RE: Running a script in each Lua thread.

["Kevin Baca" <lualist@...>]

You need to set up the globals table only once for each new thread.

The globals table will be GC'd when:

A. The thread is GC'd
B. You replace the table (and have no other refs to the old table)

The call to lua_gettable() is to retrieve the function that you're
resuming:

-- Call the doit() function
lua_pushliteral( L, "doit" )
lua_gettable( L, LUA_GLOBALSINDEX )
lua_resume( L, 0 )

One more thing:  Note that the docs mention lua_closethread().  This
function doesn't actually exist.  The thread is closed when it is GC'd.

-Kevin

> Is the setup of the table a one time thing that I have to do 
> when creating a new thread? Do I need to perform any special 
> operations to make sure it is GC'd? Also, is the call to 
> get_table before each resume to push the thread's table into 
> the global space? I'm still so new to this and appreciate the 
> help so much.
> 
> Steven
> 
> 
> 
> 
> -----Original Message-----
> From: lua-bounces@bazar2.conectiva.com.br
> [mailto:lua-bounces@bazar2.conectiva.com.br]On Behalf Of Kevin Baca
> Sent: Saturday, October 18, 2003 4:40 PM
> To: 'Lua list'
> Subject: RE: Running a script in each Lua thread.
> 
> 
> The docs on this are a little vague:
> 
> Section 3.20
> ...
> Each thread has an independent global environment table. When 
> you create a thread, this table is the same as that of the 
> given state, but you can change each one independently. ...
> 
> Where it says "you can change each one independently" that 
> means you can
> *replace* each one independently.
> 
> IOW, each thread can have a unique global table, but it's up 
> to you to actually give each thread a unique global table.
> 
> Here's some code that demonstrates this:
> 
> C code
> ------
> lua_State* LA = lua_open();
> luaopen_base( LA );	//get the base lib
> 
> lua_State* LB = lua_newthread( LA );
> 
> //LB is an independent thread, but its globals
> //table is still the same as LA's globals table,
> //so we'll replace it with a new table.
> //The new table is set up so it will still look
> //to LA's globals for items it doesn't contain.
> 
> lua_newtable( LB );    //new globals table
> lua_newtable( LB );    //metatable
> lua_pushliteral( LB, "__index" );
> lua_pushvalue( LB, LUA_GLOBALSINDEX );  //original globals 
> lua_settable( LB, -3 ); lua_setmetatable( LB, -2 );
> lua_replace( LB, LUA_GLOBALSINDEX );    //replace LB's globals
> 
> //Two scripts, each with a doit() function
> 
> lua_dofile( LA, "scriptA.lua" );
> lua_pushliteral( LA, "doit" );
> lua_gettable( LA, LUA_GLOBALSINDEX );
> lua_resume( LA, 0 );
> 
> lua_dofile( LB, "scriptB.lua" );
> lua_pushliteral( LB, "doit" );
> lua_gettable( LB, LUA_GLOBALSINDEX );
> lua_resume( LB, 0 );
> 
> scriptA.lua
> -----------
> function doit()
>     print( "Script A" )
> end
> 
> scriptB.lua
> -----------
> function doit()
>     print( "Script B" )
> end
> 
> Hope that helps.
> 
> -Kevin
> 
> >
> >
> > Hello,
> >
> > I've searched through the archives and it has been very useful in 
> > getting me started with lua. I'm at a bit of an impass 
> right now and 
> > am hoping someone on the list can help.
> >
> > Currently I am opening a lua_State, registering all of my C 
> functions 
> > with that, and then creating a new thread for each entity I 
> need using 
> > lua_newthread(). Subsequent to creatring a new thread, I 
> load a script 
> > to be run by that thread, and then use lua_getglobal(thread, 
> > "funcname") to find the function I want to call in the 
> script. then I 
> > call lua_resume(). This works perfectly as long as the function
> > name is unique. The problem is I would like to have each
> > script have an Initialize() function. Unfortunately, the
> > Initialize() lua function of whichever script was last loaded
> > gets called no matter which lua thread I am resuming.
> >
> > What is the proper way of doing this? My application, like so many 
> > others, is in a game system where I would like to be able to create 
> > new game entities, attach a lua script to then, and let the script 
> > run, using
> > lua_yield()
> > from within C functions to yield the scripts. I also would like to 
> > keep my function names identical across all scripts to simplify the 
> > calling interface from C code. I've tried using multiple lua_open() 
> > calls to create seperate lua_States for each entity, but 
> then I have 
> > to register my C Functions for each new entity. This seems somewhat 
> > expensive since we are targetting the console market where 
> memory and 
> > speed are a key requirement.
> >
> > I've seen some details in the archives but they all use
> > lua_cobegin() a function that is no longer available in lua-5.0.
> >
> > Any tips or even pointers to previous message threads about 
> this would 
> > be great. If worse comes the worse I can create a new 
> lua_State using 
> > lua_open() for each object, but that seems like too much overhead, 
> > what with having to register the C functions each time.
> >
> > Many thanks for your time.
> >
> > Steven Brekelmans
> >
>