ScopedJNIEnvironment.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#ifndef META_OCEAN_PLATFORM_ANDROID_NATIVE_SCOPED_JNI_ENVIRONMENT_H
#define META_OCEAN_PLATFORM_ANDROID_NATIVE_SCOPED_JNI_ENVIRONMENT_H
 
#include "ocean/platform/android/Android.h"
 
namespace Ocean
{
 
namespace Platform
{
 
namespace Android
{
 
/**
 * This class implements a scoped access to a JNI environment with attached current thread.
 * Do not use/call this object out of two individual threads.
 * @ingroup platformandroid
 */
class OCEAN_PLATFORM_ANDROID_EXPORT ScopedJNIEnvironment
{
    public:
 
        /**
         * Creates a new scoped object, acquires the JNI environment and attaches the thread.
         * @param javaVM The virtual Java machine, must be valid
         */
        explicit ScopedJNIEnvironment(JavaVM* javaVM);
 
        /**
         * Destructs this object.
         */
        ~ScopedJNIEnvironment();
 
        /**
         * Returns the JNI environment which is attached with the current thread.
         * @return The JNI environment, can be nullptr if invalid
         */
        inline JNIEnv* jniEnv() const;
 
        /**
         * Returns whether this scoped object holds a valid JNI environment.
         * @return True, if so
         */
        inline bool isValid() const;
 
        /**
         * Returns the JNI environment which is attached with the current thread.
         * @return The JNI environment, can be nullptr if invalid
         */
        inline JNIEnv* operator->() const;
 
        /**
         * Returns whether this scoped object holds a valid JNI environment.
         * @return True, if so
         */
        explicit inline operator bool() const;
 
    protected:
 
        /**
         * Disabled copy constructor.
         * @param scopedJNIEnvironment Object which would be copied
         */
        ScopedJNIEnvironment(const ScopedJNIEnvironment& scopedJNIEnvironment) = delete;
 
        /**
         * Disabled copy operator.
         * @param scopedJNIEnvironment Object which would be copied
         * @return Reference to this object
         */
        ScopedJNIEnvironment& operator=(const ScopedJNIEnvironment& scopedJNIEnvironment) = delete;
 
    protected:
 
        /// The virtual Java machine.
        JavaVM* javaVM_ = nullptr;
 
        /// The JNI environment.
        JNIEnv* jniEnv_ = nullptr;
 
        /// True, if the thread has been attached; False, if the thread was attached already.
        bool threadAttachedExplicitly_ = false;
};
 
inline JNIEnv* ScopedJNIEnvironment::jniEnv() const
{
    return jniEnv_;
}
 
inline bool ScopedJNIEnvironment::isValid() const
{
    return jniEnv_ != nullptr;
}
 
inline JNIEnv* ScopedJNIEnvironment::operator->() const
{
    ocean_assert(isValid());
 
    return jniEnv();
}
 
inline ScopedJNIEnvironment::operator bool() const
{
    return isValid();
}
 
}
 
}
 
}
 
#endif // META_OCEAN_PLATFORM_ANDROID_NATIVE_SCOPED_JNI_ENVIRONMENT_H