HTML MessagePort as mojo::MessagePipeHandle

content/browser/android/app_web_message_port.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/android/app_web_message_port.h"
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/bind.h"
+#include "content/browser/android/string_message_codec.h"
+#include "jni/AppWebMessagePort_jni.h"
+
+namespace content {
+
+// static
+void AppWebMessagePort::CreateAndBindToJavaObject(
+    JNIEnv* env,
+    mojo::ScopedMessagePipeHandle handle,
+    const base::android::JavaRef<jobject>& jobject) {
+  AppWebMessagePort* instance =
+      new AppWebMessagePort(env, std::move(handle), jobject);
+  Java_AppWebMessagePort_setNativeAppWebMessagePort(
+      env, jobject, reinterpret_cast<jlong>(instance));
+}
+
+// static
+std::vector<MessagePort> AppWebMessagePort::UnwrapJavaArray(
+    JNIEnv* env,
+    const base::android::JavaRef<jobjectArray>& jports) {
+  std::vector<MessagePort> ports;
+  if (!jports.is_null()) {
+    jsize num_ports = env->GetArrayLength(jports.obj());
+    for (jsize i = 0; i < num_ports; ++i) {
+      base::android::ScopedJavaLocalRef<jobject> jport(
+          env, env->GetObjectArrayElement(jports.obj(), i));
+      jlong native_port =
+          Java_AppWebMessagePort_releaseNativePortForTransfer(env, jport);
+      // Uninitialized ports should be trapper earlier at the Java layer.
+      DCHECK(native_port != -1);
+      AppWebMessagePort* instance =
+          reinterpret_cast<AppWebMessagePort*>(native_port);
+      ports.push_back(instance->port_);
+    }
+  }
+  return ports;
+}
+
+void AppWebMessagePort::CloseMessagePort(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& jcaller) {
+  // Explicitly reset the port here to ensure that OnMessagesAvailable has
+  // finished before we destroy this.
+  port_ = MessagePort();
+
+  delete this;
+}
+
+void AppWebMessagePort::PostMessage(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& jcaller,
+    const base::android::JavaParamRef<jstring>& jmessage,
+    const base::android::JavaParamRef<jobjectArray>& jports) {
+  port_.PostMessage(
+      EncodeStringMessage(base::android::ConvertJavaStringToUTF16(jmessage)),
+      UnwrapJavaArray(env, jports));
+}
+
+void AppWebMessagePort::DispatchReceivedMessages(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& jcaller) {
+  jmethodID app_web_message_port_constructor =
+      base::android::MethodID::Get<base::android::MethodID::TYPE_INSTANCE>(
+          env, AppWebMessagePort_clazz(env), "<init>", "()V");
+
+  // Consume all of the available messages.
+  // TODO(darin): Consider breaking this up across multiple PostTask calls.
+  for (;;) {
+    base::string16 encoded_message;
+    std::vector<MessagePort> ports;
+    if (!port_.GetMessage(&encoded_message, &ports))
+      return;
+
+    base::string16 message;
+    if (!DecodeStringMessage(encoded_message, &message))
+      return;
+
+    base::android::ScopedJavaLocalRef<jstring> jmessage =
+        base::android::ConvertUTF16ToJavaString(env, message);
+
+    base::android::ScopedJavaLocalRef<jobjectArray> jports;
+    if (ports.size() > 0) {
+      jports = base::android::ScopedJavaLocalRef<jobjectArray>(
+          env,
+          env->NewObjectArray(ports.size(),
+                              AppWebMessagePort_clazz(env),
+                              nullptr));
+
+      // Instantiate the Java and C++ wrappers for the transferred ports.
+      for (size_t i = 0; i < ports.size(); ++i) {
+        base::android::ScopedJavaLocalRef<jobject> jport(
+            env,
+            env->NewObject(AppWebMessagePort_clazz(env),
+                           app_web_message_port_constructor));
+        CreateAndBindToJavaObject(env, ports[i].ReleaseHandle(), jport);
+
+        env->SetObjectArrayElement(jports.obj(), i, jport.obj());
+      }
+    }
+
+    Java_AppWebMessagePort_onReceivedMessage(
+        env, java_ref_.get(env), jmessage, jports);

[sgurun-gerrit only, 2017/02/08 21:47:50]

see comment below about using weak ref.

+  }
+}
+
+void AppWebMessagePort::StartReceivingMessages(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& jcaller) {
+  port_.SetCallback(
+      base::Bind(&AppWebMessagePort::OnMessagesAvailable,
+                 base::Unretained(this)));
+}
+
+AppWebMessagePort::AppWebMessagePort(
+    JNIEnv* env,
+    mojo::ScopedMessagePipeHandle handle,
+    const base::android::JavaRef<jobject>& jobject)
+    : port_(std::move(handle)),
+      java_ref_(env, jobject) {
+}
+
+AppWebMessagePort::~AppWebMessagePort() {
+}
+
+void AppWebMessagePort::OnMessagesAvailable() {
+  // Called on the IO thread.

[sgurun-gerrit only, 2017/02/08 21:47:50]

after moving to Mojo, is this still called on IO thread or some background
thread? asking before the comment on messageport.set_callback says "a background
thread".

[darin (slow to review), 2017/02/09 00:13:17]

Yeah, good catch. This code should not assume that it is the IO thread.

+  JNIEnv* env = base::android::AttachCurrentThread();
+  Java_AppWebMessagePort_onMessagesAvailable(env, java_ref_.get(env));

[sgurun-gerrit only, 2017/02/08 21:47:50]

java_ref_ is weak. I think you need to make sure it is not null before making
the call. See an example here:

https://cs.chromium.org/chromium/src/android_webview/native/aw_contents.cc?rc...

[darin (slow to review), 2017/02/09 00:13:17]

Done.

+}
+
+bool RegisterAppWebMessagePort(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+void InitializeAppWebMessagePortPair(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jclass>& jcaller,
+    const base::android::JavaParamRef<jobjectArray>& ports) {
+  DCHECK_EQ(2, env->GetArrayLength(ports.obj()));
+
+  mojo::MessagePipe pipe;
+
+  base::android::ScopedJavaLocalRef<jobject> jport0(
+      env, env->GetObjectArrayElement(ports.obj(), 0));
+  AppWebMessagePort::CreateAndBindToJavaObject(
+      env, std::move(pipe.handle0), jport0);
+
+  base::android::ScopedJavaLocalRef<jobject> jport1(
+      env, env->GetObjectArrayElement(ports.obj(), 1));
+  AppWebMessagePort::CreateAndBindToJavaObject(
+      env, std::move(pipe.handle1), jport1);
+}
+
+}  // namespace content