/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.util;

import io.netty.util.internal.StringUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

Collection of method to handle objects that may implement ReferenceCounted. /**
 * Collection of method to handle objects that may implement {@link ReferenceCounted}.
 */
public final class ReferenceCountUtil {

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(ReferenceCountUtil.class);

    static {
        ResourceLeakDetector.addExclusions(ReferenceCountUtil.class, "touch");
    }

    
Try to call ReferenceCounted.retain() if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. /**
     * Try to call {@link ReferenceCounted#retain()} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     */
    @SuppressWarnings("unchecked")
    public static <T> T retain(T msg) {
        if (msg instanceof ReferenceCounted) {
            return (T) ((ReferenceCounted) msg).retain();
        }
        return msg;
    }

    
Try to call ReferenceCounted.retain(int) if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. /**
     * Try to call {@link ReferenceCounted#retain(int)} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     */
    @SuppressWarnings("unchecked")
    public static <T> T retain(T msg, int increment) {
        if (msg instanceof ReferenceCounted) {
            return (T) ((ReferenceCounted) msg).retain(increment);
        }
        return msg;
    }

    
Tries to call ReferenceCounted.touch() if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. /**
     * Tries to call {@link ReferenceCounted#touch()} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     */
    @SuppressWarnings("unchecked")
    public static <T> T touch(T msg) {
        if (msg instanceof ReferenceCounted) {
            return (T) ((ReferenceCounted) msg).touch();
        }
        return msg;
    }

    
Tries to call ReferenceCounted.touch(Object) if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. /**
     * Tries to call {@link ReferenceCounted#touch(Object)} if the specified message implements
     * {@link ReferenceCounted}.  If the specified message doesn't implement {@link ReferenceCounted},
     * this method does nothing.
     */
    @SuppressWarnings("unchecked")
    public static <T> T touch(T msg, Object hint) {
        if (msg instanceof ReferenceCounted) {
            return (T) ((ReferenceCounted) msg).touch(hint);
        }
        return msg;
    }

    
Try to call ReferenceCounted.release() if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. /**
     * Try to call {@link ReferenceCounted#release()} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     */
    public static boolean release(Object msg) {
        if (msg instanceof ReferenceCounted) {
            return ((ReferenceCounted) msg).release();
        }
        return false;
    }

    
Try to call ReferenceCounted.release(int) if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. /**
     * Try to call {@link ReferenceCounted#release(int)} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     */
    public static boolean release(Object msg, int decrement) {
        if (msg instanceof ReferenceCounted) {
            return ((ReferenceCounted) msg).release(decrement);
        }
        return false;
    }

    
Try to call ReferenceCounted.release() if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. Unlike release(Object) this method catches an exception raised by ReferenceCounted.release() and logs it, rather than rethrowing it to the caller. It is usually recommended to use release(Object) instead, unless you absolutely need to swallow an exception. /**
     * Try to call {@link ReferenceCounted#release()} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     * Unlike {@link #release(Object)} this method catches an exception raised by {@link ReferenceCounted#release()}
     * and logs it, rather than rethrowing it to the caller.  It is usually recommended to use {@link #release(Object)}
     * instead, unless you absolutely need to swallow an exception.
     */
    public static void safeRelease(Object msg) {
        try {
            release(msg);
        } catch (Throwable t) {
            logger.warn("Failed to release a message: {}", msg, t);
        }
    }

    
Try to call ReferenceCounted.release(int) if the specified message implements ReferenceCounted. If the specified message doesn't implement ReferenceCounted, this method does nothing. Unlike release(Object) this method catches an exception raised by ReferenceCounted.release(int) and logs it, rather than rethrowing it to the caller. It is usually recommended to use release(Object, int) instead, unless you absolutely need to swallow an exception. /**
     * Try to call {@link ReferenceCounted#release(int)} if the specified message implements {@link ReferenceCounted}.
     * If the specified message doesn't implement {@link ReferenceCounted}, this method does nothing.
     * Unlike {@link #release(Object)} this method catches an exception raised by {@link ReferenceCounted#release(int)}
     * and logs it, rather than rethrowing it to the caller.  It is usually recommended to use
     * {@link #release(Object, int)} instead, unless you absolutely need to swallow an exception.
     */
    public static void safeRelease(Object msg, int decrement) {
        try {
            release(msg, decrement);
        } catch (Throwable t) {
            if (logger.isWarnEnabled()) {
                logger.warn("Failed to release a message: {} (decrement: {})", msg, decrement, t);
            }
        }
    }

    
Schedules the specified object to be released when the caller thread terminates. Note that this operation is
intended to simplify reference counting of ephemeral objects during unit tests. Do not use it beyond the
intended use case.
Deprecated:
this may introduce a lot of memory usage so it is generally preferable to manually release objects./**
     * Schedules the specified object to be released when the caller thread terminates. Note that this operation is
     * intended to simplify reference counting of ephemeral objects during unit tests. Do not use it beyond the
     * intended use case.
     *
     * @deprecated this may introduce a lot of memory usage so it is generally preferable to manually release objects.
     */
    @Deprecated
    public static <T> T releaseLater(T msg) {
        return releaseLater(msg, 1);
    }

    
Schedules the specified object to be released when the caller thread terminates. Note that this operation is
intended to simplify reference counting of ephemeral objects during unit tests. Do not use it beyond the
intended use case.
Deprecated:
this may introduce a lot of memory usage so it is generally preferable to manually release objects./**
     * Schedules the specified object to be released when the caller thread terminates. Note that this operation is
     * intended to simplify reference counting of ephemeral objects during unit tests. Do not use it beyond the
     * intended use case.
     *
     * @deprecated this may introduce a lot of memory usage so it is generally preferable to manually release objects.
     */
    @Deprecated
    public static <T> T releaseLater(T msg, int decrement) {
        if (msg instanceof ReferenceCounted) {
            ThreadDeathWatcher.watch(Thread.currentThread(), new ReleasingTask((ReferenceCounted) msg, decrement));
        }
        return msg;
    }

    
Returns reference count of a ReferenceCounted object. If object is not type of ReferenceCounted, -1 is returned. /**
     * Returns reference count of a {@link ReferenceCounted} object. If object is not type of
     * {@link ReferenceCounted}, {@code -1} is returned.
     */
    public static int refCnt(Object msg) {
        return msg instanceof ReferenceCounted ? ((ReferenceCounted) msg).refCnt() : -1;
    }

    
Releases the objects when the thread that called ReferenceCountUtil.releaseLater(Object) has been terminated. /**
     * Releases the objects when the thread that called {@link #releaseLater(Object)} has been terminated.
     */
    private static final class ReleasingTask implements Runnable {

        private final ReferenceCounted obj;
        private final int decrement;

        ReleasingTask(ReferenceCounted obj, int decrement) {
            this.obj = obj;
            this.decrement = decrement;
        }

        @Override
        public void run() {
            try {
                if (!obj.release(decrement)) {
                    logger.warn("Non-zero refCnt: {}", this);
                } else {
                    logger.debug("Released: {}", this);
                }
            } catch (Exception ex) {
                logger.warn("Failed to release an object: {}", obj, ex);
            }
        }

        @Override
        public String toString() {
            return StringUtil.simpleClassName(obj) + ".release(" + decrement + ") refCnt: " + obj.refCnt();
        }
    }

    private ReferenceCountUtil() { }
}