Implement basic vec tree hash cache
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7af6eecb44
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@ -8,15 +8,17 @@ const HASHSIZE: usize = 32;
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const MERKLE_HASH_CHUNCK: usize = 2 * BYTES_PER_CHUNK;
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pub trait CachedTreeHash {
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type Item: CachedTreeHash;
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fn build_cache_bytes(&self) -> Vec<u8>;
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/// Return the number of bytes when this element is encoded as raw SSZ _without_ length
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/// prefixes.
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fn num_bytes(&self) -> usize;
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fn max_num_leaves(&self) -> usize;
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fn cached_hash_tree_root(
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&self,
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other: &Self,
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other: &Self::Item,
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cache: &mut TreeHashCache,
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chunk: usize,
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) -> Option<usize>;
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@ -45,6 +47,18 @@ impl TreeHashCache {
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})
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}
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pub fn maybe_update_chunk(&mut self, chunk: usize, to: &[u8]) -> Option<()> {
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let start = chunk * BYTES_PER_CHUNK;
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let end = start + BYTES_PER_CHUNK;
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if !self.chunk_equals(chunk, to)? {
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self.cache.get_mut(start..end)?.copy_from_slice(to);
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self.chunk_modified[chunk] = true;
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}
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Some(())
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}
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pub fn modify_chunk(&mut self, chunk: usize, to: &[u8]) -> Option<()> {
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let start = chunk * BYTES_PER_CHUNK;
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let end = start + BYTES_PER_CHUNK;
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@ -56,6 +70,13 @@ impl TreeHashCache {
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Some(())
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}
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pub fn chunk_equals(&mut self, chunk: usize, other: &[u8]) -> Option<bool> {
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let start = chunk * BYTES_PER_CHUNK;
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let end = start + BYTES_PER_CHUNK;
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Some(self.cache.get(start..end)? == other)
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}
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pub fn changed(&self, chunk: usize) -> Option<bool> {
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self.chunk_modified.get(chunk).cloned()
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}
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@ -119,7 +140,7 @@ pub fn merkleize(values: Vec<u8>) -> Vec<u8> {
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}
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pub fn sanitise_bytes(mut bytes: Vec<u8>) -> Vec<u8> {
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let present_leaves = num_leaves(bytes.len());
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let present_leaves = num_unsanitized_leaves(bytes.len());
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let required_leaves = present_leaves.next_power_of_two();
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if (present_leaves != required_leaves) | last_leaf_needs_padding(bytes.len()) {
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@ -133,8 +154,15 @@ fn last_leaf_needs_padding(num_bytes: usize) -> bool {
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num_bytes % HASHSIZE != 0
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}
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fn num_leaves(num_bytes: usize) -> usize {
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num_bytes / HASHSIZE
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/// Rounds up
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fn num_unsanitized_leaves(num_bytes: usize) -> usize {
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(num_bytes + HASHSIZE - 1) / HASHSIZE
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}
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/// Rounds up
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fn num_sanitized_leaves(num_bytes: usize) -> usize {
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let leaves = (num_bytes + HASHSIZE - 1) / HASHSIZE;
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leaves.next_power_of_two()
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}
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fn num_bytes(num_leaves: usize) -> usize {
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@ -1,7 +1,9 @@
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use super::*;
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use crate::ssz_encode;
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use crate::{ssz_encode, Encodable};
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impl CachedTreeHash for u64 {
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type Item = Self;
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fn build_cache_bytes(&self) -> Vec<u8> {
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merkleize(ssz_encode(self))
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}
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@ -10,10 +12,6 @@ impl CachedTreeHash for u64 {
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8
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}
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fn max_num_leaves(&self) -> usize {
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1
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}
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fn cached_hash_tree_root(
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&self,
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other: &Self,
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@ -28,3 +26,65 @@ impl CachedTreeHash for u64 {
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Some(chunk + 1)
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}
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}
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impl<T> CachedTreeHash for Vec<T>
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where
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T: CachedTreeHash + Encodable,
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{
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type Item = Self;
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fn build_cache_bytes(&self) -> Vec<u8> {
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let num_packed_bytes = self.num_bytes();
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let num_leaves = num_sanitized_leaves(num_packed_bytes);
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let mut packed = Vec::with_capacity(num_leaves * HASHSIZE);
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for item in self {
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packed.append(&mut ssz_encode(item));
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}
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let packed = sanitise_bytes(packed);
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merkleize(packed)
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}
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fn num_bytes(&self) -> usize {
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self.iter().fold(0, |acc, item| acc + item.num_bytes())
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}
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fn cached_hash_tree_root(
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&self,
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other: &Self::Item,
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cache: &mut TreeHashCache,
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chunk: usize,
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) -> Option<usize> {
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let num_packed_bytes = self.num_bytes();
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let num_leaves = num_sanitized_leaves(num_packed_bytes);
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if num_leaves != num_sanitized_leaves(other.num_bytes()) {
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panic!("Need to handle a change in leaf count");
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}
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let mut packed = Vec::with_capacity(num_leaves * HASHSIZE);
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// TODO: try and avoid fully encoding the whole list
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for item in self {
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packed.append(&mut ssz_encode(item));
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}
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let packed = sanitise_bytes(packed);
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let num_nodes = num_nodes(num_leaves);
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let num_internal_nodes = num_nodes - num_leaves;
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{
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let mut chunk = chunk + num_internal_nodes;
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for new_chunk_bytes in packed.chunks(HASHSIZE) {
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cache.maybe_update_chunk(chunk, new_chunk_bytes)?;
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chunk += 1;
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}
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}
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Some(chunk + num_nodes)
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}
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}
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@ -1,5 +1,5 @@
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use super::*;
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use int_to_bytes::int_to_bytes32;
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use int_to_bytes::{int_to_bytes32, int_to_bytes8};
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#[derive(Clone)]
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pub struct Inner {
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@ -10,6 +10,8 @@ pub struct Inner {
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}
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impl CachedTreeHash for Inner {
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type Item = Self;
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fn build_cache_bytes(&self) -> Vec<u8> {
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let mut leaves = vec![];
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@ -21,15 +23,6 @@ impl CachedTreeHash for Inner {
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merkleize(leaves)
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}
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fn max_num_leaves(&self) -> usize {
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let mut leaves = 0;
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leaves += self.a.max_num_leaves();
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leaves += self.b.max_num_leaves();
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leaves += self.c.max_num_leaves();
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leaves += self.d.max_num_leaves();
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leaves
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}
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fn num_bytes(&self) -> usize {
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let mut bytes = 0;
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bytes += self.a.num_bytes();
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@ -45,7 +38,12 @@ impl CachedTreeHash for Inner {
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cache: &mut TreeHashCache,
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chunk: usize,
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) -> Option<usize> {
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let num_leaves = self.max_num_leaves();
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let mut num_leaves: usize = 0;
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num_leaves += num_unsanitized_leaves(self.a.num_bytes());
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num_leaves += num_unsanitized_leaves(self.b.num_bytes());
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num_leaves += num_unsanitized_leaves(self.c.num_bytes());
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num_leaves += num_unsanitized_leaves(self.d.num_bytes());
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let num_nodes = num_nodes(num_leaves);
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let num_internal_nodes = num_nodes - num_leaves;
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@ -78,6 +76,26 @@ fn join(many: Vec<Vec<u8>>) -> Vec<u8> {
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all
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}
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#[test]
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fn vec_of_u64() {
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let data = join(vec![
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int_to_bytes8(1),
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int_to_bytes8(2),
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int_to_bytes8(3),
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int_to_bytes8(4),
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int_to_bytes8(5),
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vec![0; 32 - 8], // padding
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]);
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let expected = merkleize(data);
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let my_vec = vec![1, 2, 3, 4, 5];
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let cache = my_vec.build_cache_bytes();
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assert_eq!(expected, cache);
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}
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#[test]
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fn merkleize_odd() {
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let data = join(vec![
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