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Oracle Coherence Community Edition
/*
* Copyright (c) 2000, 2020, Oracle and/or its affiliates.
*
* Licensed under the Universal Permissive License v 1.0 as shown at
* http://oss.oracle.com/licenses/upl.
*/
package com.tangosol.io.nio;
import com.tangosol.util.Base;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
/**
* Manages a ByteBuffer on a file.
*
* @see ByteBuffer
*
* @author cp 2002.09.18
*
* @since Coherence 2.2
*/
public class MappedBufferManager
extends AbstractBufferManager
{
// ----- constructors ---------------------------------------------------
/**
* Construct a MappedBufferManager using defaults.
*/
public MappedBufferManager()
{
this(DEFAULT_MIN_SIZE, DEFAULT_MAX_SIZE, null);
}
/**
* Construct a MappedBufferManager that supports a buffer of a certain
* initial and maximum size.
*
* @param cbInitial the initial size
* @param cbMaximum the maximum size
* @param file the file to use, or the directory to use, or null
* to generate a temporary file in the default location
*/
public MappedBufferManager(int cbInitial, int cbMaximum, File file)
{
super(cbInitial, cbMaximum);
configureFile(file);
allocateBuffer();
}
// ----- internal -------------------------------------------------------
/**
* Configure the buffer manager based on the passed file, which may be
* null to imply a default temp file, a directory to imply that a file
* be created in that directory, or it may be the temp file itself.
*
* @param file the file to use, or the directory to use, or null
* to generate a temporary file in the default location
*/
protected void configureFile(File file)
{
try
{
boolean fTemp = false;
// ensure the temp file, and if it is created here, make sure
// it is registered for removal
if (file == null || file.isDirectory())
{
file = File.createTempFile("coherence", null, file);
fTemp = true;
}
else if (!file.exists())
{
file.createNewFile();
fTemp = true;
}
// configure random access to the file
RandomAccessFile hfile = new RandomAccessFile(file, "rw");
setFile(hfile);
if (fTemp)
{
file.deleteOnExit();
m_fileTemp = file;
}
}
catch (IOException e)
{
throw Base.ensureRuntimeException(e);
}
}
/**
* Obtain the RandomAccessFile that the buffer is constructed on.
*
* @return the RandomAccessFile object
*/
protected RandomAccessFile getFile()
{
return m_hfile;
}
/**
* Specify the RandomAccessFile that the buffer will be constructed on.
*
* @param file the RandomAccessFile object
*/
protected void setFile(RandomAccessFile file)
{
m_hfile = file;
}
/**
* Allocate a new buffer, copying old data if there is any.
*
* @see FileChannel#map(java.nio.channels.FileChannel.MapMode, long, long) FileChannel.map()
*/
protected void allocateBuffer()
{
try
{
RandomAccessFile hfile = getFile();
int cbOld = (int) hfile.length();
int cbNew = getCapacity();
if (cbNew != cbOld)
{
setBuffer(null);
// see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4857305
System.gc();
Thread.yield();
try
{
hfile.setLength(cbNew);
}
catch (IOException e)
{
// only "worry" if the file cannot grow
if (cbNew > cbOld)
{
throw e;
}
}
setBuffer(hfile.getChannel().map(FileChannel.MapMode.READ_WRITE, 0L, cbNew));
}
}
catch (IOException e)
{
throw Base.ensureRuntimeException(e);
}
}
// ----- life-cycle support ---------------------------------------------
/**
* Close the underlying resources.
*/
public void close()
{
try
{
RandomAccessFile hfile = m_hfile;
if (hfile != null)
{
// need to close the file to have it deleted on exit:
// http://developer.java.sun.com/developer/bugParade/bugs/4171239.html
// however, this may not work on Windows:
// http://developer.java.sun.com/developer/bugParade/bugs/4715154.html
// attempt to unmap before close as suggested in the bug link above
try
{
ByteBuffer buffer = getBuffer();
Method getCleanerMethod = buffer.getClass().getMethod("cleaner");
getCleanerMethod.setAccessible(true);
Object cleaner = getCleanerMethod.invoke(buffer);
Method cleanMethod = cleaner.getClass().getMethod("clean");
cleanMethod.invoke(cleaner);
}
catch (Throwable t) {}
hfile.close();
}
File fileTemp = m_fileTemp;
if (fileTemp != null)
{
if (fileTemp.delete())
{
m_fileTemp = null;
}
else
{
// Java BugID: 4715154; Closed, will not be fixed on windows
log("MappedBufferManager: " + "failed to remove " + fileTemp);
}
}
}
catch (Exception e) {}
m_hfile = null;
}
/**
* Perform cleanup during garbage collection.
*/
protected void finalize()
{
close();
}
// ----- constants ------------------------------------------------------
/**
* Default minimum size for a memory mapped file.
*/
public static final int DEFAULT_MIN_SIZE = 0x4000;
/**
* Default maximum size for a memory mapped file.
*/
public static final int DEFAULT_MAX_SIZE = Integer.MAX_VALUE;
// ----- data members ---------------------------------------------------
/**
* The underlying temporary File.
*/
private File m_fileTemp;
/**
* The underlying RandomAccessFile.
*/
private RandomAccessFile m_hfile;
}