Implement struct and arr (#243)

struct.size: Returns a non-zero actual size
rewrite use super:: => use crate::

crates/lune-std-ffi/src/carr.rs

@@ -1,6 +1,8 @@
 use libffi::middle::Type;
 use mlua::prelude::*;
 
+use crate::ctype::libffi_type_ensured_size;
+
 // This is a series of some type.
 // It provides the final size and the offset of the index,
 // but does not allow multidimensional arrays because of API complexity.
@@ -9,15 +11,29 @@ use mlua::prelude::*;
 
 // See: https://stackoverflow.com/a/43525176
 
+// Padding after each field inside the struct is set to next field can follow the alignment.
+// There is no problem even if you create a struct with n fields of a single type within the struct. Array adheres to the condition that there is no additional padding between each element. Padding to a struct is padding inside the struct. Simply think of the padding byte as a trailing unnamed field.
+
 struct CArr {
     libffi_type: Type,
+    struct_type: Type,
     length: usize,
+    field_size: usize,
     size: usize,
 }
 
 impl CArr {
-    fn new(libffi_type: Type, length: usize) {
-        Self { libffi_type }
+    fn new(libffi_type: Type, length: usize) -> LuaResult<Self> {
+        let struct_type = Type::structure(vec![libffi_type.clone(); length]);
+        let field_size = libffi_type_ensured_size(libffi_type.as_raw_ptr())?;
+
+        Ok(Self {
+            libffi_type,
+            struct_type,
+            length,
+            field_size,
+            size: field_size * length,
+        })
     }
 }
 

crates/lune-std-ffi/src/cstruct.rs

@@ -1,16 +1,17 @@
 #![allow(clippy::cargo_common_metadata)]
 
-use mlua::prelude::*;
-
-use libffi::low::ffi_abi_FFI_DEFAULT_ABI;
-use libffi::middle::{Cif, Type};
-use libffi::raw::ffi_get_struct_offsets;
 use std::vec::Vec;
 
-use crate::association::{get_association, set_association};
-use crate::ctype::{libffi_types_from_table, type_name_from_userdata};
+use libffi::{
+    low,
+    middle::{Cif, Type},
+    raw,
+};
+use mlua::prelude::*;
 
-use super::ctype::CType;
+use crate::association::{get_association, set_association};
+use crate::ctype::{libffi_types_from_table, type_name_from_userdata, CType};
+use crate::FFI_STATUS_NAMES;
 
 pub struct CStruct {
     libffi_cif: Cif,
@@ -23,35 +24,48 @@ pub struct CStruct {
 const CSTRUCT_INNER: &str = "__cstruct_inner";
 
 impl CStruct {
-    pub fn new(fields: Vec<Type>) -> Self {
+    pub fn new(fields: Vec<Type>) -> LuaResult<Self> {
         let libffi_type = Type::structure(fields.clone());
         let libffi_cfi = Cif::new(vec![libffi_type.clone()], Type::void());
-        let size = unsafe { (*libffi_type.as_raw_ptr()).size };
+
+        // Get field offsets with ffi_get_struct_offsets
         let mut offsets = Vec::<usize>::with_capacity(fields.len());
         unsafe {
-            ffi_get_struct_offsets(
-                ffi_abi_FFI_DEFAULT_ABI,
+            let offset_result: raw::ffi_status = raw::ffi_get_struct_offsets(
+                low::ffi_abi_FFI_DEFAULT_ABI,
                 libffi_type.as_raw_ptr(),
                 offsets.as_mut_ptr(),
             );
+            if offset_result != raw::ffi_status_FFI_OK {
+                return Err(LuaError::external(format!(
+                    "ffi_get_struct_offsets failed. expected result {}, got {}",
+                    FFI_STATUS_NAMES[0], FFI_STATUS_NAMES[offset_result as usize]
+                )));
+            }
             offsets.set_len(offsets.capacity());
         }
 
-        Self {
+        // Get tailing padded size of struct
+        // See http://www.chiark.greenend.org.uk/doc/libffi-dev/html/Size-and-Alignment.html
+        let size = unsafe { (*libffi_type.as_raw_ptr()).size };
+
+        Ok(Self {
             libffi_cif: libffi_cfi,
             libffi_type,
             fields,
             offsets,
             size,
-        }
+        })
     }
 
+    // Create new CStruct UserData with LuaTable.
+    // Lock and hold table for .inner ref
     pub fn from_lua_table<'lua>(
         lua: &'lua Lua,
         table: LuaTable<'lua>,
     ) -> LuaResult<LuaAnyUserData<'lua>> {
         let fields = libffi_types_from_table(&table)?;
-        let cstruct = lua.create_userdata(Self::new(fields))?;
+        let cstruct = lua.create_userdata(Self::new(fields)?)?;
         table.set_readonly(true);
         set_association(lua, CSTRUCT_INNER, cstruct.clone(), table)?;
         Ok(cstruct)
@@ -81,10 +95,6 @@ impl CStruct {
         }
     }
 
-    pub fn get_type(&self) -> Type {
-        self.libffi_type.clone()
-    }
-
     // Get byte offset of nth field
     pub fn offset(&self, index: usize) -> LuaResult<usize> {
         let offset = self
@@ -94,6 +104,10 @@ impl CStruct {
             .to_owned();
         Ok(offset)
     }
+
+    pub fn get_type(&self) -> Type {
+        self.libffi_type.clone()
+    }
 }
 
 impl LuaUserData for CStruct {

crates/lune-std-ffi/src/ctype.rs

@@ -1,12 +1,19 @@
 #![allow(clippy::cargo_common_metadata)]
 
 use std::borrow::Borrow;
+use std::ptr::{self, null_mut};
 
-use super::association::{get_association, set_association};
-use super::cstruct::CStruct;
-use libffi::middle::{Cif, Type};
+use libffi::{
+    low,
+    middle::{Cif, Type},
+    raw,
+};
 use lune_utils::fmt::{pretty_format_value, ValueFormatConfig};
 use mlua::prelude::*;
+
+use crate::association::{get_association, set_association};
+use crate::cstruct::CStruct;
+use crate::FFI_STATUS_NAMES;
 // use libffi::raw::{ffi_cif, ffi_ptrarray_to_raw};
 
 const POINTER_INNER: &str = "__pointer_inner";
@@ -18,9 +25,6 @@ pub struct CType {
     name: Option<String>,
 }
 
-// TODO: ARR
-// TODO: convert
-
 impl CType {
     pub fn new(libffi_type: Type, name: Option<String>) -> Self {
         let libffi_cfi = Cif::new(vec![libffi_type.clone()], Type::void());
@@ -201,3 +205,26 @@ pub fn type_name_from_userdata(userdata: &LuaAnyUserData) -> LuaResult<String> {
         Ok(String::from("unnamed"))
     }
 }
+
+// Ensure sizeof c-type (raw::libffi_type)
+// See: http://www.chiark.greenend.org.uk/doc/libffi-dev/html/Size-and-Alignment.html
+pub fn libffi_type_ensured_size(ffi_type: *mut raw::ffi_type) -> LuaResult<usize> {
+    let mut cif: low::ffi_cif = Default::default();
+    let result = unsafe {
+        raw::ffi_prep_cif(
+            ptr::from_mut(&mut cif),
+            raw::ffi_abi_FFI_DEFAULT_ABI,
+            0,
+            ffi_type,
+            null_mut(),
+        )
+    };
+
+    if result != raw::ffi_status_FFI_OK {
+        return Err(LuaError::external(format!(
+            "ffi_get_struct_offsets failed. expected result {}, got {}",
+            FFI_STATUS_NAMES[0], FFI_STATUS_NAMES[result as usize]
+        )));
+    }
+    unsafe { Ok((*ffi_type).size) }
+}

crates/lune-std-ffi/src/ffibox.rs

@@ -9,11 +9,13 @@
 // rather, it creates more heap space, so it should be used appropriately
 // where necessary.
 
-use super::association::set_association;
-use super::ffiref::FfiRef;
+use std::boxed::Box;
+
 use core::ffi::c_void;
 use mlua::prelude::*;
-use std::boxed::Box;
+
+use crate::association::set_association;
+use crate::ffiref::FfiRef;
 
 const BOX_REF_INNER: &str = "__box_ref";
 

crates/lune-std-ffi/src/ffilib.rs

@@ -1,9 +1,9 @@
 use std::ffi::c_void;
 
-use super::association::set_association;
 use dlopen2::symbor::Library;
 use mlua::prelude::*;
 
+use crate::association::set_association;
 use crate::ffiref::FfiRef;
 
 pub struct FfiLib(Library);

crates/lune-std-ffi/src/ffiref.rs

@@ -1,8 +1,10 @@
-use super::association::set_association;
 use core::ffi::c_void;
-use mlua::prelude::*;
 use std::ptr;
 
+use mlua::prelude::*;
+
+use crate::association::set_association;
+
 // A referenced space. It is possible to read and write through types.
 // This operation is not safe. This may cause a memory error in Lua
 // if use it incorrectly.

crates/lune-std-ffi/src/lib.rs

@@ -14,12 +14,19 @@ mod ffilib;
 mod ffiraw;
 mod ffiref;
 
-use self::association::get_table;
-use self::cfn::CFn;
-use self::cstruct::CStruct;
-use self::ctype::create_all_types;
-use self::ffibox::FfiBox;
-use self::ffilib::FfiLib;
+use crate::association::get_table;
+use crate::cfn::CFn;
+use crate::cstruct::CStruct;
+use crate::ctype::create_all_types;
+use crate::ffibox::FfiBox;
+use crate::ffilib::FfiLib;
+
+pub const FFI_STATUS_NAMES: [&str; 4] = [
+    "ffi_status_FFI_OK",
+    "ffi_status_FFI_BAD_TYPEDEF",
+    "ffi_status_FFI_BAD_ABI",
+    "ffi_status_FFI_BAD_ARGTYPE",
+];
 
 /**
     Creates the `ffi` standard library module.