127 lines
3.3 KiB
C#
127 lines
3.3 KiB
C#
//
|
|
// Comparer.cs
|
|
//
|
|
// Authors:
|
|
// Ben Maurer (bmaurer@ximian.com)
|
|
// Marek Safar (marek.safar@gmail.com)
|
|
//
|
|
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
|
|
// Copyright (C) 2012 Xamarin Inc (http://www.xamarin.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.
|
|
//
|
|
|
|
using System;
|
|
using System.Runtime.InteropServices;
|
|
|
|
namespace System.Collections.Generic {
|
|
[Serializable]
|
|
public abstract class Comparer<T> : IComparer<T>, IComparer
|
|
{
|
|
static readonly Comparer <T> _default = typeof (IComparable<T>).IsAssignableFrom (typeof (T)) ?
|
|
(Comparer<T>) Activator.CreateInstance (typeof (GenericComparer <>).MakeGenericType (typeof (T))) :
|
|
new DefaultComparer ();
|
|
|
|
public abstract int Compare (T x, T y);
|
|
|
|
public static Comparer<T> Default {
|
|
get {
|
|
return _default;
|
|
}
|
|
}
|
|
|
|
public static Comparer<T> Create (Comparison<T> comparison)
|
|
{
|
|
if (comparison == null)
|
|
throw new ArgumentNullException ("comparison");
|
|
|
|
return new ComparisonComparer<T> (comparison);
|
|
}
|
|
|
|
int IComparer.Compare (object x, object y)
|
|
{
|
|
if (x == y)
|
|
return 0;
|
|
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 ();
|
|
}
|
|
|
|
[Serializable]
|
|
sealed 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;
|
|
if (y == null)
|
|
return 1;
|
|
|
|
var i = x as IComparable;
|
|
if (i != null)
|
|
return i.CompareTo (y);
|
|
|
|
i = y as IComparable;
|
|
if (i != null)
|
|
return -i.CompareTo (x);
|
|
|
|
throw new ArgumentException ("At least one argument has to implement IComparable interface");
|
|
}
|
|
}
|
|
}
|
|
|
|
[Serializable]
|
|
sealed class GenericComparer<T> : Comparer<T> where T : IComparable<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;
|
|
if (y == null)
|
|
return 1;
|
|
|
|
return x.CompareTo (y);
|
|
}
|
|
}
|
|
[Serializable]
|
|
sealed class ComparisonComparer<T> : Comparer<T>
|
|
{
|
|
readonly Comparison<T> comparison;
|
|
|
|
public ComparisonComparer (Comparison<T> comparison)
|
|
{
|
|
this.comparison = comparison;
|
|
}
|
|
|
|
public override int Compare (T x, T y)
|
|
{
|
|
return comparison (x, y);
|
|
}
|
|
}
|
|
}
|