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+/*
+ * Copyright (C) 2010-2011 Max Kellermann <max@duempel.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef JAVA_REF_HXX
+#define JAVA_REF_HXX
+
+#include "Global.hxx"
+
+#include <jni.h>
+
+#include <assert.h>
+
+namespace Java {
+ /**
+ * Hold a local reference on a JNI object.
+ */
+ template<typename T>
+ class LocalRef {
+ JNIEnv *const env;
+ const T value;
+
+ public:
+ /**
+ * The local reference is obtained by the caller.
+ */
+ LocalRef(JNIEnv *_env, T _value):env(_env), value(_value) {
+ assert(env != nullptr);
+ assert(value != nullptr);
+ }
+
+ ~LocalRef() {
+ env->DeleteLocalRef(value);
+ }
+
+ LocalRef(const LocalRef &other) = delete;
+ LocalRef &operator=(const LocalRef &other) = delete;
+
+ T Get() const {
+ return value;
+ }
+
+ operator T() const {
+ return value;
+ }
+ };
+
+ /**
+ * Hold a global reference on a JNI object.
+ */
+ template<typename T>
+ class GlobalRef {
+ T value;
+
+ public:
+ /**
+ * Constructs an uninitialized object. The method set() must be
+ * called before it is destructed.
+ */
+ GlobalRef() = default;
+
+ GlobalRef(JNIEnv *env, T _value):value(_value) {
+ assert(env != nullptr);
+ assert(value != nullptr);
+
+ value = (T)env->NewGlobalRef(value);
+ }
+
+ ~GlobalRef() {
+ GetEnv()->DeleteGlobalRef(value);
+ }
+
+ GlobalRef(const GlobalRef &other) = delete;
+ GlobalRef &operator=(const GlobalRef &other) = delete;
+
+ /**
+ * Sets the object, ignoring the previous value. This is only
+ * allowed once after the default constructor was used.
+ */
+ void Set(JNIEnv *env, T _value) {
+ assert(_value != nullptr);
+
+ value = (T)env->NewGlobalRef(_value);
+ }
+
+ T Get() const {
+ return value;
+ }
+
+ operator T() const {
+ return value;
+ }
+ };
+
+ /**
+ * Container for a global reference to a JNI object that gets
+ * initialised and deinitialised explicitly. Since there is no
+ * implicit initialisation in the default constructor, this is a
+ * trivial C++ class. It should only be used for global variables
+ * that are implicitly initialised with zeroes.
+ */
+ template<typename T>
+ class TrivialRef {
+ T value;
+
+ public:
+ constexpr TrivialRef() {};
+
+ TrivialRef(const TrivialRef &other) = delete;
+ TrivialRef &operator=(const TrivialRef &other) = delete;
+
+ bool IsDefined() const {
+ return value != nullptr;
+ }
+
+ /**
+ * Obtain a global reference on the specified object and store it.
+ * This object must not be set already.
+ */
+ void Set(JNIEnv *env, T _value) {
+ assert(value == nullptr);
+ assert(_value != nullptr);
+
+ value = (T)env->NewGlobalRef(_value);
+ }
+
+ /**
+ * Release the global reference and clear this object.
+ */
+ void Clear(JNIEnv *env) {
+ assert(value != nullptr);
+
+ env->DeleteGlobalRef(value);
+ value = nullptr;
+ }
+
+ /**
+ * Release the global reference and clear this object. It is
+ * allowed to call this method without ever calling Set().
+ */
+ void ClearOptional(JNIEnv *env) {
+ if (value != nullptr)
+ Clear(env);
+ }
+
+ T Get() const {
+ return value;
+ }
+
+ operator T() const {
+ return value;
+ }
+ };
+}
+
+#endif