Investigate possibility to improve conversion of ethereum_types::U256 to u8 byte array about diamond_drops HOT 6 CLOSED

Ok, I made changes to use lifetimes but I think your changes are better. If there's only one parameter for the function then we shouldn't need lifetimes anymore. Here are the changes I was going to make for your reference, they were just straight from the documentation. https://github.com/Drops-of-Diamond/diamond_drops/compare/notary...ltfschoen:notary?expand=1

let mut sid: &mut [u8; 32] = &mut [0; 32]; 
u256_to_bytes32(&self.shard_id, &mut sid);

...

let mut p: &mut [u8; 32] = &mut [0; 32];
u256_to_bytes32(&self.period, &mut p);

...

fn u256_to_bytes32<'a>(u256: &'a ethereum_types::U256, dst: &'a mut [u8; 32]) -> &'a [u8; 32] {
    for i in 0..32 {
        dst[i] = u256.byte(i);
    }
    dst
}

...

let mut sid_bytes: &mut [u8; 32] = &mut [0; 32];
u256_to_bytes32(&sid, &mut sid_bytes);

...

let mut period_bytes: &mut [u8; 32] = &mut [0; 32];
u256_to_bytes32(&period, &mut period_bytes);

from diamond_drops.

One improvement that I think it needs is to return dst, and not actually take dst as an input parameter.

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Yeah, if I can figure out a way to do that with the Rust ownership and lifetime rules I'll change it.

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Yeh I'll create a PR

Reference: https://doc.rust-lang.org/book/second-edition/ch10-03-lifetime-syntax.html

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Ok I've just pushed an update to make this return the bytes array instead of requiring two inputs. Further improvements are welcome

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Looks good now. I'll close this for now.

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