src/log4net/Appender/MemoryAppender.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.Collections.Generic;
using log4net.Core;
using log4net.Util;

namespace log4net.Appender;

/// <summary>
/// Stores logging events in an array.
/// </summary>
/// <remarks>
/// <para>
/// The memory appender stores all the logging events
/// that are appended in an in-memory array.
/// </para>
/// <para>
/// Use the <see cref="PopAllEvents()"/> method to get
/// and clear the current list of events that have been appended.
/// </para>
/// <para>
/// Use the <see cref="GetEvents()"/> method to get the current
/// list of events that have been appended.  Note there is a
/// race-condition when calling <see cref="GetEvents()"/> and
/// <see cref="Clear()"/> in pairs, you better use <see
/// mref="M:PopAllEvents()"/> in that case.
/// </para>
/// <para>
/// Use the <see cref="Clear()"/> method to clear the
/// current list of events.  Note there is a
/// race-condition when calling <see cref="GetEvents()"/> and
/// <see cref="Clear()"/> in pairs, you better use <see
/// mref="M:PopAllEvents()"/> in that case.
/// </para>
/// </remarks>
/// <author>Julian Biddle</author>
/// <author>Nicko Cadell</author>
/// <author>Gert Driesen</author>
public class MemoryAppender : AppenderSkeleton
{
  /// <summary>
  /// Gets the events that have been logged.
  /// </summary>
  /// <returns>The events that have been logged</returns>
  public virtual LoggingEvent[] GetEvents()
  {
    lock (_syncRoot)
    {
      return m_eventsList.ToArray();
    }
  }

  /// <summary>
  /// Gets or sets the fields that will be fixed in the event
  /// </summary>
  /// <remarks>
  /// <para>
  /// The logging event needs to have certain thread specific values 
  /// captured before it can be buffered. See <see cref="LoggingEvent.Fix"/>
  /// for details.
  /// </para>
  /// </remarks>
  public virtual FixFlags Fix { get; set; } = FixFlags.All;

  /// <summary>
  /// This method is called by the <see cref="AppenderSkeleton.DoAppend(LoggingEvent)"/> method. 
  /// </summary>
  /// <param name="loggingEvent">the event to log</param>
  /// <remarks>
  /// <para>Stores the <paramref name="loggingEvent"/> in the events list.</para>
  /// </remarks>
  protected override void Append(LoggingEvent loggingEvent)
  {
    // Because we are caching the LoggingEvent beyond the
    // lifetime of the Append() method we must fix any
    // volatile data in the event.
    loggingEvent.EnsureNotNull().Fix = Fix;

    lock (_syncRoot)
    {
      m_eventsList.Add(loggingEvent);
    }
  }

  /// <summary>
  /// Clear the list of events
  /// </summary>
  /// <remarks>
  /// Clear the list of events
  /// </remarks>
  public virtual void Clear()
  {
    lock (_syncRoot)
    {
      m_eventsList.Clear();
    }
  }

  /// <summary>
  /// Gets the events that have been logged and clears the list of events.
  /// </summary>
  /// <returns>The events that have been logged</returns>
  public virtual LoggingEvent[] PopAllEvents()
  {
    lock (_syncRoot)
    {
      LoggingEvent[] tmp = m_eventsList.ToArray();
      m_eventsList.Clear();
      return tmp;
    }
  }

  /// <summary>
  /// The list of events that have been appended.
  /// </summary>
  // ReSharper disable once InconsistentNaming
  // ReSharper disable once FieldCanBeMadeReadOnly.Global
  [System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "CA1002:Do not expose generic lists")]
  protected List<LoggingEvent> m_eventsList = [];

  private readonly object _syncRoot = new();
}