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 {
  33                                 lock (lqueue) {
  34                                         return xqueue.Count + lqueue.Count;
  35                                 }
  36                         }
  37                 }
  38
  39                 public void Enqueue (XEvent xevent)
  40                 {
  41                         xqueue.Enqueue (xevent);
  42                 }
  43
  44                 public void EnqueueLocked (XEvent xevent)
  45                 {
  46                         lock (lqueue) {
  47                                 lqueue.Enqueue (xevent);
  48                         }
  49                 }
  50
  51                 public XEvent Dequeue ()
  52                 {
  53                         if (xqueue.Count == 0) {
  54                                 lock (lqueue) {
  55                                         return lqueue.Dequeue ();
  56                                 }
  57                         }
  58                         return xqueue.Dequeue ();
  59                 }
  60
  61                 private class XQueue {
  62
  63                         private XEvent [] xevents;
  64                         private int head;
  65                         private int tail;
  66                         private int size;
  67
  68                         public XQueue (int size)
  69                         {
  70                                 xevents = new XEvent [size];
  71                         }
  72
  73                         public int Count {
  74                                 get { return size; }
  75                         }
  76
  77                         public void Enqueue (XEvent xevent)
  78                         {
  79                                 if (size == xevents.Length)
  80                                         Grow ();
  81
  82                                 xevents [tail] = xevent;
  83                                 tail = (tail + 1) % xevents.Length;
  84                                 size++;
  85                         }
  86
  87                         public XEvent Dequeue ()
  88                         {
  89                                 if (size < 1)
  90                                         throw new Exception ("Attempt to dequeue empty queue.");
  91                                 XEvent res = xevents [head];
  92                                 head = (head + 1) % xevents.Length;
  93                                 size--;
  94                                 return res;
  95                         }
  96
  97                         private void Grow ()
  98                         {
  99                                 int newcap = (xevents.Length * 2);
 100                                 XEvent [] na = new XEvent [newcap];
 101                                 xevents.CopyTo (na, 0);
 102                                 xevents = na;
 103                                 head = 0;
 104                                 tail = head + size;
 105                         }
 106                 }
 107         }
 108 }
 109