vm.cpp

class VM {
public:

protected:
	virtual void Syscall(int32_t index, Reader& input, Writer& output) = 0;
	void DoRPC(const Writer& input, Reader& output);

private:
	NaCl::Module* module;
};

// On the VM side, the code looks very similar to the syscall handler
// void vmMain(Reader& input, Writer& output);

class GameVM {
public:
	// Example VMCall that takes a string and returns an int
	int Example(const char* str)
	{
		Writer args;
		args.WriteInt32(G_EXAMPLE_VMCALL);
		args.WriteString(cmd);
		if (args.Error())
			Com_Error(ERR_DROP, "RPC buffer overflow");

		Reader result;
		DoRPC(args, result);
		int result = result.ReadInt32();
		if (result.Error())
		return result;
	}

protected:
	// Syscall handler
	virtual void Syscall(int32_t index, Reader& input, Writer& output)
	{
		// Example syscall that takes a string and returns an int
		switch (index) {
		case G_EXAMPLE_SYSCALL:
			{
				char arg[1024];
				input.ReadString(arg, sizeof(arg));
				if (input.Error())
					Com_Error(ERR_DROP, "RPC buffer underflow");

				output.WriteInt32(atoi(arg));
				if (output.Error())
					Com_Error(ERR_DROP, "RPC buffer overflow");
			}

		default:
			Com_Error(ERR_DROP, "Invalid syscall");
		}
	}
};