org.eclipse.linuxtools.statesystem.core/src/org/eclipse/linuxtools/statesystem/core/backend/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.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.linuxtools.statesystem.core.interval.ITmfStateInterval;
  21 import org.eclipse.linuxtools.statesystem.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  * @since 3.0
  31  */
  32 public class NullBackend implements IStateHistoryBackend {
  33
  34     /**
  35      * Constructor
  36      */
  37     public NullBackend() {}
  38
  39     @Override
  40     public long getStartTime() {
  41         return 0;
  42     }
  43
  44     @Override
  45     public long getEndTime() {
  46         return 0;
  47     }
  48
  49     /**
  50      * The interval will be discarded when using a null backend.
  51      */
  52     @Override
  53     public void insertPastState(long stateStartTime, long stateEndTime,
  54             int quark, ITmfStateValue value) {
  55         /* The interval is always discarded. */
  56     }
  57
  58     @Override
  59     public void finishedBuilding(long endTime) {
  60         /* Nothing to do */
  61     }
  62
  63     @Override
  64     public FileInputStream supplyAttributeTreeReader() {
  65         return null;
  66     }
  67
  68     @Override
  69     public File supplyAttributeTreeWriterFile() {
  70         return null;
  71     }
  72
  73     @Override
  74     public long supplyAttributeTreeWriterFilePosition() {
  75         return -1;
  76     }
  77
  78     @Override
  79     public void removeFiles() {
  80         /* Nothing to do */
  81     }
  82
  83     @Override
  84     public void dispose() {
  85         /* Nothing to do */
  86     }
  87
  88     /**
  89      * Null back-ends cannot run queries. Nothing will be put in
  90      * currentStateInfo.
  91      */
  92     @Override
  93     public void doQuery(List<ITmfStateInterval> currentStateInfo, long t) {
  94         /* Cannot do past queries */
  95     }
  96
  97     /**
  98      * Null back-ends cannot run queries. 'null' will be returned.
  99      *
 100      * @return Always returns null.
 101      */
 102     @Override
 103     public ITmfStateInterval doSingularQuery(long t, int attributeQuark) {
 104         /* Cannot do past queries */
 105         return null;
 106     }
 107
 108     /**
 109      * Null back-ends cannot run queries.
 110      *
 111      * @return Always returns false.
 112      */
 113     @Override
 114     public boolean checkValidTime(long t) {
 115         /* Cannot do past queries */
 116         return false;
 117     }
 118
 119     @Override
 120     public void debugPrint(PrintWriter writer) {
 121         writer.println("Null history backend"); //$NON-NLS-1$
 122     }
 123 }