statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/backend/NullBackend.java

   1 /*******************************************************************************
   2  * Copyright (c) 2013, 2014 Ericsson
   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  * Contributors:
  10  *   Alexandre Montplaisir - Initial API and implementation
  11  *******************************************************************************/
  12
  13 package org.eclipse.tracecompass.internal.statesystem.core.backend;
  14
  15 import java.io.File;
  16 import java.io.FileInputStream;
  17 import java.util.Collections;
  18 import java.util.List;
  19
  20 import org.eclipse.jdt.annotation.NonNull;
  21 import org.eclipse.tracecompass.internal.provisional.datastore.core.condition.IntegerRangeCondition;
  22 import org.eclipse.tracecompass.internal.provisional.datastore.core.condition.TimeRangeCondition;
  23 import org.eclipse.tracecompass.statesystem.core.backend.IStateHistoryBackend;
  24 import org.eclipse.tracecompass.statesystem.core.exceptions.TimeRangeException;
  25 import org.eclipse.tracecompass.statesystem.core.interval.ITmfStateInterval;
  26 import org.eclipse.tracecompass.statesystem.core.statevalue.ITmfStateValue;
  27
  28 /**
  29  * An implement of a state history back-end to simply discards *all* the
  30  * intervals it receives. Obviously, no queries can be done on it. It is useful
  31  * for using with a StateSystem on which you will only want to do "ongoing"
  32  * requests.
  33  *
  34  * @author Alexandre Montplaisir
  35  */
  36 public class NullBackend implements IStateHistoryBackend {
  37
  38     private final @NonNull String ssid;
  39
  40     /**
  41      * Constructor
  42      *
  43      * @param ssid
  44      *            The state system's id
  45      */
  46     public NullBackend(@NonNull String ssid) {
  47         this.ssid = ssid;
  48     }
  49
  50     @Override
  51     public String getSSID() {
  52         return ssid;
  53     }
  54
  55     @Override
  56     public long getStartTime() {
  57         return 0;
  58     }
  59
  60     @Override
  61     public long getEndTime() {
  62         return 0;
  63     }
  64
  65     /**
  66      * The interval will be discarded when using a null backend.
  67      */
  68     @Override
  69     public void insertPastState(long stateStartTime, long stateEndTime,
  70             int quark, ITmfStateValue value) {
  71         /* The interval is always discarded. */
  72     }
  73
  74     @Override
  75     public void finishedBuilding(long endTime) {
  76         /* Nothing to do */
  77     }
  78
  79     @Override
  80     public FileInputStream supplyAttributeTreeReader() {
  81         return null;
  82     }
  83
  84     @Override
  85     public File supplyAttributeTreeWriterFile() {
  86         return null;
  87     }
  88
  89     @Override
  90     public long supplyAttributeTreeWriterFilePosition() {
  91         return -1;
  92     }
  93
  94     @Override
  95     public void removeFiles() {
  96         /* Nothing to do */
  97     }
  98
  99     @Override
 100     public void dispose() {
 101         /* Nothing to do */
 102     }
 103
 104     /**
 105      * Null back-ends cannot run queries. Nothing will be put in
 106      * currentStateInfo.
 107      */
 108     @Override
 109     public void doQuery(List<ITmfStateInterval> currentStateInfo, long t) {
 110         /* Cannot do past queries */
 111     }
 112
 113     /**
 114      * Null back-ends cannot run queries. 'null' will be returned.
 115      *
 116      * @return Always returns null.
 117      */
 118     @Override
 119     public ITmfStateInterval doSingularQuery(long t, int attributeQuark) {
 120         /* Cannot do past queries */
 121         return null;
 122     }
 123
 124     @Override
 125     public Iterable<@NonNull ITmfStateInterval> query2D(IntegerRangeCondition quarks,
 126             TimeRangeCondition times) throws TimeRangeException {
 127         return Collections.EMPTY_LIST;
 128     }
 129 }