mcs/class/Managed.Windows.Forms/System.Windows.Forms/XEventQueue.cs

   1 //
   2 // System.Windows.Forms.XEventQueue
   3 //
   4 // Author(s):
   5 //  Jackson Harper (jackson@ximian.com)
   6 //
   7 // Copyright (C) Novell, Inc (http://www.novell.com)
   8 //
   9
  10 using System;
  11 using System.Threading;
  12 using System.Collections;
  13
  14
  15 namespace System.Windows.Forms {
  16
  17         internal class XEventQueue {
  18
  19                 private XQueue xqueue;
  20                 private XQueue lqueue;  // Events inserted from threads other then the main X thread
  21
  22                 private static readonly int InitialXEventSize = 50;
  23                 private static readonly int InitialLXEventSize = 10;
  24
  25                 public XEventQueue ()
  26                 {
  27                         xqueue = new XQueue (InitialXEventSize);
  28                         lqueue = new XQueue (InitialLXEventSize);
  29                 }
  30
  31                 public int Count {
  32                         get { return xqueue.Count + lqueue.Count; }
  33                 }
  34
  35                 public void Enqueue (XEvent xevent)
  36                 {
  37                         xqueue.Enqueue (xevent);
  38                 }
  39
  40                 public void EnqueueLocked (XEvent xevent)
  41                 {
  42                         lock (lqueue) {
  43                                 lqueue.Enqueue (xevent);
  44                         }
  45                 }
  46
  47                 public XEvent Dequeue ()
  48                 {
  49                         if (xqueue.Count == 0) {
  50                                 lock (lqueue) {
  51                                         return lqueue.Dequeue ();
  52                                 }
  53                         }
  54                         return xqueue.Dequeue ();
  55                 }
  56
  57                 private class XQueue {
  58
  59                         private XEvent [] xevents;
  60                         private int head;
  61                         private int tail;
  62                         private int size;
  63
  64                         public XQueue (int size)
  65                         {
  66                                 xevents = new XEvent [size];
  67                         }
  68
  69                         public int Count {
  70                                 get { return size; }
  71                         }
  72
  73                         public void Enqueue (XEvent xevent)
  74                         {
  75                                 if (size == xevents.Length)
  76                                         Grow ();
  77
  78                                 xevents [tail] = xevent;
  79                                 tail = (tail + 1) % xevents.Length;
  80                                 size++;
  81                         }
  82
  83                         public XEvent Dequeue ()
  84                         {
  85                                 if (size < 1)
  86                                         throw new Exception ("Attempt to dequeue empty queue.");
  87                                 XEvent res = xevents [head];
  88                                 head = (head + 1) % xevents.Length;
  89                                 size--;
  90                                 return res;
  91                         }
  92
  93                         private void Grow ()
  94                         {
  95                                 int newcap = (xevents.Length * 2);
  96                                 XEvent [] na = new XEvent [newcap];
  97                                 xevents.CopyTo (na, 0);
  98                                 xevents = na;
  99                                 head = 0;
 100                                 tail = head + size;
 101                         }
 102                 }
 103         }
 104 }
 105