package com.leansoft.bigqueue.page;
import java.io.Closeable;
import java.io.IOException;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import org.apache.log4j.Logger;
public class MappedPageImpl implements IMappedPage, Closeable {
private final static Logger logger = Logger.getLogger(MappedPageImpl.class);
private ThreadLocalByteBuffer threadLocalBuffer;
private volatile boolean dirty = false;
private volatile boolean closed = false;
private String pageFile;
private long index;
public MappedPageImpl(MappedByteBuffer mbb, String pageFile, long index) {
this.threadLocalBuffer = new ThreadLocalByteBuffer(mbb);
this.pageFile = pageFile;
this.index = index;
}
public void close() throws IOException {
synchronized(this) {
if (closed) return;
flush();
MappedByteBuffer srcBuf = (MappedByteBuffer)threadLocalBuffer.getSourceBuffer();
unmap(srcBuf);
this.threadLocalBuffer = null; // hint GC
closed = true;
if (logger.isDebugEnabled()) {
logger.debug("Mapped page for " + this.pageFile + " was just unmapped and closed.");
}
}
}
@Override
public void setDirty(boolean dirty) {
this.dirty = dirty;
}
@Override
public void flush() {
synchronized(this) {
if (closed) return;
if (dirty) {
MappedByteBuffer srcBuf = (MappedByteBuffer)threadLocalBuffer.getSourceBuffer();
srcBuf.force(); // flush the changes
dirty = false;
if (logger.isDebugEnabled()) {
logger.debug("Mapped page for " + this.pageFile + " was just flushed.");
}
}
}
}
public byte[] getLocal(int position, int length) {
ByteBuffer buf = this.getLocal(position);
byte[] data = new byte[length];
buf.get(data);
return data;
}
@Override
public ByteBuffer getLocal(int position) {
ByteBuffer buf = this.threadLocalBuffer.get();
buf.position(position);
return buf;
}
private static void unmap(MappedByteBuffer buffer)
{
Cleaner.clean(buffer);
}
/**
* Helper class allowing to clean direct buffers.
*/
private static class Cleaner {
public static final boolean CLEAN_SUPPORTED;
private static final Method directBufferCleaner;
private static final Method directBufferCleanerClean;
static {
Method directBufferCleanerX = null;
Method directBufferCleanerCleanX = null;
boolean v;
try {
directBufferCleanerX = Class.forName("java.nio.DirectByteBuffer").getMethod("cleaner");
directBufferCleanerX.setAccessible(true);
directBufferCleanerCleanX = Class.forName("sun.misc.Cleaner").getMethod("clean");
directBufferCleanerCleanX.setAccessible(true);
v = true;
} catch (Exception e) {
v = false;
}
CLEAN_SUPPORTED = v;
directBufferCleaner = directBufferCleanerX;
directBufferCleanerClean = directBufferCleanerCleanX;
}
public static void clean(ByteBuffer buffer) {
if (buffer == null) return;
if (CLEAN_SUPPORTED && buffer.isDirect()) {
try {
Object cleaner = directBufferCleaner.invoke(buffer);
directBufferCleanerClean.invoke(cleaner);
} catch (Exception e) {
// silently ignore exception
}
}
}
}
private static class ThreadLocalByteBuffer extends ThreadLocal<ByteBuffer> {
private ByteBuffer _src;
public ThreadLocalByteBuffer(ByteBuffer src) {
_src = src;
}
public ByteBuffer getSourceBuffer() {
return _src;
}
@Override
protected synchronized ByteBuffer initialValue() {
ByteBuffer dup = _src.duplicate();
return dup;
}
}
@Override
public boolean isClosed() {
return closed;
}
public String toString() {
return "Mapped page for " + this.pageFile + ", index = " + this.index + ".";
}
@Override
public String getPageFile() {
return this.pageFile;
}
@Override
public long getPageIndex() {
return this.index;
}
}