mcs/class/System/System.Timers/Timer.cs

   1 //
   2 // System.Timers.Timer
   3 //
   4 // Authors:
   5 //      Gonzalo Paniagua Javier (gonzalo@ximian.com)
   6 //
   7 // (C) 2002 Ximian, Inc (http://www.ximian.com)
   8 // Copyright (C) 2005 Novell, Inc (http://www.novell.com)
   9 //
  10 // The docs talk about server timers and such...
  11
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining
  14 // a copy of this software and associated documentation files (the
  15 // "Software"), to deal in the Software without restriction, including
  16 // without limitation the rights to use, copy, modify, merge, publish,
  17 // distribute, sublicense, and/or sell copies of the Software, and to
  18 // permit persons to whom the Software is furnished to do so, subject to
  19 // the following conditions:
  20 //
  21 // The above copyright notice and this permission notice shall be
  22 // included in all copies or substantial portions of the Software.
  23 //
  24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  31 //
  32
  33 using System.ComponentModel;
  34 using System.Threading;
  35
  36 namespace System.Timers
  37 {
  38         [DefaultEventAttribute("Elapsed")]
  39         [DefaultProperty("Interval")]
  40         public class Timer : Component, ISupportInitialize {
  41                 double interval;
  42                 bool autoReset;
  43                 System.Threading.Timer timer;
  44                 object _lock = new object ();
  45                 ISynchronizeInvoke so;
  46                 bool enabled;
  47
  48                 [Category("Behavior")]
  49                 [TimersDescription("Occurs when the Interval has elapsed.")]
  50                 public event ElapsedEventHandler Elapsed;
  51
  52                 public Timer () : this (100)
  53                 {
  54                 }
  55
  56                 public Timer (double interval)
  57                 {
  58                         // MSBUG: https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=296761
  59                         if (interval <= 0 || interval > 0x7FFFFFFF)
  60                                 throw new ArgumentException ("Invalid value: " + interval, "interval");
  61
  62                         autoReset = true;
  63                         timer = new System.Threading.Timer (Callback, this, Timeout.Infinite, Timeout.Infinite); //disabled
  64                         Interval = interval;
  65                 }
  66
  67                 [Category("Behavior")]
  68                 [DefaultValue(true)]
  69                 [TimersDescription("Indicates whether the timer will be restarted when it is enabled.")]
  70                 public bool AutoReset
  71                 {
  72                         get { return autoReset; }
  73                         set { autoReset = value; }
  74                 }
  75
  76                 [Category("Behavior")]
  77                 [DefaultValue(false)]
  78                 [TimersDescription("Indicates whether the timer is enabled to fire events at a defined interval.")]
  79                 public bool Enabled
  80                 {
  81                         get {
  82                                 lock (_lock)
  83                                         return enabled && timer != null;
  84                         }
  85                         set {
  86                                 lock (_lock) {
  87                                         if (timer == null)
  88                                                 throw new ObjectDisposedException (GetType ().ToString (), "The object has been disposed");
  89
  90                                         if (enabled == value)
  91                                                 return;
  92
  93                                         if (value) {
  94                                                 // As per MS docs (throw this only when the timer becomes enabled): http://msdn.microsoft.com/en-us/library/system.timers.timer.enabled(v=vs.110).aspx
  95                                                 if (interval > Int32.MaxValue)
  96                                                         throw new ArgumentException ("Invalid value: " + interval, "interval");
  97                                                 enabled = true;
  98                                                 timer.Change ((int)interval, autoReset ? (int)interval : 0);
  99                                         } else {
 100                                                 enabled = false;
 101                                                 timer.Change (Timeout.Infinite, Timeout.Infinite);
 102                                         }
 103                                 }
 104                         }
 105                 }
 106
 107                 [Category("Behavior")]
 108                 [DefaultValue(100)]
 109                 [RecommendedAsConfigurable(true)]
 110                 [TimersDescription( "The number of milliseconds between timer events.")]
 111                 public double Interval
 112                 {
 113                         get { return interval; }
 114                         set {
 115                                 // The doc says 'less than 0', but 0 also throws the exception
 116                                 if (value <= 0)
 117                                         throw new ArgumentException ("Invalid value: " + value);
 118                                 // As per MS docs (throw only if enabled, otherwise postpone throwing until it becomes enabled): http://msdn.microsoft.com/en-us/library/system.timers.timer.interval(v=vs.110).aspx
 119                                 if (value > Int32.MaxValue && enabled)
 120                                         throw new ArgumentException ("Invalid value: " + value);
 121
 122                                 lock (_lock) {
 123                                         if (timer == null)
 124                                                 return;
 125                                         interval = value;
 126                                         //call Change only if enabled, otherwise it will be called when Enabled = true, see the comment above on throwing ArgumentException
 127                                         if (enabled)
 128                                                 timer.Change ((int)interval, autoReset? (int)interval: 0);
 129                                 }
 130                         }
 131                 }
 132
 133                 public override ISite Site
 134                 {
 135                         get { return base.Site; }
 136                         set { base.Site = value; }
 137                 }
 138
 139                 [DefaultValue(null)]
 140                 [TimersDescriptionAttribute("The object used to marshal the event handler calls issued " +
 141                                             "when an interval has elapsed.")]
 142                 [Browsable (false)]
 143                 public ISynchronizeInvoke SynchronizingObject
 144                 {
 145                         get { return so; }
 146                         set { so = value; }
 147                 }
 148
 149                 public void BeginInit ()
 150                 {
 151                         // Nothing to do
 152                 }
 153
 154                 public void Close ()
 155                 {
 156                         lock (_lock)
 157                                 Dispose (true);
 158                 }
 159
 160                 public void EndInit ()
 161                 {
 162                         // Nothing to do
 163                 }
 164
 165                 public void Start ()
 166                 {
 167                         Enabled = true;
 168                 }
 169
 170                 public void Stop ()
 171                 {
 172                         Enabled = false;
 173                 }
 174
 175                 protected override void Dispose (bool disposing)
 176                 {
 177                         // Could call Close() twice
 178                         if (timer == null)
 179                                 return;
 180
 181                         // If we're disposing explicitly, clear all
 182                         // fields. If not, all fields will have been
 183                         // nulled by the GC during finalization, so
 184                         // trying to lock on _lock will blow up.
 185                         if (disposing)
 186                         {
 187                                 timer.Dispose ();
 188                                 timer = null;
 189                         }
 190
 191                         base.Dispose (disposing);
 192                 }
 193
 194                 static void Callback (object state)
 195                 {
 196                         Timer timer = (Timer) state;
 197                         if (timer.Enabled == false)
 198                                 return;
 199                         ElapsedEventHandler events = timer.Elapsed;
 200
 201                         try
 202                         {
 203                                 if (!timer.autoReset)
 204                                         timer.Enabled = false; //this could throw ObjectDisposed if timer.Close() was just called, after the check for Enabled above
 205                         }
 206                         catch (ObjectDisposedException) {
 207                                 //Probably the Elapsed event should not fire if this Timer is found here to be closed
 208                                 return;
 209                         }
 210
 211                         //If another thread calls Close() when this thread is right here (of further down), the Elapsed event might get called once more after this Timer was Closed()
 212                         //It's not a problem, it happens with all Timers, but it's good to know...
 213
 214                         if (events == null)
 215                                 return;
 216
 217                         ElapsedEventArgs arg = new ElapsedEventArgs (DateTime.Now);
 218
 219                         if (timer.so != null && timer.so.InvokeRequired) {
 220                                 timer.so.BeginInvoke (events, new object [2] {timer, arg});
 221                         } else {
 222                                 try {
 223                                         events (timer, arg);
 224                                 } catch {
 225                                 }
 226                         }
 227                 }
 228
 229         }
 230 }