Clog: Client Logging, Silverlight Edition

/*
<File>
	<Copyright>Copyright © 2007, Daniel Vaughan. All rights reserved.</Copyright>
	<License see="prj:///Documentation/License.txt"/>
	<Owner Name="Daniel Vaughan" Email="dbvaughan@gmail.com"/>
	<CreationDate>2007/11/19 20:00</CreationDate>
	<LastSubmissionDate>$Date: $</LastSubmissionDate>
	<Version>$Revision: $</Version>
</File>
*/

using System.Configuration;
using System.Net;

namespace Orpius.Logging.Filters
{
	/// <summary>
	/// Restricts logging based on an IP address range.
	/// </summary>
	class IPAddressRangeFilter : FilterBase
	{
		uint begin;
		uint end;

		public IPAddressRangeFilter()
		{
			Init += IPAddressRangeFilter_Init;
		}

		void IPAddressRangeFilter_Init(object sender, System.EventArgs e)
		{
			begin = ToUInt(IPAddress.Parse(FilterElement.Begin));
			end = ToUInt(IPAddress.Parse(FilterElement.End));

			if (Action == FilterAction.Default)
			{
				Action = FilterAction.Allow;
			}
			if (Action != FilterAction.Allow && Action != FilterAction.Deny)
			{
				throw new ConfigurationErrorsException(InvalidActionMessage);
			}
		}

		public override bool IsValid(LogEntryOrigin origin, IClientInfo info)
		{
			string addressValue = info.IPAddress;

			bool withinRange = IsWithinRange(begin, addressValue, end);
			switch (Action)
			{
				case FilterAction.Allow:
					return withinRange;
				case FilterAction.Deny:
					return !withinRange;
			}
			
			throw new ConfigurationErrorsException(InvalidActionMessage);
		}

		static bool IsWithinRange(uint beginAddress, string addressValue, uint endAddress)
		{
			IPAddress address = IPAddress.Parse(addressValue);
			uint ip = ToUInt(address);
			return ip >= beginAddress && ip <= endAddress;
		}

		/// <summary>
		/// Converts and <see cref="IPAddress"/> to an unsigned int.
		/// </summary>
		/// <param name="ipAddress">The ip address to convert.</param>
		/// <returns>A <code>uint</code> representing 
		/// the specified ipAddress.</returns>
		static uint ToUInt(IPAddress ipAddress)
		{
			byte[] bytes = ipAddress.GetAddressBytes();
			
			uint result = (uint)bytes[0] << 24;
			result += (uint)bytes[1] << 16;
			result += (uint)bytes[2] << 8;
			result += bytes[3];

			return result;
		}
	}
}