Rename CachedTreeHash trait, add readme

eth2/utils/tree_hash/README.md

@@ -0,0 +1,76 @@
+# Tree hashing
+
+Provides both cached and non-cached tree hashing methods.
+
+## Standard Tree Hash
+
+```rust
+use tree_hash_derive::TreeHash;
+
+#[derive(TreeHash)]
+struct Foo {
+	a: u64,
+	b: Vec<u64>,
+}
+
+fn main() {
+	let foo = Foo {
+		a: 42,
+		b: vec![1, 2, 3]
+	}
+
+	println!("root: {}", foo.tree_hash_root());
+}
+```
+
+## Cached Tree Hash
+
+
+```rust
+use tree_hash_derive::{TreeHash, CachedTreeHash};
+
+#[derive(TreeHash, CachedTreeHash)]
+struct Foo {
+	a: u64,
+	b: Vec<u64>,
+}
+
+#[derive(TreeHash, CachedTreeHash)]
+struct Bar {
+	a: Vec<Foo>,
+	b: u64,
+}
+
+fn main() {
+	let bar = Bar {
+		a: vec![
+			Foo {
+				a: 42,
+				b: vec![1, 2, 3]
+			}
+		],
+		b: 42
+	};
+
+	let modified_bar = Bar {
+		a: vec![
+			Foo {
+				a: 100,
+				b: vec![1, 2, 3, 4, 5, 6]
+			}
+			Foo {
+				a: 42,
+				b: vec![]
+			}
+		],
+		b: 99
+	};
+
+
+    let mut hasher = CachedTreeHasher::new(&bar).unwrap();
+	hasher.update(&modified_bar);
+
+	// Assert that the cached tree hash matches a standard tree hash.
+	assert_eq!(hasher.tree_hash_root(), modified_bar.tree_hash_root());
+}
+```

eth2/utils/tree_hash/src/cached_tree_hash.rs

@@ -19,7 +19,7 @@ pub struct CachedTreeHasher {
 impl CachedTreeHasher {
     pub fn new<T>(item: &T) -> Result<Self, Error>
     where
-        T: CachedTreeHashSubTree<T>,
+        T: CachedTreeHash<T>,
     {
         Ok(Self {
             cache: TreeHashCache::new(item, 0)?,
@@ -28,7 +28,7 @@ impl CachedTreeHasher {
 
     pub fn update<T>(&mut self, item: &T) -> Result<(), Error>
     where
-        T: CachedTreeHashSubTree<T>,
+        T: CachedTreeHash<T>,
     {
         // Reset the per-hash counters.
         self.cache.chunk_index = 0;
@@ -66,15 +66,7 @@ pub enum Error {
     NotLeafNode(usize),
 }
 
-pub trait CachedTreeHash<T>: CachedTreeHashSubTree<T> + Sized {
+pub trait CachedTreeHash<Item>: TreeHash {
-    fn update_internal_tree_hash_cache(self, old: T) -> Result<(Self, Self), Error>;
-
-    fn cached_tree_hash_root(&self) -> Option<Vec<u8>>;
-
-    fn clone_without_tree_hash_cache(&self) -> Self;
-}
-
-pub trait CachedTreeHashSubTree<Item>: TreeHash {
     fn tree_hash_cache_overlay(
         &self,
         chunk_offset: usize,

eth2/utils/tree_hash/src/cached_tree_hash/btree_overlay.rs

@@ -11,7 +11,7 @@ pub struct BTreeOverlay {
 impl BTreeOverlay {
     pub fn new<T>(item: &T, initial_offset: usize, depth: usize) -> Result<Self, Error>
     where
-        T: CachedTreeHashSubTree<T>,
+        T: CachedTreeHash<T>,
     {
         item.tree_hash_cache_overlay(initial_offset, depth)
     }

eth2/utils/tree_hash/src/cached_tree_hash/impls.rs

@@ -2,7 +2,7 @@ use super::*;
 
 mod vec;
 
-impl CachedTreeHashSubTree<u64> for u64 {
+impl CachedTreeHash<u64> for u64 {
     fn new_tree_hash_cache(&self, _depth: usize) -> Result<TreeHashCache, Error> {
         Ok(TreeHashCache::from_bytes(
             merkleize(self.to_le_bytes().to_vec()),
@@ -35,7 +35,7 @@ impl CachedTreeHashSubTree<u64> for u64 {
     }
 }
 
-impl CachedTreeHashSubTree<usize> for usize {
+impl CachedTreeHash<usize> for usize {
     fn new_tree_hash_cache(&self, _depth: usize) -> Result<TreeHashCache, Error> {
         Ok(TreeHashCache::from_bytes(
             merkleize(self.to_le_bytes().to_vec()),

eth2/utils/tree_hash/src/cached_tree_hash/impls/vec.rs

@@ -1,8 +1,8 @@
 use super::*;
 
-impl<T> CachedTreeHashSubTree<Vec<T>> for Vec<T>
+impl<T> CachedTreeHash<Vec<T>> for Vec<T>
 where
-    T: CachedTreeHashSubTree<T> + TreeHash,
+    T: CachedTreeHash<T> + TreeHash,
 {
     fn new_tree_hash_cache(&self, depth: usize) -> Result<TreeHashCache, Error> {
         let mut overlay = self.tree_hash_cache_overlay(0, depth)?;
@@ -186,7 +186,7 @@ where
 
 fn get_packed_leaves<T>(vec: &Vec<T>) -> Result<Vec<u8>, Error>
 where
-    T: CachedTreeHashSubTree<T>,
+    T: CachedTreeHash<T>,
 {
     let num_packed_bytes = (BYTES_PER_CHUNK / T::tree_hash_packing_factor()) * vec.len();
     let num_leaves = num_sanitized_leaves(num_packed_bytes);

eth2/utils/tree_hash/src/cached_tree_hash/tree_hash_cache.rs

@@ -19,7 +19,7 @@ impl Into<Vec<u8>> for TreeHashCache {
 impl TreeHashCache {
     pub fn new<T>(item: &T, depth: usize) -> Result<Self, Error>
     where
-        T: CachedTreeHashSubTree<T>,
+        T: CachedTreeHash<T>,
     {
         item.new_tree_hash_cache(depth)
     }
@@ -30,7 +30,7 @@ impl TreeHashCache {
         depth: usize,
     ) -> Result<Self, Error>
     where
-        T: CachedTreeHashSubTree<T>,
+        T: CachedTreeHash<T>,
     {
         let overlay = BTreeOverlay::new(item, 0, depth)?;
 

eth2/utils/tree_hash/src/lib.rs

@@ -6,7 +6,7 @@ pub const BYTES_PER_CHUNK: usize = 32;
 pub const HASHSIZE: usize = 32;
 pub const MERKLE_HASH_CHUNCK: usize = 2 * BYTES_PER_CHUNK;
 
-pub use cached_tree_hash::{BTreeOverlay, CachedTreeHashSubTree, Error, TreeHashCache};
+pub use cached_tree_hash::{BTreeOverlay, CachedTreeHash, Error, TreeHashCache};
 pub use signed_root::SignedRoot;
 pub use standard_tree_hash::{merkle_root, TreeHash};
 

eth2/utils/tree_hash/tests/tests.rs

@@ -1,8 +1,8 @@
 use int_to_bytes::int_to_bytes32;
 use tree_hash::cached_tree_hash::*;
-use tree_hash_derive::{CachedTreeHashSubTree, TreeHash};
+use tree_hash_derive::{CachedTreeHash, TreeHash};
 
-#[derive(Clone, Debug, TreeHash, CachedTreeHashSubTree)]
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
 pub struct NestedStruct {
     pub a: u64,
     pub b: Inner,
@@ -10,7 +10,7 @@ pub struct NestedStruct {
 
 fn test_routine<T>(original: T, modified: Vec<T>)
 where
-    T: CachedTreeHashSubTree<T>,
+    T: CachedTreeHash<T>,
 {
     let mut hasher = CachedTreeHasher::new(&original).unwrap();
 
@@ -113,7 +113,7 @@ fn test_nested_list_of_u64() {
     test_routine(original, modified);
 }
 
-#[derive(Clone, Debug, TreeHash, CachedTreeHashSubTree)]
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
 pub struct StructWithVec {
     pub a: u64,
     pub b: Inner,
@@ -224,7 +224,7 @@ fn test_vec_of_struct_with_vec() {
     test_routine(original, modified);
 }
 
-#[derive(Clone, Debug, TreeHash, CachedTreeHashSubTree)]
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
 pub struct StructWithVecOfStructs {
     pub a: u64,
     pub b: Inner,
@@ -302,7 +302,7 @@ fn test_struct_with_vec_of_structs() {
     test_routine(f, variants);
 }
 
-#[derive(Clone, Debug, TreeHash, CachedTreeHashSubTree)]
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
 pub struct Inner {
     pub a: u64,
     pub b: u64,
@@ -481,7 +481,7 @@ fn works_when_embedded() {
     assert_eq!(&merkle[0..32], &root[..]);
 }
 
-impl CachedTreeHashSubTree<InternalCache> for InternalCache {
+impl CachedTreeHash<InternalCache> for InternalCache {
     fn new_tree_hash_cache(&self) -> Result<TreeHashCache, Error> {
         let tree = TreeHashCache::from_leaves_and_subtrees(
             self,
@@ -562,7 +562,7 @@ impl TreeHash for Inner {
     }
 }
 
-impl CachedTreeHashSubTree<Inner> for Inner {
+impl CachedTreeHash<Inner> for Inner {
     fn new_tree_hash_cache(&self) -> Result<TreeHashCache, Error> {
         let tree = TreeHashCache::from_leaves_and_subtrees(
             self,
@@ -646,7 +646,7 @@ impl TreeHash for Outer {
     }
 }
 
-impl CachedTreeHashSubTree<Outer> for Outer {
+impl CachedTreeHash<Outer> for Outer {
     fn new_tree_hash_cache(&self) -> Result<TreeHashCache, Error> {
         let tree = TreeHashCache::from_leaves_and_subtrees(
             self,

eth2/utils/tree_hash_derive/src/lib.rs

@@ -37,10 +37,10 @@ fn should_skip_hashing(field: &syn::Field) -> bool {
         .any(|attr| attr.into_token_stream().to_string() == "# [ tree_hash ( skip_hashing ) ]")
 }
 
-/// Implements `tree_hash::CachedTreeHashSubTree` for some `struct`.
+/// Implements `tree_hash::CachedTreeHash` for some `struct`.
 ///
 /// Fields are hashed in the order they are defined.
-#[proc_macro_derive(CachedTreeHashSubTree, attributes(tree_hash))]
+#[proc_macro_derive(CachedTreeHash, attributes(tree_hash))]
 pub fn subtree_derive(input: TokenStream) -> TokenStream {
     let item = parse_macro_input!(input as DeriveInput);
 
@@ -58,7 +58,7 @@ pub fn subtree_derive(input: TokenStream) -> TokenStream {
     let num_items = idents_a.len();
 
     let output = quote! {
-        impl tree_hash::CachedTreeHashSubTree<#name> for #name {
+        impl tree_hash::CachedTreeHash<#name> for #name {
             fn new_tree_hash_cache(&self, depth: usize) -> Result<tree_hash::TreeHashCache, tree_hash::Error> {
                 let tree = tree_hash::TreeHashCache::from_leaves_and_subtrees(
                     self,

eth2/utils/tree_hash_derive/tests/tests.rs

@@ -1,7 +1,7 @@
-use tree_hash::{CachedTreeHashSubTree, SignedRoot, TreeHash};
+use tree_hash::{CachedTreeHash, SignedRoot, TreeHash};
-use tree_hash_derive::{CachedTreeHashSubTree, SignedRoot, TreeHash};
+use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
-#[derive(Clone, Debug, TreeHash, CachedTreeHashSubTree)]
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
 pub struct Inner {
     pub a: u64,
     pub b: u64,
@@ -11,7 +11,7 @@ pub struct Inner {
 
 fn test_standard_and_cached<T>(original: &T, modified: &T)
 where
-    T: CachedTreeHashSubTree<T>,
+    T: CachedTreeHash<T>,
 {
     let mut cache = original.new_tree_hash_cache().unwrap();
 
@@ -44,7 +44,7 @@ fn inner_standard_vs_cached() {
     test_standard_and_cached(&original, &modified);
 }
 
-#[derive(Clone, Debug, TreeHash, CachedTreeHashSubTree)]
+#[derive(Clone, Debug, TreeHash, CachedTreeHash)]
 pub struct Uneven {
     pub a: u64,
     pub b: u64,