src/java/iotcloud/SlotBuffer.java

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