[vm] Add NativePort static extension to dart:ffi

This can be used in combination with `dart:ffi` to allow C code to post
messages asynchronously back to Dart.

Issue #38544

Change-Id: I0293337785a3555b4147e25f1a904f333da62c52
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118565
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Samir Jindel <sjindel@google.com>

Author: mkustermann

sdk/lib/_internal/vm/lib/ffi_dynamic_library_patch.dart

@@ -6,6 +6,7 @@
 // the patches are applied.
 import "dart:_internal" show patch;
 import 'dart:typed_data';
+import 'dart:isolate';
 
 DynamicLibrary _open(String name) native "Ffi_dl_open";
 DynamicLibrary _processLibrary() native "Ffi_dl_processLibrary";

sdk/lib/_internal/vm/lib/ffi_native_type_patch.dart

@@ -6,6 +6,7 @@
 // the patches are applied.
 import "dart:_internal" show patch;
 import 'dart:typed_data';
+import 'dart:isolate';
 
 // NativeType is not private, because it is used in type arguments.
 // NativeType is abstract because it not used with const constructors in

sdk/lib/_internal/vm/lib/ffi_patch.dart

@@ -6,6 +6,7 @@
 // the patches are applied.
 import "dart:_internal" show patch;
 import 'dart:typed_data';
+import 'dart:isolate';
 
 const Map<Type, int> _knownSizes = {
   Int8: 1,
@@ -442,3 +443,8 @@ extension StructPointer<T extends Struct> on Pointer<T> {
   @patch
   T operator [](int index) => _loadStruct(this, index);
 }
+
+extension NativePort on SendPort {
+  @patch
+  int get nativePort native "SendPortImpl_get_id";
+}

sdk/lib/ffi/ffi.dart

@@ -15,6 +15,7 @@
 library dart.ffi;
 
 import 'dart:typed_data';
+import 'dart:isolate';
 
 part "native_type.dart";
 part "annotations.dart";
@@ -609,3 +610,13 @@ extension StructPointer<T extends Struct> on Pointer<T> {
   /// the platform.
   external T operator [](int index);
 }
+
+/// Extension to retrieve the native `Dart_Port` from a [SendPort].
+extension NativePort on SendPort {
+  /// The native port of this [SendPort].
+  ///
+  /// The returned native port can for example be used by C code to post
+  /// messages to the connected [ReceivePort] via `Dart_PostCObject()` - see
+  /// `dart_native_api.h`.
+  external int get nativePort;
+}

sdk_nnbd/lib/_internal/vm/lib/ffi_dynamic_library_patch.dart

@@ -8,6 +8,7 @@
 // the patches are applied.
 import "dart:_internal" show patch;
 import 'dart:typed_data';
+import 'dart:isolate';
 
 DynamicLibrary _open(String name) native "Ffi_dl_open";
 DynamicLibrary _processLibrary() native "Ffi_dl_processLibrary";

sdk_nnbd/lib/_internal/vm/lib/ffi_native_type_patch.dart

@@ -8,6 +8,7 @@
 // the patches are applied.
 import "dart:_internal" show patch;
 import 'dart:typed_data';
+import 'dart:isolate';
 
 // NativeType is not private, because it is used in type arguments.
 // NativeType is abstract because it not used with const constructors in

sdk_nnbd/lib/_internal/vm/lib/ffi_patch.dart

@@ -8,6 +8,7 @@
 // the patches are applied.
 import "dart:_internal" show patch;
 import 'dart:typed_data';
+import 'dart:isolate';
 
 const Map<Type, int> _knownSizes = {
   Int8: 1,
@@ -444,3 +445,8 @@ extension StructPointer<T extends Struct> on Pointer<T> {
   @patch
   T operator [](int index) => _loadStruct(this, index);
 }
+
+extension NativePort on SendPort {
+  @patch
+  int get nativePort native "SendPortImpl_get_id";
+}

sdk_nnbd/lib/ffi/ffi.dart

@@ -611,3 +611,13 @@ extension StructPointer<T extends Struct> on Pointer<T> {
   /// the platform.
   external T operator [](int index);
 }
+
+/// Extension to retrieve the native `Dart_Port` from a [SendPort].
+extension NativePort on SendPort {
+  /// The native port of this [SendPort].
+  ///
+  /// The returned native port can for example be used by C code to post
+  /// messages to the connected [ReceivePort] via `Dart_PostCObject()` - see
+  /// `dart_native_api.h`.
+  external int get nativePort;
+}

tests/ffi/send_port_id_test.dart

@@ -0,0 +1,37 @@
+// 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.
+
+import 'dart:async';
+import 'dart:ffi';
+import 'dart:isolate';
+
+import 'package:expect/expect.dart';
+
+typedef Dart_PostIntegerNFT = IntPtr Function(Int64 port, Int64 message);
+typedef Dart_PostIntegerFT = int Function(int port, int message);
+
+main() async {
+  const int message = 112344556677888;
+
+  final completer = Completer();
+
+  final receivePort = ReceivePort()
+    ..listen((receivedMessage) => completer.complete(receivedMessage));
+
+  final executableSymbols = DynamicLibrary.executable();
+
+  final postInteger =
+      executableSymbols.lookupFunction<Dart_PostIntegerNFT, Dart_PostIntegerFT>(
+          "Dart_PostInteger");
+
+  // Issue(dartbug.com/38545): The dart:ffi doesn't have a bool type yet.
+  final bool success =
+      postInteger(receivePort.sendPort.nativePort, message) != 0;
+  Expect.isTrue(success);
+
+  final postedMessage = await completer.future;
+  Expect.equals(message, postedMessage);
+
+  receivePort.close();
+}