EEI: charge for memory gas cost in useGas

Author: axic

Diff for: src/eei.cpp

@@ -41,6 +41,8 @@ Literal EthereumInterface::callImport(Import *import, LiteralList& arguments) {
       cout << gas << "\n";
 
       takeGas(gas);
+      // FIXME: this may overflow
+      takeGas(gas * memory.size() / memory_page_size * memory_cost);
 
       return Literal();
     }

Diff for: src/eei.h

@@ -98,6 +98,9 @@ struct EthereumInterface : ShellExternalInterface {
   std::vector<uint8_t> const& code;
   struct evm_message const& msg;
   ExecutionResult result;
+
+  static constexpr unsigned memory_page_size = 65536;
+  static constexpr unsigned memory_cost = 1;
 };
 
 }