如何从c函数回调lua函数 [英] how to callback a lua function from a c function

问题描述

我有一个C函数（A） test_callback 接受指向函数（B）的指针作为参数，A将回调B.

I have a C function (A) test_callback accepting a pointer to a function(B) as the parameter and A will "callback" B.

//typedef int(*data_callback_t)(int i);
int test_callback(data_callback_t f)
{
    f(3);   
}


int datacallback(int a )
{
    printf("called back %d\n",a);
    return 0;
}


//example 
test_callback(datacallback); // print : called back 3 

现在，我想换 test_callback ，以便它们可以从lua调用，假设名称为 lua_test_callback ;并且它的输入参数将是lua函数。我应该如何实现这个目标？

Now, I want to wrap test_callback so that they can be called from lua, suppose the name is lua_test_callback ;and also the input parameter to it would be a lua function. How should I achieve this goal?

function lua_datacallback (a )
    print "hey , this is callback in lua" ..a
end


lua_test_callback(lua_datacallback)  //expect to get "hey this is callback in lua 3 "

编辑：

此链接提供了一种存储回调函数供以后使用的方法。

This link provide a way to store the callback function for later use .

//save function for later use 
callback_function = luaL_ref(L,LUA_REGISTRYINDEX);


//retrive function and call it 
lua_rawgeti(L,LUA_REGISTRYINDEX,callback_function);
//push the parameters and call it
lua_pushnumber(L, 5); // push first argument to the function
lua_pcall(L, 1, 0, 0); // call a function with one argument and no return values

推荐答案

我不知道我理解你的问题，如果你问什么 lua_test_callback 看看C，它应该是这样

I'm not sure I understand your question, if you are asking what would lua_test_callback look in C, it should be something like this

int lua_test_callback(lua_State* lua)
{
    if (lua_gettop(lua) == 1 && // make sure exactly one argument is passed
       lua_isfunction(lua, -1)) // and that argument (which is on top of the stack) is a function
    {
        lua_pushnumber(lua, 3); // push first argument to the function
        lua_pcall(lua, 1, 0, 0); // call a function with one argument and no return values
    }
    return 0; // no values are returned from this function
}

$ c> test_callback ，您需要完全不同的实现来调用Lua函数。

You cannot just wrap test_callback, you need entirely different implementation to call Lua functions.

（edit：changed lua_call 到 lua_pcall ，我仍然省略任何错误处理为简洁）

(edit: changed lua_call to lua_pcall as suggested by Nick. I still omitted any error handling for brevity)

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