EEI: charge for memory gas cost in useGas

Author: axic

src/eei.cpp

@@ -146,6 +146,8 @@ namespace HeraVM {
       HERA_DEBUG << "useGas " << gas << "\n";
 
       takeGas(gas);
+      // FIXME: this may overflow
+      takeGas(gas * memory.size() / memory_page_size * memory_cost);
 
       return Literal();
     }

src/eei.h

@@ -113,6 +113,9 @@ struct EthereumInterface : ShellExternalInterface {
   struct evm_message const& msg;
   std::vector<uint8_t> lastReturnData;
   ExecutionResult & result;
+
+  static constexpr unsigned memory_page_size = 65536;
+  static constexpr unsigned memory_cost = 1;
 };
 
 struct GasSchedule {