// ==++==
//
//
// Copyright (c) 2006 Microsoft Corporation. All rights reserved.
//
// The use and distribution terms for this software are contained in the file
// named license.txt, which can be found in the root of this distribution.
// By using this software in any fashion, you are agreeing to be bound by the
// terms of this license.
//
// You must not remove this notice, or any other, from this software.
//
//
// ==--==
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<T> : IEqualityComparer, IEqualityComparer<T>
{
static EqualityComparer<T> defaultComparer;
public static EqualityComparer<T> Default {
get {
EqualityComparer<T> comparer = defaultComparer;
if (comparer == null) {
comparer = CreateComparer();
defaultComparer = comparer;
}
return comparer;
}
}
private static EqualityComparer<T> CreateComparer() {
Type t = typeof(T);
// Specialize type byte for performance reasons
if (t == typeof(byte)) {
return (EqualityComparer<T>)(object)(new ByteEqualityComparer());
}
// If T implements IEquatable<T> return a GenericEqualityComparer<T>
if (typeof(IEquatable<T>).IsAssignableFrom(t)) {
//return (EqualityComparer<T>)Activator.CreateInstance(typeof(GenericEqualityComparer<>).MakeGenericType(t));
return (EqualityComparer<T>)(typeof(GenericEqualityComparer<int>).TypeHandle.CreateInstanceForAnotherGenericParameter(t));
}
// If T is a Nullable<U> where U implements IEquatable<U> return a NullableEqualityComparer<U>
if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>)) {
Type u = t.GetGenericArguments()[0];
if (typeof(IEquatable<>).MakeGenericType(u).IsAssignableFrom(u)) {
//return (EqualityComparer<T>)Activator.CreateInstance(typeof(NullableEqualityComparer<>).MakeGenericType(u));
return (EqualityComparer<T>)(typeof(NullableEqualityComparer<int>).TypeHandle.CreateInstanceForAnotherGenericParameter(u));
}
}
// Otherwise return an ObjectEqualityComparer<T>
return new ObjectEqualityComparer<T>();
}
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<T>.Equals(T) instead of Object.Equals(Object)
[Serializable()]
internal class GenericEqualityComparer<T>: EqualityComparer<T> where T: IEquatable<T>
{
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<T> comparer = obj as GenericEqualityComparer<T>;
return comparer != null;
}
public override int GetHashCode() {
return this.GetType().Name.GetHashCode();
}
}
[Serializable()]
internal class NullableEqualityComparer<T> : EqualityComparer<Nullable<T>> where T : struct, IEquatable<T>
{
public override bool Equals(Nullable<T> x, Nullable<T> 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<T> obj) {
return obj.GetHashCode();
}
internal override int IndexOf(Nullable<T>[] array, Nullable<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 && array[i].value.Equals(value.value)) return i;
}
}
return -1;
}
internal override int LastIndexOf(Nullable<T>[] array, Nullable<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 && array[i].value.Equals(value.value)) return i;
}
}
return -1;
}
// Equals method for the comparer itself.
public override bool Equals(Object obj){
NullableEqualityComparer<T> comparer = obj as NullableEqualityComparer<T>;
return comparer != null;
}
public override int GetHashCode() {
return this.GetType().Name.GetHashCode();
}
}
[Serializable()]
internal class ObjectEqualityComparer<T>: EqualityComparer<T>
{
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<T> comparer = obj as ObjectEqualityComparer<T>;
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<byte>
{
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();
}
}
}
