BitArrayBin xref

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    1   /***
    2    *
    3    * Copyright 2004 Protique Ltd
    4    *
    5    * Licensed under the Apache License, Version 2.0 (the "License");
    6    * you may not use this file except in compliance with the License.
    7    * You may obtain a copy of the License at
    8    *
    9    * http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   *
    17   **/
    18
    19  package org.codehaus.activemq.util;
    20  import java.util.LinkedList;
    21
    22  /***
    23   * Holder for many bitArrays - used for message audit
    24   *
    25   * @version $Revision: 1.2 $
    26   */
    27  public class BitArrayBin {
    28      private LinkedList list;
    29      private int maxNumberOfArrays;
    30      private int currentIndex;
    31      private int firstIndex = -1;
    32      private int firstBin = -1;
    33      private int windowSize;
    34
    35      /***
    36       * Create a BitArrayBin to a certain window size (number of messages to keep)
    37       *
    38       * @param windowSize
    39       */
    40      public BitArrayBin(int windowSize) {
    41          this.windowSize = windowSize;
    42          maxNumberOfArrays = ((windowSize + 1) / BitArray.LONG_SIZE) + 1;
    43          maxNumberOfArrays = Math.max(maxNumberOfArrays, 1);
    44          list = new LinkedList();
    45          for (int i = 0;i < maxNumberOfArrays;i++) {
    46              list.add(new BitArray());
    47          }
    48      }
    49
    50      /***
    51       * Set a bit
    52       *
    53       * @param index
    54       * @param value
    55       * @return
    56       */
    57      public boolean setBit(long index, boolean value) {
    58          boolean answer = true;
    59          BitArray ba = getBitArray(index);
    60          if (ba != null) {
    61              int offset = getOffset(index);
    62              if (offset >= 0) {
    63                  answer = ba.set(offset, value);
    64              }
    65          }
    66          return answer;
    67      }
    68
    69      /***
    70       * Get the boolean value at the index
    71       *
    72       * @param index
    73       * @return true/false
    74       */
    75      public boolean getBit(long index) {
    76          boolean answer = index >= firstIndex;
    77          BitArray ba = getBitArray(index);
    78          if (ba != null) {
    79              int offset = getOffset(index);
    80              if (offset >= 0) {
    81                  answer = ba.get(offset);
    82                  return answer;
    83              }
    84          }
    85          else {
    86              //gone passed range for previous bins so assume set
    87              answer = true;
    88          }
    89          return answer;
    90      }
    91
    92      /***
    93       * Get the BitArray for the index
    94       *
    95       * @param index
    96       * @return
    97       */
    98      private BitArray getBitArray(long index) {
    99          int bin = getBin(index);
    100         BitArray answer = null;
    101         if (bin >= 0) {
    102             if (firstIndex < 0) {
    103                 firstIndex = 0;
    104             }
    105             if (bin >= list.size()) {
    106                 list.removeFirst();
    107                 firstIndex += BitArray.LONG_SIZE;
    108                 list.add(new BitArray());
    109                 bin = list.size() - 1;
    110             }
    111             answer = (BitArray) list.get(bin);
    112         }
    113         return answer;
    114     }
    115
    116     /***
    117      * Get the index of the bin from the total index
    118      *
    119      * @param index
    120      * @return the index of the bin
    121      */
    122     private int getBin(long index) {
    123         int answer = 0;
    124         if (firstBin < 0) {
    125             firstBin = 0;
    126         }
    127         else if (firstIndex >= 0) {
    128             answer = (int) ((index - firstIndex) / BitArray.LONG_SIZE);
    129         }
    130         return answer;
    131     }
    132
    133     /***
    134      * Get the offset into a bin from the total index
    135      *
    136      * @param index
    137      * @return the relative offset into a bin
    138      */
    139     private int getOffset(long index) {
    140         int answer = 0;
    141         if (firstIndex >= 0) {
    142             //System.out.println("getOffset(" + index + ") firstIndex = " + firstIndex + " bin = " + getBin(index));
    143             answer = (int) ((index - firstIndex) - (BitArray.LONG_SIZE * getBin(index)));
    144         }
    145         return answer;
    146     }
    147 }