41 lines
1.4 KiB
Python
41 lines
1.4 KiB
Python
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from typing import Sequence, Optional
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from eth2spec.deneb.mainnet import BLSFieldElement
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from .common import BLS_MODULUS
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from .poly import Polynomial
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ExtendedData = Sequence[Optional[BLSFieldElement]]
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def encode(polynomial: Polynomial, factor: int, roots_of_unity: Sequence[int]) -> ExtendedData:
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"""
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Encode a polynomial extending to the given factor
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Parameters:
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polynomial: Polynomial to be encoded
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factor: Encoding factor
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roots_of_unity: Powers of 2 sequence
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Returns:
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list: Extended data set
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"""
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assert factor >= 2
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assert len(polynomial)*factor <= len(roots_of_unity)
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return [polynomial.eval(e) for e in roots_of_unity[:len(polynomial)*factor]]
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def decode(encoded: ExtendedData, roots_of_unity: Sequence[BLSFieldElement], original_len: int) -> Polynomial:
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"""
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Decode a polynomial from an extended data-set and the roots of unity, cap to original length
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Parameters:
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encoded: Extended data set
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roots_of_unity: Powers of 2 sequence
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original_len: Original length of the encoded polynomial
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Returns:
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Polynomial: original polynomial
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"""
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encoded, roots_of_unity = zip(*((point, root) for point, root in zip(encoded, roots_of_unity) if point is not None))
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coefs = Polynomial.interpolate(list(map(int, encoded)), list(map(int, roots_of_unity)))[:original_len]
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return Polynomial([int(c) for c in coefs], BLS_MODULUS)
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