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 const generics support for the structs.
* Added implementation for array of any const size `N`.
* 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 +20,36 @@ 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 {
+    uint8_t idx[1];
+} uint8_1_array_t;
+
+typedef struct {
+    uint8_1_array_t idx[2];
+} uint8_1_array_2_array_t;
+
+typedef struct {
+    uint8_1_array_2_array_t idx[3];
+} uint8_1_array_2_array_3_array_t;
+
+typedef struct ArraysStruct {
+    float_3_array_t floats;
+
+    size_5_array_t sizes;
+
+    uint8_1_array_2_array_t dim_2;
+
+    uint8_1_array_2_array_3_array_t dim_3;
+} ArraysStruct_t;
+
 #define FOO ...
 
 typedef enum Bar {
@@ -36,6 +66,34 @@ typedef struct next_generation {
     void * (*cb)(bool);
 } next_generation_t;
 
+typedef struct ConstGenericStruct_uint8_1 {
+    uint8_1_array_t data;
+} ConstGenericStruct_uint8_1_t;
+
+typedef struct {
+    uint8_t idx[2];
+} uint8_2_array_t;
+
+typedef struct ConstGenericStruct_uint8_2 {
+    uint8_2_array_t data;
+} ConstGenericStruct_uint8_2_t;
+
+typedef struct {
+    uint16_t idx[3];
+} uint16_3_array_t;
+
+typedef struct ConstGenericStruct_uint16_3 {
+    uint16_3_array_t data;
+} ConstGenericStruct_uint16_3_t;
+
+typedef struct SpecificConstGenericContainer {
+    ConstGenericStruct_uint8_1_t field1;
+
+    ConstGenericStruct_uint8_2_t field2;
+
+    ConstGenericStruct_uint16_3_t field3;
+} SpecificConstGenericContainer_t;
+
 typedef enum triforce {
     TRIFORCE_DIN,
     TRIFORCE_FARORE,

ffi_tests/generated.cs

@@ -33,6 +33,47 @@ 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 = 1)]
+public unsafe struct uint8_1_array_t {
+    public fixed byte arr[1];
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 2)]
+public unsafe struct uint8_1_array_2_array_t {
+    public uint8_1_array_t _0;
+    public uint8_1_array_t _1;
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 6)]
+public unsafe struct uint8_1_array_2_array_3_array_t {
+    public uint8_1_array_2_array_t _0;
+    public uint8_1_array_2_array_t _1;
+    public uint8_1_array_2_array_t _2;
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 64)]
+public unsafe struct ArraysStruct_t {
+    public float_3_array_t floats;
+
+    public size_5_array_t sizes;
+
+    public uint8_1_array_2_array_t dim_2;
+
+    public uint8_1_array_2_array_3_array_t dim_3;
+}
+
 public unsafe partial class Ffi {
     public const Int32 FOO = 42;
 }
@@ -66,6 +107,40 @@ public unsafe struct next_generation_t {
     public void_ptr_bool_fptr cb;
 }
 
+[StructLayout(LayoutKind.Sequential, Size = 1)]
+public unsafe struct ConstGenericStruct_uint8_1_t {
+    public uint8_1_array_t data;
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 2)]
+public unsafe struct uint8_2_array_t {
+    public fixed byte arr[2];
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 2)]
+public unsafe struct ConstGenericStruct_uint8_2_t {
+    public uint8_2_array_t data;
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 6)]
+public unsafe struct uint16_3_array_t {
+    public fixed UInt16 arr[3];
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 6)]
+public unsafe struct ConstGenericStruct_uint16_3_t {
+    public uint16_3_array_t data;
+}
+
+[StructLayout(LayoutKind.Sequential, Size = 10)]
+public unsafe struct SpecificConstGenericContainer_t {
+    public ConstGenericStruct_uint8_1_t field1;
+
+    public ConstGenericStruct_uint8_2_t field2;
+
+    public ConstGenericStruct_uint16_3_t field3;
+}
+
 /// <summary>
 /// Hello, <c>World</c>!
 /// </summary>

ffi_tests/generated.h

@@ -39,6 +39,41 @@ 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 {
+    uint8_t idx[1];
+} uint8_1_array_t;
+
+typedef struct {
+    uint8_1_array_t idx[2];
+} uint8_1_array_2_array_t;
+
+typedef struct {
+    uint8_1_array_2_array_t idx[3];
+} uint8_1_array_2_array_3_array_t;
+
+/** <No documentation available> */
+typedef struct ArraysStruct {
+    /** <No documentation available> */
+    float_3_array_t floats;
+
+    /** <No documentation available> */
+    size_5_array_t sizes;
+
+    /** <No documentation available> */
+    uint8_1_array_2_array_t dim_2;
+
+    /** <No documentation available> */
+    uint8_1_array_2_array_3_array_t dim_3;
+} ArraysStruct_t;
+
 /** <No documentation available> */
 #define FOO ((int32_t) 42)
 
@@ -76,6 +111,44 @@ typedef struct next_generation {
     void * (*cb)(bool);
 } next_generation_t;
 
+/** <No documentation available> */
+typedef struct ConstGenericStruct_uint8_1 {
+    /** <No documentation available> */
+    uint8_1_array_t data;
+} ConstGenericStruct_uint8_1_t;
+
+typedef struct {
+    uint8_t idx[2];
+} uint8_2_array_t;
+
+/** <No documentation available> */
+typedef struct ConstGenericStruct_uint8_2 {
+    /** <No documentation available> */
+    uint8_2_array_t data;
+} ConstGenericStruct_uint8_2_t;
+
+typedef struct {
+    uint16_t idx[3];
+} uint16_3_array_t;
+
+/** <No documentation available> */
+typedef struct ConstGenericStruct_uint16_3 {
+    /** <No documentation available> */
+    uint16_3_array_t data;
+} ConstGenericStruct_uint16_3_t;
+
+/** <No documentation available> */
+typedef struct SpecificConstGenericContainer {
+    /** <No documentation available> */
+    ConstGenericStruct_uint8_1_t field1;
+
+    /** <No documentation available> */
+    ConstGenericStruct_uint8_2_t field2;
+
+    /** <No documentation available> */
+    ConstGenericStruct_uint16_3_t field3;
+} SpecificConstGenericContainer_t;
+
 /** \brief
  *  Hello, `World`!
  */