47 lines
1.5 KiB
C#
47 lines
1.5 KiB
C#
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using System.Runtime.CompilerServices;
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namespace System.Collections.Generic
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{
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partial class Comparer<T>
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{
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static volatile Comparer<T> defaultComparer;
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public static Comparer<T> Default {
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get {
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Comparer<T> comparer = defaultComparer;
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if (comparer == null) {
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comparer = CreateComparer();
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defaultComparer = comparer;
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}
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return comparer;
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}
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}
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static Comparer<T> CreateComparer() {
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RuntimeType t = (RuntimeType)typeof(T);
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if (typeof(IComparable<T>).IsAssignableFrom(t))
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return (Comparer<T>)RuntimeType.CreateInstanceForAnotherGenericParameter (typeof(GenericComparer<>), t);
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// If T is a Nullable<U> where U implements IComparable<U> return a NullableComparer<U>
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if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>)) {
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RuntimeType u = (RuntimeType)t.GetGenericArguments()[0];
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if (typeof(IComparable<>).MakeGenericType (u).IsAssignableFrom (u))
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return (Comparer<T>)RuntimeType.CreateInstanceForAnotherGenericParameter (typeof(NullableComparer<>), u);
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}
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if (t.IsEnum)
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return (Comparer<T>)RuntimeType.CreateInstanceForAnotherGenericParameter (typeof(EnumComparer<>), t);
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// Otherwise return an ObjectComparer<T>
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return new ObjectComparer<T> ();
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}
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}
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partial class EnumComparer<T>
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{
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[MethodImpl (MethodImplOptions.AggressiveInlining)]
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public override int Compare (T x, T y) => JitHelpers.EnumCompareTo (x, y);
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}
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}
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