From e6c33e1b60e560fb7539c0965f441dccb6af277d Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Mon, 15 Apr 2019 11:44:44 +1000
Subject: [PATCH] Remove child_nodes method from CachedTreeHash

---
 eth2/utils/tree_hash/src/impls.rs   | 14 ++---------
 eth2/utils/tree_hash/src/lib.rs     |  2 --
 eth2/utils/tree_hash/tests/tests.rs | 37 ++++++-----------------------
 3 files changed, 9 insertions(+), 44 deletions(-)

diff --git a/eth2/utils/tree_hash/src/impls.rs b/eth2/utils/tree_hash/src/impls.rs
index 9149cf8aa..4349d73d8 100644
--- a/eth2/utils/tree_hash/src/impls.rs
+++ b/eth2/utils/tree_hash/src/impls.rs
@@ -14,18 +14,14 @@ impl CachedTreeHash<u64> for u64 {
         )?)
     }
 
-    fn btree_overlay(&self, _chunk_offset: usize) -> Result<BTreeOverlay, Error> {
-        Err(Error::ShouldNotProduceBTreeOverlay)
+    fn btree_overlay(&self, chunk_offset: usize) -> Result<BTreeOverlay, Error> {
+        BTreeOverlay::from_lengths(chunk_offset, vec![1])
     }
 
     fn num_bytes(&self) -> usize {
         8
     }
 
-    fn num_child_nodes(&self) -> usize {
-        0
-    }
-
     fn packed_encoding(&self) -> Vec<u8> {
         ssz_encode(self)
     }
@@ -72,7 +68,6 @@ where
     }
 
     fn btree_overlay(&self, chunk_offset: usize) -> Result<BTreeOverlay, Error> {
-        //
         let lengths = match T::item_type() {
             ItemType::Basic => vec![1; self.len() / T::packing_factor()],
             ItemType::Composite | ItemType::List => {
@@ -89,11 +84,6 @@ where
         BTreeOverlay::from_lengths(chunk_offset, lengths)
     }
 
-    fn num_child_nodes(&self) -> usize {
-        // TODO
-        42
-    }
-
     fn num_bytes(&self) -> usize {
         self.iter().fold(0, |acc, item| acc + item.num_bytes())
     }
diff --git a/eth2/utils/tree_hash/src/lib.rs b/eth2/utils/tree_hash/src/lib.rs
index e356210a4..4e1cff0e8 100644
--- a/eth2/utils/tree_hash/src/lib.rs
+++ b/eth2/utils/tree_hash/src/lib.rs
@@ -47,8 +47,6 @@ pub trait CachedTreeHash<Item>: Debug {
 
     fn btree_overlay(&self, chunk_offset: usize) -> Result<BTreeOverlay, Error>;
 
-    fn num_child_nodes(&self) -> usize;
-
     fn packed_encoding(&self) -> Vec<u8>;
 
     fn packing_factor() -> usize;
diff --git a/eth2/utils/tree_hash/tests/tests.rs b/eth2/utils/tree_hash/tests/tests.rs
index af4204cc2..a315feeed 100644
--- a/eth2/utils/tree_hash/tests/tests.rs
+++ b/eth2/utils/tree_hash/tests/tests.rs
@@ -47,26 +47,14 @@ impl CachedTreeHash<Inner> for Inner {
     fn btree_overlay(&self, chunk_offset: usize) -> Result<BTreeOverlay, Error> {
         let mut lengths = vec![];
 
-        lengths.push(self.a.num_child_nodes() + 1);
-        lengths.push(self.b.num_child_nodes() + 1);
-        lengths.push(self.c.num_child_nodes() + 1);
-        lengths.push(self.d.num_child_nodes() + 1);
+        lengths.push(BTreeOverlay::new(&self.a, 0)?.total_nodes());
+        lengths.push(BTreeOverlay::new(&self.b, 0)?.total_nodes());
+        lengths.push(BTreeOverlay::new(&self.c, 0)?.total_nodes());
+        lengths.push(BTreeOverlay::new(&self.d, 0)?.total_nodes());
 
         BTreeOverlay::from_lengths(chunk_offset, lengths)
     }
 
-    fn num_child_nodes(&self) -> usize {
-        let mut children = 0;
-        let leaves = 4;
-
-        children += self.a.num_child_nodes();
-        children += self.b.num_child_nodes();
-        children += self.c.num_child_nodes();
-        children += self.d.num_child_nodes();
-
-        num_nodes(leaves) + children - 1
-    }
-
     fn packed_encoding(&self) -> Vec<u8> {
         panic!("Struct should never be packed")
     }
@@ -135,23 +123,12 @@ impl CachedTreeHash<Outer> for Outer {
         bytes
     }
 
-    fn num_child_nodes(&self) -> usize {
-        let mut children = 0;
-        let leaves = 3;
-
-        children += self.a.num_child_nodes();
-        children += self.b.num_child_nodes();
-        children += self.c.num_child_nodes();
-
-        num_nodes(leaves) + children - 1
-    }
-
     fn btree_overlay(&self, chunk_offset: usize) -> Result<BTreeOverlay, Error> {
         let mut lengths = vec![];
 
-        lengths.push(self.a.num_child_nodes() + 1);
-        lengths.push(self.b.num_child_nodes() + 1);
-        lengths.push(self.c.num_child_nodes() + 1);
+        lengths.push(BTreeOverlay::new(&self.a, 0)?.total_nodes());
+        lengths.push(BTreeOverlay::new(&self.b, 0)?.total_nodes());
+        lengths.push(BTreeOverlay::new(&self.c, 0)?.total_nodes());
 
         BTreeOverlay::from_lengths(chunk_offset, lengths)
     }