http://netty.io/netty-all/: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients. (The Netty Project) 
/*
 * 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.EmptyArrays;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.SystemPropertyUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.lang.ref.WeakReference;
import java.lang.ref.ReferenceQueue;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

import static io.netty.util.internal.StringUtil.EMPTY_STRING;
import static io.netty.util.internal.StringUtil.NEWLINE;
import static io.netty.util.internal.StringUtil.simpleClassName;

public class ResourceLeakDetector<T> {

    private static final String PROP_LEVEL_OLD = "io.netty.leakDetectionLevel";
    private static final String PROP_LEVEL = "io.netty.leakDetection.level";
    private static final Level DEFAULT_LEVEL = Level.SIMPLE;

    private static final String PROP_TARGET_RECORDS = "io.netty.leakDetection.targetRecords";
    private static final int DEFAULT_TARGET_RECORDS = 4;

    private static final int TARGET_RECORDS;

    
Represents the level of resource leak detection.

/**
     * Represents the level of resource leak detection.
     */
    public enum Level {
        
Disables resource leak detection.

/**
         * Disables resource leak detection.
         */
        DISABLED,
        
Enables simplistic sampling resource leak detection which reports there is a leak or not,
at the cost of small overhead (default).

/**
         * Enables simplistic sampling resource leak detection which reports there is a leak or not,
         * at the cost of small overhead (default).
         */
        SIMPLE,
        
Enables advanced sampling resource leak detection which reports where the leaked object was accessed
recently at the cost of high overhead.

/**
         * Enables advanced sampling resource leak detection which reports where the leaked object was accessed
         * recently at the cost of high overhead.
         */
        ADVANCED,
        
Enables paranoid resource leak detection which reports where the leaked object was accessed recently,
at the cost of the highest possible overhead (for testing purposes only).

/**
         * Enables paranoid resource leak detection which reports where the leaked object was accessed recently,
         * at the cost of the highest possible overhead (for testing purposes only).
         */
        PARANOID;

        
Returns level based on string value. Accepts also string that represents ordinal number of enum.

Params:
  • levelStr – - level string : DISABLED, SIMPLE, ADVANCED, PARANOID. Ignores case.
Returns:corresponding level or SIMPLE level in case of no match.
/**
         * Returns level based on string value. Accepts also string that represents ordinal number of enum.
         *
         * @param levelStr - level string : DISABLED, SIMPLE, ADVANCED, PARANOID. Ignores case.
         * @return corresponding level or SIMPLE level in case of no match.
         */
        static Level parseLevel(String levelStr) {
            String trimmedLevelStr = levelStr.trim();
            for (Level l : values()) {
                if (trimmedLevelStr.equalsIgnoreCase(l.name()) || trimmedLevelStr.equals(String.valueOf(l.ordinal()))) {
                    return l;
                }
            }
            return DEFAULT_LEVEL;
        }
    }

    private static Level level;

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

    static {
        final boolean disabled;
        if (SystemPropertyUtil.get("io.netty.noResourceLeakDetection") != null) {
            disabled = SystemPropertyUtil.getBoolean("io.netty.noResourceLeakDetection", false);
            logger.debug("-Dio.netty.noResourceLeakDetection: {}", disabled);
            logger.warn(
                    "-Dio.netty.noResourceLeakDetection is deprecated. Use '-D{}={}' instead.",
                    PROP_LEVEL, DEFAULT_LEVEL.name().toLowerCase());
        } else {
            disabled = false;
        }

        Level defaultLevel = disabled? Level.DISABLED : DEFAULT_LEVEL;

        // First read old property name
        String levelStr = SystemPropertyUtil.get(PROP_LEVEL_OLD, defaultLevel.name());

        // If new property name is present, use it
        levelStr = SystemPropertyUtil.get(PROP_LEVEL, levelStr);
        Level level = Level.parseLevel(levelStr);

        TARGET_RECORDS = SystemPropertyUtil.getInt(PROP_TARGET_RECORDS, DEFAULT_TARGET_RECORDS);

        ResourceLeakDetector.level = level;
        if (logger.isDebugEnabled()) {
            logger.debug("-D{}: {}", PROP_LEVEL, level.name().toLowerCase());
            logger.debug("-D{}: {}", PROP_TARGET_RECORDS, TARGET_RECORDS);
        }
    }

    // There is a minor performance benefit in TLR if this is a power of 2.
    static final int DEFAULT_SAMPLING_INTERVAL = 128;

    
Deprecated:Use setLevel(Level) instead.
/**
     * @deprecated Use {@link #setLevel(Level)} instead.
     */
    @Deprecated
    public static void setEnabled(boolean enabled) {
        setLevel(enabled? Level.SIMPLE : Level.DISABLED);
    }

    
Returns true if resource leak detection is enabled. 
/**
     * Returns {@code true} if resource leak detection is enabled.
     */
    public static boolean isEnabled() {
        return getLevel().ordinal() > Level.DISABLED.ordinal();
    }

    
Sets the resource leak detection level.

/**
     * Sets the resource leak detection level.
     */
    public static void setLevel(Level level) {
        if (level == null) {
            throw new NullPointerException("level");
        }
        ResourceLeakDetector.level = level;
    }

    
Returns the current resource leak detection level.

/**
     * Returns the current resource leak detection level.
     */
    public static Level getLevel() {
        return level;
    }

    
the collection of active resources 
/** the collection of active resources */
    private final ConcurrentMap<DefaultResourceLeak<?>, LeakEntry> allLeaks = PlatformDependent.newConcurrentHashMap();

    private final ReferenceQueue<Object> refQueue = new ReferenceQueue<Object>();
    private final ConcurrentMap<String, Boolean> reportedLeaks = PlatformDependent.newConcurrentHashMap();

    private final String resourceType;
    private final int samplingInterval;

    
Deprecated:use ResourceLeakDetectorFactory.newResourceLeakDetector(Class<Object>, int, long).
/**
     * @deprecated use {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class, int, long)}.
     */
    @Deprecated
    public ResourceLeakDetector(Class<?> resourceType) {
        this(simpleClassName(resourceType));
    }

    
Deprecated:use ResourceLeakDetectorFactory.newResourceLeakDetector(Class<Object>, int, long).
/**
     * @deprecated use {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class, int, long)}.
     */
    @Deprecated
    public ResourceLeakDetector(String resourceType) {
        this(resourceType, DEFAULT_SAMPLING_INTERVAL, Long.MAX_VALUE);
    }

    
Params:
  • maxActive – This is deprecated and will be ignored.
Deprecated:Use ResourceLeakDetector(Class, int). 
 This should not be used directly by users of ResourceLeakDetector. Please use ResourceLeakDetectorFactory.newResourceLeakDetector(Class<Object>) or ResourceLeakDetectorFactory.newResourceLeakDetector(Class<Object>, int, long)
/**
     * @deprecated Use {@link ResourceLeakDetector#ResourceLeakDetector(Class, int)}.
     * <p>
     * This should not be used directly by users of {@link ResourceLeakDetector}.
     * Please use {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class)}
     * or {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class, int, long)}
     *
     * @param maxActive This is deprecated and will be ignored.
     */
    @Deprecated
    public ResourceLeakDetector(Class<?> resourceType, int samplingInterval, long maxActive) {
        this(resourceType, samplingInterval);
    }

    /**
     * This should not be used directly by users of {@link ResourceLeakDetector}.
     * Please use {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class)}
     * or {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class, int, long)}
     */
    @SuppressWarnings("deprecation")
    public ResourceLeakDetector(Class<?> resourceType, int samplingInterval) {
        this(simpleClassName(resourceType), samplingInterval, Long.MAX_VALUE);
    }

    
Params:
  • maxActive – This is deprecated and will be ignored.
Deprecated:use ResourceLeakDetectorFactory.newResourceLeakDetector(Class<Object>, int, long). 
/**
     * @deprecated use {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class, int, long)}.
     * <p>
     * @param maxActive This is deprecated and will be ignored.
     */
    @Deprecated
    public ResourceLeakDetector(String resourceType, int samplingInterval, long maxActive) {
        if (resourceType == null) {
            throw new NullPointerException("resourceType");
        }

        this.resourceType = resourceType;
        this.samplingInterval = samplingInterval;
    }

    
Creates a new ResourceLeak which is expected to be closed via ResourceLeak.close() when the related resource is deallocated. 
Returns:the ResourceLeak or null
Deprecated:use track(Object)
/**
     * Creates a new {@link ResourceLeak} which is expected to be closed via {@link ResourceLeak#close()} when the
     * related resource is deallocated.
     *
     * @return the {@link ResourceLeak} or {@code null}
     * @deprecated use {@link #track(Object)}
     */
    @Deprecated
    public final ResourceLeak open(T obj) {
        return track0(obj);
    }

    
Creates a new ResourceLeakTracker which is expected to be closed via ResourceLeakTracker.close(Object) when the related resource is deallocated. 
Returns:the ResourceLeakTracker or null
/**
     * Creates a new {@link ResourceLeakTracker} which is expected to be closed via
     * {@link ResourceLeakTracker#close(Object)} when the related resource is deallocated.
     *
     * @return the {@link ResourceLeakTracker} or {@code null}
     */
    @SuppressWarnings("unchecked")
    public final ResourceLeakTracker<T> track(T obj) {
        return track0(obj);
    }

    @SuppressWarnings("unchecked")
    private DefaultResourceLeak track0(T obj) {
        Level level = ResourceLeakDetector.level;
        if (level == Level.DISABLED) {
            return null;
        }

        if (level.ordinal() < Level.PARANOID.ordinal()) {
            if ((PlatformDependent.threadLocalRandom().nextInt(samplingInterval)) == 0) {
                reportLeak();
                return new DefaultResourceLeak(obj, refQueue, allLeaks);
            }
            return null;
        }
        reportLeak();
        return new DefaultResourceLeak(obj, refQueue, allLeaks);
    }

    private void clearRefQueue() {
        for (;;) {
            @SuppressWarnings("unchecked")
            DefaultResourceLeak ref = (DefaultResourceLeak) refQueue.poll();
            if (ref == null) {
                break;
            }
            ref.dispose();
        }
    }

    private void reportLeak() {
        if (!logger.isErrorEnabled()) {
            clearRefQueue();
            return;
        }

        // Detect and report previous leaks.
        for (;;) {
            @SuppressWarnings("unchecked")
            DefaultResourceLeak ref = (DefaultResourceLeak) refQueue.poll();
            if (ref == null) {
                break;
            }

            if (!ref.dispose()) {
                continue;
            }

            String records = ref.toString();
            if (reportedLeaks.putIfAbsent(records, Boolean.TRUE) == null) {
                if (records.isEmpty()) {
                    reportUntracedLeak(resourceType);
                } else {
                    reportTracedLeak(resourceType, records);
                }
            }
        }
    }

    
This method is called when a traced leak is detected. It can be overridden for tracking how many times leaks
have been detected.

/**
     * This method is called when a traced leak is detected. It can be overridden for tracking how many times leaks
     * have been detected.
     */
    protected void reportTracedLeak(String resourceType, String records) {
        logger.error(
                "LEAK: {}.release() was not called before it's garbage-collected. " +
                "See http://netty.io/wiki/reference-counted-objects.html for more information.{}",
                resourceType, records);
    }

    
This method is called when an untraced leak is detected. It can be overridden for tracking how many times leaks
have been detected.

/**
     * This method is called when an untraced leak is detected. It can be overridden for tracking how many times leaks
     * have been detected.
     */
    protected void reportUntracedLeak(String resourceType) {
        logger.error("LEAK: {}.release() was not called before it's garbage-collected. " +
                "Enable advanced leak reporting to find out where the leak occurred. " +
                "To enable advanced leak reporting, " +
                "specify the JVM option '-D{}={}' or call {}.setLevel() " +
                "See http://netty.io/wiki/reference-counted-objects.html for more information.",
                resourceType, PROP_LEVEL, Level.ADVANCED.name().toLowerCase(), simpleClassName(this));
    }

    
Deprecated:This method will no longer be invoked by ResourceLeakDetector.
/**
     * @deprecated This method will no longer be invoked by {@link ResourceLeakDetector}.
     */
    @Deprecated
    protected void reportInstancesLeak(String resourceType) {
    }

    @SuppressWarnings("deprecation")
    private static final class DefaultResourceLeak<T>
            extends WeakReference<Object> implements ResourceLeakTracker<T>, ResourceLeak {

        @SuppressWarnings("unchecked") // generics and updaters do not mix.
        private static final AtomicReferenceFieldUpdater<DefaultResourceLeak<?>, Record> headUpdater =
                (AtomicReferenceFieldUpdater)
                        AtomicReferenceFieldUpdater.newUpdater(DefaultResourceLeak.class, Record.class, "head");

        @SuppressWarnings("unchecked") // generics and updaters do not mix.
        private static final AtomicIntegerFieldUpdater<DefaultResourceLeak<?>> droppedRecordsUpdater =
                (AtomicIntegerFieldUpdater)
                        AtomicIntegerFieldUpdater.newUpdater(DefaultResourceLeak.class, "droppedRecords");

        @SuppressWarnings("unused")
        private volatile Record head;
        @SuppressWarnings("unused")
        private volatile int droppedRecords;

        private final ConcurrentMap<DefaultResourceLeak<?>, LeakEntry> allLeaks;
        private final int trackedHash;

        DefaultResourceLeak(
                Object referent,
                ReferenceQueue<Object> refQueue,
                ConcurrentMap<DefaultResourceLeak<?>, LeakEntry> allLeaks) {
            super(referent, refQueue);

            assert referent != null;

            // Store the hash of the tracked object to later assert it in the close(...) method.
            // It's important that we not store a reference to the referent as this would disallow it from
            // be collected via the WeakReference.
            trackedHash = System.identityHashCode(referent);
            allLeaks.put(this, LeakEntry.INSTANCE);
            // Create a new Record so we always have the creation stacktrace included.
            headUpdater.set(this, new Record(Record.BOTTOM));
            this.allLeaks = allLeaks;
        }

        @Override
        public void record() {
            record0(null);
        }

        @Override
        public void record(Object hint) {
            record0(hint);
        }

        
This method works by exponentially backing off as more records are present in the stack. Each record has a
1 / 2^n chance of dropping the top most record and replacing it with itself. This has a number of convenient
properties:

    

  1.   The current record is always recorded. This is due to the compare and swap dropping the top most
      record, rather than the to-be-pushed record.

  2.   The very last access will always be recorded. This comes as a property of 1.

  3.   It is possible to retain more records than the target, based upon the probability distribution.

  4.   It is easy to keep a precise record of the number of elements in the stack, since each element has to
    know how tall the stack is.

 In this particular implementation, there are also some advantages. A thread local random is used to decide if something should be recorded. This means that if there is a deterministic access pattern, it is now possible to see what other accesses occur, rather than always dropping them. Second, after ResourceLeakDetector<T>.TARGET_RECORDS accesses, backoff occurs. This matches typical access patterns, where there are either a high number of accesses (i.e. a cached buffer), or low (an ephemeral buffer), but not many in between. The use of atomics avoids serializing a high number of accesses, when most of the records will be thrown away. High contention only happens when there are very few existing records, which is only likely when the object isn't shared! If this is a problem, the loop can be aborted and the record dropped, because another thread won the race. 
/**
         * This method works by exponentially backing off as more records are present in the stack. Each record has a
         * 1 / 2^n chance of dropping the top most record and replacing it with itself. This has a number of convenient
         * properties:
         *
         * <ol>
         * <li>  The current record is always recorded. This is due to the compare and swap dropping the top most
         *       record, rather than the to-be-pushed record.
         * <li>  The very last access will always be recorded. This comes as a property of 1.
         * <li>  It is possible to retain more records than the target, based upon the probability distribution.
         * <li>  It is easy to keep a precise record of the number of elements in the stack, since each element has to
         *     know how tall the stack is.
         * </ol>
         *
         * In this particular implementation, there are also some advantages. A thread local random is used to decide
         * if something should be recorded. This means that if there is a deterministic access pattern, it is now
         * possible to see what other accesses occur, rather than always dropping them. Second, after
         * {@link #TARGET_RECORDS} accesses, backoff occurs. This matches typical access patterns,
         * where there are either a high number of accesses (i.e. a cached buffer), or low (an ephemeral buffer), but
         * not many in between.
         *
         * The use of atomics avoids serializing a high number of accesses, when most of the records will be thrown
         * away. High contention only happens when there are very few existing records, which is only likely when the
         * object isn't shared! If this is a problem, the loop can be aborted and the record dropped, because another
         * thread won the race.
         */
        private void record0(Object hint) {
            // Check TARGET_RECORDS > 0 here to avoid similar check before remove from and add to lastRecords
            if (TARGET_RECORDS > 0) {
                Record oldHead;
                Record prevHead;
                Record newHead;
                boolean dropped;
                do {
                    if ((prevHead = oldHead = headUpdater.get(this)) == null) {
                        // already closed.
                        return;
                    }
                    final int numElements = oldHead.pos + 1;
                    if (numElements >= TARGET_RECORDS) {
                        final int backOffFactor = Math.min(numElements - TARGET_RECORDS, 30);
                        if (dropped = PlatformDependent.threadLocalRandom().nextInt(1 << backOffFactor) != 0) {
                            prevHead = oldHead.next;
                        }
                    } else {
                        dropped = false;
                    }
                    newHead = hint != null ? new Record(prevHead, hint) : new Record(prevHead);
                } while (!headUpdater.compareAndSet(this, oldHead, newHead));
                if (dropped) {
                    droppedRecordsUpdater.incrementAndGet(this);
                }
            }
        }

        boolean dispose() {
            clear();
            return allLeaks.remove(this, LeakEntry.INSTANCE);
        }

        @Override
        public boolean close() {
            // Use the ConcurrentMap remove method, which avoids allocating an iterator.
            if (allLeaks.remove(this, LeakEntry.INSTANCE)) {
                // Call clear so the reference is not even enqueued.
                clear();
                headUpdater.set(this, null);
                return true;
            }
            return false;
        }

        @Override
        public boolean close(T trackedObject) {
            // Ensure that the object that was tracked is the same as the one that was passed to close(...).
            assert trackedHash == System.identityHashCode(trackedObject);

            // We need to actually do the null check of the trackedObject after we close the leak because otherwise
            // we may get false-positives reported by the ResourceLeakDetector. This can happen as the JIT / GC may
            // be able to figure out that we do not need the trackedObject anymore and so already enqueue it for
            // collection before we actually get a chance to close the enclosing ResourceLeak.
            return close() && trackedObject != null;
        }

        @Override
        public String toString() {
            Record oldHead = headUpdater.getAndSet(this, null);
            if (oldHead == null) {
                // Already closed
                return EMPTY_STRING;
            }

            final int dropped = droppedRecordsUpdater.get(this);
            int duped = 0;

            int present = oldHead.pos + 1;
            // Guess about 2 kilobytes per stack trace
            StringBuilder buf = new StringBuilder(present * 2048).append(NEWLINE);
            buf.append("Recent access records: ").append(NEWLINE);

            int i = 1;
            Set<String> seen = new HashSet<String>(present);
            for (; oldHead != Record.BOTTOM; oldHead = oldHead.next) {
                String s = oldHead.toString();
                if (seen.add(s)) {
                    if (oldHead.next == Record.BOTTOM) {
                        buf.append("Created at:").append(NEWLINE).append(s);
                    } else {
                        buf.append('#').append(i++).append(':').append(NEWLINE).append(s);
                    }
                } else {
                    duped++;
                }
            }

            if (duped > 0) {
                buf.append(": ")
                        .append(dropped)
                        .append(" leak records were discarded because they were duplicates")
                        .append(NEWLINE);
            }

            if (dropped > 0) {
                buf.append(": ")
                   .append(dropped)
                   .append(" leak records were discarded because the leak record count is targeted to ")
                   .append(TARGET_RECORDS)
                   .append(". Use system property ")
                   .append(PROP_TARGET_RECORDS)
                   .append(" to increase the limit.")
                   .append(NEWLINE);
            }

            buf.setLength(buf.length() - NEWLINE.length());
            return buf.toString();
        }
    }

    private static final AtomicReference<String[]> excludedMethods =
            new AtomicReference<String[]>(EmptyArrays.EMPTY_STRINGS);

    public static void addExclusions(Class clz, String ... methodNames) {
        Set<String> nameSet = new HashSet<String>(Arrays.asList(methodNames));
        // Use loop rather than lookup. This avoids knowing the parameters, and doesn't have to handle
        // NoSuchMethodException.
        for (Method method : clz.getDeclaredMethods()) {
            if (nameSet.remove(method.getName()) && nameSet.isEmpty()) {
                break;
            }
        }
        if (!nameSet.isEmpty()) {
            throw new IllegalArgumentException("Can't find '" + nameSet + "' in " + clz.getName());
        }
        String[] oldMethods;
        String[] newMethods;
        do {
            oldMethods = excludedMethods.get();
            newMethods = Arrays.copyOf(oldMethods, oldMethods.length + 2 * methodNames.length);
            for (int i = 0; i < methodNames.length; i++) {
                newMethods[oldMethods.length + i * 2] = clz.getName();
                newMethods[oldMethods.length + i * 2 + 1] = methodNames[i];
            }
        } while (!excludedMethods.compareAndSet(oldMethods, newMethods));
    }

    private static final class Record extends Throwable {
        private static final long serialVersionUID = 6065153674892850720L;

        private static final Record BOTTOM = new Record();

        private final String hintString;
        private final Record next;
        private final int pos;

        Record(Record next, Object hint) {
            // This needs to be generated even if toString() is never called as it may change later on.
            hintString = hint instanceof ResourceLeakHint ? ((ResourceLeakHint) hint).toHintString() : hint.toString();
            this.next = next;
            this.pos = next.pos + 1;
        }

        Record(Record next) {
           hintString = null;
           this.next = next;
           this.pos = next.pos + 1;
        }

        // Used to terminate the stack
        private Record() {
            hintString = null;
            next = null;
            pos = -1;
        }

        @Override
        public String toString() {
            StringBuilder buf = new StringBuilder(2048);
            if (hintString != null) {
                buf.append("\tHint: ").append(hintString).append(NEWLINE);
            }

            // Append the stack trace.
            StackTraceElement[] array = getStackTrace();
            // Skip the first three elements.
            out: for (int i = 3; i < array.length; i++) {
                StackTraceElement element = array[i];
                // Strip the noisy stack trace elements.
                String[] exclusions = excludedMethods.get();
                for (int k = 0; k < exclusions.length; k += 2) {
                    if (exclusions[k].equals(element.getClassName())
                            && exclusions[k + 1].equals(element.getMethodName())) {
                        continue out;
                    }
                }

                buf.append('\t');
                buf.append(element.toString());
                buf.append(NEWLINE);
            }
            return buf.toString();
        }
    }

    private static final class LeakEntry {
        static final LeakEntry INSTANCE = new LeakEntry();
        private static final int HASH = System.identityHashCode(INSTANCE);

        private LeakEntry() {
        }

        @Override
        public int hashCode() {
            return HASH;
        }

        @Override
        public boolean equals(Object obj) {
            return obj == this;
        }
    }
}