Automatically turns LuaJIT FFI declarations into valid Lua-Language-Server meta files.

• LuaJIT
• LLVM (for libclang)
• C compiler (to compile utilities.c)

First, compile utilities.c

cc $(llvm-config --cflags) utilities.c -shared -o utilities.so -L$(llvm-config --libdir) -lclang

Then, run the script:

luajit ffi-to-lls.lua <input defs.h> [-o <output file>] [--remove-prefix <prefix>] [--no-auxiliary-types] [--module-name <name>]

• <input defs.h>: The header file containing the FFI declarations.
• -o <output file>: The output file to write the LLS meta file to. If not specified, the output will be written to stdout.
• --remove-prefix <prefix>: Remove the specified prefix from the function names in the output. This is useful when the FFI declarations are prefixed with a common string, such as lua_ or lj_.
• --no-auxiliary-types: Do not generate auxiliary types such as c.pointer<T>. This is useful when the generated file is used with another file that already defines these types.
• --module-name <name>: The name of the module to be usede in generation

Given the a definitions file such as:

struct MyStruct {
  int a;
  int b;
};

struct MyStruct *mylib_MyStruct_create(int a, int b);

void mylib_MyStruct_free(struct MyStruct *s);

We can generate definitions with

luajit ffi-to-lls.lua mylib.h -o mylib.lua --remove-prefix mylib_

A file like this would be generated:

---Automatically generated bindings generated by ffi-to-lls.lua (https://github.com/Frityet/ffi-to-lls/)
---You can edit this file!
---The following prefix was removed: `mylib_`
---Lua language server will autocomplete both with and without the prefix.
---@meta mylib

---You may remove this, or generate this file again with --no-auxiliary-types, to supress redefinition warnings
---@class c.pointer<T> : { [integer] : T }, ffi.cdata*
---@class mylib
local mylib = {}

---@class MyStruct
---@field a integer
---@field b integer

---@param a integer
---@param b integer
---@return c.pointer<MyStruct>
function mylib.mylib_MyStruct_create(a, b) end
mylib.MyStruct_create = mylib.mylib_MyStruct_create

---@param s c.pointer<MyStruct>
---@return nil
function mylib.mylib_MyStruct_free(s) end
mylib.MyStruct_free = mylib.mylib_MyStruct_free

return mylib