Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Collections / Generic / EqualityComparer.cs / 1 / EqualityComparer.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== using System; using System.Collections; using System.Collections.Generic; namespace System.Collections.Generic { using System.Globalization; using System.Runtime.CompilerServices; [Serializable()] [TypeDependencyAttribute("System.Collections.Generic.GenericEqualityComparer`1")] public abstract class EqualityComparer: IEqualityComparer, IEqualityComparer { static EqualityComparer defaultComparer; public static EqualityComparer Default { get { EqualityComparer comparer = defaultComparer; if (comparer == null) { comparer = CreateComparer(); defaultComparer = comparer; } return comparer; } } private static EqualityComparer CreateComparer() { Type t = typeof(T); // Specialize type byte for performance reasons if (t == typeof(byte)) { return (EqualityComparer )(object)(new ByteEqualityComparer()); } // If T implements IEquatable return a GenericEqualityComparer if (typeof(IEquatable ).IsAssignableFrom(t)) { //return (EqualityComparer )Activator.CreateInstance(typeof(GenericEqualityComparer<>).MakeGenericType(t)); return (EqualityComparer )(typeof(GenericEqualityComparer ).TypeHandle.CreateInstanceForAnotherGenericParameter(t)); } // If T is a Nullable where U implements IEquatable return a NullableEqualityComparer if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>)) { Type u = t.GetGenericArguments()[0]; if (typeof(IEquatable<>).MakeGenericType(u).IsAssignableFrom(u)) { //return (EqualityComparer )Activator.CreateInstance(typeof(NullableEqualityComparer<>).MakeGenericType(u)); return (EqualityComparer )(typeof(NullableEqualityComparer ).TypeHandle.CreateInstanceForAnotherGenericParameter(u)); } } // Otherwise return an ObjectEqualityComparer return new ObjectEqualityComparer (); } public abstract bool Equals(T x, T y); public abstract int GetHashCode(T obj); internal virtual int IndexOf(T[] array, T value, int startIndex, int count) { int endIndex = startIndex + count; for (int i = startIndex; i < endIndex; i++) { if (Equals(array[i], value)) return i; } return -1; } internal virtual int LastIndexOf(T[] array, T value, int startIndex, int count) { int endIndex = startIndex - count + 1; for (int i = startIndex; i >= endIndex; i--) { if (Equals(array[i], value)) return i; } return -1; } int IEqualityComparer.GetHashCode(object obj) { if (obj == null) return 0; if (obj is T) return GetHashCode((T)obj); ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison); return 0; } bool IEqualityComparer.Equals(object x, object y) { if (x == y) return true; if (x == null || y == null) return false; if ((x is T) && (y is T)) return Equals((T)x, (T)y); ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison); return false; } } // The methods in this class look identical to the inherited methods, but the calls // to Equal bind to IEquatable .Equals(T) instead of Object.Equals(Object) [Serializable()] internal class GenericEqualityComparer : EqualityComparer where T: IEquatable { public override bool Equals(T x, T y) { if (x != null) { if (y != null) return x.Equals(y); return false; } if (y != null) return false; return true; } public override int GetHashCode(T obj) { if (obj == null) return 0; return obj.GetHashCode(); } 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; } // Equals method for the comparer itself. public override bool Equals(Object obj){ GenericEqualityComparer comparer = obj as GenericEqualityComparer ; return comparer != null; } public override int GetHashCode() { return this.GetType().Name.GetHashCode(); } } [Serializable()] internal class NullableEqualityComparer : EqualityComparer > where T : struct, IEquatable { public override bool Equals(Nullable x, Nullable y) { if (x.HasValue) { if (y.HasValue) return x.value.Equals(y.value); return false; } if (y.HasValue) return false; return true; } public override int GetHashCode(Nullable obj) { return obj.GetHashCode(); } internal override int IndexOf(Nullable [] array, Nullable 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 && array[i].value.Equals(value.value)) return i; } } return -1; } internal override int LastIndexOf(Nullable [] array, Nullable 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 && array[i].value.Equals(value.value)) return i; } } return -1; } // Equals method for the comparer itself. public override bool Equals(Object obj){ NullableEqualityComparer comparer = obj as NullableEqualityComparer ; return comparer != null; } public override int GetHashCode() { return this.GetType().Name.GetHashCode(); } } [Serializable()] internal class ObjectEqualityComparer : EqualityComparer { public override bool Equals(T x, T y) { if (x != null) { if (y != null) return x.Equals(y); return false; } if (y != null) return false; return true; } public override int GetHashCode(T obj) { if (obj == null) return 0; return obj.GetHashCode(); } 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; } // Equals method for the comparer itself. public override bool Equals(Object obj){ ObjectEqualityComparer comparer = obj as ObjectEqualityComparer ; return comparer != null; } public override int GetHashCode() { return this.GetType().Name.GetHashCode(); } } // Performance of IndexOf on byte array is very important for some scenarios. // We will call the C runtime function memchr, which is optimized. [Serializable()] internal class ByteEqualityComparer: EqualityComparer { public override bool Equals(byte x, byte y) { return x == y; } public override int GetHashCode(byte b) { return b.GetHashCode(); } internal unsafe override int IndexOf(byte[] array, byte value, int startIndex, int count) { if (array==null) throw new ArgumentNullException("array"); if (startIndex < 0) throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index")); if (count < 0) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_Count")); if (count > array.Length - startIndex) throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); if (count == 0) return -1; fixed (byte* pbytes = array) { return Buffer.IndexOfByte(pbytes, value, startIndex, count); } } internal override int LastIndexOf(byte[] array, byte value, int startIndex, int count) { int endIndex = startIndex - count + 1; for (int i = startIndex; i >= endIndex; i--) { if (array[i] == value) return i; } return -1; } // Equals method for the comparer itself. public override bool Equals(Object obj){ ByteEqualityComparer comparer = obj as ByteEqualityComparer; return comparer != null; } public override int GetHashCode() { return this.GetType().Name.GetHashCode(); } } }
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