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I would use a bunch of user data types for each simple C type and associate all operations you normally do with variables using metatables. The assignment would either use "call" event or "index" event for some predefined name, say, "set". Such userdata would hold an address of a single C variable.Basically the C interface would look somthing like this 

struct cMonster_tag
{
   int mHealth;
   char* mName;
} cMonster;

// creates new game object  and sets it as light user data into the table
// bind all functions
// structure fields by address as user data
int CreateNewTable_Monster(L);

// takes the object type string
int CreateNewObject(L); // would call functions like CreateNewTable_Monster(L); internally
// creates userdata for pC and sets a metatable for it to handle all events (+, *, /, <, index for "set", etc.) 
//
void Bind<C-type>Var(C-type* pC, const char* name, int table_index);
CreateNewTable_Monster(L); would call Bind<C-type>Var internally for all it's data members that you would wanto access from Lua. 
For instance,
   BindCIntVar(&monster->mHealth, "health", -1);
   BindCStringVar(&monster->mName, "name", -1);
And then you would be able to do everything transparently in Lua except assignments, which would use "set" method 

monster.health.set(0).

or a "call" event and function call syntax

monster.health(0)
I think this kind of binding would have the lowest runtime overhead and can be used for any C-var elsewhere in your code. 

Overall, in Lua your would say something like this

monster = CreateNewObject("monster")
monster.health(100)
monster.name("Mean Killer Bee")

or even

monster = NewObject("monster", {health  = 100, name = "Mean Killer Bee"})
...
monster.health(2)
if (monster.health < 6)
then
   monster:die()
end

jose_marin2 wrote:


Hi!
I'm looking for a good (fast!) way of sharing the C structs of my game with the Lua code. 
For example, in C I have the struct:

struct MonsterInfo{
char name[MAX_NAME];
int health;
};

and in Lua I could have 2  functions:

------------------------------------
function NewMonster(name, health)

local tbl = {}

tbl.name = name;

tbl.health = health;

function tbl:Die()
 ...
end
return tbl 
end

function Damage(ent, amount)

 ent.health = ent.healt - amount

 if ent.health <= 0 then
   ent:Die()
 end

end

------------------------------------
The problem is how to (fast and easy) keep in the same data (struct) in Lua and in C.