package com.fasterxml.jackson.core.util;

import java.lang.ref.SoftReference;

Helper entity used to control access to simple buffer recyling scheme used for
some encoding, decoding tasks.
See Also:
BufferRecycler
Since:
2.9.2/**
 * Helper entity used to control access to simple buffer recyling scheme used for
 * some encoding, decoding tasks.
 *
 * @see BufferRecycler
 *
 * @since 2.9.2
 */
public class BufferRecyclers
{
    
System property that is checked to see if recycled buffers (see BufferRecycler) should be tracked, for purpose of forcing release of all such buffers, typically during major classloading. 
Since:
2.9.6/**
     * System property that is checked to see if recycled buffers (see {@link BufferRecycler})
     * should be tracked, for purpose of forcing release of all such buffers, typically
     * during major classloading.
     *
     * @since 2.9.6
     */
    public final static String SYSTEM_PROPERTY_TRACK_REUSABLE_BUFFERS
        = "com.fasterxml.jackson.core.util.BufferRecyclers.trackReusableBuffers";

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */

    
Flag that indicates whether BufferRecycler instances should be tracked. /**
     * Flag that indicates whether {@link BufferRecycler} instances should be tracked.
     */
    private final static ThreadLocalBufferManager _bufferRecyclerTracker;
    static {
        boolean trackReusableBuffers = false;
        try {
            trackReusableBuffers = "true".equals(System.getProperty(SYSTEM_PROPERTY_TRACK_REUSABLE_BUFFERS));
        } catch (SecurityException e) { }

        _bufferRecyclerTracker = trackReusableBuffers ? ThreadLocalBufferManager.instance() : null;
    }

    /*
    /**********************************************************
    /* BufferRecyclers for parsers, generators
    /**********************************************************
     */

    
This ThreadLocal contains a SoftReference to a BufferRecycler used to provide a low-cost buffer recycling between reader and writer instances. /**
     * This <code>ThreadLocal</code> contains a {@link java.lang.ref.SoftReference}
     * to a {@link BufferRecycler} used to provide a low-cost
     * buffer recycling between reader and writer instances.
     */
    final protected static ThreadLocal<SoftReference<BufferRecycler>> _recyclerRef
        = new ThreadLocal<SoftReference<BufferRecycler>>();

    
Main accessor to call for accessing possibly recycled BufferRecycler instance. /**
     * Main accessor to call for accessing possibly recycled {@link BufferRecycler} instance.
     */
    public static BufferRecycler getBufferRecycler()
    {
        SoftReference<BufferRecycler> ref = _recyclerRef.get();
        BufferRecycler br = (ref == null) ? null : ref.get();

        if (br == null) {
            br = new BufferRecycler();
            if (_bufferRecyclerTracker != null) {
                ref = _bufferRecyclerTracker.wrapAndTrack(br);
            } else {
                ref = new SoftReference<BufferRecycler>(br);
            }
            _recyclerRef.set(ref);
        }
        return br;
    }

    
Specialized method that will release all recycled BufferRecycler if (and only if) recycler tracking has been enabled (see SYSTEM_PROPERTY_TRACK_REUSABLE_BUFFERS). This method is usually called on shutdown of the container like Application Server to ensure that no references are reachable via ThreadLocals as this may cause unintentional retention of sizable amounts of memory. It may also be called regularly if GC for some reason does not clear up SoftReferences aggressively enough. 
Returns:
Number of buffers released, if tracking enabled (zero or more); -1 if tracking not enabled.
Since:
2.9.6/**
     * Specialized method that will release all recycled {@link BufferRecycler} if
     * (and only if) recycler tracking has been enabled
     * (see {@link #SYSTEM_PROPERTY_TRACK_REUSABLE_BUFFERS}).
     * This method is usually called on shutdown of the container like Application Server
     * to ensure that no references are reachable via {@link ThreadLocal}s as this may cause
     * unintentional retention of sizable amounts of memory. It may also be called regularly
     * if GC for some reason does not clear up {@link SoftReference}s aggressively enough.
     *
     * @return Number of buffers released, if tracking enabled (zero or more); -1 if tracking not enabled.
     *
     * @since 2.9.6
     */
    public static int releaseBuffers() {
        if (_bufferRecyclerTracker != null) {
            return _bufferRecyclerTracker.releaseBuffers();
        }
        return -1;
    }
}