sdk/samples/ffi/coordinate.dart

// 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.

library FfiTest;

import 'dart:ffi' as ffi;

/// Sample struct for dart:ffi library.
@ffi.struct
class Coordinate extends ffi.Pointer<ffi.Void> {
  @ffi.Double()
  double x;

  @ffi.Double()
  double y;

  @ffi.Pointer()
  Coordinate next;

  // Implementation generated by @ffi.struct annotation.
  external static int sizeOf();

  Coordinate offsetBy(int offsetInBytes) =>
      super.offsetBy(offsetInBytes).cast();

  Coordinate elementAt(int index) => offsetBy(sizeOf() * index);

  static Coordinate allocate({int count: 1}) =>
      ffi.allocate<ffi.Uint8>(count: count * sizeOf()).cast();

  /// Allocate a new [Coordinate] in C memory and populate its fields.
  factory Coordinate(double x, double y, Coordinate next) {
    Coordinate result = Coordinate.allocate()
      ..x = x
      ..y = y
      ..next = next;
    return result;
  }
}