src/it/lilik/capturemjpeg/utils/CircularBuffer.java

   1 /**
   2  *
   3  */
   4 package it.lilik.capturemjpeg.utils;
   5
   6 import java.io.ByteArrayInputStream;
   7
   8 /**
   9  * A circular buffer of <code>ByteArrayInputStream</code>
  10  *
  11  * @author Alessio Caiazza
  12  * @author Cosimo Cecchi
  13  *
  14  */
  15 public class CircularBuffer {
  16
  17         /** data storage */
  18         private ByteArrayInputStream buffer[];
  19         /** last item in <code>CircularBuffer</code> */
  20         private int lastIdx;
  21         /** first valid item in <code>CircularBuffer</code> */
  22         private int firstIdx;
  23         /** size of <code>CircularBuffer</code> */
  24         private int size;
  25
  26         private boolean empty;
  27
  28         /** default size */
  29         static final int DEFAULT_SIZE = 5;
  30
  31         /**
  32          * @param size
  33          */
  34         public CircularBuffer(int size) {
  35                 this.size = size;
  36                 this.firstIdx = 0;
  37                 this.lastIdx = 0;
  38                 this.empty = true;
  39                 this.buffer = new ByteArrayInputStream[size];
  40         }
  41
  42         /**
  43          *
  44          */
  45         public CircularBuffer() {
  46                 this(CircularBuffer.DEFAULT_SIZE);
  47         }
  48
  49         /**
  50          * @return the lastIdx
  51          */
  52         public synchronized int getLastIdx() {
  53                 return lastIdx;
  54         }
  55
  56         /**
  57          * @return the firstIdx
  58          */
  59         public synchronized int getFirstIdx() {
  60                 return firstIdx;
  61         }
  62
  63         /**
  64          * Add a an element to the <code>CircularBuffer</code>
  65          *
  66          * @param data the new element
  67          */
  68         public synchronized void push(ByteArrayInputStream data) {
  69                 buffer[this.lastIdx] = data;
  70                 if( this.lastIdx == this.firstIdx && !this.empty) {
  71                         //we have overwritten an element
  72                         this.firstIdx++;
  73                         this.firstIdx %= this.size;
  74                 }
  75                 if (this.empty)
  76                         this.empty = false;
  77                 this.lastIdx++;
  78                 this.lastIdx %= this.size;
  79         }
  80
  81         /**
  82          * It counts elements in buffer
  83          * @return the number of valid elements
  84          */
  85         public synchronized int getLength() {
  86                 if (this.empty)
  87                         return 0;
  88                 int len = this.lastIdx - this.firstIdx;
  89                 if (len < 0)
  90                         len = this.size + len;
  91                 return len == 0 ? this.size-1 : len;
  92         }
  93
  94
  95         /**
  96          * Get the first available element.
  97          *
  98          * @return the first element
  99          * @throws IndexOutOfVoundsExceptions
 100          */
 101         public synchronized ByteArrayInputStream pop() {
 102                 if (isEmpty()) {
 103                         //TODO:change Exception type
 104                         throw new IndexOutOfBoundsException("Empty buffer");
 105                 }
 106                 ByteArrayInputStream res = buffer[this.firstIdx];
 107                 buffer[this.firstIdx] = null;
 108                 this.firstIdx++;
 109                 this.firstIdx %= this.size;
 110                 if (this.firstIdx == this.lastIdx)
 111                         this.empty = true;
 112                 return res;
 113         }
 114
 115         /**
 116          *
 117          * @return the status of the buffer
 118          */
 119         public synchronized boolean isEmpty() {
 120                 return this.empty;
 121         }
 122
 123         public int getSize() {
 124                 return this.size;
 125         }
 126 }