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Rustify some code, removing a TODO #720

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8cce8a5
Rustify some code, removing a TODO
rkuris Sep 15, 2024
df3e698
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rkuris Sep 28, 2024
3dad44e
Merge branch 'main' into rkuris/fix-todo
rkuris Oct 7, 2024
0cf9517
Merge branch 'main' into rkuris/fix-todo
rkuris Oct 8, 2024
12a6eaf
Merge branch 'main' into rkuris/fix-todo
rkuris Oct 9, 2024
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24 changes: 14 additions & 10 deletions firewood/src/proof.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
use crate::merkle::MerkleError;
use sha2::{Digest, Sha256};
use storage::{
BranchNode, Hashable, NibblesIterator, PathIterItem, Preimage, TrieHash, ValueDigest,
BranchNode, Child, Hashable, NibblesIterator, PathIterItem, Preimage, TrieHash, ValueDigest,
};
use thiserror::Error;

Expand Down Expand Up @@ -71,15 +71,19 @@ impl Hashable for ProofNode {

impl From<PathIterItem> for ProofNode {
fn from(item: PathIterItem) -> Self {
let mut child_hashes: [Option<TrieHash>; BranchNode::MAX_CHILDREN] = Default::default();

if let Some(branch) = item.node.as_branch() {
// TODO danlaine: can we avoid indexing?
#[allow(clippy::indexing_slicing)]
for (i, hash) in branch.children_iter() {
child_hashes[i] = Some(hash.clone());
}
}
let child_hashes = if let Some(branch) = item.node.as_branch() {
let mut iter = branch.children.iter().map(|child| match child {
None => None,
Some(Child::Node(_)) => unreachable!("TODO make unreachable"),
Some(Child::AddressWithHash(_, hash)) => Some(hash.clone()),
});
std::array::from_fn(|_| {
iter.next()
.expect("there will always be the correct number of values")
})
} else {
Default::default()
};
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I would write the whole From implementation like this:

impl From<PathIterItem> for ProofNode {
    fn from(item: PathIterItem) -> Self {
        let PathIterItem {
            key_nibbles: key,
            node,
            ..
        } = item;

        let (value, child_hashes) = match node.as_ref() {
            storage::Node::Branch(branch_node) => {
                let value = branch_node.value.clone();
                let mut iter = branch_node.children.iter().map(|child| {
                    child.as_ref().map(|child| match child {
                        Child::AddressWithHash(_, hash) => *hash,
                        Child::Node(_) => {
                            unreachable!("cannot create `ProofNode` from in-memory `Node`")
                        }
                    })
                });

                (
                    value,
                    std::array::from_fn(move |_| iter.next().expect("always the same size")),
                )
            }
            storage::Node::Leaf(leaf_node) => (Some(leaf_node.value.clone()), Default::default()),
        };

        let value_digest = value.map(ValueDigest::Value);

        Self {
            key,
            value_digest,
            child_hashes,
        }
    }
}

You need to derive Copy for storage::TrieHash for this to work, but you should do that anyway. There are a bunch of places where you could remove a call to clone. I'm not sure that you'll get an actual speed up as I would hope that the compiler is smart enough not to perform any allocations on clone.

I've also removed the to_vec call on value since it's already a boxed slice.

You could further reduce allocations if you used bytes::Bytes for the value as I'm guessing it's rare that this changes.

Is it ever the case the children array contains both a mix of Child::Node and ChildAddressWithHash? If not, I would recommend wrapping the array in an enum:

enum Children {
    WithHashes([(LinearAddress, TrieHash); SIZE]),
    Mixed([Child; SIZE]),
}

Then you could just use the map function for the WithHashes case since the [(LinearAddress, TrieHash); SIZE] type is Copy.


Self {
key: item.key_nibbles,
Expand Down
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