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//
// System.Nullable
//
// Martin Baulig (martin@ximian.com)
//
// (C) 2004 Novell, Inc.
//
//
// 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.
//
using System.Reflection;
#if NET_2_0
using System.Collections.Generic;
#endif
using System.Runtime.CompilerServices;
#if NET_2_0
namespace System {
public static class Nullable {
public static int Compare<T> (Nullable<T> left, Nullable<T> right) where T: struct
{
IComparable icomparable = left.value as IComparable;
if (icomparable == null)
throw new ArgumentException ("At least one object must implement IComparable.");
if (left.has_value == false && right.has_value == false)
return 0;
if (!left.has_value)
return -1;
if (!right.has_value)
return 1;
return icomparable.CompareTo (right.value);
}
public static bool Equals<T> (Nullable <T> value1, Nullable<T> value2) where T: struct
{
return value1.Equals (value2);
}
public static Type GetUnderlyingType (Type nullableType)
{
if (nullableType == null)
throw new ArgumentNullException ("nullableType");
if (nullableType.IsGenericType && nullableType.GetGenericTypeDefinition () == typeof (Nullable<>))
return nullableType.GetGenericArguments ()[0];
else
return null;
}
}
[Serializable]
public struct Nullable<T> where T: struct
{
#region Sync with runtime code
internal T value;
internal bool has_value;
#endregion
public Nullable (T value)
{
this.has_value = true;
this.value = value;
}
public bool HasValue {
get { return has_value; }
}
public T Value {
get {
if (!has_value)
throw new InvalidOperationException ("Nullable object must have a value.");
return value;
}
}
public override bool Equals (object other)
{
if (other == null)
return has_value == false;
if (!(other is Nullable<T>))
return false;
return Equals ((Nullable <T>) other);
}
bool Equals (Nullable<T> other)
{
Nullable<T> no = (Nullable<T>) other;
if (no.has_value != has_value)
return false;
if (has_value == false)
return true;
return no.value.Equals (value);
}
public override int GetHashCode ()
{
if (!has_value)
return 0;
return value.GetHashCode ();
}
public T GetValueOrDefault ()
{
return GetValueOrDefault (default (T));
}
public T GetValueOrDefault (T def_value)
{
if (!has_value)
return def_value;
else
return value;
}
public override string ToString ()
{
if (has_value)
return value.ToString ();
else
return String.Empty;
}
public static implicit operator Nullable<T> (T value)
{
return new Nullable<T> (value);
}
public static explicit operator T (Nullable<T> value)
{
return value.Value;
}
// These are called by the JIT
// Ironicly, the C# code is the same for these two,
// however, on the inside they do somewhat different things
static object Box (T? o)
{
if (o == null)
return null;
return (T) o;
}
static T? Unbox (object o)
{
if (o == null)
return null;
return (T) o;
}
}
}
#endif
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