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         }
  14
  15         int size() {
  16                 if (head >= tail)
  17                         return head - tail;
  18                 return (array.length + head) - tail;
  19         }
  20
  21         void resize(int newsize) {
  22                 if (newsize == (array.length-1))
  23                         return;
  24                 Slot[] newarray = new Slot[newsize+1];
  25                 int currsize = size();
  26                 int index = tail;
  27                 for(int i=0; i < currsize; i++) {
  28                         newarray[i] = array[index];
  29                         if ((++index) == array.length)
  30                                 index = 0;
  31                 }
  32                 array = newarray;
  33                 tail = currsize;
  34                 head = 0;
  35         }
  36
  37         void putSlot(Slot s) {
  38                 array[head]=s;
  39                 head++;
  40                 if (oldestseqn==0)
  41                         oldestseqn = s.getSequenceNumber();
  42
  43                 if (head==tail) {
  44                         tail++;
  45                         oldestseqn++;
  46                 }
  47         }
  48
  49         Slot getSlot(long seqnum) {
  50                 int diff=(int) (seqnum-oldestseqn);
  51                 int index=diff + tail;
  52                 if (index > array.length) {
  53                         if (head >= tail)
  54                                 return null;
  55                         index-= array.length;
  56                 }
  57
  58                 if (index >= array.length ||
  59                                 index >= head)
  60                         return null;
  61
  62                 return array[index];
  63         }
  64
  65         long getOldestSeqNum() {
  66                 return oldestseqn;
  67         }
  68
  69         long getNewestSeqNum() {
  70                 return oldestseqn + size();
  71         }
  72 }