From af245f2e828503fa71a7e78cffdc395deda14009 Mon Sep 17 00:00:00 2001
From: Wei Tang <hi@that.world>
Date: Mon, 8 Jun 2020 11:12:48 +0200
Subject: [PATCH] pallet-ethereum: add number to hash mapping for Ethereum
 headers (#29)

---
 Cargo.lock                | 3 +++
 frame/ethereum/src/lib.rs | 7 +++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index e15cbf3a7..12572bcb3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1100,10 +1100,13 @@ dependencies = [
  "pallet-ethereum 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-scale-codec",
  "rlp",
+ "sc-client-api",
+ "sc-service",
  "sha3",
  "sp-api",
  "sp-consensus",
  "sp-runtime",
+ "sp-storage",
  "sp-transaction-pool",
 ]
 
diff --git a/frame/ethereum/src/lib.rs b/frame/ethereum/src/lib.rs
index 3bdc2255a..2a60b9730 100644
--- a/frame/ethereum/src/lib.rs
+++ b/frame/ethereum/src/lib.rs
@@ -57,7 +57,8 @@ decl_storage! {
 	// storage items are isolated from other pallets.
 	// ---------------------------------vvvvvvv
 	trait Store for Module<T: Trait> as Example {
-		BlocksAndReceipts: map hasher(blake2_128_concat) T::BlockNumber => Option<(ethereum::Block, Vec<ethereum::Receipt>)>;
+		BlocksAndReceipts: map hasher(blake2_128_concat) H256 => Option<(ethereum::Block, Vec<ethereum::Receipt>)>;
+		BlockNumbers: map hasher(blake2_128_concat) T::BlockNumber => H256;
 		PendingTransactionsAndReceipts: Vec<(ethereum::Transaction, ethereum::Receipt)>;
 		TransactionStatuses: map hasher(blake2_128_concat) H256 => Option<TransactionStatus>;
 	}
@@ -182,6 +183,7 @@ decl_module! {
 				mix_hash: H256::default(),
 				nonce: H64::default(),
 			};
+			let hash = H256::from_slice(Keccak256::digest(&rlp::encode(&header)).as_slice());
 
 			let block = ethereum::Block {
 				header,
@@ -189,7 +191,8 @@ decl_module! {
 				ommers,
 			};
 
-			BlocksAndReceipts::<T>::insert(n, (block, receipts));
+			BlocksAndReceipts::insert(hash, (block, receipts));
+			BlockNumbers::<T>::insert(n, hash);
 		}
 
 		// A runtime code run after every block and have access to extended set of APIs.