/*
    * Copyright (C) 2008, Google Inc.
    * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
   */
  
  package org.eclipse.jgit.lib;
  
  import java.util.zip.Inflater;
  
  /**
   * Creates zlib based inflaters as necessary for object decompression.
   */
  public class InflaterCache {
  	private static final int SZ = 4;
  
  	private static final Inflater[] inflaterCache;
  
  	private static int openInflaterCount;
  
  	static {
  		inflaterCache = new Inflater[SZ];
  	}
  
  	/**
  	 * Obtain an Inflater for decompression.
  	 * <p>
  	 * Inflaters obtained through this cache should be returned (if possible) by
  	 * {@link #release(Inflater)} to avoid garbage collection and reallocation.
  	 *
  	 * @return an available inflater. Never null.
  	 */
  	public static Inflater get() {
  		final Inflater r = getImpl();
  		return r != null ? r : new Inflater(false);
  	}
  
  	private static synchronized Inflater getImpl() {
  		if (openInflaterCount > 0) {
  			final Inflater r = inflaterCache[--openInflaterCount];
  			inflaterCache[openInflaterCount] = null;
  			return r;
  		}
  		return null;
  	}
  
  	/**
  	 * Release an inflater previously obtained from this cache.
  	 *
  	 * @param i
  	 *            the inflater to return. May be null, in which case this method
  	 *            does nothing.
  	 */
  	public static void release(Inflater i) {
  		if (i != null) {
  			i.reset();
  			if (releaseImpl(i))
  				i.end();
  		}
  	}
  
  	private static synchronized boolean releaseImpl(Inflater i) {
  		if (openInflaterCount < SZ) {
  			inflaterCache[openInflaterCount++] = i;
  			return false;
  		}
  		return true;
  	}
  
  	private InflaterCache() {
  		throw new UnsupportedOperationException();
  	}
  }