src/log4net/Util/QuietTextWriter.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.IO;

using log4net.Core;

namespace log4net.Util;

/// <summary>
/// <see cref="TextWriter"/> that does not leak exceptions
/// </summary>
/// <remarks>
/// <para>
/// <see cref="QuietTextWriter"/> does not throw exceptions when things go wrong. 
/// Instead, it delegates error handling to its <see cref="IErrorHandler"/>.
/// </para>
/// </remarks>
/// <author>Nicko Cadell</author>
/// <author>Gert Driesen</author>
public class QuietTextWriter : TextWriterAdapter
{
  /// <summary>
  /// Constructor
  /// </summary>
  /// <param name="writer">the writer to actually write to</param>
  /// <param name="errorHandler">the error handler to report error to</param>
  /// <remarks>
  /// <para>
  /// Create a new QuietTextWriter using a writer and error handler
  /// </para>
  /// </remarks>
  public QuietTextWriter(TextWriter writer, IErrorHandler errorHandler)
    : base(writer)
    => this._errorHandler = errorHandler.EnsureNotNull();

  /// <summary>
  /// Gets or sets the error handler that all errors are passed to.
  /// </summary>
  /// <value>
  /// The error handler that all errors are passed to.
  /// </value>
  /// <remarks>
  /// <para>
  /// Gets or sets the error handler that all errors are passed to.
  /// </para>
  /// </remarks>
  public IErrorHandler ErrorHandler
  {
    get => _errorHandler;
    set => _errorHandler = value.EnsureNotNull();
  }

  /// <summary>
  /// Gets a value indicating whether this writer is closed.
  /// </summary>
  /// <value>
  /// <c>true</c> if this writer is closed, otherwise <c>false</c>.
  /// </value>
  /// <remarks>
  /// <para>
  /// Gets a value indicating whether this writer is closed.
  /// </para>
  /// </remarks>
  public bool Closed { get; private set; }

  /// <summary>
  /// Writes a character to the underlying writer
  /// </summary>
  /// <param name="value">the char to write</param>
  /// <remarks>
  /// <para>
  /// Writes a character to the underlying writer
  /// </para>
  /// </remarks>
  public override void Write(char value)
  {
    try
    {
      base.Write(value);
    }
    catch (Exception e) when (!e.IsFatal())
    {
      _errorHandler.Error($"Failed to write [{value}].", e, ErrorCode.WriteFailure);
    }
  }

  /// <summary>
  /// Writes a buffer to the underlying writer
  /// </summary>
  /// <param name="buffer">the buffer to write</param>
  /// <param name="index">the start index to write from</param>
  /// <param name="count">the number of characters to write</param>
  /// <remarks>
  /// <para>
  /// Writes a buffer to the underlying writer
  /// </para>
  /// </remarks>
  public override void Write(char[] buffer, int index, int count)
  {
    try
    {
      base.Write(buffer, index, count);
    }
    catch (Exception e) when (!e.IsFatal())
    {
      _errorHandler.Error("Failed to write buffer.", e, ErrorCode.WriteFailure);
    }
  }

  /// <summary>
  /// Writes a string to the output.
  /// </summary>
  /// <param name="value">The string data to write to the output.</param>
  public override void Write(string? value)
  {
    try
    {
      base.Write(value);
    }
    catch (Exception e) when (!e.IsFatal())
    {
      _errorHandler.Error($"Failed to write [{value}].", e, ErrorCode.WriteFailure);
    }
  }

  /// <summary>
  /// Closes the underlying output writer.
  /// </summary>
  /// <remarks>
  /// <para>
  /// Closes the underlying output writer.
  /// </para>
  /// </remarks>
  public override void Close()
  {
    Closed = true;
    base.Close();
  }

  /// <summary>
  /// The error handler instance to pass all errors to
  /// </summary>
  private IErrorHandler _errorHandler;
}