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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Runtime.CompilerServices;
using System.Diagnostics;
namespace System.Collections.Generic
{
public abstract partial class EqualityComparer<T> : IEqualityComparer, IEqualityComparer<T>
{
// To minimize generic instantiation overhead of creating the comparer per type, we keep the generic portion of the code as small
// as possible and define most of the creation logic in a non-generic class.
public static EqualityComparer<T> Default { [Intrinsic] get; } = (EqualityComparer<T>)ComparerHelpers.CreateDefaultEqualityComparer(typeof(T));
}
public sealed partial class GenericEqualityComparer<T> : EqualityComparer<T> where T : IEquatable<T>?
{
internal override int IndexOf(T[] array, T value, int startIndex, int count)
{
int endIndex = startIndex + count;
if (value == null)
{
for (int i = startIndex; i < endIndex; i++)
{
if (array[i] == null) return i;
}
}
else
{
for (int i = startIndex; i < endIndex; i++)
{
if (array[i] != null && array[i]!.Equals(value)) return i;
}
}
return -1;
}
internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
{
int endIndex = startIndex - count + 1;
if (value == null)
{
for (int i = startIndex; i >= endIndex; i--)
{
if (array[i] == null) return i;
}
}
else
{
for (int i = startIndex; i >= endIndex; i--)
{
if (array[i] != null && array[i]!.Equals(value)) return i;
}
}
return -1;
}
}
public sealed partial class NullableEqualityComparer<T> : EqualityComparer<T?> where T : struct
{
internal override int IndexOf(T?[] array, T? value, int startIndex, int count)
{
int endIndex = startIndex + count;
if (!value.HasValue)
{
for (int i = startIndex; i < endIndex; i++)
{
if (!array[i].HasValue) return i;
}
}
else
{
for (int i = startIndex; i < endIndex; i++)
{
if (array[i].HasValue && EqualityComparer<T>.Default.Equals(array[i].value, value.value)) return i;
}
}
return -1;
}
internal override int LastIndexOf(T?[] array, T? value, int startIndex, int count)
{
int endIndex = startIndex - count + 1;
if (!value.HasValue)
{
for (int i = startIndex; i >= endIndex; i--)
{
if (!array[i].HasValue) return i;
}
}
else
{
for (int i = startIndex; i >= endIndex; i--)
{
if (array[i].HasValue && EqualityComparer<T>.Default.Equals(array[i].value, value.value)) return i;
}
}
return -1;
}
}
public sealed partial class ObjectEqualityComparer<T> : EqualityComparer<T>
{
internal override int IndexOf(T[] array, T value, int startIndex, int count)
{
int endIndex = startIndex + count;
if (value == null)
{
for (int i = startIndex; i < endIndex; i++)
{
if (array[i] == null) return i;
}
}
else
{
for (int i = startIndex; i < endIndex; i++)
{
if (array[i] != null && array[i]!.Equals(value)) return i;
}
}
return -1;
}
internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
{
int endIndex = startIndex - count + 1;
if (value == null)
{
for (int i = startIndex; i >= endIndex; i--)
{
if (array[i] == null) return i;
}
}
else
{
for (int i = startIndex; i >= endIndex; i--)
{
if (array[i] != null && array[i]!.Equals(value)) return i;
}
}
return -1;
}
}
public sealed partial class ByteEqualityComparer : EqualityComparer<byte>
{
#if DEBUG
internal override int IndexOf(byte[] array, byte value, int startIndex, int count)
{
Debug.Fail("Should not get here.");
return -1;
}
internal override int LastIndexOf(byte[] array, byte value, int startIndex, int count)
{
Debug.Fail("Should not get here.");
return -1;
}
#endif
}
public sealed partial class EnumEqualityComparer<T> : EqualityComparer<T> where T : struct, Enum
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public override bool Equals(T x, T y)
{
return System.Runtime.CompilerServices.RuntimeHelpers.EnumEquals(x, y);
}
internal override int IndexOf(T[] array, T value, int startIndex, int count)
{
int endIndex = startIndex + count;
for (int i = startIndex; i < endIndex; i++)
{
if (System.Runtime.CompilerServices.RuntimeHelpers.EnumEquals(array[i], value)) return i;
}
return -1;
}
internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
{
int endIndex = startIndex - count + 1;
for (int i = startIndex; i >= endIndex; i--)
{
if (System.Runtime.CompilerServices.RuntimeHelpers.EnumEquals(array[i], value)) return i;
}
return -1;
}
}
}
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