update to use less copy

src/tendermint_hash.rs

@@ -2,22 +2,25 @@ use sha2::{Sha256, Digest};
 
 use crate::simple_merkle::tree::MerkleHash;
 
-fn hash(bytes: &[u8]) -> [u8; 32] {
-    let mut hasher = Sha256::new();
-    hasher.update(bytes);
-    let result: [u8; 32] = hasher.finalize().into();
-    result
-}
-
 const LEAF_PREFIX: &[u8] = &[0];
 const INNER_PREFIX: &[u8] = &[1];
 
 fn leaf_hash(bytes: &[u8]) -> [u8; 32] {
-    hash([LEAF_PREFIX, bytes].concat().as_slice())
+    //hash([LEAF_PREFIX, bytes].concat().as_slice())
+    let mut hasher = Sha256::new();
+    hasher.update(LEAF_PREFIX);
+    hasher.update(bytes);
+    let result: [u8; 32] = hasher.finalize().into();
+    result
 }
 
 fn inner_hash(left: &[u8], right: &[u8]) -> [u8; 32] {
-    hash([INNER_PREFIX, left, right].concat().as_slice())
+    let mut hasher = Sha256::new();
+    hasher.update(INNER_PREFIX);
+    hasher.update(left);
+    hasher.update(right);
+    let result: [u8; 32] = hasher.finalize().into();
+    result
 }
 
 /// A sha256 hasher, compatible with [Tendermint merkle hash](https://github.com/informalsystems/tendermint-rs/blob/979456c9f33463944f97f7ea3900640e59f7ea6d/tendermint/src/merkle.rs)