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https://github.com/codex-storage/nim-poseidon2.git
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35 lines
1.4 KiB
Nim
35 lines
1.4 KiB
Nim
import ./types
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import constantine/math/arithmetic
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import constantine/math/io/io_bigints
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import constantine/math/config/curves
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func unmarshal*(_: type F, bytes: openArray[byte]): F =
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## Converts bytes into a field element. The byte array is interpreted as a
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## canonical little-endian big integer. The array should be of length 31 bytes
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## or less to ensure that it fits in a field of 254 bits. The remaining
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## 6 most-significant bits are set to 0.
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assert bytes.len <= 31
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var padded: array[32, byte]
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copyMem(addr padded[0], unsafeAddr bytes[0], bytes.len)
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let bigint = B.unmarshal(padded, littleEndian)
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return F.fromBig(bigint)
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func unmarshal*(_: type seq[F], bytes: openArray[byte]): seq[F] =
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## Converts bytes into field elements. The byte array is converted 31 bytes at
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## a time with the `F.unmarshal()` function.
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const chunkLen = 31
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var elements: seq[F]
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var chunkStart = 0
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while chunkStart < bytes.len:
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let chunkEnd = min(chunkStart + 31, bytes.len)
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let element = F.unmarshal(bytes.toOpenArray(chunkStart, chunkEnd - 1))
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elements.add(element)
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chunkStart += chunkLen
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return elements
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func marshal*(element: F): array[32, byte] =
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## Converts a field element into its canonical representation in little-endian
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## byte order. Uses at most 254 bits, the remaining 6 most-significant bits
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## are set to 0.
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assert marshal(result, element.toBig(), littleEndian)
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