Issue #5287 - rework CompressionPool to use the jetty-util pool

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-util/src/main/java/org/eclipse/jetty/util/compression/CompressionPool.java

@@ -18,19 +18,14 @@
 
 package org.eclipse.jetty.util.compression;
 
-import java.util.Queue;
-import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.atomic.AtomicInteger;
-
+import org.eclipse.jetty.util.Pool;
 import org.eclipse.jetty.util.component.AbstractLifeCycle;
 
 public abstract class CompressionPool<T> extends AbstractLifeCycle
 {
     public static final int INFINITE_CAPACITY = -1;
 
-    private final Queue<T> _pool;
-    private final AtomicInteger _numObjects = new AtomicInteger(0);
-    private int _capacity;
+    private final Pool<T> _pool;
 
     /**
      * Create a Pool of {@link T} instances.
@@ -43,8 +38,7 @@ public abstract class CompressionPool<T> extends AbstractLifeCycle
      */
     public CompressionPool(int capacity)
     {
-        _capacity = capacity;
-        _pool = new ConcurrentLinkedQueue<>();
+        _pool = new Pool<T>(capacity, 1);
     }
 
     public int getCapacity()
@@ -66,73 +60,61 @@ public void setCapacity(int capacity)
     /**
      * @return Object taken from the pool if it is not empty or a newly created Object
      */
-    public T acquire()
+    public Entry acquire()
     {
-        T object;
-
-        if (_capacity == 0)
-            object = newObject();
-        else
-        {
-            object = _pool.poll();
-            if (object == null)
-                object = newObject();
-            else if (_capacity > 0)
-                _numObjects.decrementAndGet();
-        }
-
-        return object;
+        return new Entry(_pool.acquire(e -> newObject()));
     }
 
     /**
-     * @param object returns this Object to the pool or calls {@link #end(Object)} if the pool is full.
+     * @param entry returns this Object to the pool or calls {@link #end(Object)} if the pool is full.
      */
-    public void release(T object)
+    public void release(Entry entry)
+    {
+        entry.release();
+    }
+
+    @Override
+    public void doStop()
+    {
+        // TODO: We can't use this because it will not end the entries after it removes them.
+        // _pool.close();
+    }
+
+    public class Entry
     {
-        if (object == null)
-            return;
+        private T _value;
+        private Pool<T>.Entry _entry;
 
-        if (_capacity == 0 || !isRunning())
+        Entry(Pool<T>.Entry entry)
         {
-            end(object);
+            _entry = entry;
+            _value = (_entry != null) ? _entry.getPooled() : newObject();
         }
-        else if (_capacity < 0)
+
+        public T get()
         {
-            reset(object);
-            _pool.add(object);
+            return _value;
         }
-        else
-        {
-            while (true)
-            {
-                int d = _numObjects.get();
 
-                if (d >= _capacity)
-                {
-                    end(object);
-                    break;
-                }
+        public void release()
+        {
+            // Reset the value for the next usage.
+            reset(_value);
 
-                if (_numObjects.compareAndSet(d, d + 1))
+            if (_entry != null)
+            {
+                // If release return false, the entry should be removed and the object should be disposed.
+                if (!_pool.release(_entry))
                 {
-                    reset(object);
-                    _pool.add(object);
-                    break;
+                    // TODO: what does it mean if this returns false???
+                    if (_pool.remove(_entry))
+                        end(_value);
                 }
             }
-        }
-    }
 
-    @Override
-    public void doStop()
-    {
-        T t = _pool.poll();
-        while (t != null)
-        {
-            end(t);
-            t = _pool.poll();
+            _value = null;
+            _entry = null;
         }
-        _numObjects.set(0);
     }
 
     @Override