EEI: charge for memory gas cost in useGas

Author: axic

Diff for: src/eei.cpp

@@ -198,6 +198,8 @@ string toHex(evmc_uint256be const& value) {
       HERA_DEBUG << "useGas " << gas << "\n";
 
       takeGas(gas);
+      // FIXME: this may overflow
+      takeGas(gas * memory.size() / GasSchedule::memoryPageSize * GasSchedule::memoryCostPerPage);
 
       return Literal();
     }

Diff for: src/eei.h

@@ -99,9 +99,13 @@ struct EthereumInterface : ShellExternalInterface {
   evmc_message const& msg;
   std::vector<uint8_t> lastReturnData;
   ExecutionResult & result;
+
 };
 
 struct GasSchedule {
+  static constexpr unsigned memoryPageSize = 65536;
+  static constexpr unsigned memoryCostPerPage = 1;
+
   static constexpr unsigned storageLoad = 200;
   static constexpr unsigned storageStoreCreate = 20000;
   static constexpr unsigned storageStoreChange = 5000;