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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.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
namespace System
{
[Serializable]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public abstract class StringComparer : IComparer, IEqualityComparer, IComparer<string?>, IEqualityComparer<string?>
{
public static StringComparer InvariantCulture => CultureAwareComparer.InvariantCaseSensitiveInstance;
public static StringComparer InvariantCultureIgnoreCase => CultureAwareComparer.InvariantIgnoreCaseInstance;
public static StringComparer CurrentCulture =>
new CultureAwareComparer(CultureInfo.CurrentCulture, CompareOptions.None);
public static StringComparer CurrentCultureIgnoreCase =>
new CultureAwareComparer(CultureInfo.CurrentCulture, CompareOptions.IgnoreCase);
public static StringComparer Ordinal => OrdinalCaseSensitiveComparer.Instance;
public static StringComparer OrdinalIgnoreCase => OrdinalIgnoreCaseComparer.Instance;
// Convert a StringComparison to a StringComparer
public static StringComparer FromComparison(StringComparison comparisonType)
{
return comparisonType switch
{
StringComparison.CurrentCulture => CurrentCulture,
StringComparison.CurrentCultureIgnoreCase => CurrentCultureIgnoreCase,
StringComparison.InvariantCulture => InvariantCulture,
StringComparison.InvariantCultureIgnoreCase => InvariantCultureIgnoreCase,
StringComparison.Ordinal => Ordinal,
StringComparison.OrdinalIgnoreCase => OrdinalIgnoreCase,
_ => throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType)),
};
}
public static StringComparer Create(CultureInfo culture, bool ignoreCase)
{
ArgumentNullException.ThrowIfNull(culture);
return new CultureAwareComparer(culture, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
}
public static StringComparer Create(CultureInfo culture, CompareOptions options)
{
ArgumentNullException.ThrowIfNull(culture);
return new CultureAwareComparer(culture, options);
}
/// <summary>
/// Determines whether the specified <see cref="IEqualityComparer{String}"/> is a well-known ordinal string comparer.
/// </summary>
/// <param name="comparer">The comparer to query.</param>
/// <param name="ignoreCase">When this method returns, contains a value stating whether <paramref name="comparer"/>
/// is case-insensitive. Set to <see langword="false"/> if this method returns <see langword="false"/>.</param>
/// <returns>
/// <see langword="true"/> if <paramref name="comparer"/> is a well-known ordinal string comparer;
/// otherwise, <see langword="false"/>.
/// </returns>
/// <remarks>
/// A "well-known ordinal comparer" describes a comparer which behaves identically to <see cref="Ordinal"/>
/// when passed to <see cref="Dictionary{String, TValue}.Dictionary"/> or <see cref="HashSet{String}.HashSet"/>.
/// For example, <see cref="EqualityComparer{String}.Default"/> is a well-known ordinal comparer because
/// a <see cref="Dictionary{String, TValue}"/> given <see cref="EqualityComparer{String}.Default"/> as a constructor
/// argument will behave identically to a <see cref="Dictionary{String, TValue}"/> given <see cref="Ordinal"/>
/// as a constructor argument. If <paramref name="ignoreCase"/> is <see langword="true"/> on method exit,
/// then <paramref name="comparer"/> behaves identically to <see cref="OrdinalIgnoreCase"/> when passed to the
/// constructor of such a collection.
/// </remarks>
public static bool IsWellKnownOrdinalComparer(IEqualityComparer<string?>? comparer, out bool ignoreCase)
{
if (comparer is IInternalStringEqualityComparer internalStringComparer)
{
comparer = internalStringComparer.GetUnderlyingEqualityComparer(); // unwrap if necessary
}
switch (comparer)
{
case StringComparer stringComparer:
return stringComparer.IsWellKnownOrdinalComparerCore(out ignoreCase);
case GenericEqualityComparer<string>:
// special-case EqualityComparer<string>.Default, which is Ordinal-equivalent
ignoreCase = false;
return true;
default:
// unknown comparer
ignoreCase = default;
return false;
}
}
private protected virtual bool IsWellKnownOrdinalComparerCore(out bool ignoreCase)
{
// unless specialized comparer overrides this, we're not a well-known ordinal comparer
ignoreCase = default;
return false;
}
/// <summary>
/// Determines whether the specified <see cref="IEqualityComparer{String}"/> is a well-known culture-aware string comparer.
/// </summary>
/// <param name="comparer">The comparer to query.</param>
/// <param name="compareInfo">When this method returns, contains a value indicating which <see cref="CompareInfo"/> was used
/// to create <paramref name="comparer"/>. Set to <see langword="null"/> if this method returns <see langword="false"/>.</param>
/// <param name="compareOptions">When this method returns, contains a value indicating which <see cref="CompareOptions"/> was used
/// to create <paramref name="comparer"/>. Set to <see cref="CompareOptions.None"/> if this method returns <see langword="false"/>.</param>
/// whether <paramref name="comparer"/>
/// <returns>
/// <see langword="true"/> if <paramref name="comparer"/> is a well-known culture-aware string comparer;
/// otherwise, <see langword="false"/>.
/// </returns>
/// <remarks>
/// A "well-known culture-aware comparer" describes a comparer which is tied to a specific <see cref="CompareInfo"/> using
/// some defined <see cref="CompareOptions"/>. To create a <see cref="StringComparer"/> instance wrapped around a
/// <see cref="CompareInfo"/> and <see cref="CompareOptions"/>, use <see cref="GlobalizationExtensions.GetStringComparer(CompareInfo, CompareOptions)"/>.
/// This method returns <see langword="false"/> when given <see cref="Ordinal"/> and other non-linguistic comparers as input.
/// </remarks>
public static bool IsWellKnownCultureAwareComparer(IEqualityComparer<string?>? comparer, [NotNullWhen(true)] out CompareInfo? compareInfo, out CompareOptions compareOptions)
{
if (comparer is IInternalStringEqualityComparer internalStringComparer)
{
comparer = internalStringComparer.GetUnderlyingEqualityComparer(); // unwrap if necessary
}
if (comparer is StringComparer stringComparer)
{
return stringComparer.IsWellKnownCultureAwareComparerCore(out compareInfo, out compareOptions);
}
else
{
// unknown comparer
compareInfo = default;
compareOptions = default;
return false;
}
}
private protected virtual bool IsWellKnownCultureAwareComparerCore([NotNullWhen(true)] out CompareInfo? compareInfo, out CompareOptions compareOptions)
{
// unless specialized comparer overrides this, we're not a well-known culture-aware comparer
compareInfo = default;
compareOptions = default;
return false;
}
public int Compare(object? x, object? y)
{
if (x == y) return 0;
if (x == null) return -1;
if (y == null) return 1;
if (x is string sa)
{
if (y is string sb)
{
return Compare(sa, sb);
}
}
if (x is IComparable ia)
{
return ia.CompareTo(y);
}
throw new ArgumentException(SR.Argument_ImplementIComparable);
}
public new bool Equals(object? x, object? y)
{
if (x == y) return true;
if (x == null || y == null) return false;
if (x is string sa)
{
if (y is string sb)
{
return Equals(sa, sb);
}
}
return x.Equals(y);
}
public int GetHashCode(object obj)
{
ArgumentNullException.ThrowIfNull(obj);
if (obj is string s)
{
return GetHashCode(s);
}
return obj.GetHashCode();
}
public abstract int Compare(string? x, string? y);
public abstract bool Equals(string? x, string? y);
#pragma warning disable CS8614 // Remove warning disable when nullable attributes are respected
public abstract int GetHashCode(string obj);
#pragma warning restore CS8614
}
[Serializable]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public sealed class CultureAwareComparer : StringComparer, ISerializable
{
internal static readonly CultureAwareComparer InvariantCaseSensitiveInstance = new CultureAwareComparer(CompareInfo.Invariant, CompareOptions.None);
internal static readonly CultureAwareComparer InvariantIgnoreCaseInstance = new CultureAwareComparer(CompareInfo.Invariant, CompareOptions.IgnoreCase);
private const CompareOptions ValidCompareMaskOffFlags = ~(CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType | CompareOptions.StringSort);
private readonly CompareInfo _compareInfo; // Do not rename (binary serialization)
private readonly CompareOptions _options;
internal CultureAwareComparer(CultureInfo culture, CompareOptions options) : this(culture.CompareInfo, options) { }
internal CultureAwareComparer(CompareInfo compareInfo, CompareOptions options)
{
_compareInfo = compareInfo;
if ((options & ValidCompareMaskOffFlags) != 0)
{
throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
}
_options = options;
}
private CultureAwareComparer(SerializationInfo info, StreamingContext context)
{
_compareInfo = (CompareInfo)info.GetValue("_compareInfo", typeof(CompareInfo))!;
bool ignoreCase = info.GetBoolean("_ignoreCase");
object? obj = info.GetValueNoThrow("_options", typeof(CompareOptions));
if (obj != null)
_options = (CompareOptions)obj;
// fix up the _options value in case we are getting old serialized object not having _options
_options |= ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None;
}
public override int Compare(string? x, string? y)
{
if (ReferenceEquals(x, y)) return 0;
if (x == null) return -1;
if (y == null) return 1;
return _compareInfo.Compare(x, y, _options);
}
public override bool Equals(string? x, string? y)
{
if (ReferenceEquals(x, y)) return true;
if (x == null || y == null) return false;
return _compareInfo.Compare(x, y, _options) == 0;
}
public override int GetHashCode(string obj)
{
ArgumentNullException.ThrowIfNull(obj);
return _compareInfo.GetHashCode(obj, _options);
}
// Equals method for the comparer itself.
public override bool Equals([NotNullWhen(true)] object? obj)
{
return
obj is CultureAwareComparer comparer &&
_options == comparer._options &&
_compareInfo.Equals(comparer._compareInfo);
}
public override int GetHashCode()
{
return _compareInfo.GetHashCode() ^ ((int)_options & 0x7FFFFFFF);
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.AddValue("_compareInfo", _compareInfo);
info.AddValue("_options", _options);
info.AddValue("_ignoreCase", (_options & CompareOptions.IgnoreCase) != 0);
}
private protected override bool IsWellKnownCultureAwareComparerCore([NotNullWhen(true)] out CompareInfo? compareInfo, out CompareOptions compareOptions)
{
compareInfo = _compareInfo;
compareOptions = _options;
return true;
}
}
[Serializable]
[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public class OrdinalComparer : StringComparer
{
private readonly bool _ignoreCase; // Do not rename (binary serialization)
internal OrdinalComparer(bool ignoreCase)
{
_ignoreCase = ignoreCase;
}
public override int Compare(string? x, string? y)
{
if (ReferenceEquals(x, y))
return 0;
if (x == null)
return -1;
if (y == null)
return 1;
if (_ignoreCase)
{
return Globalization.Ordinal.CompareStringIgnoreCase(ref x.GetRawStringData(), x.Length, ref y.GetRawStringData(), y.Length);
}
return string.CompareOrdinal(x, y);
}
public override bool Equals(string? x, string? y)
{
if (ReferenceEquals(x, y))
return true;
if (x == null || y == null)
return false;
if (_ignoreCase)
{
if (x.Length != y.Length)
{
return false;
}
return Globalization.Ordinal.EqualsIgnoreCase(ref x.GetRawStringData(), ref y.GetRawStringData(), x.Length);
}
return x.Equals(y);
}
public override int GetHashCode(string obj)
{
if (obj == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
}
if (_ignoreCase)
{
return obj.GetHashCodeOrdinalIgnoreCase();
}
return obj.GetHashCode();
}
// Equals method for the comparer itself.
public override bool Equals([NotNullWhen(true)] object? obj)
{
if (!(obj is OrdinalComparer comparer))
{
return false;
}
return this._ignoreCase == comparer._ignoreCase;
}
public override int GetHashCode()
{
int hashCode = nameof(OrdinalComparer).GetHashCode();
return _ignoreCase ? (~hashCode) : hashCode;
}
private protected override bool IsWellKnownOrdinalComparerCore(out bool ignoreCase)
{
ignoreCase = _ignoreCase;
return true;
}
}
[Serializable]
internal sealed class OrdinalCaseSensitiveComparer : OrdinalComparer, ISerializable
{
internal static readonly OrdinalCaseSensitiveComparer Instance = new OrdinalCaseSensitiveComparer();
private OrdinalCaseSensitiveComparer() : base(false)
{
}
public override int Compare(string? x, string? y) => string.CompareOrdinal(x, y);
public override bool Equals(string? x, string? y) => string.Equals(x, y);
public override int GetHashCode(string obj)
{
if (obj == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
}
return obj.GetHashCode();
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.SetType(typeof(OrdinalComparer));
info.AddValue("_ignoreCase", false);
}
}
[Serializable]
internal sealed class OrdinalIgnoreCaseComparer : OrdinalComparer, ISerializable
{
internal static readonly OrdinalIgnoreCaseComparer Instance = new OrdinalIgnoreCaseComparer();
private OrdinalIgnoreCaseComparer() : base(true)
{
}
public override int Compare(string? x, string? y)
{
if (ReferenceEquals(x, y))
{
return 0;
}
if (x == null)
{
return -1;
}
if (y == null)
{
return 1;
}
return Globalization.Ordinal.CompareStringIgnoreCase(ref x.GetRawStringData(), x.Length, ref y.GetRawStringData(), y.Length);
}
public override bool Equals(string? x, string? y)
{
if (ReferenceEquals(x, y))
{
return true;
}
if (x is null || y is null)
{
return false;
}
if (x.Length != y.Length)
{
return false;
}
return Globalization.Ordinal.EqualsIgnoreCase(ref x.GetRawStringData(), ref y.GetRawStringData(), x.Length);
}
public override int GetHashCode(string obj)
{
if (obj == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
}
return obj.GetHashCodeOrdinalIgnoreCase();
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.SetType(typeof(OrdinalComparer));
info.AddValue("_ignoreCase", true);
}
}
}
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