starkom-poseidon2 2.0.0

Starkom's implementation of the Poseidon2 algebraic hash.
Documentation 
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use ff::PrimeField;

/// Helper function to decode a binary file of packed 256-bit constants.
pub(crate) fn decode_constants<F: PrimeField, const N: usize>(bytes: &[u8]) -> [F; N] {
    let repr_size = ((F::NUM_BITS >> 3) + ((F::NUM_BITS & 7) != 0) as u32) as usize;
    assert_eq!(repr_size, 32);
    assert_eq!(bytes.len(), N * 32);
    let mut constants = [F::ZERO; N];
    for i in 0..N {
        let bytes: [u8; 32] = bytes[(i * 32)..((i + 1) * 32)].try_into().unwrap();
        let mut repr = F::Repr::default();
        repr.as_mut().copy_from_slice(&bytes);
        constants[i] = F::from_repr_vartime(repr).unwrap();
    }
    constants
}