1 /*
   2  * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package gc.g1.plab.lib;
  24 
  25 /**
  26  * The MemoryConsumer is used for consuming different amount of memory.
  27  * Class will store not more than 'capacity' number of objects with 'chunk' size.
  28  * If we exceed capacity, object will be stored at existing entries,
  29  * all previously added objects will be overwritten.
  30  * If capacity=1, only last object will be saved.
  31  */
  32 public class MemoryConsumer {
  33 
  34     private int capacity;
  35     private int chunk;
  36 
  37     private Object[] array;
  38     private int index;
  39 
  40     /**
  41      * Create MemoryConsumer object with defined capacity
  42      *
  43      * @param capacity
  44      * @param chunk
  45      */
  46     public MemoryConsumer(int capacity, int chunk) {
  47         if (capacity <= 0) {
  48             throw new IllegalArgumentException("Items number should be greater than 0.");
  49         }
  50         if (chunk <= 0) {
  51             throw new IllegalArgumentException("Chunk size should be greater than 0.");
  52         }
  53         this.capacity = capacity;
  54         this.chunk = chunk;
  55         index = 0;
  56         array = new Object[this.capacity];
  57     }
  58 
  59     /**
  60      * Store object into Storage.
  61      *
  62      * @param o - Object to store
  63      */
  64     private void store(Object o) {
  65         if (array == null) {
  66             throw new RuntimeException("Capacity should be set before storing");
  67         }
  68         array[index % capacity] = o;
  69         ++index;
  70     }
  71 
  72     public void consume(long memoryToFill) {
  73         long allocated = 0;
  74         while (allocated < memoryToFill) {
  75             store(new byte[chunk]);
  76             allocated += chunk;
  77         }
  78     }
  79 
  80     /**
  81      * Clear all stored objects.
  82      */
  83     public void clear() {
  84         array = null;
  85     }
  86 }