance(value, int):
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# ints are stored as byte strings
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value = _int_to_bytes(value)
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# sanity check: `str` is a Sequence so it would be incorrectly
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# picked up by the Sequence branch below
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assert not isinstance(value, str)
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# check for bytes type first, because bytes is a Sequence too
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if isinstance(value, bytes):
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header_byte = 0x80
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elif isinstance(value, Sequence):
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header_byte = 0xC0
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value = b"".join(encode(item) for item in value)
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else:
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raise TypeError("Unsupported type")
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return _encode_with_length(value, header_byte)
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