VASSAL.tools.lang.MemoryUtils.java Source code

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Here is the source code for VASSAL.tools.lang.MemoryUtils.java

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/*
 * $Id$
 *
 * Copyright (c) 2009, 2010 by Joel Uckelman
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License (LGPL) as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, copies are available
 * at http://www.opensource.org.
 */
package VASSAL.tools.lang;

import java.lang.management.ManagementFactory;

import org.apache.commons.lang.SystemUtils;

import VASSAL.tools.jna.Kernel32;

import com.sun.jna.Native;
import com.sun.jna.Pointer;
import com.sun.jna.ptr.PointerByReference;

import com.sun.management.OperatingSystemMXBean;

/**
 * A utility class for getting information about system memory.
 */
public class MemoryUtils {
    protected MemoryUtils() {
    }

    /**
     * Gets the amount of physical memory (RAM) in this machine, in bytes.
     *
     * @return the amount of RAM, in bytes; or -1 if the amount of RAM
     * cannot be queried.
     */
    public static long getPhysicalMemory() {
        if (!SystemUtils.IS_OS_WINDOWS || SystemUtils.IS_OS_WINDOWS_98 || SystemUtils.IS_OS_WINDOWS_ME) {
            // Windows 98, ME support a maximum of 2GB RAM, so are unaffected
            // by the bug which causes incorrect reporting over 2GB. Hence,
            // we can handle them in the normal way.
            final Object o = ManagementFactory.getOperatingSystemMXBean();

            try {
                if (o instanceof OperatingSystemMXBean) {
                    final OperatingSystemMXBean osb = (OperatingSystemMXBean) o;
                    return osb.getTotalPhysicalMemorySize();
                }
            } catch (NoClassDefFoundError e) {
                // com.sun.management.OperatingSystemMXBean doesn't exist in this JVM
            }

            // We didn't get a com.sun.management.OperatingSystemMXBean.
            return -1;
        } else {
            // FIXME: totalPhysicalMemorySize() doesn't return the correct result
            // on Windows machines with more than 2GB RAM, so we have to call
            // GlobalMemoryStatusEx ourselves instead of letting the bean do it
            // for us. See Sun Bug 6853676. This case can be removed when the bug
            // is fixed in a released JVM.

            // The Windows Kernel32 call GlobalMemoryStatusEx() fills a
            // MEMORYSTATUSEX structure with various facts about memory usage.
            final Kernel32.MEMORYSTATUSEX mstat = new Kernel32.MEMORYSTATUSEX();

            if (Kernel32.INSTANCE.GlobalMemoryStatusEx(mstat)) {
                return mstat.ullTotalPhys;
            } else {
                // GlobalMemoryStatusEx failed
                final PointerByReference lpBuffer = new PointerByReference();
                final int errno = Native.getLastError();
                final int msglen = Kernel32.INSTANCE.FormatMessage(
                        Kernel32.FORMAT_MESSAGE_ALLOCATE_BUFFER | Kernel32.FORMAT_MESSAGE_FROM_SYSTEM, Pointer.NULL,
                        errno, 0, lpBuffer, 0, Pointer.NULL);

                final String message = msglen > 0 ? lpBuffer.getValue().getStringArray(0)[0] : "no message";

                throw new RuntimeException("Error " + errno + ": " + message);
            }
        }
    }

    public static void main(String[] args) {
        final long ram = getPhysicalMemory();
        if (ram >= 0) {
            System.out.println("System reports " + (ram >> 20) + "MB RAM");
        } else {
            System.out.println("Could not determine amount of RAM");
        }
    }
}