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//
// Comparer
//
// Authors:
// Ben Maurer (bmaurer@ximian.com)
//
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// 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.
//
#if NET_2_0
using System;
using System.Runtime.InteropServices;
namespace System.Collections.Generic {
[Serializable]
public abstract class Comparer<T> : IComparer<T>, System.Collections.IComparer {
static Comparer ()
{
if (typeof (IComparable<T>).IsAssignableFrom (typeof (T)))
_default = (Comparer<T>) Activator.CreateInstance (typeof (IComparableOfTComparer <>).MakeGenericType (typeof (T)));
else
_default = new DefaultComparer ();
}
public abstract int Compare (T x, T y);
static readonly Comparer <T> _default;
public static Comparer <T> Default {
get {
return _default;
}
}
int System.Collections.IComparer.Compare (object x, object y)
{
if (x == null)
return y == null ? 0 : -1;
if (y == null)
return 1;
if (x is T && y is T)
return Compare ((T) x, (T) y);
throw new ArgumentException ();
}
class DefaultComparer : Comparer<T> {
public override int Compare (T x, T y)
{
// `null' is less than any other ref type
if (x == null)
return y == null ? 0 : -1;
else if (y == null)
return 1;
if (x is IComparable<T>)
return ((IComparable<T>) x).CompareTo (y);
else if (x is IComparable)
return ((IComparable) x).CompareTo (y);
else
throw new ArgumentException ("does not implement right interface");
}
}
}
class IComparableOfTComparer <T> : Comparer <T> where T : IComparable {
public override int Compare (T x, T y)
{
// `null' is less than any other ref type
if (x == null)
return y == null ? 0 : -1;
else if (y == null)
return 1;
return x.CompareTo (y);
}
}
}
#endif
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