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+/*
+ * Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef MODULES_UTILITY_INCLUDE_JVM_ANDROID_H_
+#define MODULES_UTILITY_INCLUDE_JVM_ANDROID_H_
+
+#include <jni.h>
+
+#include <memory>
+#include <string>
+
+#include "api/sequence_checker.h"
+#include "modules/utility/include/helpers_android.h"
+
+namespace webrtc {
+
+// RAII JavaVM AttachCurrentThread/DetachCurrentThread object.
+//
+// The JNI interface pointer (JNIEnv) is valid only in the current thread.
+// Should another thread need to access the Java VM, it must first call
+// AttachCurrentThread() to attach itself to the VM and obtain a JNI interface
+// pointer. The native thread remains attached to the VM until it calls
+// DetachCurrentThread() to detach.
+class JvmThreadConnector {
+ public:
+ JvmThreadConnector();
+ ~JvmThreadConnector();
+
+ private:
+ SequenceChecker thread_checker_;
+ bool attached_;
+};
+
+// This class is created by the NativeRegistration class and is used to wrap
+// the actual Java object handle (jobject) on which we can call methods from
+// C++ in to Java. See example in JVM for more details.
+// TODO(henrika): extend support for type of function calls.
+class GlobalRef {
+ public:
+ GlobalRef(JNIEnv* jni, jobject object);
+ ~GlobalRef();
+
+ jboolean CallBooleanMethod(jmethodID methodID, ...);
+ jint CallIntMethod(jmethodID methodID, ...);
+ void CallVoidMethod(jmethodID methodID, ...);
+
+ private:
+ JNIEnv* const jni_;
+ const jobject j_object_;
+};
+
+// Wraps the jclass object on which we can call GetMethodId() functions to
+// query method IDs.
+class JavaClass {
+ public:
+ JavaClass(JNIEnv* jni, jclass clazz) : jni_(jni), j_class_(clazz) {}
+ ~JavaClass() {}
+
+ jmethodID GetMethodId(const char* name, const char* signature);
+ jmethodID GetStaticMethodId(const char* name, const char* signature);
+ jobject CallStaticObjectMethod(jmethodID methodID, ...);
+ jint CallStaticIntMethod(jmethodID methodID, ...);
+
+ protected:
+ JNIEnv* const jni_;
+ jclass const j_class_;
+};
+
+// Adds support of the NewObject factory method to the JavaClass class.
+// See example in JVM for more details on how to use it.
+class NativeRegistration : public JavaClass {
+ public:
+ NativeRegistration(JNIEnv* jni, jclass clazz);
+ ~NativeRegistration();
+
+ std::unique_ptr<GlobalRef> NewObject(const char* name,
+ const char* signature,
+ ...);
+
+ private:
+ JNIEnv* const jni_;
+};
+
+// This class is created by the JVM class and is used to expose methods that
+// needs the JNI interface pointer but its main purpose is to create a
+// NativeRegistration object given name of a Java class and a list of native
+// methods. See example in JVM for more details.
+class JNIEnvironment {
+ public:
+ explicit JNIEnvironment(JNIEnv* jni);
+ ~JNIEnvironment();
+
+ // Registers native methods with the Java class specified by `name`.
+ // Note that the class name must be one of the names in the static
+ // `loaded_classes` array defined in jvm_android.cc.
+ // This method must be called on the construction thread.
+ std::unique_ptr<NativeRegistration> RegisterNatives(
+ const char* name,
+ const JNINativeMethod* methods,
+ int num_methods);
+
+ // Converts from Java string to std::string.
+ // This method must be called on the construction thread.
+ std::string JavaToStdString(const jstring& j_string);
+
+ private:
+ SequenceChecker thread_checker_;
+ JNIEnv* const jni_;
+};
+
+// Main class for working with Java from C++ using JNI in WebRTC.
+//
+// Example usage:
+//
+// // At initialization (e.g. in JNI_OnLoad), call JVM::Initialize.
+// JNIEnv* jni = ::base::android::AttachCurrentThread();
+// JavaVM* jvm = NULL;
+// jni->GetJavaVM(&jvm);
+// webrtc::JVM::Initialize(jvm);
+//
+// // Header (.h) file of example class called User.
+// std::unique_ptr<JNIEnvironment> env;
+// std::unique_ptr<NativeRegistration> reg;
+// std::unique_ptr<GlobalRef> obj;
+//
+// // Construction (in .cc file) of User class.
+// User::User() {
+// // Calling thread must be attached to the JVM.
+// env = JVM::GetInstance()->environment();
+// reg = env->RegisterNatives("org/webrtc/WebRtcTest", ,);
+// obj = reg->NewObject("<init>", ,);
+// }
+//
+// // Each User method can now use `reg` and `obj` and call Java functions
+// // in WebRtcTest.java, e.g. boolean init() {}.
+// bool User::Foo() {
+// jmethodID id = reg->GetMethodId("init", "()Z");
+// return obj->CallBooleanMethod(id);
+// }
+//
+// // And finally, e.g. in JNI_OnUnLoad, call JVM::Uninitialize.
+// JVM::Uninitialize();
+class JVM {
+ public:
+ // Stores global handles to the Java VM interface.
+ // Should be called once on a thread that is attached to the JVM.
+ static void Initialize(JavaVM* jvm);
+ // Like the method above but also passes the context to the ContextUtils
+ // class. This method should be used by pure-C++ Android users that can't call
+ // ContextUtils.initialize directly.
+ static void Initialize(JavaVM* jvm, jobject context);
+ // Clears handles stored in Initialize(). Must be called on same thread as
+ // Initialize().
+ static void Uninitialize();
+ // Gives access to the global Java VM interface pointer, which then can be
+ // used to create a valid JNIEnvironment object or to get a JavaClass object.
+ static JVM* GetInstance();
+
+ // Creates a JNIEnvironment object.
+ // This method returns a NULL pointer if AttachCurrentThread() has not been
+ // called successfully. Use the AttachCurrentThreadIfNeeded class if needed.
+ std::unique_ptr<JNIEnvironment> environment();
+
+ // Returns a JavaClass object given class `name`.
+ // Note that the class name must be one of the names in the static
+ // `loaded_classes` array defined in jvm_android.cc.
+ // This method must be called on the construction thread.
+ JavaClass GetClass(const char* name);
+
+ // TODO(henrika): can we make these private?
+ JavaVM* jvm() const { return jvm_; }
+
+ protected:
+ JVM(JavaVM* jvm);
+ ~JVM();
+
+ private:
+ JNIEnv* jni() const { return GetEnv(jvm_); }
+
+ SequenceChecker thread_checker_;
+ JavaVM* const jvm_;
+};
+
+} // namespace webrtc
+
+#endif // MODULES_UTILITY_INCLUDE_JVM_ANDROID_H_