org.eclipse.linuxtools.tmf.core/src/org/eclipse/linuxtools/internal/tmf/core/statesystem/backends/NullBackend.java

   1 /*******************************************************************************
   2  * Copyright (c) 2013 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.linuxtools.internal.tmf.core.statesystem.backends;
  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.linuxtools.tmf.core.interval.ITmfStateInterval;
  21 import org.eclipse.linuxtools.tmf.core.statevalue.ITmfStateValue;
  22
  23 /**
  24  * An implement of a state history back-end to simply discards *all* the
  25  * intervals it receives. Obviously, no queries can be done on it. It is useful
  26  * for using with a StateSystem on which you will only want to do "ongoing"
  27  * requests.
  28  *
  29  * @author Alexandre Montplaisir
  30  */
  31 public class NullBackend implements IStateHistoryBackend {
  32
  33     /**
  34      * Constructor
  35      */
  36     public NullBackend() {}
  37
  38     @Override
  39     public long getStartTime() {
  40         return 0;
  41     }
  42
  43     @Override
  44     public long getEndTime() {
  45         return 0;
  46     }
  47
  48     /**
  49      * The interval will be discarded when using a null backend.
  50      */
  51     @Override
  52     public void insertPastState(long stateStartTime, long stateEndTime,
  53             int quark, ITmfStateValue value) {
  54         /* The interval is always discarded. */
  55     }
  56
  57     @Override
  58     public void finishedBuilding(long endTime) {
  59         /* Nothing to do */
  60     }
  61
  62     @Override
  63     public FileInputStream supplyAttributeTreeReader() {
  64         return null;
  65     }
  66
  67     @Override
  68     public File supplyAttributeTreeWriterFile() {
  69         return null;
  70     }
  71
  72     @Override
  73     public long supplyAttributeTreeWriterFilePosition() {
  74         return -1;
  75     }
  76
  77     @Override
  78     public void removeFiles() {
  79         /* Nothing to do */
  80     }
  81
  82     @Override
  83     public void dispose() {
  84         /* Nothing to do */
  85     }
  86
  87     /**
  88      * Null back-ends cannot run queries. Nothing will be put in
  89      * currentStateInfo.
  90      */
  91     @Override
  92     public void doQuery(List<ITmfStateInterval> currentStateInfo, long t) {
  93         /* Cannot do past queries */
  94     }
  95
  96     /**
  97      * Null back-ends cannot run queries. 'null' will be returned.
  98      *
  99      * @return Always returns null.
 100      */
 101     @Override
 102     public ITmfStateInterval doSingularQuery(long t, int attributeQuark) {
 103         /* Cannot do past queries */
 104         return null;
 105     }
 106
 107     /**
 108      * Null back-ends cannot run queries.
 109      *
 110      * @return Always returns false.
 111      */
 112     @Override
 113     public boolean checkValidTime(long t) {
 114         /* Cannot do past queries */
 115         return false;
 116     }
 117
 118     @Override
 119     public void debugPrint(PrintWriter writer) {
 120         writer.println("Null history backend"); //$NON-NLS-1$
 121     }
 122 }