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// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
part of dart.ffi;
/// The supertype of all FFI compound types.
/// FFI struct types should extend [Struct]. For more information see the
/// documentation on this class.
abstract class _Compound extends NativeType {
final Object _typedDataBase;
_Compound._() : _typedDataBase = nullptr;
/// The supertype of all FFI struct types.
/// FFI struct types should extend this class and declare fields corresponding
/// to the underlying native structure.
/// Field declarations in a [Struct] subclass declaration are automatically
/// given a setter and getter implementation which accesses the native struct's
/// field in memory.
/// All field declarations in a [Struct] subclass declaration must either have
/// type [int] or [double] and be annotated with a [NativeType] representing the
/// native type, or must be of type [Pointer]. For example:
/// ```c
/// typedef struct {
/// int a;
/// float b;
/// void* c;
/// } my_struct;
/// ```
/// ```dart
/// class MyStruct extends Struct {
/// @Int32()
/// external int a;
/// @Float()
/// external double b;
/// external Pointer<Void> c;
/// }
/// ```
/// All field declarations in a [Struct] subclass declaration must be marked
/// `external`. You cannot create instances of the class, only have it point to
/// existing native memory, so there is no memory in which to store non-native
/// fields. External fields also cannot be initialized by constructors since no
/// Dart object is being created.
/// Instances of a subclass of [Struct] have reference semantics and are backed
/// by native memory or typed data. They may allocated via allocation or loaded
/// from a [Pointer] or created by ffi calls or callbacks. They cannot be
/// created by a generative constructor.
abstract class Struct extends _Compound {
/// Construct a reference to the [nullptr].
/// Use [StructPointer]'s `.ref` to gain references to native memory backed
/// structs.
Struct() : super._();
Struct._fromTypedDataBase(Object typedDataBase)
: super._fromTypedDataBase(typedDataBase);
/// Annotation to specify on `Struct` subtypes to indicate that its members
/// need to be packed.
/// Valid values for [memberAlignment] are 1, 2, 4, 8, and 16.
class Packed {
final int memberAlignment;
const Packed(this.memberAlignment);