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[C/C++] use some script without reloading again and again

 
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chaos



Joined: 03 Dec 2009
Posts: 2
PostPosted: Thu Dec 03, 2009 5:16 pm    Post subject: [C/C++] use some script without reloading again and again Reply with quote
Hi, sorry to my bad English !

I'm working on a shmup engine, i use XML to script everything and now i want implement LUA to more flexibility. I tried some example but now i'm lost.

To increase performance i want load script at the beginning from my program et launch script later. I understand how to load and run a script but no how to load everything and launch it when i want.

I don't know if it's clear :p, for example i'm creating LUA state et loading sub library :

Code:

lua_State * state;
state = lua_open();
luaopen_string(state);
luaopen_math(state);


now i want load my scripts with something like this

Code:

luaL_loadstring(state, script1);
luaL_loadstring(state, script2);
luaL_loadstring(state, script3);


an later use the bytecode generated when i need it
Code:

If something
  Call Script 1
Else
 Call Script 2
Else
...
End



any idea ?

Last edited by chaos on Fri Dec 04, 2009 7:08 am; edited 1 time in total
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lhf



Joined: 20 Feb 2006
Posts: 175
Location: Rio de Janeiro, Brazil
PostPosted: Fri Dec 04, 2009 4:23 am    Post subject: Reply with quote
luaL_loadstring returns a function corresponding to the body of the script.
luaL_loadstring does not run the script.
So, simply save the function left on the stack by luaL_loadstring and run it as many times as you need.
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chaos



Joined: 03 Dec 2009
Posts: 2
PostPosted: Fri Dec 04, 2009 7:22 am    Post subject: Reply with quote
i know this but i'm lost with how to use the stack.

Example, i use this class to generate a trunk (my tools generate it, while the engine load an use it)

Code:

    class Script
    {
        public:
            Script(){size=0; data=NULL;}
            static int Append(lua_State* L, const void* p, size_t size, void* u)
            {
                Script* script = (Script*)u;
                if(size == 0)
                    script->data = malloc(size);
                else
                    script->data = realloc(script->data, script->size + size);
                memcpy((void*)((char*)script->data + script->size), p, size);
                script->size += size;
                return 0;
            }

            static Script* Generate(string script)
            {
                lua_State * state;
                state = lua_open();
                luaopen_string(state);
                luaopen_math(state);
                if(luaL_loadstring(state, script.c_str()) != 0)
                    return NULL;
                Proto* f = clvalue(state->top+(-1))->l.p;
                lua_lock(state);
                Script* trunk = new Script();
                luaU_dump(state,f,Script::Append,trunk, 0);
                lua_unlock(state);
                lua_close(state);
                if(trunk->GetSize()==0)
                {
                    delete trunk;
                    return NULL;
                }
                return trunk;
            }

            void* GetData(){return data;}
            size_t GetSize(){return size;}
        private:
            void* data;
            size_t size;
    };



i use it like this :

Code:

Script* test1 = Script::Generate("test = test + math.cos(1)");
Script* test2 = Script::Generate("test = test + math.cos(2)");
.
.
.
.
.
Script* testn = Script::Generate("test = test + math.cos(n)");


i can load a script with

Code:

luaL_loadbuffer (state, (char*)test1->GetData(), test1->GetSize(), NULL);
luaL_loadbuffer (state, (char*)test2->GetData(), test2->GetSize(), NULL);
.
.
.
.
luaL_loadbuffer (state, (char*)testn ->GetData(), testn ->GetSize(), NULL);



But now i don't know how to play with the stack
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lhf



Joined: 20 Feb 2006
Posts: 175
Location: Rio de Janeiro, Brazil
PostPosted: Fri Dec 04, 2009 7:32 am    Post subject: Reply with quote
Use the registry or any other table to cache the script functions. So when you want to run a script, first test whether there's a function store at the key given by the script name. If there isn't, luaL_loadstring it and store the result in the cache.
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