(2015-04-02)

Calling C Function From Lua Mac
Call C Function From Lua Example
Calling C Function From Assembly

From the point of view of C, a C function gets as its single argument the Lua state and returns (in C) an integer with the number of values it is returning (in Lua). Therefore, the function does not need to clear the stack before pushing its results. After it returns, Lua automatically removes whatever is in the stack below the results. One Way to Call a Lua Function from C. Now that we have the Lua code to draw mazes, let’s see how to write a C program that can run the Lua file. As examples of why this is useful, you could run a Lua script from Objective-C in an iOS app, or run a cross-platform Lua script from platform-specific C or C code.

As of last time, we can set global variables, read global variables, and call Lua functions.However, once inside Lua, we cannot make calls that return to C++.These could be useful in many situations.For example, numerical code can be written in C++ for greater speed, then called from Lua.Alternatively, the Lua code may be a callback in a GUI framework, which needs to call C++ functions to change the state of the GUI.

Any C++ function called from within Lua must have a particular signature, and must assume a particular calling convention.The arguments are pushed onto the Lua stack, then the function is called.The function then acts, pushing its return values onto the stack.Finally, the function returns the number of arguments to be returned to Lua.

Because functions in C and Lua work so differently, exposing a C function to Lua can get a bit tricky. All C functions that Lua can call must follow the signature of luaCFunction, which is defined in lua.h as the following. 1 day ago I'm trying to do a nested function call from C to Lua. It looks like this in Lua: function1(function2('string')) luagetfield and luacall is all I need I think, but I just can't construct it. Can somebody help me to call it from C? C c lua lua-api. Improve this question. These videos describe how to embed Lua into a native application and interface with the Lua C API. They do not cover how to use the scripting language itself.

As an example, to wrap the average() function defined below, I would need the following wrapper code.

It could then be exposed to Lua as follows.

Calling C Function From Lua Mac

This works, but requires significant new code.I want to avoid needing to rewrite the wrapper code for each new function.To do this, rather than passing a function lua_average, I will pass in userdata.

Lua userdata is memory that is managed by Lua, but can only be modified in the surrounding program.This could be used, for example, to store a pointer to a class.That class could hold a function to be called.First, let’s set up the framework that we will need.

Now, so long as the first argument to call_lua_callable() is a pointer to a LuaCallable, the function can be called.This isn’t good enough.I want to be able to call functions directly.My Lua code should not constantly be littered with calls to call_lua_callable().

Instead, I will attach a metatable to the userdata.Among other things, a metatable can specify a __call method, which allows the userdata to act as a function.Let’s make a Push() variant to attach a metatable.

Now, the LuaCallable can be called directly.All that is left is to make an implementation of the base class.

With this, the following code can provide the average() function to be used in Lua.

This worked quite well.Rather than needing to write a wrapper for each function, now a wrapper is only necessary for each function signature.Let’s use some templates to make even this step unnecessary.

Note the template magic with indices and build_indices.These are necessary to extract call Read() with multiple different indices, and will be explained in a later post.

With this, it is now possible to write a generic Push() function that accepts any C++ function.

Now, finally, C++ functions can be exposed to Lua without any extra hassle.

Now, C++ functions can be exposed for use from within Lua.With trivial modifications, this can be extended to any std::function, not just C-style function pointers.

After cleaning up a few small details, we’ll be starting to expose C++ classes for use in Lua.

Call C Function From Lua Example

Calling C Function From Assembly

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