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About

This is a library for calling C function and manipulating C types from lua. It is designed to be interface compatible with the FFI library in luajit (see http://luajit.org/ext_ffi.html). It can parse C function declarations and struct definitions that have been directly copied out of C header files and into lua source as a string.

License

Copyright (c) 2011 James R. McKaskill. MIT same as Lua 5.1. See full license text in ffi.h.

Source

https://github.com/jmckaskill/luaffi

Platforms

Currently supported:

Currently only dll builds are supported (ie no static).

Runs with both Lua 5.1 and Lua 5.2 beta.

Build

On windows use msvcbuild.bat in a visual studio cmd prompt. Available targets are:

Edit msvcbuild.bat if your lua exe, lib, lua include path, or lua dll name differ from c:\Lua5.1 and lua5.1.dll.

The build script does not build for CE as this is non-trivial and very dependent on which CE profile (or even a custom one). Instead to build on CE, add generate_call_h.bat as a pre-build event and then build *.c with UNDER_CE defined plus whatever defines windows.h requires.

On posix use make. Available targets are:

Edit the Makefile if your lua exe differs from lua5.1 or if you can't get the include and lib arguments from pkg-config.

Known Issues

Todo

See Github issues for the most up to date list.

How it works

Types are represented by a struct ctype structure and an associated user value table. The table is shared between all related types for structs, unions, and functions. It's members have the types of struct members, function argument types, etc. The struct ctype structure then contains the modifications from the base type (eg number of pointers, array size, etc).

Types are pushed into lua as a userdata containing the struct ctype with a user value (or fenv in 5.1) set to the shared type table.

Boxed cdata types are pushed into lua as a userdata containing the struct cdata structure (which contains the struct ctype of the data as its header) followed by the boxed data.

The functions in ffi.c provide the cdata and ctype metatables and ffi.* functions which manipulate these two types.

C functions (and function pointers) are pushed into lua as a lua c function with the function pointer cdata as the first upvalue. The actual code is JITed using dynasm (see call_x86.dasc). The JITed code does the following in order:

  1. Calls the needed unpack functions in ffi.c placing each argument on the HW stack
  2. Updates errno
  3. Performs the c call
  4. Retrieves errno
  5. Pushes the result back into lua from the HW register or stack