src/Appender/RollingFileAppender.cs

#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;
using System.Collections;
using System.Globalization;
using System.IO;

using log4net.Util;
using log4net.Core;
using System.Threading;

namespace log4net.Appender
{
#if CONFIRM_WIN32_FILE_SHAREMODES
	// The following sounds good, and I though it was the case, but after
	// further testing on Windows I have not been able to confirm it.

	/// On the Windows platform if another process has a write lock on the file 
	/// that is to be deleted, but allows shared read access to the file then the
	/// file can be moved, but cannot be deleted. If the other process also allows 
	/// shared delete access to the file then the file will be deleted once that 
	/// process closes the file. If it is necessary to open the log file or any
	/// of the backup files outside of this appender for either read or 
	/// write access please ensure that read and delete share modes are enabled.
#endif

	/// <summary>
	/// Appender that rolls log files based on size or date or both.
	/// </summary>
	/// <remarks>
	/// <para>
	/// RollingFileAppender can roll log files based on size or date or both
	/// depending on the setting of the <see cref="RollingStyle"/> property.
	/// When set to <see cref="RollingMode.Size"/> the log file will be rolled
	/// once its size exceeds the <see cref="MaximumFileSize"/>.
	/// When set to <see cref="RollingMode.Date"/> the log file will be rolled
	/// once the date boundary specified in the <see cref="DatePattern"/> property
	/// is crossed.
	/// When set to <see cref="RollingMode.Composite"/> the log file will be
	/// rolled once the date boundary specified in the <see cref="DatePattern"/> property
	/// is crossed, but within a date boundary the file will also be rolled
	/// once its size exceeds the <see cref="MaximumFileSize"/>.
	/// When set to <see cref="RollingMode.Once"/> the log file will be rolled when
	/// the appender is configured. This effectively means that the log file can be
	/// rolled once per program execution.
	/// </para>
	/// <para>
	/// A of few additional optional features have been added:
	/// <list type="bullet">
	/// <item>Attach date pattern for current log file <see cref="StaticLogFileName"/></item>
	/// <item>Backup number increments for newer files <see cref="CountDirection"/></item>
	/// <item>Infinite number of backups by file size <see cref="MaxSizeRollBackups"/></item>
	/// </list>
	/// </para>
	/// 
	/// <note>
	/// <para>
	/// For large or infinite numbers of backup files a <see cref="CountDirection"/> 
	/// greater than zero is highly recommended, otherwise all the backup files need
	/// to be renamed each time a new backup is created.
	/// </para>
	/// <para>
	/// When Date/Time based rolling is used setting <see cref="StaticLogFileName"/> 
	/// to <see langword="true"/> will reduce the number of file renamings to few or none.
	/// </para>
	/// </note>
	/// 
	/// <note type="caution">
	/// <para>
	/// Changing <see cref="StaticLogFileName"/> or <see cref="CountDirection"/> without clearing
	/// the log file directory of backup files will cause unexpected and unwanted side effects.  
	/// </para>
	/// </note>
	/// 
	/// <para>
	/// If Date/Time based rolling is enabled this appender will attempt to roll existing files
	/// in the directory without a Date/Time tag based on the last write date of the base log file.
	/// The appender only rolls the log file when a message is logged. If Date/Time based rolling 
	/// is enabled then the appender will not roll the log file at the Date/Time boundary but
	/// at the point when the next message is logged after the boundary has been crossed.
	/// </para>
	/// 
	/// <para>
	/// The <see cref="RollingFileAppender"/> extends the <see cref="FileAppender"/> and
	/// has the same behavior when opening the log file.
	/// The appender will first try to open the file for writing when <see cref="ActivateOptions"/>
	/// is called. This will typically be during configuration.
	/// If the file cannot be opened for writing the appender will attempt
	/// to open the file again each time a message is logged to the appender.
	/// If the file cannot be opened for writing when a message is logged then
	/// the message will be discarded by this appender.
	/// </para>
	/// <para>
	/// When rolling a backup file necessitates deleting an older backup file the
	/// file to be deleted is moved to a temporary name before being deleted.
	/// </para>
	/// 
	/// <note type="caution">
	/// <para>
	/// A maximum number of backup files when rolling on date/time boundaries is not supported.
	/// </para>
	/// </note>
	/// </remarks>
	/// <author>Nicko Cadell</author>
	/// <author>Gert Driesen</author>
	/// <author>Aspi Havewala</author>
	/// <author>Douglas de la Torre</author>
	/// <author>Edward Smit</author>
	public class RollingFileAppender : FileAppender
    {
        #region Public Enums

        /// <summary>
		/// Style of rolling to use
		/// </summary>
		/// <remarks>
		/// <para>
		/// Style of rolling to use
		/// </para>
		/// </remarks>
		public enum RollingMode
		{
			/// <summary>
			/// Roll files once per program execution
			/// </summary>
			/// <remarks>
			/// <para>
			/// Roll files once per program execution.
			/// Well really once each time this appender is
			/// configured.
			/// </para>
			/// <para>
			/// Setting this option also sets <c>AppendToFile</c> to
			/// <c>false</c> on the <c>RollingFileAppender</c>, otherwise
			/// this appender would just be a normal file appender.
			/// </para>
			/// </remarks>
			Once		= 0,

			/// <summary>
			/// Roll files based only on the size of the file
			/// </summary>
			Size		= 1,

			/// <summary>
			/// Roll files based only on the date
			/// </summary>
			Date		= 2,

			/// <summary>
			/// Roll files based on both the size and date of the file
			/// </summary>
			Composite	= 3
		}

		#endregion

		#region Protected Enums

		/// <summary>
		/// The code assumes that the following 'time' constants are in a increasing sequence.
		/// </summary>
		/// <remarks>
		/// <para>
		/// The code assumes that the following 'time' constants are in a increasing sequence.
		/// </para>
		/// </remarks>
		protected enum RollPoint
		{
			/// <summary>
			/// Roll the log not based on the date
			/// </summary>
			InvalidRollPoint	=-1,

			/// <summary>
			/// Roll the log for each minute
			/// </summary>
			TopOfMinute			= 0,

			/// <summary>
			/// Roll the log for each hour
			/// </summary>
			TopOfHour			= 1,

			/// <summary>
			/// Roll the log twice a day (midday and midnight)
			/// </summary>
			HalfDay				= 2,

			/// <summary>
			/// Roll the log each day (midnight)
			/// </summary>
			TopOfDay			= 3,

			/// <summary>
			/// Roll the log each week
			/// </summary>
			TopOfWeek			= 4,

			/// <summary>
			/// Roll the log each month
			/// </summary>
			TopOfMonth			= 5
		}

		#endregion Protected Enums

		#region Public Instance Constructors

		/// <summary>
		/// Initializes a new instance of the <see cref="RollingFileAppender" /> class.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Default constructor.
		/// </para>
		/// </remarks>
		public RollingFileAppender() 
		{
		}

		/// <summary>
		/// Cleans up all resources used by this appender.
		/// </summary>
		~RollingFileAppender()
		{
#if !NETCF
			if (m_mutexForRolling != null)
			{
#if NET_4_0 || MONO_4_0 || NETSTANDARD1_3
				m_mutexForRolling.Dispose();
#else
				m_mutexForRolling.Close();
#endif
				m_mutexForRolling = null;
			}
#endif
		}

		#endregion Public Instance Constructors

		#region Public Instance Properties

#if !NET_1_0 && !CLI_1_0 && !NETCF
        /// <summary>
		/// Gets or sets the strategy for determining the current date and time. The default
		/// implementation is to use LocalDateTime which internally calls through to DateTime.Now. 
		/// DateTime.UtcNow may be used on frameworks newer than .NET 1.0 by specifying
		/// <see cref="RollingFileAppender.UniversalDateTime"/>.
		/// </summary>
		/// <value>
		/// An implementation of the <see cref="RollingFileAppender.IDateTime"/> interface which returns the current date and time.
		/// </value>
		/// <remarks>
		/// <para>
		/// Gets or sets the <see cref="RollingFileAppender.IDateTime"/> used to return the current date and time.
		/// </para>
        /// <para>
        /// There are two built strategies for determining the current date and time, 
		/// <see cref="RollingFileAppender.LocalDateTime"/>
        /// and <see cref="RollingFileAppender.UniversalDateTime"/>.
        /// </para>
        /// <para>
		/// The default strategy is <see cref="RollingFileAppender.LocalDateTime"/>.
		/// </para>
		/// </remarks>
#else
        /// <summary>
		/// Gets or sets the strategy for determining the current date and time. The default
		/// implementation is to use LocalDateTime which internally calls through to DateTime.Now. 
		/// </summary>
		/// <value>
		/// An implementation of the <see cref="RollingFileAppender.IDateTime"/> interface which returns the current date and time.
		/// </value>
		/// <remarks>
		/// <para>
		/// Gets or sets the <see cref="RollingFileAppender.IDateTime"/> used to return the current date and time.
		/// </para>
        /// <para>
		/// The default strategy is <see cref="RollingFileAppender.LocalDateTime"/>.
		/// </para>
		/// </remarks>
#endif
        public IDateTime DateTimeStrategy
		{
			get { return m_dateTime; }
			set { m_dateTime = value; }
		}

		/// <summary>
		/// Gets or sets the date pattern to be used for generating file names
		/// when rolling over on date.
		/// </summary>
		/// <value>
		/// The date pattern to be used for generating file names when rolling 
		/// over on date.
		/// </value>
		/// <remarks>
		/// <para>
		/// Takes a string in the same format as expected by 
		/// <see cref="log4net.DateFormatter.SimpleDateFormatter" />.
		/// </para>
		/// <para>
		/// This property determines the rollover schedule when rolling over
		/// on date.
		/// </para>
		/// </remarks>
		public string DatePattern
		{
			get { return m_datePattern; }
			set { m_datePattern = value; }
		}
  
		/// <summary>
		/// Gets or sets the maximum number of backup files that are kept before
		/// the oldest is erased.
		/// </summary>
		/// <value>
		/// The maximum number of backup files that are kept before the oldest is
		/// erased.
		/// </value>
		/// <remarks>
		/// <para>
		/// If set to zero, then there will be no backup files and the log file 
		/// will be truncated when it reaches <see cref="MaxFileSize"/>.  
		/// </para>
		/// <para>
		/// If a negative number is supplied then no deletions will be made.  Note 
		/// that this could result in very slow performance as a large number of 
		/// files are rolled over unless <see cref="CountDirection"/> is used.
		/// </para>
		/// <para>
		/// The maximum applies to <b>each</b> time based group of files and 
		/// <b>not</b> the total.
		/// </para>
		/// </remarks>
		public int MaxSizeRollBackups
		{
			get { return m_maxSizeRollBackups; }
			set { m_maxSizeRollBackups = value; }
		}
  
		/// <summary>
		/// Gets or sets the maximum size that the output file is allowed to reach
		/// before being rolled over to backup files.
		/// </summary>
		/// <value>
		/// The maximum size in bytes that the output file is allowed to reach before being 
		/// rolled over to backup files.
		/// </value>
		/// <remarks>
		/// <para>
		/// This property is equivalent to <see cref="MaximumFileSize"/> except
		/// that it is required for differentiating the setter taking a
		/// <see cref="long"/> argument from the setter taking a <see cref="string"/> 
		/// argument.
		/// </para>
		/// <para>
		/// The default maximum file size is 10MB (10*1024*1024).
		/// </para>
		/// </remarks>
		public long MaxFileSize
		{
			get { return m_maxFileSize; }
			set { m_maxFileSize = value; }
		}
  
		/// <summary>
		/// Gets or sets the maximum size that the output file is allowed to reach
		/// before being rolled over to backup files.
		/// </summary>
		/// <value>
		/// The maximum size that the output file is allowed to reach before being 
		/// rolled over to backup files.
		/// </value>
		/// <remarks>
		/// <para>
		/// This property allows you to specify the maximum size with the
		/// suffixes "KB", "MB" or "GB" so that the size is interpreted being 
		/// expressed respectively in kilobytes, megabytes or gigabytes. 
		/// </para>
		/// <para>
		/// For example, the value "10KB" will be interpreted as 10240 bytes.
		/// </para>
		/// <para>
		/// The default maximum file size is 10MB.
		/// </para>
		/// <para>
		/// If you have the option to set the maximum file size programmatically
		/// consider using the <see cref="MaxFileSize"/> property instead as this
		/// allows you to set the size in bytes as a <see cref="Int64"/>.
		/// </para>
		/// </remarks>
		public string MaximumFileSize
		{
			get { return m_maxFileSize.ToString(NumberFormatInfo.InvariantInfo); }
			set { m_maxFileSize = OptionConverter.ToFileSize(value, m_maxFileSize + 1); }
		}

		/// <summary>
		/// Gets or sets the rolling file count direction. 
		/// </summary>
		/// <value>
		/// The rolling file count direction.
		/// </value>
		/// <remarks>
		/// <para>
		/// Indicates if the current file is the lowest numbered file or the
		/// highest numbered file.
		/// </para>
		/// <para>
		/// By default newer files have lower numbers (<see cref="CountDirection" /> &lt; 0),
		/// i.e. log.1 is most recent, log.5 is the 5th backup, etc...
		/// </para>
		/// <para>
		/// <see cref="CountDirection" /> &gt;= 0 does the opposite i.e.
		/// log.1 is the first backup made, log.5 is the 5th backup made, etc.
		/// For infinite backups use <see cref="CountDirection" /> &gt;= 0 to reduce 
		/// rollover costs.
		/// </para>
		/// <para>The default file count direction is -1.</para>
		/// </remarks>
		public int CountDirection
		{
			get { return m_countDirection; }
			set { m_countDirection = value; }
		}
  
		/// <summary>
		/// Gets or sets the rolling style.
		/// </summary>
		/// <value>The rolling style.</value>
		/// <remarks>
		/// <para>
		/// The default rolling style is <see cref="RollingMode.Composite" />.
		/// </para>
		/// <para>
		/// When set to <see cref="RollingMode.Once"/> this appender's
		/// <see cref="FileAppender.AppendToFile"/> property is set to <c>false</c>, otherwise
		/// the appender would append to a single file rather than rolling
		/// the file each time it is opened.
		/// </para>
		/// </remarks>
		public RollingMode RollingStyle
		{
			get { return m_rollingStyle; }
			set
			{
				m_rollingStyle = value;
				switch (m_rollingStyle) 
				{
					case RollingMode.Once:
						m_rollDate = false;
						m_rollSize = false;

						this.AppendToFile = false;
						break;

					case RollingMode.Size:
						m_rollDate = false;
						m_rollSize = true;
						break;

					case RollingMode.Date:
						m_rollDate = true;
						m_rollSize = false;
						break;

					case RollingMode.Composite:
						m_rollDate = true;
						m_rollSize = true;
						break;	  
				}
			}
		}

        /// <summary>
        /// Gets or sets a value indicating whether to preserve the file name extension when rolling.
        /// </summary>
        /// <value>
        /// <c>true</c> if the file name extension should be preserved.
        /// </value>
        /// <remarks>
        /// <para>
        /// By default file.log is rolled to file.log.yyyy-MM-dd or file.log.curSizeRollBackup.
        /// However, under Windows the new file name will loose any program associations as the
        /// extension is changed. Optionally file.log can be renamed to file.yyyy-MM-dd.log or
        /// file.curSizeRollBackup.log to maintain any program associations.
        /// </para>
        /// </remarks>
        public bool PreserveLogFileNameExtension
        {
            get { return m_preserveLogFileNameExtension; }
            set { m_preserveLogFileNameExtension = value; }
        }

		/// <summary>
		/// Gets or sets a value indicating whether to always log to
		/// the same file.
		/// </summary>
		/// <value>
		/// <c>true</c> if always should be logged to the same file, otherwise <c>false</c>.
		/// </value>
		/// <remarks>
		/// <para>
		/// By default file.log is always the current file.  Optionally
		/// file.log.yyyy-mm-dd for current formatted datePattern can by the currently
		/// logging file (or file.log.curSizeRollBackup or even
		/// file.log.yyyy-mm-dd.curSizeRollBackup).
		/// </para>
		/// <para>
		/// This will make time based rollovers with a large number of backups 
		/// much faster as the appender it won't have to rename all the backups!
		/// </para>
		/// </remarks>
		public bool StaticLogFileName
		{
			get { return m_staticLogFileName; }
			set { m_staticLogFileName = value; }
		}

		#endregion Public Instance Properties

	    #region Private Static Fields

	    /// <summary>
	    /// The fully qualified type of the RollingFileAppender class.
	    /// </summary>
	    /// <remarks>
	    /// Used by the internal logger to record the Type of the
	    /// log message.
	    /// </remarks>
	    private readonly static Type declaringType = typeof(RollingFileAppender);

	    #endregion Private Static Fields

		#region Override implementation of FileAppender 
  
		/// <summary>
		/// Sets the quiet writer being used.
		/// </summary>
		/// <remarks>
		/// This method can be overridden by sub classes.
		/// </remarks>
		/// <param name="writer">the writer to set</param>
		override protected void SetQWForFiles(TextWriter writer) 
		{
			QuietWriter = new CountingQuietTextWriter(writer, ErrorHandler);
		}

		/// <summary>
		/// Write out a logging event.
		/// </summary>
		/// <param name="loggingEvent">the event to write to file.</param>
		/// <remarks>
		/// <para>
		/// Handles append time behavior for RollingFileAppender.  This checks
		/// if a roll over either by date (checked first) or time (checked second)
		/// is need and then appends to the file last.
		/// </para>
		/// </remarks>
		override protected void Append(LoggingEvent loggingEvent) 
		{
			AdjustFileBeforeAppend();
			base.Append(loggingEvent);
		}
  
 		/// <summary>
		/// Write out an array of logging events.
		/// </summary>
		/// <param name="loggingEvents">the events to write to file.</param>
		/// <remarks>
		/// <para>
		/// Handles append time behavior for RollingFileAppender.  This checks
		/// if a roll over either by date (checked first) or time (checked second)
		/// is need and then appends to the file last.
		/// </para>
		/// </remarks>
		override protected void Append(LoggingEvent[] loggingEvents) 
		{
			AdjustFileBeforeAppend();
			base.Append(loggingEvents);
		}

		/// <summary>
		/// Performs any required rolling before outputting the next event
		/// </summary>
		/// <remarks>
		/// <para>
		/// Handles append time behavior for RollingFileAppender.  This checks
		/// if a roll over either by date (checked first) or time (checked second)
		/// is need and then appends to the file last.
		/// </para>
		/// </remarks>
		virtual protected void AdjustFileBeforeAppend()
		{
			// reuse the file appenders locking model to lock the rolling
#if !NETCF
			try
			{
				// if rolling should be locked, acquire the lock
				if (m_mutexForRolling != null)
				{
					m_mutexForRolling.WaitOne();
				}
#endif
				if (m_rollDate)
				{
					DateTime n = m_dateTime.Now;
					if (n >= m_nextCheck)
					{
						m_now = n;
						m_nextCheck = NextCheckDate(m_now, m_rollPoint);

						RollOverTime(true);
					}
				}

				if (m_rollSize)
				{
					if ((File != null) && ((CountingQuietTextWriter)QuietWriter).Count >= m_maxFileSize)
					{
						RollOverSize();
					}
				}
#if !NETCF
			}
			finally
			{
				// if rolling should be locked, release the lock
				if (m_mutexForRolling != null)
				{
					m_mutexForRolling.ReleaseMutex();
				}
			}
#endif
		}

		/// <summary>
		/// Creates and opens the file for logging.  If <see cref="StaticLogFileName"/>
		/// is false then the fully qualified name is determined and used.
		/// </summary>
		/// <param name="fileName">the name of the file to open</param>
		/// <param name="append">true to append to existing file</param>
		/// <remarks>
		/// <para>This method will ensure that the directory structure
		/// for the <paramref name="fileName"/> specified exists.</para>
		/// </remarks>
		override protected void OpenFile(string fileName, bool append)
		{
			lock(this)
			{
				fileName = GetNextOutputFileName(fileName);

				// Calculate the current size of the file
				long currentCount = 0;
				if (append) 
				{
					using(SecurityContext.Impersonate(this))
					{
						if (System.IO.File.Exists(fileName))
						{
							currentCount = (new FileInfo(fileName)).Length;
						}
					}
				}
				else
				{
					if (LogLog.IsErrorEnabled)
					{
						// Internal check that the file is not being overwritten
						// If not Appending to an existing file we should have rolled the file out of the
						// way. Therefore we should not be over-writing an existing file.
						// The only exception is if we are not allowed to roll the existing file away.
						if (m_maxSizeRollBackups != 0 && FileExists(fileName))
						{
							LogLog.Error(declaringType, "RollingFileAppender: INTERNAL ERROR. Append is False but OutputFile ["+fileName+"] already exists.");
						}
					}
				}

				if (!m_staticLogFileName) 
				{
					m_scheduledFilename = fileName;
				}

				// Open the file (call the base class to do it)
				base.OpenFile(fileName, append);

				// Set the file size onto the counting writer
				((CountingQuietTextWriter)QuietWriter).Count = currentCount;
			}
		}

		/// <summary>
		/// Get the current output file name
		/// </summary>
		/// <param name="fileName">the base file name</param>
		/// <returns>the output file name</returns>
		/// <remarks>
		/// The output file name is based on the base fileName specified.
		/// If <see cref="StaticLogFileName"/> is set then the output 
		/// file name is the same as the base file passed in. Otherwise
		/// the output file depends on the date pattern, on the count
		/// direction or both.
		/// </remarks>
		protected string GetNextOutputFileName(string fileName)
		{
			if (!m_staticLogFileName) 
			{
				fileName = fileName.Trim();

				if (m_rollDate)
				{
                    fileName = CombinePath(fileName, m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo));
				}

				if (m_countDirection >= 0) 
				{
                    fileName = CombinePath(fileName, "." + m_curSizeRollBackups);
				}
			}

			return fileName;
		}

		#endregion

		#region Initialize Options

		/// <summary>
		///	Determines curSizeRollBackups (only within the current roll point)
		/// </summary>
		private void DetermineCurSizeRollBackups()
		{
			m_curSizeRollBackups = 0;
	
			string fullPath = null;
			string fileName = null;

			using(SecurityContext.Impersonate(this))
			{
				fullPath = System.IO.Path.GetFullPath(m_baseFileName);
				fileName = System.IO.Path.GetFileName(fullPath);
			}

			ArrayList arrayFiles = GetExistingFiles(fullPath);
			InitializeRollBackups(fileName, arrayFiles);

			LogLog.Debug(declaringType, "curSizeRollBackups starts at ["+m_curSizeRollBackups+"]");
		}

		/// <summary>
		/// Generates a wildcard pattern that can be used to find all files
		/// that are similar to the base file name.
		/// </summary>
		/// <param name="baseFileName"></param>
		/// <returns></returns>
		private string GetWildcardPatternForFile(string baseFileName)
		{
            if (m_preserveLogFileNameExtension)
            {
                return Path.GetFileNameWithoutExtension(baseFileName) + "*" + Path.GetExtension(baseFileName);
            }
            else
            {
                return baseFileName + '*';
            }
		}

		/// <summary>
		/// Builds a list of filenames for all files matching the base filename plus a file
		/// pattern.
		/// </summary>
		/// <param name="baseFilePath"></param>
		/// <returns></returns>
		private ArrayList GetExistingFiles(string baseFilePath)
		{
			ArrayList alFiles = new ArrayList();

			string directory = null;

			using(SecurityContext.Impersonate(this))
			{
				string fullPath = Path.GetFullPath(baseFilePath);

				directory = Path.GetDirectoryName(fullPath);
				if (Directory.Exists(directory))
				{
					string baseFileName = Path.GetFileName(fullPath);

					string[] files = Directory.GetFiles(directory, GetWildcardPatternForFile(baseFileName));
	
					if (files != null)
					{
						for (int i = 0; i < files.Length; i++) 
						{
							string curFileName = Path.GetFileName(files[i]);
							if (curFileName.StartsWith(Path.GetFileNameWithoutExtension(baseFileName)))
							{
								alFiles.Add(curFileName);
							}
						}
					}
				}
			}
			LogLog.Debug(declaringType, "Searched for existing files in ["+directory+"]");
			return alFiles;
		}

		/// <summary>
		/// Initiates a roll over if needed for crossing a date boundary since the last run.
		/// </summary>
		private void RollOverIfDateBoundaryCrossing()
		{
			if (m_staticLogFileName && m_rollDate) 
			{
				if (FileExists(m_baseFileName)) 
				{
					DateTime last;
					using(SecurityContext.Impersonate(this)) {
#if !NET_1_0 && !CLI_1_0 && !NETCF
                        if (DateTimeStrategy is UniversalDateTime)
						{
							last = System.IO.File.GetLastWriteTimeUtc(m_baseFileName);
						}
						else
						{
#endif
							last = System.IO.File.GetLastWriteTime(m_baseFileName);
#if !NET_1_0 && !CLI_1_0 && !NETCF
                        }
#endif
                    }
					LogLog.Debug(declaringType, "["+last.ToString(m_datePattern,System.Globalization.DateTimeFormatInfo.InvariantInfo)+"] vs. ["+m_now.ToString(m_datePattern,System.Globalization.DateTimeFormatInfo.InvariantInfo)+"]");

					if (!(last.ToString(m_datePattern,System.Globalization.DateTimeFormatInfo.InvariantInfo).Equals(m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo)))) 
					{
						m_scheduledFilename = CombinePath(m_baseFileName, last.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo));
						LogLog.Debug(declaringType, "Initial roll over to ["+m_scheduledFilename+"]");
						RollOverTime(false);
						LogLog.Debug(declaringType, "curSizeRollBackups after rollOver at ["+m_curSizeRollBackups+"]");
					}
				}
			}
		}

		/// <summary>
		/// Initializes based on existing conditions at time of <see cref="ActivateOptions"/>.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Initializes based on existing conditions at time of <see cref="ActivateOptions"/>.
		/// The following is done
		/// <list type="bullet">
		///	<item>determine curSizeRollBackups (only within the current roll point)</item>
		///	<item>initiates a roll over if needed for crossing a date boundary since the last run.</item>
		///	</list>
		///	</para>
		/// </remarks>
		protected void ExistingInit() 
		{
			DetermineCurSizeRollBackups();
			RollOverIfDateBoundaryCrossing();

			// If file exists and we are not appending then roll it out of the way
			if (AppendToFile == false)
			{
				bool fileExists = false;
				string fileName = GetNextOutputFileName(m_baseFileName);

				using(SecurityContext.Impersonate(this))
				{
					fileExists = System.IO.File.Exists(fileName);
				}

				if (fileExists)
				{
					if (m_maxSizeRollBackups == 0)
					{
						LogLog.Debug(declaringType, "Output file ["+fileName+"] already exists. MaxSizeRollBackups is 0; cannot roll. Overwriting existing file.");
					}
					else
					{
						LogLog.Debug(declaringType, "Output file ["+fileName+"] already exists. Not appending to file. Rolling existing file out of the way.");

						RollOverRenameFiles(fileName);
					}
				}
			}
		}

		/// <summary>
		/// Does the work of bumping the 'current' file counter higher
		/// to the highest count when an incremental file name is seen.
		/// The highest count is either the first file (when count direction
		/// is greater than 0) or the last file (when count direction less than 0).
		/// In either case, we want to know the highest count that is present.
		/// </summary>
		/// <param name="baseFile"></param>
		/// <param name="curFileName"></param>
		private void InitializeFromOneFile(string baseFile, string curFileName)
		{
            if (curFileName.StartsWith(Path.GetFileNameWithoutExtension(baseFile)) == false)
			{
				// This is not a log file, so ignore
				return;
			}
			if (curFileName.Equals(baseFile)) 
			{
				// Base log file is not an incremented logfile (.1 or .2, etc)
				return;
			}
	
            /*
			if (m_staticLogFileName) 
			{
				int endLength = curFileName.Length - index;
				if (baseFile.Length + endLength != curFileName.Length) 
				{
					// file is probably scheduledFilename + .x so I don't care
					return;
				}
			}
            */
	
			// Only look for files in the current roll point
			if (m_rollDate && !m_staticLogFileName)
			{
				string date = m_dateTime.Now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo);
				string prefix = m_preserveLogFileNameExtension ? Path.GetFileNameWithoutExtension(baseFile) + date : baseFile + date;
				string suffix = m_preserveLogFileNameExtension ? Path.GetExtension(baseFile) : "";
				if (!curFileName.StartsWith(prefix) || !curFileName.EndsWith(suffix))
				{
					LogLog.Debug(declaringType, "Ignoring file ["+curFileName+"] because it is from a different date period");
					return;
				}
			}
            
			try 
			{
				// Bump the counter up to the highest count seen so far
                int backup = GetBackUpIndex(curFileName);
                
                // caution: we might get a false positive when certain
                // date patterns such as yyyyMMdd are used...those are
                // valid number but aren't the kind of back up index
                // we're looking for
                if (backup > m_curSizeRollBackups)
                {
                    if (0 == m_maxSizeRollBackups)
                    {
                        // Stay at zero when zero backups are desired
                    }
                    else if (-1 == m_maxSizeRollBackups)
                    {
                        // Infinite backups, so go as high as the highest value
                        m_curSizeRollBackups = backup;
                    }
                    else
                    {
                        // Backups limited to a finite number
                        if (m_countDirection >= 0)
                        {
                            // Go with the highest file when counting up
                            m_curSizeRollBackups = backup;
                        }
                        else
                        {
                            // Clip to the limit when counting down
                            if (backup <= m_maxSizeRollBackups)
                            {
                                m_curSizeRollBackups = backup;
                            }
                        }
                    }
                    LogLog.Debug(declaringType, "File name [" + curFileName + "] moves current count to [" + m_curSizeRollBackups + "]");
                }
			} 
			catch(FormatException) 
			{
				//this happens when file.log -> file.log.yyyy-MM-dd which is normal
				//when staticLogFileName == false
				LogLog.Debug(declaringType, "Encountered a backup file not ending in .x ["+curFileName+"]");
			}
		}

        /// <summary>
        /// Attempts to extract a number from the end of the file name that indicates
        /// the number of the times the file has been rolled over.
        /// </summary>
        /// <remarks>
        /// Certain date pattern extensions like yyyyMMdd will be parsed as valid backup indexes.
        /// </remarks>
        /// <param name="curFileName"></param>
        /// <returns></returns>
	    private int GetBackUpIndex(string curFileName)
	    {
            int backUpIndex = -1;
            string fileName = curFileName;

            if (m_preserveLogFileNameExtension)
            {
                fileName = Path.GetFileNameWithoutExtension(fileName);
            }
            
            int index = fileName.LastIndexOf(".");
            if (index > 0)
            {
                // if the "yyyy-MM-dd" component of file.log.yyyy-MM-dd is passed to TryParse
                // it will gracefully fail and return backUpIndex will be 0
                SystemInfo.TryParse(fileName.Substring(index + 1), out backUpIndex);
            }

            return backUpIndex;
	    }

	    /// <summary>
		/// Takes a list of files and a base file name, and looks for 
		/// 'incremented' versions of the base file.  Bumps the max
		/// count up to the highest count seen.
		/// </summary>
		/// <param name="baseFile"></param>
		/// <param name="arrayFiles"></param>
		private void InitializeRollBackups(string baseFile, ArrayList arrayFiles)
		{
			if (null != arrayFiles)
			{
				string baseFileLower = baseFile.ToLower(System.Globalization.CultureInfo.InvariantCulture);

				foreach(string curFileName in arrayFiles)
				{
					InitializeFromOneFile(baseFileLower, curFileName.ToLower(System.Globalization.CultureInfo.InvariantCulture));
				}
			}
		}

		/// <summary>
		/// Calculates the RollPoint for the datePattern supplied.
		/// </summary>
		/// <param name="datePattern">the date pattern to calculate the check period for</param>
		/// <returns>The RollPoint that is most accurate for the date pattern supplied</returns>
		/// <remarks>
		/// Essentially the date pattern is examined to determine what the
		/// most suitable roll point is. The roll point chosen is the roll point
		/// with the smallest period that can be detected using the date pattern
		/// supplied. i.e. if the date pattern only outputs the year, month, day 
		/// and hour then the smallest roll point that can be detected would be
		/// and hourly roll point as minutes could not be detected.
		/// </remarks>
		private RollPoint ComputeCheckPeriod(string datePattern) 
		{
			// s_date1970 is 1970-01-01 00:00:00 this is UniversalSortableDateTimePattern 
			// (based on ISO 8601) using universal time. This date is used for reference
			// purposes to calculate the resolution of the date pattern.

			// Get string representation of base line date
			string r0 = s_date1970.ToString(datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo);

			// Check each type of rolling mode starting with the smallest increment.
			for(int i = (int)RollPoint.TopOfMinute; i <= (int)RollPoint.TopOfMonth; i++) 
			{
				// Get string representation of next pattern
				string r1 = NextCheckDate(s_date1970, (RollPoint)i).ToString(datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo);

				LogLog.Debug(declaringType, "Type = ["+i+"], r0 = ["+r0+"], r1 = ["+r1+"]");

				// Check if the string representations are different
				if (r0 != null && r1 != null && !r0.Equals(r1)) 
				{
					// Found highest precision roll point
					return (RollPoint)i;
				}
			}

			return RollPoint.InvalidRollPoint; // Deliberately head for trouble...
		}

		/// <summary>
		/// Initialize the appender based on the options set
		/// </summary>
		/// <remarks>
		/// <para>
		/// This is part of the <see cref="IOptionHandler"/> delayed object
		/// activation scheme. The <see cref="ActivateOptions"/> method must 
		/// be called on this object after the configuration properties have
		/// been set. Until <see cref="ActivateOptions"/> is called this
		/// object is in an undefined state and must not be used. 
		/// </para>
		/// <para>
		/// If any of the configuration properties are modified then 
		/// <see cref="ActivateOptions"/> must be called again.
		/// </para>
		/// <para>
		/// Sets initial conditions including date/time roll over information, first check,
		/// scheduledFilename, and calls <see cref="ExistingInit"/> to initialize
		/// the current number of backups.
		/// </para>
		/// </remarks>
		override public void ActivateOptions() 
		{
			if (m_dateTime == null)
			{
				m_dateTime = new LocalDateTime();
			}

			if (m_rollDate && m_datePattern != null) 
			{
				m_now = m_dateTime.Now;
				m_rollPoint = ComputeCheckPeriod(m_datePattern);

				if (m_rollPoint == RollPoint.InvalidRollPoint)
				{
					throw new ArgumentException("Invalid RollPoint, unable to parse ["+m_datePattern+"]");
				}

				// next line added as this removes the name check in rollOver
				m_nextCheck = NextCheckDate(m_now, m_rollPoint);
			} 
			else 
			{
				if (m_rollDate)
				{
					ErrorHandler.Error("Either DatePattern or rollingStyle options are not set for ["+Name+"].");
				}
			}

			if (SecurityContext == null)
			{
				SecurityContext = SecurityContextProvider.DefaultProvider.CreateSecurityContext(this);
			}

			using(SecurityContext.Impersonate(this))
			{
				// Must convert the FileAppender's m_filePath to an absolute path before we
				// call ExistingInit(). This will be done by the base.ActivateOptions() but
				// we need to duplicate that functionality here first.
				base.File = ConvertToFullPath(base.File.Trim());

				// Store fully qualified base file name
				m_baseFileName = base.File;
			}

#if !NETCF
			// initialize the mutex that is used to lock rolling
			m_mutexForRolling = new Mutex(false, m_baseFileName.Replace("\\", "_").Replace(":", "_").Replace("/", "_"));
#endif

			if (m_rollDate && File != null && m_scheduledFilename == null)
			{
                m_scheduledFilename = CombinePath(File, m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo));
			}

			ExistingInit();
	
			base.ActivateOptions();
		}

		#endregion
  
		#region Roll File

        /// <summary>
        /// 
        /// </summary>
        /// <param name="path1"></param>
        /// <param name="path2">.1, .2, .3, etc.</param>
        /// <returns></returns>
        private string CombinePath(string path1, string path2)
        {
            string extension = Path.GetExtension(path1);
            if (m_preserveLogFileNameExtension && extension.Length > 0)
            {
                return Path.Combine(Path.GetDirectoryName(path1), Path.GetFileNameWithoutExtension(path1) + path2 + extension);
            }
            else
            {
                return path1 + path2;
            }
        }

		/// <summary>
		/// Rollover the file(s) to date/time tagged file(s).
		/// </summary>
		/// <param name="fileIsOpen">set to true if the file to be rolled is currently open</param>
		/// <remarks>
		/// <para>
		/// Rollover the file(s) to date/time tagged file(s).
		/// Resets curSizeRollBackups. 
		/// If fileIsOpen is set then the new file is opened (through SafeOpenFile).
		/// </para>
		/// </remarks>
		protected void RollOverTime(bool fileIsOpen) 
		{
			if (m_staticLogFileName) 
			{
				// Compute filename, but only if datePattern is specified
				if (m_datePattern == null) 
				{
					ErrorHandler.Error("Missing DatePattern option in rollOver().");
					return;
				}
	  
				//is the new file name equivalent to the 'current' one
				//something has gone wrong if we hit this -- we should only
				//roll over if the new file will be different from the old
				string dateFormat = m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo);
                if (m_scheduledFilename.Equals(CombinePath(File, dateFormat))) 
				{
                    ErrorHandler.Error("Compare " + m_scheduledFilename + " : " + CombinePath(File, dateFormat));
					return;
				}
	  
				if (fileIsOpen)
				{
					// close current file, and rename it to datedFilename
					this.CloseFile();
				}
	  
				//we may have to roll over a large number of backups here
				for (int i = 1; i <= m_curSizeRollBackups; i++) 
				{
                    string from = CombinePath(File, "." + i);
                    string to = CombinePath(m_scheduledFilename, "." + i);
					RollFile(from, to);
				}
	  
				RollFile(File, m_scheduledFilename);
			}
	
			//We've cleared out the old date and are ready for the new
			m_curSizeRollBackups = 0; 
	
			//new scheduled name
            m_scheduledFilename = CombinePath(File, m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo));

			if (fileIsOpen)
			{
				// This will also close the file. This is OK since multiple close operations are safe.
				SafeOpenFile(m_baseFileName, false);
			}
		}
  
		/// <summary>
		/// Renames file <paramref name="fromFile"/> to file <paramref name="toFile"/>.
		/// </summary>
		/// <param name="fromFile">Name of existing file to roll.</param>
		/// <param name="toFile">New name for file.</param>
		/// <remarks>
		/// <para>
		/// Renames file <paramref name="fromFile"/> to file <paramref name="toFile"/>. It
		/// also checks for existence of target file and deletes if it does.
		/// </para>
		/// </remarks>
		protected void RollFile(string fromFile, string toFile) 
		{
			if (FileExists(fromFile))
			{
				// Delete the toFile if it exists
				DeleteFile(toFile);

				// We may not have permission to move the file, or the file may be locked
				try
				{
					LogLog.Debug(declaringType, "Moving [" + fromFile + "] -> [" + toFile + "]");
					using(SecurityContext.Impersonate(this))
					{
						System.IO.File.Move(fromFile, toFile);
					}
				}
				catch(Exception moveEx)
				{
					ErrorHandler.Error("Exception while rolling file [" + fromFile + "] -> [" + toFile + "]", moveEx, ErrorCode.GenericFailure);
				}
			}
			else
			{
				LogLog.Warn(declaringType, "Cannot RollFile [" + fromFile + "] -> [" + toFile + "]. Source does not exist");
			}
		}

		/// <summary>
		/// Test if a file exists at a specified path
		/// </summary>
		/// <param name="path">the path to the file</param>
		/// <returns>true if the file exists</returns>
		/// <remarks>
		/// <para>
		/// Test if a file exists at a specified path
		/// </para>
		/// </remarks>
		protected bool FileExists(string path)
		{
			using(SecurityContext.Impersonate(this))
			{
				return System.IO.File.Exists(path);
			}
		}
  
		/// <summary>
		/// Deletes the specified file if it exists.
		/// </summary>
		/// <param name="fileName">The file to delete.</param>
		/// <remarks>
		/// <para>
		/// Delete a file if is exists.
		/// The file is first moved to a new filename then deleted.
		/// This allows the file to be removed even when it cannot
		/// be deleted, but it still can be moved.
		/// </para>
		/// </remarks>
		protected void DeleteFile(string fileName) 
		{
			if (FileExists(fileName)) 
			{
				// We may not have permission to delete the file, or the file may be locked

				string fileToDelete = fileName;

				// Try to move the file to temp name.
				// If the file is locked we may still be able to move it
				string tempFileName = fileName + "." + Environment.TickCount + ".DeletePending";
				try
				{
					using(SecurityContext.Impersonate(this))
					{
						System.IO.File.Move(fileName, tempFileName);
					}
					fileToDelete = tempFileName;
				}
				catch(Exception moveEx)
				{
					LogLog.Debug(declaringType, "Exception while moving file to be deleted [" + fileName + "] -> [" + tempFileName + "]", moveEx);
				}

				// Try to delete the file (either the original or the moved file)
				try
				{
					using(SecurityContext.Impersonate(this))
					{
						System.IO.File.Delete(fileToDelete);
					}
					LogLog.Debug(declaringType, "Deleted file [" + fileName + "]");
				}
				catch(Exception deleteEx)
				{
					if (fileToDelete == fileName)
					{
						// Unable to move or delete the file
						ErrorHandler.Error("Exception while deleting file [" + fileToDelete + "]", deleteEx, ErrorCode.GenericFailure);
					}
					else
					{
						// Moved the file, but the delete failed. File is probably locked.
						// The file should automatically be deleted when the lock is released.
						LogLog.Debug(declaringType, "Exception while deleting temp file [" + fileToDelete + "]", deleteEx);
					}
				}
			}
		}
  
		/// <summary>
		/// Implements file roll base on file size.
		/// </summary>
		/// <remarks>
		/// <para>
		/// If the maximum number of size based backups is reached
		/// (<c>curSizeRollBackups == maxSizeRollBackups</c>) then the oldest
		/// file is deleted -- its index determined by the sign of countDirection.
		/// If <c>countDirection</c> &lt; 0, then files
		/// {<c>File.1</c>, ..., <c>File.curSizeRollBackups -1</c>}
		/// are renamed to {<c>File.2</c>, ...,
		/// <c>File.curSizeRollBackups</c>}. Moreover, <c>File</c> is
		/// renamed <c>File.1</c> and closed.
		/// </para>
		/// <para>
		/// A new file is created to receive further log output.
		/// </para>
		/// <para>
		/// If <c>maxSizeRollBackups</c> is equal to zero, then the
		/// <c>File</c> is truncated with no backup files created.
		/// </para>
		/// <para>
		/// If <c>maxSizeRollBackups</c> &lt; 0, then <c>File</c> is
		/// renamed if needed and no files are deleted.
		/// </para>
		/// </remarks>
		protected void RollOverSize() 
		{
			this.CloseFile(); // keep windows happy.
	
			LogLog.Debug(declaringType, "rolling over count ["+((CountingQuietTextWriter)QuietWriter).Count+"]");
			LogLog.Debug(declaringType, "maxSizeRollBackups ["+m_maxSizeRollBackups+"]");
			LogLog.Debug(declaringType, "curSizeRollBackups ["+m_curSizeRollBackups+"]");
			LogLog.Debug(declaringType, "countDirection ["+m_countDirection+"]");

			RollOverRenameFiles(File);
	
			if (!m_staticLogFileName && m_countDirection >= 0) 
			{
				m_curSizeRollBackups++;
			}

			// This will also close the file. This is OK since multiple close operations are safe.
			SafeOpenFile(m_baseFileName, false);
		}

		/// <summary>
		/// Implements file roll.
		/// </summary>
		/// <param name="baseFileName">the base name to rename</param>
		/// <remarks>
		/// <para>
		/// If the maximum number of size based backups is reached
		/// (<c>curSizeRollBackups == maxSizeRollBackups</c>) then the oldest
		/// file is deleted -- its index determined by the sign of countDirection.
		/// If <c>countDirection</c> &lt; 0, then files
		/// {<c>File.1</c>, ..., <c>File.curSizeRollBackups -1</c>}
		/// are renamed to {<c>File.2</c>, ...,
		/// <c>File.curSizeRollBackups</c>}. 
		/// </para>
		/// <para>
		/// If <c>maxSizeRollBackups</c> is equal to zero, then the
		/// <c>File</c> is truncated with no backup files created.
		/// </para>
		/// <para>
		/// If <c>maxSizeRollBackups</c> &lt; 0, then <c>File</c> is
		/// renamed if needed and no files are deleted.
		/// </para>
		/// <para>
		/// This is called by <see cref="RollOverSize"/> to rename the files.
		/// </para>
		/// </remarks>
		protected void RollOverRenameFiles(string baseFileName) 
		{
			// If maxBackups <= 0, then there is no file renaming to be done.
			if (m_maxSizeRollBackups != 0) 
			{
				if (m_countDirection < 0) 
				{
					// Delete the oldest file, to keep Windows happy.
					if (m_curSizeRollBackups == m_maxSizeRollBackups) 
					{
                        DeleteFile(CombinePath(baseFileName, "." + m_maxSizeRollBackups));
						m_curSizeRollBackups--;
					}
	
					// Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2}
					for (int i = m_curSizeRollBackups; i >= 1; i--) 
					{
                        RollFile((CombinePath(baseFileName, "." + i)), (CombinePath(baseFileName, "." + (i + 1))));
					}
	
					m_curSizeRollBackups++;

					// Rename fileName to fileName.1
                    RollFile(baseFileName, CombinePath(baseFileName, ".1"));
				} 
				else 
				{
					//countDirection >= 0
					if (m_curSizeRollBackups >= m_maxSizeRollBackups && m_maxSizeRollBackups > 0) 
					{
						//delete the first and keep counting up.
						int oldestFileIndex = m_curSizeRollBackups - m_maxSizeRollBackups;

						// If static then there is 1 file without a number, therefore 1 less archive
						if (m_staticLogFileName)
						{
							oldestFileIndex++;
						}

						// If using a static log file then the base for the numbered sequence is the baseFileName passed in
						// If not using a static log file then the baseFileName will already have a numbered postfix which
						// we must remove, however it may have a date postfix which we must keep!
						string archiveFileBaseName = baseFileName;
						if (!m_staticLogFileName)
						{
                                                    if (m_preserveLogFileNameExtension)
                                                    {
                                                        string extension = Path.GetExtension(archiveFileBaseName);
                                                        string baseName = Path.GetFileNameWithoutExtension(archiveFileBaseName);
							int lastDotIndex = baseName.LastIndexOf(".");
							if (lastDotIndex >= 0)
							{
								archiveFileBaseName = baseName.Substring(0, lastDotIndex) + extension;
							}
                                                    }
                                                    else
                                                    {
							int lastDotIndex = archiveFileBaseName.LastIndexOf(".");
							if (lastDotIndex >= 0) 
							{
								archiveFileBaseName = archiveFileBaseName.Substring(0, lastDotIndex);
							}
                                                    }
						}

						// Delete the archive file
                        DeleteFile(CombinePath(archiveFileBaseName, "." + oldestFileIndex));
					}
	
					if (m_staticLogFileName) 
					{
						m_curSizeRollBackups++;
                        RollFile(baseFileName, CombinePath(baseFileName, "." + m_curSizeRollBackups));
					}
				}
			}
		}

		#endregion

		#region NextCheckDate

		/// <summary>
		/// Get the start time of the next window for the current rollpoint
		/// </summary>
		/// <param name="currentDateTime">the current date</param>
		/// <param name="rollPoint">the type of roll point we are working with</param>
		/// <returns>the start time for the next roll point an interval after the currentDateTime date</returns>
		/// <remarks>
		/// <para>
		/// Returns the date of the next roll point after the currentDateTime date passed to the method.
		/// </para>
		/// <para>
		/// The basic strategy is to subtract the time parts that are less significant
		/// than the rollpoint from the current time. This should roll the time back to
		/// the start of the time window for the current rollpoint. Then we add 1 window
		/// worth of time and get the start time of the next window for the rollpoint.
		/// </para>
		/// </remarks>
		protected DateTime NextCheckDate(DateTime currentDateTime, RollPoint rollPoint) 
		{
			// Local variable to work on (this does not look very efficient)
			DateTime current = currentDateTime;

			// Do slightly different things depending on what the type of roll point we want.
			switch(rollPoint) 
			{
				case RollPoint.TopOfMinute:
					current = current.AddMilliseconds(-current.Millisecond);
					current = current.AddSeconds(-current.Second);
					current = current.AddMinutes(1);
					break;

				case RollPoint.TopOfHour:
					current = current.AddMilliseconds(-current.Millisecond);
					current = current.AddSeconds(-current.Second);
					current = current.AddMinutes(-current.Minute);
					current = current.AddHours(1);
					break;

				case RollPoint.HalfDay:
					current = current.AddMilliseconds(-current.Millisecond);
					current = current.AddSeconds(-current.Second);
					current = current.AddMinutes(-current.Minute);

					if (current.Hour < 12) 
					{
						current = current.AddHours(12 - current.Hour);
					} 
					else 
					{
						current = current.AddHours(-current.Hour);
						current = current.AddDays(1);
					}
					break;

				case RollPoint.TopOfDay:
					current = current.AddMilliseconds(-current.Millisecond);
					current = current.AddSeconds(-current.Second);
					current = current.AddMinutes(-current.Minute);
					current = current.AddHours(-current.Hour);
					current = current.AddDays(1);
					break;

				case RollPoint.TopOfWeek:
					current = current.AddMilliseconds(-current.Millisecond);
					current = current.AddSeconds(-current.Second);
					current = current.AddMinutes(-current.Minute);
					current = current.AddHours(-current.Hour);
					current = current.AddDays(7 - (int)current.DayOfWeek);
					break;

				case RollPoint.TopOfMonth:
					current = current.AddMilliseconds(-current.Millisecond);
					current = current.AddSeconds(-current.Second);
					current = current.AddMinutes(-current.Minute);
					current = current.AddHours(-current.Hour);
					current = current.AddDays(1 - current.Day); /* first day of month is 1 not 0 */
					current = current.AddMonths(1);
					break;
			}	  
			return current;
		}

		#endregion

		#region Private Instance Fields

		/// <summary>
		/// This object supplies the current date/time.  Allows test code to plug in
		/// a method to control this class when testing date/time based rolling. The default
		/// implementation uses the underlying value of DateTime.Now.
		/// </summary>
		private IDateTime m_dateTime = null;

		/// <summary>
		/// The date pattern. By default, the pattern is set to <c>".yyyy-MM-dd"</c> 
		/// meaning daily rollover.
		/// </summary>
		private string m_datePattern = ".yyyy-MM-dd";
  
		/// <summary>
		/// The actual formatted filename that is currently being written to
		/// or will be the file transferred to on roll over
		/// (based on staticLogFileName).
		/// </summary>
		private string m_scheduledFilename = null;
  
		/// <summary>
		/// The timestamp when we shall next recompute the filename.
		/// </summary>
		private DateTime m_nextCheck = DateTime.MaxValue;
  
		/// <summary>
		/// Holds date of last roll over
		/// </summary>
		private DateTime m_now;
  
		/// <summary>
		/// The type of rolling done
		/// </summary>
		private RollPoint m_rollPoint;
  
		/// <summary>
		/// The default maximum file size is 10MB
		/// </summary>
		private long m_maxFileSize = 10*1024*1024;
  
		/// <summary>
		/// There is zero backup files by default
		/// </summary>
		private int m_maxSizeRollBackups  = 0;

		/// <summary>
		/// How many sized based backups have been made so far
		/// </summary>
		private int m_curSizeRollBackups = 0;
  
		/// <summary>
		/// The rolling file count direction. 
		/// </summary>
		private int m_countDirection = -1;
  
		/// <summary>
		/// The rolling mode used in this appender.
		/// </summary>
		private RollingMode m_rollingStyle = RollingMode.Composite;

		/// <summary>
		/// Cache flag set if we are rolling by date.
		/// </summary>
		private bool m_rollDate = true;

		/// <summary>
		/// Cache flag set if we are rolling by size.
		/// </summary>
		private bool m_rollSize = true;
  
		/// <summary>
		/// Value indicating whether to always log to the same file.
		/// </summary>
		private bool m_staticLogFileName = true;
  
   		/// <summary>
		/// Value indicating whether to preserve the file name extension when rolling.
		/// </summary>
		private bool m_preserveLogFileNameExtension = false;


		/// <summary>
		/// FileName provided in configuration.  Used for rolling properly
		/// </summary>
		private string m_baseFileName;

#if !NETCF
		/// <summary>
		/// A mutex that is used to lock rolling of files.
		/// </summary>
		private Mutex m_mutexForRolling;
#endif

		#endregion Private Instance Fields

		#region Static Members

		/// <summary>
		/// The 1st of January 1970 in UTC
		/// </summary>
		private static readonly DateTime s_date1970 = new DateTime(1970, 1, 1);

		#endregion

		#region DateTime

		/// <summary>
		/// This interface is used to supply Date/Time information to the <see cref="RollingFileAppender"/>.
		/// </summary>
		/// <remarks>
		/// This interface is used to supply Date/Time information to the <see cref="RollingFileAppender"/>.
		/// Used primarily to allow test classes to plug themselves in so they can
		/// supply test date/times.
		/// </remarks>
		public interface IDateTime
		{
			/// <summary>
			/// Gets the <i>current</i> time.
			/// </summary>
			/// <value>The <i>current</i> time.</value>
			/// <remarks>
			/// <para>
			/// Gets the <i>current</i> time.
			/// </para>
			/// </remarks>
			DateTime Now { get; }
		}

		/// <summary>
		/// Default implementation of <see cref="IDateTime"/> that returns the current time.
		/// </summary>
		private class LocalDateTime : IDateTime
		{
			/// <summary>
			/// Gets the <b>current</b> time.
			/// </summary>
			/// <value>The <b>current</b> time.</value>
			/// <remarks>
			/// <para>
			/// Gets the <b>current</b> time.
			/// </para>
			/// </remarks>
			public DateTime Now
			{
				get { return DateTime.Now; }
			}
		}

#if !NET_1_0 && !CLI_1_0 && !NETCF
        /// <summary>
		/// Implementation of <see cref="IDateTime"/> that returns the current time as the coordinated universal time (UTC).
		/// </summary>
		private class UniversalDateTime : IDateTime
		{
			/// <summary>
			/// Gets the <b>current</b> time.
			/// </summary>
			/// <value>The <b>current</b> time.</value>
			/// <remarks>
			/// <para>
			/// Gets the <b>current</b> time.
			/// </para>
			/// </remarks>
			public DateTime Now
			{
				get { return DateTime.UtcNow; }
			}
		}
#endif

        #endregion DateTime
	}
}