source: branches/Async/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Utils/IFreezable.cs @ 13401

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// 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;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;

namespace ICSharpCode.AvalonEdit.Utils
{
  interface IFreezable
  {
    /// <summary>
    /// Gets if this instance is frozen. Frozen instances are immutable and thus thread-safe.
    /// </summary>
    bool IsFrozen { get; }
    
    /// <summary>
    /// Freezes this instance.
    /// </summary>
    void Freeze();
  }
  
  static class FreezableHelper
  {
    public static void ThrowIfFrozen(IFreezable freezable)
    {
      if (freezable.IsFrozen)
        throw new InvalidOperationException("Cannot mutate frozen " + freezable.GetType().Name);
    }
    
    public static IList<T> FreezeListAndElements<T>(IList<T> list)
    {
      if (list != null) {
        foreach (T item in list)
          Freeze(item);
      }
      return FreezeList(list);
    }
    
    public static IList<T> FreezeList<T>(IList<T> list)
    {
      if (list == null || list.Count == 0)
        return Empty<T>.Array;
      if (list.IsReadOnly) {
        // If the list is already read-only, return it directly.
        // This is important, otherwise we might undo the effects of interning.
        return list;
      } else {
        return new ReadOnlyCollection<T>(list.ToArray());
      }
    }
    
    public static void Freeze(object item)
    {
      IFreezable f = item as IFreezable;
      if (f != null)
        f.Freeze();
    }
    
    public static T FreezeAndReturn<T>(T item) where T : IFreezable
    {
      item.Freeze();
      return item;
    }
    
    /// <summary>
    /// If the item is not frozen, this method creates and returns a frozen clone.
    /// If the item is already frozen, it is returned without creating a clone.
    /// </summary>
    public static T GetFrozenClone<T>(T item) where T : IFreezable, ICloneable
    {
      if (!item.IsFrozen) {
        item = (T)item.Clone();
        item.Freeze();
      }
      return item;
    }
  }

  [Serializable]
  abstract class AbstractFreezable : IFreezable
  {
    bool isFrozen;
    
    /// <summary>
    /// Gets if this instance is frozen. Frozen instances are immutable and thus thread-safe.
    /// </summary>
    public bool IsFrozen {
      get { return isFrozen; }
    }
    
    /// <summary>
    /// Freezes this instance.
    /// </summary>
    public void Freeze()
    {
      if (!isFrozen) {
        FreezeInternal();
        isFrozen = true;
      }
    }
    
    protected virtual void FreezeInternal()
    {
    }
  }
}