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/*******************************************************************************
* Copyright (c) 2012, 2013 Ericsson
* Copyright (c) 2010, 2011 École Polytechnique de Montréal
* Copyright (c) 2010, 2011 Alexandre Montplaisir <alexandre.montplaisir@gmail.com>
*
* All rights reserved. This program and the accompanying materials are
* made available under the terms of the Eclipse Public License v1.0 which
* accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
*******************************************************************************/
package org.eclipse.linuxtools.internal.tmf.core.statesystem.backends.historytree;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
/**
* This class exists mainly for code isolation/clarification purposes. It
* contains all the methods and descriptors to handle reading/writing to the
* tree-file on disk and all the caching mechanisms. Every HistoryTree should
* contain 1 and only 1 HT_IO element.
*
* @author alexmont
*
*/
class HT_IO {
/* reference to the tree to which this IO-object belongs */
private final HistoryTree tree;
/* Fields related to the file I/O */
private final File historyTreeFile;
private final FileInputStream fis;
private final FileOutputStream fos;
private final FileChannel fcIn;
private final FileChannel fcOut;
private final int CACHE_SIZE = 256;
private final HTNode fNodeCache[] = new HTNode[CACHE_SIZE];
/**
* Standard constructor
*
* @param tree
* @param newFile
* Are we creating a new file from scratch?
* @throws IOException
*/
HT_IO(HistoryTree tree, boolean newFile) throws IOException {
this.tree = tree;
historyTreeFile = tree.getConfig().getStateFile();
boolean success1 = true;
if (newFile) {
/* Create a new empty History Tree file */
if (historyTreeFile.exists()) {
success1 = historyTreeFile.delete();
}
boolean success2 = historyTreeFile.createNewFile();
if (!(success1 && success2)) {
/* It seems we do not have permission to create the new file */
throw new IOException("Cannot create new file at " + //$NON-NLS-1$
historyTreeFile.getName());
}
fis = new FileInputStream(historyTreeFile);
fos = new FileOutputStream(historyTreeFile, false);
} else {
/*
* We want to open an existing file, make sure we don't squash the
* existing content when opening the fos!
*/
this.fis = new FileInputStream(historyTreeFile);
this.fos = new FileOutputStream(historyTreeFile, true);
}
this.fcIn = fis.getChannel();
this.fcOut = fos.getChannel();
}
/**
* Generic "read node" method, which checks if the node is in memory first,
* and if it's not it goes to disk to retrieve it.
*
* @param seqNumber
* Sequence number of the node we want
* @return The wanted node in object form
* @throws ClosedChannelException
* If the channel was closed before we could read
*/
HTNode readNode(int seqNumber) throws ClosedChannelException {
HTNode node = readNodeFromMemory(seqNumber);
if (node == null) {
return readNodeFromDisk(seqNumber);
}
return node;
}
private HTNode readNodeFromMemory(int seqNumber) {
for (HTNode node : tree.getLatestBranch()) {
if (node.getSequenceNumber() == seqNumber) {
return node;
}
}
return null;
}
/**
* This method here isn't private, if we know for sure the node cannot be in
* memory it's a bit faster to use this directly (when opening a file from
* disk for example)
*
* @throws ClosedChannelException
* Usually happens because the file was closed while we were
* reading. Instead of using a big reader-writer lock, we'll
* just catch this exception.
*/
synchronized HTNode readNodeFromDisk(int seqNumber) throws ClosedChannelException {
/* Do a cache lookup */
int offset = seqNumber & (CACHE_SIZE - 1);
HTNode readNode = fNodeCache[offset];
if (readNode != null && readNode.getSequenceNumber() == seqNumber) {
return readNode;
}
/* Lookup on disk */
try {
seekFCToNodePos(fcIn, seqNumber);
readNode = HTNode.readNode(tree, fcIn);
/* Put the node in the cache. */
fNodeCache[offset] = readNode;
return readNode;
} catch (ClosedChannelException e) {
throw e;
} catch (IOException e) {
/* Other types of IOExceptions shouldn't happen at this point though */
e.printStackTrace();
return null;
}
}
void writeNode(HTNode node) {
try {
/* Insert the node into the cache. */
int seqNumber = node.getSequenceNumber();
int offset = seqNumber & (CACHE_SIZE - 1);
fNodeCache[offset] = node;
/* Position ourselves at the start of the node and write it */
seekFCToNodePos(fcOut, seqNumber);
node.writeSelf(fcOut);
} catch (IOException e) {
/* If we were able to open the file, we should be fine now... */
e.printStackTrace();
}
}
FileChannel getFcOut() {
return this.fcOut;
}
FileInputStream supplyATReader() {
try {
/*
* Position ourselves at the start of the Mapping section in the
* file (which is right after the Blocks)
*/
seekFCToNodePos(fcIn, tree.getNodeCount());
} catch (IOException e) {
e.printStackTrace();
}
return fis;
}
File supplyATWriterFile() {
return tree.getConfig().getStateFile();
}
long supplyATWriterFilePos() {
return HistoryTree.TREE_HEADER_SIZE
+ ((long) tree.getNodeCount() * tree.getConfig().getBlockSize());
}
synchronized void closeFile() {
try {
fis.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
synchronized void deleteFile() {
closeFile();
if (!historyTreeFile.delete()) {
/* We didn't succeed in deleting the file */
//TODO log it?
}
}
/**
* Seek the given FileChannel to the position corresponding to the node that
* has seqNumber
*
* @param seqNumber
* @throws IOException
*/
private void seekFCToNodePos(FileChannel fc, int seqNumber)
throws IOException {
fc.position(HistoryTree.TREE_HEADER_SIZE + (long) seqNumber
* tree.getConfig().getBlockSize());
/*
* cast to (long) is needed to make sure the result is a long too and
* doesn't get truncated
*/
}
}
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