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How do you think LUA handles script functions?
Author
Hi I readed lua tutorial found here in gamedev and according to that lua can register function''s very easily like this:
lua_register( luaVM, "addNPC", l_addNPC );
So can some one brighten a bit how does that register work? First the info about parameters what l_addNPC uses must be stored and then maybe some sort of asm code to call the function. Or?
Hey,
Sorry, I don''t have the source in front of me atm, but lua_register is just a macro. Find the definition in one of the headers and it''s all right there.
Kory
Sorry, I don''t have the source in front of me atm, but lua_register is just a macro. Find the definition in one of the headers and it''s all right there.
Kory
Author
quote: Original post by kspansel
Hey,
Sorry, I don''t have the source in front of me atm, but lua_register is just a macro. Find the definition in one of the headers and it''s all right there.
Kory
Oh right actualy I knew it''s a macro but ain''t that code unavaible becose it''s in libary? Well i''ll look it for more.
lua is free, and open source.
You can get the source code for free, and find out for yourself.
You can get the source code for free, and find out for yourself.
quote: Original post by CraazerAll functions registered to Lua must take one argument, a pointer to a lua_state, and return an integer. RTFM.
So can some one brighten a bit how does that register work? First the info about parameters what l_addNPC uses must be stored and then maybe some sort of asm code to call the function. Or?
How appropriate. You fight like a cow.
he''s not asking how to use the functions, he''s asking what
the lua interpreter code is actually doing when you register
a function, and when you call it...
As was mentioned before, you can look through the lua code,
as it''s open source, and discover this for yourself. I assume
it adds some new entry in the lua_state so the interpreter
will recognize the function, and when called, makes an external call by mangling the C function name you give it.
the lua interpreter code is actually doing when you register
a function, and when you call it...
As was mentioned before, you can look through the lua code,
as it''s open source, and discover this for yourself. I assume
it adds some new entry in the lua_state so the interpreter
will recognize the function, and when called, makes an external call by mangling the C function name you give it.
just because something is open source doesn''t mean it''s wasy for everyone to understand every little thing it does. Do all of you understand every tidbit of carmack''s work? Don''t lie.
Give the guy a break would you?
Give the guy a break would you?
quote: Original post by Craazer
Hi I readed lua tutorial found here in gamedev and according to that lua can register function''s very easily like this:
lua_register( luaVM, "addNPC", l_addNPC );
So can some one brighten a bit how does that register work? First the info about parameters what l_addNPC uses must be stored and then maybe some sort of asm code to call the function. Or?
I don''t know how the first part work, maybe lua just don''t do any check (params ar put on the stack, the function is called and that''s all).
The second part, yes, is some little asm code.
This is taken for an article by Scott Bilas, and I used it in my scripting engine
DWORD Call_cdecl( const void* args, size_t sz, DWORD func ){ DWORD rc; // here''s our return value... __asm { mov ecx, sz // get size of buffer mov esi, args // get buffer sub esp, ecx // allocate stack space mov edi, esp // start of destination stack frame shr ecx, 2 // make it dwords rep movsd // copy params to real stack call [func] // call the function mov rc, eax // save the return value add esp, sz // restore the stack pointer } return ( rc );} DWORD Call_stdcall( const void* args, size_t sz, DWORD func ){ DWORD rc; // here''s our return value... __asm { mov ecx, sz // get size of buffer mov esi, args // get buffer sub esp, ecx // allocate stack space mov edi, esp // start of destination stack frame shr ecx, 2 // make it dwords rep movsd // copy it call [func] // call the function mov rc, eax // save the return value } return ( rc );}
Why do you need ASM? What''s wrong with C? And what does that last post have to do with any of this? Aren''t we talking about LUA?
quote: Original post by Craazer
Hi I readed lua tutorial found here in gamedev and according to that lua can register function''s very easily like this:
lua_register( luaVM, "addNPC", l_addNPC );
So can some one brighten a bit how does that register work? First the info about parameters what l_addNPC uses must be stored and then maybe some sort of asm code to call the function. Or?
As far as I know, all it does is associate the string ''addNPC'' with a function pointer to l_addNPC in a table inside luaVM. There''s no ASM, and no need to store details about parameters because all functions that you give to Lua have the same parameters. This is possible because everything in Lua is done via the stack that is provided to you. It just looks up the relevant function pointer whenever the specified name is found in the script you give it.
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