Add Lua language support.

Lua FFI has a few notable differrences from regular generated C headers:
* Custom prelude/epilogue with `ffi.cdef` directive.
* Constants defined using `static const` syntax instead of `#define`.
* Different comments format using `--` or `[[` instead of `/* */`.
* Doesn't support `#include`, `#ifdef` or other macros.

Lua FFI described in more details at http://luajit.org/ext_ffi.html

Other changes:
* Added implementation for more common array sizes, e.g. 36 for UUID.
* Added `try_as_str` implementation for `str_ref`.

.github/workflows/gh-pages.yml

@@ -173,7 +173,15 @@ jobs:
           command: test
           args: --features docs
 
-      - name: FFI test (C & C#?)
+      - name: Install LuaJIT and LuaRocks (Ubuntu)
+        run: sudo apt-get install -y luajit
+        if: matrix.os == 'ubuntu-latest'
+
+      - name: Install LuaJIT and LuaRocks (macOS)
+        run: brew install luajit
+        if: matrix.os == 'macos-latest'
+
+      - name: FFI test (C & C# & Lua?)
         run: make -C ffi_tests
         if: runner.os != 'Windows'
         env:

ffi_tests/generated.cffi

@@ -20,6 +20,20 @@ typedef struct AnUnusedStruct {
     Wow_t are_you_still_there;
 } AnUnusedStruct_t;
 
+typedef struct {
+    float idx[3];
+} float_3_array_t;
+
+typedef struct {
+    size_t idx[5];
+} size_5_array_t;
+
+typedef struct ArraysStruct {
+    float_3_array_t floats;
+
+    size_5_array_t sizes;
+} ArraysStruct_t;
+
 #define FOO ...
 
 typedef enum Bar {

ffi_tests/generated.cs

@@ -33,6 +33,25 @@ public unsafe struct AnUnusedStruct_t {
     public Wow_t are_you_still_there;
 }
 
+[StructLayout(LayoutKind.Sequential, Size = 12)]
+public unsafe struct float_3_array_t {
+    public float _0;
+    public float _1;
+    public float _2;
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 40)]
+public unsafe struct size_5_array_t {
+    public fixed UIntPtr arr[5];
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 56)]
+public unsafe struct ArraysStruct_t {
+    public float_3_array_t floats;
+
+    public size_5_array_t sizes;
+}
+
 public unsafe partial class Ffi {
     public const Int32 FOO = 42;
 }

ffi_tests/generated.h

@@ -39,6 +39,23 @@ typedef struct AnUnusedStruct {
     Wow_t are_you_still_there;
 } AnUnusedStruct_t;
 
+typedef struct {
+    float idx[3];
+} float_3_array_t;
+
+typedef struct {
+    size_t idx[5];
+} size_5_array_t;
+
+/** <No documentation available> */
+typedef struct ArraysStruct {
+    /** <No documentation available> */
+    float_3_array_t floats;
+
+    /** <No documentation available> */
+    size_5_array_t sizes;
+} ArraysStruct_t;
+
 /** <No documentation available> */
 #define FOO ((int32_t) 42)
 

ffi_tests/generated.lua

@@ -0,0 +1,301 @@
+-- File auto-generated by `::safer_ffi`.
+--
+-- Do not manually edit this file.
+
+local ffi = require "ffi"
+
+ffi.cdef [[
+
+// <No documentation available>
+// enum has the same ABI as `uint8_t`
+typedef enum Wow {
+    // <No documentation available>
+    WOW_LEROY,
+    // <No documentation available>
+    WOW_JENKINS,
+}; typedef uint8_t Wow_t;
+// <No documentation available>
+typedef struct AnUnusedStruct {
+    // <No documentation available>
+    Wow_t are_you_still_there;
+} AnUnusedStruct_t;
+
+typedef float float_3_array_t[3];
+
+typedef size_t size_5_array_t[5];
+
+// <No documentation available>
+typedef struct ArraysStruct {
+    // <No documentation available>
+    float_3_array_t floats;
+
+    // <No documentation available>
+    size_5_array_t sizes;
+} ArraysStruct_t;
+
+// <No documentation available>
+static const int32_t FOO = 42;
+
+// <No documentation available>
+// enum has the same ABI as `int8_t`
+typedef enum Bar {
+    // <No documentation available>
+    BAR_A = 43,
+    // <No documentation available>
+    BAR_B = 42,
+}; typedef int8_t Bar_t;
+// Hello, `World`!
+typedef struct next_generation {
+    // I test some `gen`-eration.
+    Bar_t gen;
+
+    // with function pointers and everything!
+    void * (*cb)(bool);
+} next_generation_t;
+
+// Hello, `World`!
+// enum has the same ABI as `uint8_t`
+typedef enum triforce {
+    // <No documentation available>
+    TRIFORCE_DIN = 3,
+    // <No documentation available>
+    TRIFORCE_FARORE = 1,
+    // <No documentation available>
+    TRIFORCE_NARYU,
+}; typedef uint8_t triforce_t;
+// https://github.com/getditto/safer_ffi/issues/45
+int32_t
+_issue_45 (
+    int32_t __arg_0);
+
+// <No documentation available>
+int32_t
+async_get_ft (void);
+
+// `Arc<dyn Send + Sync + Fn() -> Ret>`
+typedef struct ArcDynFn0_void {
+    // <No documentation available>
+    void * env_ptr;
+
+    // <No documentation available>
+    void (*call)(void *);
+
+    // <No documentation available>
+    void (*release)(void *);
+
+    // <No documentation available>
+    void (*retain)(void *);
+} ArcDynFn0_void_t;
+
+// <No documentation available>
+void
+call_in_the_background (
+    ArcDynFn0_void_t f);
+
+// This is a `#[repr(C)]` enum, which leads to a classic enum def.
+typedef enum SomeReprCEnum {
+    // This is some variant.
+    SOME_REPR_C_ENUM_SOME_VARIANT,
+} SomeReprCEnum_t;
+// <No documentation available>
+void
+check_SomeReprCEnum (
+    SomeReprCEnum_t _baz);
+
+// <No documentation available>
+void
+check_bar (
+    Bar_t _bar);
+
+// Concatenate the two input strings into a new one.
+//
+// The returned string must be freed using `free_char_p`.
+char *
+concat (
+    char const * fst,
+    char const * snd);
+
+// Frees a string created by `concat`.
+void
+free_char_p (
+    char * _string);
+
+// <No documentation available>
+typedef struct foo foo_t;
+
+// <No documentation available>
+void
+free_foo (
+    foo_t * foo);
+
+// `&'lt [T]` but with a guaranteed `#[repr(C)]` layout.
+//
+// # C layout (for some given type T)
+//
+// ```c
+// typedef struct {
+// // Cannot be NULL
+// T * ptr;
+// size_t len;
+// } slice_T;
+// ```
+//
+// # Nullable pointer?
+//
+// If you want to support the above typedef, but where the `ptr` field is
+// allowed to be `NULL` (with the contents of `len` then being undefined)
+// use the `Option< slice_ptr<_> >` type.
+typedef struct slice_ref_int32 {
+    // Pointer to the first element (if any).
+    int32_t const * ptr;
+
+    // Element count
+    size_t len;
+} slice_ref_int32_t;
+
+// Returns a pointer to the maximum integer of the input slice, or `NULL` if
+// it is empty.
+int32_t const *
+max (
+    slice_ref_int32_t xs);
+
+// <No documentation available>
+foo_t *
+new_foo (void);
+
+// <No documentation available>
+int32_t
+read_foo (
+    foo_t const * foo);
+
+// <No documentation available>
+uint16_t (*
+returns_a_fn_ptr (void))(uint8_t);
+
+// The layout of `core::task::wake::Context` is opaque/subject to changes.
+typedef struct Opaque_Context Opaque_Context_t;
+
+// <No documentation available>
+ArcDynFn0_void_t
+rust_future_task_context_get_waker (
+    Opaque_Context_t const * task_context);
+
+// <No documentation available>
+void
+rust_future_task_context_wake (
+    Opaque_Context_t const * task_context);
+
+// <No documentation available>
+typedef struct Erased Erased_t;
+
+// An FFI-safe `Poll<()>`.
+// enum has the same ABI as `int8_t`
+typedef enum PollFuture {
+    // <No documentation available>
+    POLL_FUTURE_COMPLETED = 0,
+    // <No documentation available>
+    POLL_FUTURE_PENDING = -1,
+}; typedef int8_t PollFuture_t;
+// <No documentation available>
+typedef struct FfiFutureVTable {
+    // <No documentation available>
+    void (*release_vptr)(Erased_t *);
+
+    // <No documentation available>
+    PollFuture_t (*dyn_poll)(Erased_t *, Opaque_Context_t *);
+} FfiFutureVTable_t;
+
+// <No documentation available>
+typedef struct VirtualPtr__Erased_ptr_FfiFutureVTable {
+    // <No documentation available>
+    Erased_t * ptr;
+
+    // <No documentation available>
+    FfiFutureVTable_t vtable;
+} VirtualPtr__Erased_ptr_FfiFutureVTable_t;
+
+// `Box<dyn 'static + Send + FnMut() -> Ret>`
+typedef struct BoxDynFnMut0_void {
+    // <No documentation available>
+    void * env_ptr;
+
+    // <No documentation available>
+    void (*call)(void *);
+
+    // <No documentation available>
+    void (*free)(void *);
+} BoxDynFnMut0_void_t;
+
+// <No documentation available>
+typedef struct DropGlueVTable {
+    // <No documentation available>
+    void (*release_vptr)(Erased_t *);
+} DropGlueVTable_t;
+
+// <No documentation available>
+typedef struct VirtualPtr__Erased_ptr_DropGlueVTable {
+    // <No documentation available>
+    Erased_t * ptr;
+
+    // <No documentation available>
+    DropGlueVTable_t vtable;
+} VirtualPtr__Erased_ptr_DropGlueVTable_t;
+
+// <No documentation available>
+typedef struct FfiFutureExecutorVTable {
+    // <No documentation available>
+    void (*release_vptr)(Erased_t *);
+
+    // <No documentation available>
+    Erased_t * (*retain_vptr)(Erased_t const *);
+
+    // <No documentation available>
+    VirtualPtr__Erased_ptr_FfiFutureVTable_t (*dyn_spawn)(Erased_t const *, VirtualPtr__Erased_ptr_FfiFutureVTable_t);
+
+    // <No documentation available>
+    VirtualPtr__Erased_ptr_FfiFutureVTable_t (*dyn_spawn_blocking)(Erased_t const *, BoxDynFnMut0_void_t);
+
+    // <No documentation available>
+    void (*dyn_block_on)(Erased_t const *, VirtualPtr__Erased_ptr_FfiFutureVTable_t);
+
+    // <No documentation available>
+    VirtualPtr__Erased_ptr_DropGlueVTable_t (*dyn_enter)(Erased_t const *);
+} FfiFutureExecutorVTable_t;
+
+// <No documentation available>
+typedef struct VirtualPtr__Erased_ptr_FfiFutureExecutorVTable {
+    // <No documentation available>
+    Erased_t * ptr;
+
+    // <No documentation available>
+    FfiFutureExecutorVTable_t vtable;
+} VirtualPtr__Erased_ptr_FfiFutureExecutorVTable_t;
+
+// <No documentation available>
+int32_t
+test_spawner (
+    VirtualPtr__Erased_ptr_FfiFutureExecutorVTable_t executor);
+
+// `&'lt mut (dyn 'lt + Send + FnMut(A1) -> Ret)`
+typedef struct RefDynFnMut1_void_char_const_ptr {
+    // <No documentation available>
+    void * env_ptr;
+
+    // <No documentation available>
+    void (*call)(void *, char const *);
+} RefDynFnMut1_void_char_const_ptr_t;
+
+// Same as `concat`, but with a callback-based API to auto-free the created
+// string.
+void
+with_concat (
+    char const * fst,
+    char const * snd,
+    RefDynFnMut1_void_char_const_ptr_t cb);
+
+// <No documentation available>
+bool
+with_foo (
+    void (*cb)(foo_t *));
+
+]]