How to change ownership without clone()

help
1

Hi, I'm new to Rust so this might be a dumb question. The following code doesn't work because elgamal_key_bytes is 'moved' when it's passed into write() and therefore it cannot be used again in evaluate(). How can I fix this ownership issue without using expensive operations like clone()?

    let elgamal_key_bytes = vec![];
    elgamal_key.write(elgamal_key_bytes);
    
    let h_prev_bytes = vec![];
    let h_prev = <CRH::<ConstraintF<C>, MyPoseidonParams> as TwoToOneCRH>::evaluate(&poseidon_params, &elgamal_key_bytes, &[i_prev]).unwrap();
    h_prev.write(h_prev_bytes);

    let i: u8 = 10;
    let h_cur = <CRH::<ConstraintF<C>, MyPoseidonParams> as TwoToOneCRH>::evaluate(&poseidon_params, &elgamal_key_bytes, &[i]).unwrap();
2

I don't know the type of elgamal_key, which limits how useful I can be, but you might try

    let mut elgamal_key_bytes = vec![];
    elgamal_key.write(&mut elgamal_key_bytes);

This would be the conventional way to treat a vector like a writeable stream. Vec<u8> implements Write, and &mut W implements Write whenever W implements Write, so &mut Vec<u8> should be able to be written to.

If that doesn't work, show us the types and the actual error.

3

Oh that worked! Thank you!

4

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