statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/backend/historytree/HistoryTreeFactory.java

   1 /*******************************************************************************
   2  * Copyright (c) 2016 École Polytechnique de Montréal
   3  *
   4  * All rights reserved. This program and the accompanying materials are
   5  * made available under the terms of the Eclipse Public License v1.0 which
   6  * accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *******************************************************************************/
   9
  10 package org.eclipse.tracecompass.internal.statesystem.core.backend.historytree;
  11
  12 import java.io.IOException;
  13 import java.nio.ByteBuffer;
  14 import java.nio.ByteOrder;
  15 import java.nio.channels.ReadableByteChannel;
  16 import java.nio.file.Files;
  17 import java.nio.file.Path;
  18 import java.nio.file.StandardOpenOption;
  19
  20 import org.eclipse.jdt.annotation.NonNullByDefault;
  21 import org.eclipse.tracecompass.internal.statesystem.core.backend.historytree.classic.HistoryTreeClassic;
  22
  23 /**
  24  * Class that contains factory methods to build different types of history trees
  25  *
  26  * @author Geneviève Bastien
  27  */
  28 @NonNullByDefault
  29 public final class HistoryTreeFactory {
  30
  31     private HistoryTreeFactory() {
  32     }
  33
  34     /**
  35      * Create a new State History from scratch, using a {@link HTConfig} object
  36      * for configuration.
  37      *
  38      * @param conf
  39      *            The config to use for this History Tree.
  40      * @return the new state history tree
  41      * @throws IOException
  42      *             If an error happens trying to open/write to the file
  43      *             specified in the config
  44      */
  45     public static IHistoryTree createHistoryTree(HTConfig conf) throws IOException {
  46         return new HistoryTreeClassic(conf);
  47     }
  48
  49     /**
  50      * "Reader" factory : instantiate a SHTree from an existing tree file on
  51      * disk
  52      *
  53      * @param existingStateFile
  54      *            Path/filename of the history-file we are to open
  55      * @param expectedProviderVersion
  56      *            The expected version of the state provider
  57      * @return The history tree
  58      * @throws IOException
  59      *             If an error happens reading the file
  60      */
  61     public static IHistoryTree createFromFile(Path existingStateFile, int expectedProviderVersion) throws IOException {
  62         /*
  63          * Check the file exists and has a positive length. These verifications
  64          * will also be done in the HT's constructor.
  65          */
  66         if (!Files.isReadable(existingStateFile)) {
  67             throw new IOException("Selected state file does not exist or is not readable."); //$NON-NLS-1$
  68         }
  69         if (Files.size(existingStateFile) <= 0) {
  70             throw new IOException("Empty target file"); //$NON-NLS-1$
  71         }
  72
  73         /* Read the magic number from the history tree file */
  74         ByteBuffer buffer = ByteBuffer.allocate(Integer.BYTES);
  75         try (ReadableByteChannel channel = Files.newByteChannel(existingStateFile, StandardOpenOption.READ);) {
  76             buffer.order(ByteOrder.LITTLE_ENDIAN);
  77             buffer.clear();
  78             channel.read(buffer);
  79             buffer.flip();
  80         }
  81
  82         /*
  83          * Check the magic number to see which history tree class to create
  84          */
  85         int magicNumber = buffer.getInt();
  86         switch (magicNumber) {
  87         case HistoryTreeClassic.HISTORY_FILE_MAGIC_NUMBER:
  88             return new HistoryTreeClassic(existingStateFile.toFile(), expectedProviderVersion);
  89         default:
  90             throw new IOException("Not a known history tree file"); //$NON-NLS-1$
  91         }
  92     }
  93 }