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/**
* @file lualistener.h
* @author Nat Goodspeed
* @date 2024-02-06
* @brief Define LuaListener class
*
* $LicenseInfo:firstyear=2024&license=viewerlgpl$
* Copyright (c) 2024, Linden Research, Inc.
* $/LicenseInfo$
*/
#if ! defined(LL_LUALISTENER_H)
#define LL_LUALISTENER_H
#include "llevents.h"
#include "llinstancetracker.h"
#include "llsd.h"
#include "llthreadsafequeue.h"
#include <iosfwd> // std::ostream
#include <memory> // std::unique_ptr
#include <string>
#include <utility> // std::pair
struct lua_State;
class LLLeapListener;
/**
* LuaListener is based on LLLeap. It serves an analogous function.
*
* Each LuaListener instance has an int key, generated randomly to
* inconvenience malicious Lua scripts wanting to mess with others. The idea
* is that a given lua_State stores in its Registry:
* - "event.listener": the int key of the corresponding LuaListener, if any
* The original thought was that LuaListener would itself store the Lua
* function -- but surprisingly, there is no C/C++ type in the API that stores
* a Lua function.
*
* (We considered storing in "event.listener" the LuaListener pointer itself
* as a light userdata, but the problem would be if Lua code overwrote that.
* We want to prevent any Lua script from crashing the viewer, intentionally
* or otherwise. Safer to use a key lookup.)
*
* Like LLLeap, each LuaListener instance also has an associated
* LLLeapListener to respond to LLEventPump management commands.
*/
class LuaListener: public LLInstanceTracker<LuaListener, int>
{
using super = LLInstanceTracker<LuaListener, int>;
public:
LuaListener(lua_State* L);
LuaListener(const LuaListener&) = delete;
LuaListener& operator=(const LuaListener&) = delete;
~LuaListener();
std::string getReplyName() const;
std::string getCommandName() const;
/**
* LuaListener enqueues reply events from its LLLeapListener on mQueue.
* Call getNext() to retrieve the next such event. Blocks the calling
* coroutine if the queue is empty.
*/
using PumpData = std::pair<std::string, LLSD>;
PumpData getNext();
friend std::ostream& operator<<(std::ostream& out, const LuaListener& self);
private:
static int getUniqueKey();
bool queueEvent(const std::string& pump, const LLSD& data);
LLThreadSafeQueue<PumpData> mQueue;
std::unique_ptr<LLLeapListener> mListener;
LLTempBoundListener mShutdownConnection;
};
#endif /* ! defined(LL_LUALISTENER_H) */
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