core/state: implement GetCodeSize for VerkleDB (ethereum#75)

implement core/state: implement GetCodeSize for VerkleDB

core/state/database.go

@@ -270,7 +270,16 @@ func (db *VerkleDB) ContractCode(addrHash, codeHash common.Hash) ([]byte, error)
 
 // ContractCodeSize retrieves a particular contracts code's size.
 func (db *VerkleDB) ContractCodeSize(addrHash, codeHash common.Hash) (int, error) {
-	panic("need to merge #31 for this to work")
+	if code := db.codeCache.Get(nil, codeHash.Bytes()); len(code) > 0 {
+		return len(code), nil
+	}
+	code := rawdb.ReadCode(db.db.DiskDB(), codeHash)
+	if len(code) > 0 {
+		db.codeCache.Set(codeHash.Bytes(), code)
+		db.codeSizeCache.Add(codeHash, len(code))
+		return len(code), nil
+	}
+	return 0, nil
 }
 
 // TrieDB retrieves the low level trie database used for data storage.