src/java/iotcloud/SlotBuffer.java

   1 package iotcloud;
   2
   3 /**
   4  * Buffer that holds the live set of slots.
   5  * @author Brian Demsky
   6  * @version 1.0
   7  */
   8
   9 class SlotBuffer {
  10         static final int DEFAULT_SIZE = 128;
  11
  12         private Slot[] array;
  13         private int head;
  14         private int tail;
  15         private long oldestseqn;
  16
  17         SlotBuffer() {
  18                 array=new Slot[DEFAULT_SIZE+1];
  19                 head=tail=0;
  20                 oldestseqn=0;
  21         }
  22
  23         int size() {
  24                 if (head >= tail)
  25                         return head - tail;
  26                 return (array.length + head) - tail;
  27         }
  28
  29         int capacity() {
  30                 return array.length - 1;
  31         }
  32
  33         void resize(int newsize) {
  34                 if (newsize == (array.length-1))
  35                         return;
  36                 Slot[] newarray = new Slot[newsize+1];
  37                 int currsize = size();
  38                 int index = tail;
  39                 for(int i=0; i < currsize; i++) {
  40                         newarray[i] = array[index];
  41                         if ((++index) == array.length)
  42                                 index = 0;
  43                 }
  44                 array = newarray;
  45                 tail = 0;
  46                 head = currsize;
  47         }
  48
  49         private void incrementHead() {
  50                 head++;
  51                 if (head >= array.length)
  52                         head=0;
  53         }
  54
  55         private void incrementTail() {
  56                 tail++;
  57                 if (tail >= array.length)
  58                         tail=0;
  59         }
  60
  61         void putSlot(Slot s) {
  62                 array[head]=s;
  63                 incrementHead();
  64
  65                 if (oldestseqn==0)
  66                         oldestseqn = s.getSequenceNumber();
  67
  68                 if (head==tail) {
  69                         incrementTail();
  70                         oldestseqn++;
  71                 }
  72         }
  73
  74         Slot getSlot(long seqnum) {
  75                 int diff=(int) (seqnum-oldestseqn);
  76                 int index=diff + tail;
  77                 if (index >= array.length) {
  78                         if (head >= tail)
  79                                 return null;
  80                         index-= array.length;
  81                 }
  82
  83                 if (index >= array.length)
  84                         return null;
  85
  86                 if (head >= tail && index >= head)
  87                         return null;
  88
  89                 return array[index];
  90         }
  91
  92         long getOldestSeqNum() {
  93                 return oldestseqn;
  94         }
  95
  96         long getNewestSeqNum() {
  97                 return oldestseqn + size() - 1;
  98         }
  99 }