Re: C calls Lua or Lua calls C?
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: C calls Lua or Lua calls C?
- From: Sean Conner <sean@...>
- Date: 2011年1月20日 00:07:10 -0500
It was thus said that the Great Steve Litt once stated:
> On Wednesday 19 January 2011 20:56:18 HyperHacker wrote:
>
> > however are a Lua script that loads a bunch of modules (some of which
> > are written in C); it's not infeasible that a game engine could be
> > done that way.
>
> I'm glad you responded. In my research I've found no examples of how to start
> in Lua and load C modules, nor any documentation of same. Do you know of a
> trivial "hello world" application of calling C from Lua for Lua 5.1?
Here's one for Unix (tested under Linux) I wrote. Creates a table, fills
it with a few values, the current working directory, the current PID and the
load average (an array); the load average has a metatable controlling how
it's printed.
[spc]lucy:/tmp>gcc -g -shared -fPIC -o silly.so silly.c
[spc]lucy:/tmp>lua
Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio
> require "silly"
> x = silly.info()
> print(x.cwd,x.pid,x.loadave)
/tmp 22647 (0.06 0.04 0.01)
> os.exit()
[spc]lucy:/tmp>
-spc (Code follows ... )
/****************************************************************************
*
* A silly example of extending lua via the shared object method.
* Here's how this is done under Linux:
*
* gcc -g -fPIC -shared -o silly.so silly.c
*
* You will then have a shared object you can load into the lua interpreter.
*
*****************************************************************************/
#define _BSD_SOURCE
#include <stddef.h>
#include <string.h>
#include <stdlib.h>
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>
#include <unistd.h>
/******************************************************************/
static int silly_loadave__toprint(lua_State *L)
{
char buffer[BUFSIZ];
lua_Number load[3];
int i;
if (lua_type(L,1) != LUA_TTABLE)
return luaL_error(L,"Expecting table, but got %s",luaL_typename(L,1));
for (i = 0 ; i < 3 ; i++)
{
lua_pushinteger(L,i + 1);
lua_gettable(L,1);
load[i] = luaL_checknumber(L,-1);
}
sprintf(buffer,"(%.2f %.2f %.2f)",load[0],load[1],load[2]);
lua_pushstring(L,buffer);
return 1;
}
/*******************************************************************/
static int silly_loadave__newindex(lua_State *L)
{
return luaL_error(L,"Attempting to upate a read-only table");
}
/******************************************************************/
static int info(lua_State *L)
{
lua_newtable(L);
lua_pushliteral(L,"pid");
lua_pushnumber(L,getpid());
lua_settable(L,-3);
char buffer[FILENAME_MAX];
getcwd(buffer,FILENAME_MAX);
lua_pushliteral(L,"cwd");
lua_pushlstring(L,buffer,strlen(buffer));
lua_settable(L,-3);
double load[3];
if (getloadavg(load,3) != -1)
{
/*----------------------------------------------
; equiv of
; loadave = {}
; loadave[1] = x;
; loadave[2] = y;
; loadave[3] = z;
;----------------------------------------------*/
lua_pushliteral(L,"loadave");
lua_createtable(L,3,0);
lua_pushnumber(L,1);
lua_pushnumber(L,load[0]);
lua_settable(L,-3);
lua_pushnumber(L,2);
lua_pushnumber(L,load[1]);
lua_settable(L,-3);
lua_pushnumber(L,3);
lua_pushnumber(L,load[2]);
lua_settable(L,-3);
/*---------------------------------------------
; mt = {}
; mt.__tostring = silly_loadave__toprint
; mt.__newindex = silly_loadave__newindex
; setmetable(loadave,mt);
;---------------------------------------------*/
lua_createtable(L,0,2);
lua_pushliteral(L,"__tostring");
lua_pushcfunction(L,silly_loadave__toprint);
lua_settable(L,-3);
lua_pushliteral(L,"__newindex");
lua_pushcfunction(L,silly_loadave__newindex);
lua_settable(L,-3);
lua_setmetatable(L,-2);
lua_settable(L,-3);
}
return 1;
}
/************************************************************************/
static const struct luaL_reg reg_silly[] =
{
{ "info" , info },
{ NULL , NULL }
};
int luaopen_silly(lua_State *L)
{
luaL_register(L,"silly", reg_silly);
return 1;
}
/************************************************************************/