Re: Setting Global Tables

[mnicolet <mnicolet@...>]

Hello
I am not sure I understand your exact problem.
See attached a code snip to do some table manipulation from C, and a gzipped
tarball with my
own api to lua, and usage examples. If you like, you can ´dive´ into the
luapi.c code, to gain
some insight regarding lua interfacing,  also, if you like it, you can use
or adapt luapi.c to your own
taste. A word of caution: luapi and the examples were compiled and linked
with the 5.0-alpha
release, I am waiting to have some time to try and maybe, adapt it to
lua-5.0-beta.
But the main core is the same.
Sorry, the api is not fully documented. It was the reason because I don´t
posted it to the wiki.
But seeing the examples ( host.c and udtest.c ) may be helpful.
The doc refers to a makefile for hosttest. I excluded it from the tarball
because is very broken.
Good luck
----- Original Message -----
From: "Andrew Teirney" <andrew@teirney.net>
To: "Multiple recipients of list" <lua-l@tecgraf.puc-rio.br>
Sent: Sunday, February 16, 2003 7:12 PM
Subject: Setting Global Tables


> Hi there,
>
>     I am a fairly new person to lua, the version of lua i am using is
> 5.0(beta), since i don't have heaps of time to delve over documents etc i
> thought i might post this message to the users list in the hope someone
> might be able to explain a few things.
>
>     In my current system which is an embedded project i have what i call a
> managment system (written in c), along with a number of support modules.
> These support modules will be available to the lua scripts. The intended
use
> of the lua scripts is to be able to give the software new behaviour
without
> having the need to compile to native code etc. Lua suit my needs
perfectly,
> well from what i can see.
>
>     Anyway, one of my support modules is responsible for processing a
stream
> of text input, it breaks it up into fields as it comes in and so forth.
When
> a particular sequence of character is received an event is generated. This
> event in turn causes either one or multiple scripts to execute depending
on
> the configuration. The problem i am facing, probably due to my infancy of
> knowledge with lua is how can i make these string that the module has
split
> up avaible to lua.
>
>     So far i have thought of having a global table, lets say called
> 'fields'. on getting a new field to add at the c source level somehow poke
> it into the lua environment into that 'fields' table. When the scripts
have
> finished executing then simply assign nil to the 'fields' value and have
the
> lua strings GC'd etc. I think i can see how this is done if lua calls a c
> function. But i am unsure how to do this when lua does not call a c
function
> from lua land.
>
>     If anyone can provide me with information on how i can do this, this
> would be greatly appreciated. Also i forgot to mention that when c code is
> running lua code is not, its is a single threaded system, based on
> co-operative multi-tasking. Depending on how long lua takes to execute its
> scripts it may or maynot become a pre-emptive multi-threaded system, this
is
> yet to be determined.
>
>     Also on another note, when lua loads a chunk presumably it stores it
in
> memory, when the chunk has finished loading and then execution has
> subsequantly finished is the memory the chunk occupied free'd up?
>
> Cheers,
>
>     Andrew Stanley Teirney
>
>
>

suppose 'tname' is the table name
        'key'   is a 'string key' ( remember, tables may be indexed this way )
        'value' is a 'string value' for the 'key'

   int sp = lua_gettop( L ); // play safe: store the current stack 'pointer'

   lua_pushlstring( L, tname, strlen( tname ) );

   lua_gettable( L, LUA_GLOBALSINDEX );

// if 'tname' exists in the globals table, the the object is on top of stack
// if not, nil was pushed
// so, check if the object is a LUA_TTABLE

   if ( lua_type( L, lua_gettop( L ) ) != LUA_TTABLE ) {
      return some error ind ...
   }

// new 'pushs' goes on top of stack ...

   lua_pushlstring( L, key, strlen( key ) );     // push the key
   lua_pushlstring( L, value, strlen( value ) ); // push the value
   lua_settable( L, -3 );                        // 'bind' them to the object 
                                                 // which is 3 sp 'slots'
                                                 // 'above'

   lua_settop( L, sp );

   return ok;

key or value may be numbers 
   so ...
   lua_pushnumber( L, nkey ); 
   or 
   lua_pushnumber( L, nvalue );

to wipe out an entry

   lua_push...( L, key, ... )
   lua_pushnil( L );
   lua_settable( L, -3 );                        // 'bind' them to the object 
   

to wipe out the entire table

   lua_pushlstring( L, tname, strlen( tname ) );

   lua_pushnil( L );

   lua_settable( L, LUA_GLOBALSINDEX );




   lua_settable( L, -2 );

Attachment: luapi-5.0a.tgz
Description: application/compressed