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[Altair] Clarity around BeaconState THC leaf count #2339

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Merged
merged 1 commit into from
May 10, 2021
Merged

[Altair] Clarity around BeaconState THC leaf count #2339

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11 changes: 8 additions & 3 deletions consensus/types/src/beacon_state/tree_hash_cache.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,13 @@ use std::cmp::Ordering;
use std::iter::ExactSizeIterator;
use tree_hash::{mix_in_length, MerkleHasher, TreeHash};

/// The number of fields on a beacon state.
const NUM_BEACON_STATE_HASHING_FIELDS: usize = 20;
/// The number of leaves (including padding) on the `BeaconState` Merkle tree.
///
/// ## Note
///
/// This constant is set with the assumption that there are `> 16` and `<= 32` fields on the
/// `BeaconState`. **Tree hashing will fail if this value is set incorrectly.**
const NUM_BEACON_STATE_HASH_TREE_ROOT_LEAVES: usize = 32;

/// The number of nodes in the Merkle tree of a validator record.
const NODES_PER_VALIDATOR: usize = 15;
Expand Down Expand Up @@ -202,7 +207,7 @@ impl<T: EthSpec> BeaconTreeHashCacheInner<T> {
}
}

let mut hasher = MerkleHasher::with_leaves(NUM_BEACON_STATE_HASHING_FIELDS);
let mut hasher = MerkleHasher::with_leaves(NUM_BEACON_STATE_HASH_TREE_ROOT_LEAVES);

hasher.write(state.genesis_time().tree_hash_root().as_bytes())?;
hasher.write(state.genesis_validators_root().tree_hash_root().as_bytes())?;
Expand Down