mono/mcs/class/System/System.Diagnostics/Switch.cs

//
// System.Diagnostics.Switch.cs
//
// Comments from John R. Hicks <[email protected]> original implementation 
// can be found at: /mcs/docs/apidocs/xml/en/System.Diagnostics
//
// Author:
//      John R. Hicks  ([email protected])
//      Jonathan Pryor ([email protected])
//
// (C) 2001-2002
//

//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System.Collections;

namespace System.Diagnostics
{
	public abstract class Switch
	{
		private string name = "";
		private string description = "";
		private int switchSetting = 0;

		// MS Behavior is that (quoting from MSDN for OnSwitchSettingChanged()):
		// 		"...It is invoked the first time a switch reads its value from the
		// 		configuration file..."
		// The docs + testing implies two things:
		// 	1. The value of the switch is not read in from the constructor
		// 	2. The value is instead read in on the first time get_SwitchSetting is
		// 		invoked
		// Assuming that OnSwitchSettingChanged() is invoked on a .config file
		// read and on all changes
		//
		// Thus, we need to keep track of whether or not switchSetting has been
		// initialized.  Using `switchSetting=-1' seems logical, but if someone
		// actually wants to use -1 as a switch value that would cause problems.
		private bool initialized = false;

		protected Switch(string displayName, string description)
		{
			this.name = displayName;
			this.description = description;
		}

		public string Description {
			get {return description;}
		}

		public string DisplayName {
			get {return name;}
		}

		protected int SwitchSetting {
			get {
				if (!initialized) {
					initialized = true;
					GetConfigFileSetting ();
					OnSwitchSettingChanged ();
				}
				return switchSetting;
			}
			set {
				if(switchSetting != value) {
					switchSetting = value;
					OnSwitchSettingChanged();
				}
				initialized = true;
			}
		}

		private void GetConfigFileSetting ()
		{
			try {
				
				// Load up the specified switch
				IDictionary d = (IDictionary) DiagnosticsConfiguration.Settings ["switches"];
				if (d != null)
					switchSetting = int.Parse (d [name].ToString());
			} catch {
				switchSetting = 0;
			}
		}

		protected virtual void OnSwitchSettingChanged()
		{
			// Do nothing.  This is merely provided for derived classes to know when
			// the value of SwitchSetting has changed.
		}
	}
}