001/* MemoryUsage.java - Information on the usage of a memory pool.
002   Copyright (C) 2006 Free Software Foundation
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.lang.management;
039
040import javax.management.openmbean.CompositeData;
041import javax.management.openmbean.CompositeType;
042import javax.management.openmbean.SimpleType;
043/**
044 * <p>
045 * Retains information on the usage of a particular memory
046 * pool, or heap/non-heap memory as a whole.  Memory usage
047 * is represented by four values (all in bytes):
048 * </p>
049 * <ul>
050 * <li><strong>Initial Level</strong>: This is the initial
051 * amount of memory allocated for the pool by the operating
052 * system.  This value may be undefined.</li>
053 * <li><strong>Used Level</strong>: This is the amount of
054 * memory currently in use.</li>
055 * <li><strong>Committed Level</strong>: This is the current
056 * amount of memory allocated for the pool by the operating
057 * system.  This value will always be equal to or greater than
058 * the current amount of memory in use.  It may drop below
059 * the initial amount, if the virtual machine judges this to
060 * be practical.</li>
061 * <li><strong>Maximum Level</strong>: This is the maximum
062 * amount of memory that may be allocated for the pool by
063 * the operating system.  Like the initial amount, it may
064 * be undefined.  If it is defined, it will be greater than
065 * or equal to the used and committed amounts and may change
066 * over time.  It is not guaranteed that the maximum amount
067 * of memory may actually be allocated to the pool.  For
068 * example, a request for an amount of memory greater than
069 * the current committed level, but less than the maximum,
070 * may still fail due to resources at the operating system
071 * level not being sufficient to fulfill the demand.</li>
072 * </ul>
073 *
074 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
075 * @since 1.5
076 * @see MemoryMXBean
077 * @see MemoryPoolMXBean
078 */
079public class MemoryUsage
080{
081
082  /**
083   * The initial amount of memory allocated.
084   */
085  private long init;
086
087  /**
088   * The amount of memory used.
089   */
090  private long used;
091
092  /**
093   * The amount of memory committed for use.
094   */
095  private long committed;
096
097  /**
098   * The maximum amount of memory available.
099   */
100  private long maximum;
101
102  /**
103   * Constructs a new {@link MemoryUsage} object with
104   * the specified allocation levels.
105   *
106   * @param init the initial amount of memory allocated,
107   *             or -1 if this value is undefined.  Must
108   *             be >= -1.
109   * @param used the amount of memory used.  Must be >= 0,
110   *             and <= committed.
111   * @param committed the amount of memory committed for use
112   *                  at present.  Must be >= 0 and <=
113   *                  maximum (if defined).
114   * @param maximum the maximum amount of memory that may be
115   *                used, or -1 if this value is undefined.
116   *                Must be >= -1.
117   * @throws IllegalArgumentException if the values break any
118   *                                  of the limits specified
119   *                                  above.
120   */
121  public MemoryUsage(long init, long used, long committed,
122                     long maximum)
123  {
124    if (init < -1)
125      throw new IllegalArgumentException("Initial value of "
126                                         + init + " is too small.");
127    if (used < 0)
128      throw new IllegalArgumentException("Used value of "
129                                         + used + " is too small.");
130    if (committed < 0)
131      throw new IllegalArgumentException("Committed value of "
132                                         + committed + " is too small.");
133    if (committed < used)
134      throw new IllegalArgumentException("Committed value of "
135                                         + committed + " is below "
136                                         + used + ", the amount used.");
137    if (maximum < -1)
138      throw new IllegalArgumentException("Maximum value of "
139                                         + maximum + " is too small.");
140    if (maximum != -1 && maximum < committed)
141      throw new IllegalArgumentException("Maximum value of " 
142                                         + maximum + " is below "
143                                         + committed + ", the amount "
144                                         + "committed.");
145    this.init = init;
146    this.used = used;
147    this.committed = committed;
148    this.maximum = maximum;
149  }
150
151  /**
152   * <p>
153   * Returns a {@link MemoryUsage} instance using the values
154   * given in the supplied
155   * {@link javax.management.openmbean.CompositeData} object.
156   * The composite data instance should contain the following
157   * attributes:
158   * </p>
159   * <ul>
160   * <li>init</li>
161   * <li>used</li>
162   * <li>committed</li>
163   * <li>max</li>
164   * </ul>
165   * <p>
166   * All should have the type, <code>java.lang.Long</code>.
167   * </p>
168   * 
169   * @param data the composite data structure to take values from.
170   * @return a new instance containing the values from the 
171   *         composite data structure, or <code>null</code>
172   *         if the data structure was also <code>null</code>.
173   * @throws IllegalArgumentException if the composite data structure
174   *                                  does not match the structure
175   *                                  outlined above, or the values
176   *                                  are invalid.
177   */
178  public static MemoryUsage from(CompositeData data)
179  {
180    if (data == null)
181      return null;
182    CompositeType type = data.getCompositeType();
183    ThreadInfo.checkAttribute(type, "Init", SimpleType.LONG);
184    ThreadInfo.checkAttribute(type, "Used", SimpleType.LONG);
185    ThreadInfo.checkAttribute(type, "Committed", SimpleType.LONG);
186    ThreadInfo.checkAttribute(type, "Max", SimpleType.LONG);
187    return new MemoryUsage(((Long) data.get("Init")).longValue(),
188                           ((Long) data.get("Used")).longValue(),
189                           ((Long) data.get("Committed")).longValue(),
190                           ((Long) data.get("Max")).longValue());
191  }
192
193  /**
194   * Returns the amount of memory committed for use by this
195   * memory pool (in bytes).  This amount is guaranteed to
196   * be available, unlike the maximum.
197   *
198   * @return the committed amount of memory.
199   */
200  public long getCommitted()
201  {
202    return committed;
203  }
204
205  /**
206   * Returns the initial amount of memory allocated to the
207   * pool (in bytes).  This method may return -1, if the
208   * value is undefined.
209   *
210   * @return the initial amount of memory allocated, or -1
211   *         if this value is undefined.
212   */
213  public long getInit()
214  {
215    return init;
216  }
217
218  /**
219   * Returns the maximum amount of memory available for this
220   * pool (in bytes).  This amount is not guaranteed to 
221   * actually be usable.  This method may return -1, if the
222   * value is undefined.
223   *
224   * @return the maximum amount of memory available, or -1
225   *         if this value is undefined.
226   */
227  public long getMax()
228  {
229    return maximum;
230  }
231
232  /**
233   * Returns the amount of memory used (in bytes).
234   *
235   * @return the amount of used memory.
236   */
237  public long getUsed()
238  {
239    return used;
240  }
241
242  /**
243   * Returns a {@link java.lang.String} representation of
244   * this {@link MemoryUsage} object.  This takes the form
245   * <code>java.lang.management.MemoryUsage[init=i, used=u,
246   * committed=c, maximum=m]</code>, where <code>i</code>
247   * is the initial level, <code>u</code> is the used level,
248   * <code>c</code> is the committed level and <code>m</code>
249   * is the maximum level.
250   *
251   * @return the string specified above.
252   */
253  public String toString()
254  {
255    int megabyte = 1024 * 1024;
256    return getClass().getName() +
257      "[init=" + init + " bytes (~" + (init / megabyte) +
258      "MB), used=" + used + " bytes (~" + (used / megabyte) +
259      "MB), committed=" + committed + " bytes (~" + (committed / megabyte) +
260      "MB), maximum=" + maximum + " bytes (~" + (maximum / megabyte) +
261      "MB)]";
262  }
263
264}
265