core: minor evm polishes and optimizations

1 files changed, 16 insertions, 3 deletions

diff --git a/core/evm.go b/core/evm.go
index 55db53927..596ea95fb 100644
--- a/core/evm.go
+++ b/core/evm.go
@@ -60,13 +60,26 @@ func NewEVMContext(msg Message, header *types.Header, chain ChainContext, author
 
 // GetHashFn returns a GetHashFunc which retrieves header hashes by number
 func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
+	var cache map[uint64]common.Hash
+
 	return func(n uint64) common.Hash {
+		// If there's no hash cache yet, make one
+		if cache == nil {
+			cache = map[uint64]common.Hash{
+				ref.Number.Uint64() - 1: ref.ParentHash,
+			}
+		}
+		// Try to fulfill the request from the cache
+		if hash, ok := cache[n]; ok {
+			return hash
+		}
+		// Not cached, iterate the blocks and cache the hashes
 		for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
-			if header.Number.Uint64() == n {
-				return header.Hash()
+			cache[header.Number.Uint64()-1] = header.ParentHash
+			if n == header.Number.Uint64()-1 {
+				return header.ParentHash
 			}
 		}
-
 		return common.Hash{}
 	}
 }