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