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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.inputmethod.research;
     18 
     19 import java.util.LinkedList;
     20 
     21 /**
     22  * Maintain a FIFO queue of LogUnits.
     23  *
     24  * This class provides an unbounded queue.  This is useful when the user is aware that their actions
     25  * are being recorded, such as when they are trying to reproduce a bug.  In this case, there should
     26  * not be artificial restrictions on how many events that can be saved.
     27  */
     28 public class LogBuffer {
     29     // TODO: Gracefully handle situations in which this LogBuffer is consuming too much memory.
     30     // This may happen, for example, if the user has forgotten that data is being logged.
     31     private final LinkedList<LogUnit> mLogUnits;
     32 
     33     public LogBuffer() {
     34         mLogUnits = new LinkedList<LogUnit>();
     35     }
     36 
     37     protected LinkedList<LogUnit> getLogUnits() {
     38         return mLogUnits;
     39     }
     40 
     41     public void clear() {
     42         mLogUnits.clear();
     43     }
     44 
     45     public void shiftIn(final LogUnit logUnit) {
     46         mLogUnits.add(logUnit);
     47     }
     48 
     49     public LogUnit unshiftIn() {
     50         if (mLogUnits.isEmpty()) {
     51             return null;
     52         }
     53         return mLogUnits.removeLast();
     54     }
     55 
     56     public LogUnit peekLastLogUnit() {
     57         if (mLogUnits.isEmpty()) {
     58             return null;
     59         }
     60         return mLogUnits.peekLast();
     61     }
     62 
     63     public boolean isEmpty() {
     64         return mLogUnits.isEmpty();
     65     }
     66 
     67     public LogUnit shiftOut() {
     68         if (isEmpty()) {
     69             return null;
     70         }
     71         return mLogUnits.removeFirst();
     72     }
     73 }
     74