source: branches/CodeEditor/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory-5.5.0/TypeSystem/Implementation/SimpleInterningProvider.cs @ 11700

// Copyright (c) 2010-2013 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
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// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Runtime.CompilerServices;

using ICSharpCode.NRefactory.Utils;

namespace ICSharpCode.NRefactory.TypeSystem.Implementation
{
  /// <summary>
  /// Simple interning provider.
  /// </summary>
  public sealed class SimpleInterningProvider : InterningProvider
  {
    sealed class InterningComparer : IEqualityComparer<ISupportsInterning>
    {
      public bool Equals(ISupportsInterning x, ISupportsInterning y)
      {
        return x.EqualsForInterning(y);
      }
      
      public int GetHashCode(ISupportsInterning obj)
      {
        return obj.GetHashCodeForInterning();
      }
    }
    
    sealed class ListComparer : IEqualityComparer<IEnumerable>
    {
      public bool Equals(IEnumerable a, IEnumerable b)
      {
        if (a.GetType() != b.GetType())
          return false;
        IEnumerator e1 = a.GetEnumerator();
        IEnumerator e2 = b.GetEnumerator();
        while (e1.MoveNext()) {
          // e1 has more elements than e2; or elements are different
          if (!e2.MoveNext() || e1.Current != e2.Current)
            return false;
        }
        if (e2.MoveNext()) // e2 has more elements than e1
          return false;
        // No need to dispose e1/e2: non-generic IEnumerator doesn't implement IDisposable,
        // and the underlying enumerator will likely be a List<T>.Enumerator which has an empty Dispose() method.
        return true;
      }
      
      public int GetHashCode(IEnumerable obj)
      {
        int hashCode = obj.GetType().GetHashCode();
        unchecked {
          foreach (object o in obj) {
            hashCode *= 27;
            hashCode += RuntimeHelpers.GetHashCode(o);
          }
        }
        return hashCode;
      }
    }
    
    Dictionary<object, object> byValueDict = new Dictionary<object, object>();
    Dictionary<ISupportsInterning, ISupportsInterning> supportsInternDict = new Dictionary<ISupportsInterning, ISupportsInterning>(new InterningComparer());
    Dictionary<IEnumerable, IEnumerable> listDict = new Dictionary<IEnumerable, IEnumerable>(new ListComparer());
    
    public override ISupportsInterning Intern(ISupportsInterning obj)
    {
      if (obj == null)
        return null;
      
      // ensure objects are frozen when we put them into the dictionary
      // note that Freeze may change the hash code of the object
      FreezableHelper.Freeze(obj);

      ISupportsInterning output;
      if (supportsInternDict.TryGetValue(obj, out output)) {
        return output;
      } else {
        supportsInternDict.Add(obj, obj);
        return obj;
      }
    }
    
    public override string Intern(string text)
    {
      if (text == null)
        return null;
      
      object output;
      if (byValueDict.TryGetValue(text, out output))
        return (string)output;
      else
        return text;
    }
    
    public override object InternValue(object obj)
    {
      if (obj == null)
        return null;
      
      object output;
      if (byValueDict.TryGetValue(obj, out output))
        return output;
      else
        return obj;
    }
    
    public override IList<T> InternList<T>(IList<T> list)
    {
      if (list == null)
        return null;
      if (list.Count == 0)
        return EmptyList<T>.Instance;
      if (!list.IsReadOnly)
        list = new ReadOnlyCollection<T>(list);
      IEnumerable output;
      if (listDict.TryGetValue(list, out output))
        list = (IList<T>)output;
      else
        listDict.Add(list, list);
      return list;
    }
  }
}