1.1 从C程序调用LUA函数
LUA的函数和普通变量一样也是First Class Variable类型,可以看作函数指针变量参与栈操作。因此调用过程分为如下几个步骤:
- 请求LUA函数(指针)入(GLOBAL)栈。
- 将函数需要的参数入栈,入栈顺序按照参数被声明的顺序。
- 告知LUA虚拟机入栈参数的个数、函数返回值的个数,并调用此LUA函数。
- 从栈定获得返回值,先返回的先入栈,然后将返回值显式出栈。
1.2 从LUA脚本调用C函数
LUA没有提供PYTHON那样丰富的类库,因此复杂的功能需要在C程序中定义好,然后通过lua决定调用时机。在LUA库中定义了可以被LUA虚拟机识别的C函数模型:
int functionName (lua_State* L) {....; return 1;}
这样的函数被是一个合法的lua_CFunction类型,将函数注册到LUA虚拟机中以后,就可以在LUA中以普通LUA函数的方式被调用。注册一个C函数的步骤如下:
- 声明并定义一个满足上述模型的函数 (eg. myFunInC)
- 用字符串为此C函数取一个名称并入栈(eg. myFunInLua)
- 将函数(指针)入栈
- 调用LUA库的注册函数功能,将上述的名称与函数指针关联
这样就可以在LUA中用myFunInLua()来调用C中的int myFunInC()了
2. 从C调用LUA函数示例
在下面的代码中,我们调用了LUA脚本中的fnEx2函数,返回值从栈中取得,并且要手动出栈。这里,入栈的函数参数会由pcall自动清理。
2.1 LUA测试脚本代码
function fnex2(str_a, num_b, num_c)
print(str_a);
return num_b*100 + num_c*10, "Thank you";
end;
2.2 VC代码
//初始化LUA虚拟机
void InitLuaState(lua_State* L)
{
/* Load Libraries */
luaopen_base(L);
luaopen_table(L);
luaL_openlibs(L);
luaopen_string(L);
luaopen_math(L);
}
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/None.gif)
int call_lua_function(void)
{
const char* szInParam = "This is an [IN] parameter";
const int iParam1 = 20, iParam2 = 50;
cout << "=================================" << endl
<< "02_Call_Function" << endl
<< "=================================" << endl
<< "This demo calls functions in LUA scripts." << endl
<< "Argument 1:" << szInParam << endl
<< "Argument 2:" << iParam1 << endl
<< "Argument 3:" << iParam2 << endl
<< "---------------------------------" << endl
<< "#OUTPUTS#" << endl;
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
lua_State* L = lua_open();
InitLuaState(L);
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
int iError;
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* Load Script */
iError = luaL_loadfile(L, "../test02.lua");
if (iError)
{
cout << "Load script FAILED!"
<< lua_tostring(L, -1)
<< endl;
lua_close(L);
return 1;
}
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* Run Script */
iError = lua_pcall(L, 0, 0, 0);
if (iError)
{
cout << "pcall FAILED"
<< lua_tostring(L, -1)
<< iError
<< endl;
lua_close(L);
return 1; } /* Push a FUNCTION_VAR to STACK */ lua_getglobal(L, "fnex2"); /* Push PARAMETERS to STACK */ lua_pushstring(L, szInParam); lua_pushnumber(L, iParam1); lua_pushnumber(L, iParam2); /* Call FUNCTION in LUA */ iError = lua_pcall( L, //VMachine 3, //Argument Count 2, //Return Value Count 0 ); if (iError) { cout << "pcall FAILED" << lua_tostring(L, -1) << iError << endl; lua_close(L); } /* Check Return Value Types */ if (lua_isstring(L, -1) && lua_isnumber(L, -2)) { cout << "Ret_1(string): " << lua_tostring(L, -1) << endl; cout << "Rec_2(double): " << lua_tonumber(L, -2) << endl; } else { cout << "Wrong Return Values" << endl; } /* POP STACK */ lua_pop(L,2); //只需要清理Return Value,pcall调用的入栈参数会自动清理 lua_close(L); return 0;}
2.3 工具
下面的宏可以简化调用lua函数的代码:
#define CallLuaFunc(FuncName, Params, Results)
{
lua_getglobal (g_pLuaState, FuncName);
lua_call (g_pLuaState, Params, Results);
}![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/None.gif)
3. 从LUA调用C函数示例
在下面的例子中,我们注册一个名为rmath的LUA函数,他在C中的函数名为RMath_LUA()
3.1 LUA脚本代码
print (">>> LUA程序开始运行了 ");
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/None.gif)
function fnex3(num_a, num_b)
local c = rmath(num_a, num_b);
print("LUA PRINTTING:", c);
return c;
end;
3.2 VC程序代码
//LUA脚本调用C函数
int call_c_function(void)
{
int iArg1 = 3, iArg2 = 10, iError;
cout << "=================================" << endl
<< "下面的程序演示从LUA脚本中调用C函数" << endl
<< "Argument 1:" << iArg1 << endl
<< "Argument 2:" << iArg2 << endl
<< "---------------------------------" << endl
<< "#OUTPUTS#" << endl;
lua_State* L = lua_open();
InitLuaState(L);
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
iError = luaL_loadfile(L, "../test03.lua");
if (iError) cout << "载入脚本失败" << endl;
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
iError = lua_pcall(L, 0, 0, 0);
if (iError) cout << "执行LUA脚本失败" << endl;
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* 将C函数(指针)压栈 */
lua_pushstring(L, "rmath");
lua_pushcfunction(L, RMath_LUA);
lua_settable(L, LUA_GLOBALSINDEX);
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* LUA函数也是变量(指针),可以压入栈 */
lua_getglobal(L, "fnex3");
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* 将提供给LUA函数的参数入栈 */
lua_pushnumber(L, iArg1);
lua_pushnumber(L, iArg2);
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* 调用LUA函数(pcall函数会自动清除入栈的变量) */
int Error = lua_pcall( L, //虚拟机指针
2, //2个参数
1, //1个返回值
0 );
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
if (Error) cout << "pcall调用fnex3函数失败" << endl;
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/InBlock.gif)
/* 检验返回值类型 */
if (lua_isnumber(L, -1))
{
cout << "有1个(double)返回值 = "
<< lua_tonumber(L, -1)
<< endl; } /* 将LUA函数返回值出栈 */ lua_pop(L, 1); lua_close(L); return 0;}//可供LUA调用的C函数原型int RMath_LUA(lua_State* L){ if (!lua_isnumber(L, 1)) { lua_pushstring(L, "Arg_1不是数字"); lua_error(L); } if (!lua_isnumber(L, 2)) { lua_pushstring(L, "Arg_2不是数字"); lua_error(L); } /* GET ARGUMENT FROM STACK */ double a = lua_tonumber(L, 1); double b = lua_tonumber(L, 2); /* PUSH RESULT TO STACK */ lua_pushnumber(L, a * b); /* COUNT OF RETURN VARS*/ return 1;}
4. 程序解释
4.1 调用LUA脚本中的函数
调用LUA脚本函数主要用到如下几个LUA库函数:
/* Push a FUNCTION_VAR to STACK */
lua_getglobal(L, "fnex2");
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/None.gif)
/* Push PARAMETERS to STACK */
lua_pushstring(L, szInParam);
lua_pushnumber(L, iParam1);
lua_pushnumber(L, iParam2);
![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/None.gif)
/* Call FUNCTION in LUA */
iError = lua_pcall( L,3,2,0);
通过lua_getglobal请求函数(指针)入栈,然后将函数参数按声明顺序入栈,调用lua_pcall执行函数。lua_pcall的第一个参数 指向LUA虚拟机,第二个参数表示栈顶有多少个函数参数,第三个参数表示此函数将返回几个值。(pcall自动清理入栈的参数,返回值则需要手动 pop。)
4.2 从LUA调用C函数
主要用到如下几个函数,为求方便您也可以自己定义这样的一个宏。
lua_pushstring(L, "rmath");
lua_pushcfunction(L, RMath_LUA);
lua_settable(L, LUA_GLOBALSINDEX);![](file:///C:/Documents%20and%20Settings/Administrator/%E6%A1%8C%E9%9D%A2/[LUA%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B003]LUA%E5%87%BD%E6%95%B0%E5%92%8CC%E5%87%BD%E6%95%B0%E7%9A%84%E7%9B%B8%E4%BA%92%E8%B0%83%E7%94%A8.files/None.gif)
- 函数名入栈
- lua_CFunction类型的函数指针入栈
- 调用lua_settable注册函数
这样就可以在lua脚本中调用rmath()函数了。