statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/statesystem/core/backend/IStateHistoryBackend.java

   1 /*******************************************************************************
   2  * Copyright (c) 2012, 2014 Ericsson
   3  * Copyright (c) 2010, 2011 École Polytechnique de Montréal
   4  * Copyright (c) 2010, 2011 Alexandre Montplaisir <alexandre.montplaisir@gmail.com>
   5  *
   6  * All rights reserved. This program and the accompanying materials are
   7  * made available under the terms of the Eclipse Public License v1.0 which
   8  * accompanies this distribution, and is available at
   9  * http://www.eclipse.org/legal/epl-v10.html
  10  *
  11  *******************************************************************************/
  12
  13 package org.eclipse.tracecompass.statesystem.core.backend;
  14
  15 import java.io.File;
  16 import java.io.FileInputStream;
  17 import java.io.PrintWriter;
  18 import java.util.List;
  19
  20 import org.eclipse.jdt.annotation.NonNull;
  21 import org.eclipse.jdt.annotation.Nullable;
  22 import org.eclipse.tracecompass.statesystem.core.exceptions.StateSystemDisposedException;
  23 import org.eclipse.tracecompass.statesystem.core.exceptions.TimeRangeException;
  24 import org.eclipse.tracecompass.statesystem.core.interval.ITmfStateInterval;
  25 import org.eclipse.tracecompass.statesystem.core.statevalue.ITmfStateValue;
  26
  27 /**
  28  * The main difference between StateSystem and StateHistorySystem is that SHS
  29  * allows 'seeking' back in time to reload a Current State at a previous time.
  30  * "How to go back in time" is defined by the implementation of the
  31  * HistoryBackend.
  32  *
  33  * A StateHistorySystem contains one and only one HistoryBackend. If you want to
  34  * use a paradigm with more than one provider (eg. more or less precision
  35  * depending on what's asked by the user), implement one wrapper HistoryBackend
  36  * which can then contain your 2-3 other backends underneath.
  37  *
  38  * @author Alexandre Montplaisir
  39  */
  40 public interface IStateHistoryBackend {
  41
  42     /**
  43      * Get the ID of the state system that populates this backend.
  44      *
  45      * @return The state system's ID.
  46      * @since 1.0
  47      */
  48     @NonNull String getSSID();
  49
  50     /**
  51      * Get the start time of this state history. This is usually the same as the
  52      * start time of the originating trace.
  53      *
  54      * @return The start time
  55      */
  56     long getStartTime();
  57
  58     /**
  59      * Get the current end time of the state history. It will change as the
  60      * history is being built.
  61      *
  62      * @return The end time
  63      */
  64     long getEndTime();
  65
  66     /**
  67      * Main method to insert state intervals into the history.
  68      *
  69      * @param stateStartTime
  70      *            The start time of the interval
  71      * @param stateEndTime
  72      *            The end time of the interval
  73      * @param quark
  74      *            The quark of the attribute this interval refers to
  75      * @param value
  76      *            The StateValue represented by this interval
  77      * @throws TimeRangeException
  78      *             If the start or end time are invalid
  79      */
  80     // FIXME change to IStateInterval?
  81     void insertPastState(long stateStartTime, long stateEndTime,
  82             int quark, @NonNull ITmfStateValue value) throws TimeRangeException;
  83
  84     /**
  85      * Indicate to the provider that we are done building the history (so it can
  86      * close off, stop threads, etc.)
  87      *
  88      * @param endTime
  89      *            The end time to assign to this state history. It could be
  90      *            farther in time than the last state inserted, for example.
  91      * @throws TimeRangeException
  92      *             If the requested time makes no sense.
  93      */
  94     void finishedBuilding(long endTime) throws TimeRangeException;
  95
  96     /**
  97      * It is the responsibility of the backend to define where to save the
  98      * Attribute Tree (since it's only useful to "reopen" an Attribute Tree if
  99      * we have the matching History).
 100      *
 101      * This method defines where to read for the attribute tree when opening an
 102      * already-existing history. Refer to the file format documentation.
 103      *
 104      * @return A FileInputStream object pointing to the correct file/location in
 105      *         the file where to read the attribute tree information.
 106      */
 107     FileInputStream supplyAttributeTreeReader();
 108
 109     // FIXME change to FOS too?
 110     /**
 111      * Supply the File object to which we will write the attribute tree. The
 112      * position in this file is supplied by -TreeWriterFilePosition.
 113      *
 114      * @return The target File
 115      */
 116     File supplyAttributeTreeWriterFile();
 117
 118     /**
 119      * Supply the position in the file where we should write the attribute tree
 120      * when asked to.
 121      *
 122      * @return The file position (we will seek() to it)
 123      */
 124     long supplyAttributeTreeWriterFilePosition();
 125
 126     /**
 127      * Delete any generated files or anything that might have been created by
 128      * the history backend (either temporary or save files). By calling this, we
 129      * return to the state as it was before ever building the history.
 130      *
 131      * You might not want to call automatically if, for example, you want an
 132      * index file to persist on disk. This could be limited to actions
 133      * originating from the user.
 134      */
 135     void removeFiles();
 136
 137     /**
 138      * Notify the state history back-end that the trace is being closed, so it
 139      * should release its file descriptors, close its connections, etc.
 140      */
 141     void dispose();
 142
 143     // ------------------------------------------------------------------------
 144     // Query methods
 145     // ------------------------------------------------------------------------
 146
 147     /**
 148      * Complete "give me the state at a given time" method 'currentStateInfo' is
 149      * an "out" parameter, that is, write to it the needed information and
 150      * return. DO NOT 'new' currentStateInfo, it will be lost and nothing will
 151      * be returned!
 152      *
 153      * @param currentStateInfo
 154      *            List of StateValues (index == quark) to fill up
 155      * @param t
 156      *            Target timestamp of the query
 157      * @throws TimeRangeException
 158      *             If the timestamp is outside of the history/trace
 159      * @throws StateSystemDisposedException
 160      *             If the state system is disposed while a request is ongoing.
 161      */
 162     void doQuery(@NonNull List<@Nullable ITmfStateInterval> currentStateInfo, long t)
 163             throws TimeRangeException, StateSystemDisposedException;
 164
 165     /**
 166      * Some providers might want to specify a different way to obtain just a
 167      * single StateValue instead of updating the whole list. If the method to
 168      * use is the same, then feel free to just implement this as a wrapper using
 169      * doQuery().
 170      *
 171      * @param t
 172      *            The target timestamp of the query.
 173      * @param attributeQuark
 174      *            The single attribute for which you want the state interval
 175      * @return The state interval matching this timestamp/attribute pair, or
 176      *         null if it was not found
 177      * @throws TimeRangeException
 178      *             If the timestamp was invalid
 179      * @throws StateSystemDisposedException
 180      *             If the state system is disposed while a request is ongoing.
 181      */
 182     ITmfStateInterval doSingularQuery(long t, int attributeQuark)
 183             throws TimeRangeException, StateSystemDisposedException;
 184
 185     /**
 186      * Debug method to print the contents of the history backend.
 187      *
 188      * @param writer
 189      *            The PrintWriter where to write the output
 190      */
 191     void debugPrint(PrintWriter writer);
 192 }