Cpp Lua Data Passing

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After Running the Program

[C++] Passing 'arg' array to script

[C++] Running script

[lua] These args were passed into the script from C

1       45

2       99

[lua] Script returning data back to C

[C++] These values were returned from the script

script returned 1

script returned 9

script returned a table

The C++ code

extern "C"

{

   #include <lua.h>

   #include <lauxlib.h>

   #include <lualib.h>

}

#include <iostream>



// a list of libs to expose for use in scripts

static const luaL_reg lualibs[] = 

{

  {"base", luaopen_base},

  {"table", luaopen_table},

  {"io", luaopen_io},

  {"string", luaopen_string},

  {"math", luaopen_math},

  {"debug", luaopen_debug},

  {"loadlib", luaopen_loadlib}, 

  /* add your libraries here */

  {NULL, NULL}

};



// load the list of libs

static void openstdlibs( lua_State *l ) 

{

  const luaL_reg *lib = lualibs;

  for (; lib->func; lib++) 

  {

    lib->func(l);  /* open library */

    lua_settop(l, 0);  /* discard any results */

  }

}



int main()

{

   int status;

   lua_State* state = lua_open();



  

   openstdlibs( state );

   status = luaL_loadfile( state, "args.lua" );



   std::cout << "[C++] Passing 'arg' array to script" << std::endl;



   // start array structure

   lua_newtable( state );



   // set first element "1" to value 45

   lua_pushnumber( state, 1 );

   lua_pushnumber( state, 45 );

   lua_rawset( state, -3 );



   // set second element "2" to value 99

   lua_pushnumber( state, 2 );

   lua_pushnumber( state, 99 );

   lua_rawset( state, -3 );

  

   // set the number of elements (index to the last array element)

   lua_pushliteral( state, "n" );

   lua_pushnumber( state, 2 );

   lua_rawset( state, -3 );



   // set the name of the array that the script will access

   lua_setglobal( state, "arg" );





   std::cout << "[C++] Running script" << std::endl;

   

   int result = 0;

   if (status == 0)

      result = lua_pcall( state, 0, LUA_MULTRET, 0 );

   else

      std::cout << "bad" << std::endl;

   

   if (result != 0)

      std::cerr << "[C++] script failed" << std::endl;



   std::cout << "[C++] These values were returned from the script" << std::endl;

   while (lua_gettop( state ))

   {

      switch (lua_type( state, lua_gettop( state ) ))

      {

         case LUA_TNUMBER: std::cout << "script returned " << lua_tonumber( state, lua_gettop( state ) ) << std::endl; break;

         case LUA_TTABLE:  std::cout << "script returned a table" << std::endl; break;

         case LUA_TSTRING: std::cout << "script returned " << lua_tostring( state, lua_gettop( state ) ) << std::endl; break;

         case LUA_TBOOLEAN:std::cout << "script returned " << lua_toboolean( state, lua_gettop( state ) ) << std::endl; break;

         default: std::cout << "script returned unknown param" << std::endl; break;

      }

      lua_pop( state, 1 );

   }

   lua_close( state );

   return 0;

}

The Lua Script "args.lua"

io.write( "[lua] These args were passed into the script from C\n" );



for i=1,table.getn(arg) do

   print(i,arg[i])

end



io.write("[lua] Script returning data back to C\n")



local temp = {}

temp[1]=9

temp[2]=8

temp[3]=7

temp[4]=6

temp[5]=5



return temp,9,1