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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.Generic;
using System.Diagnostics;
namespace System.Collections.Frozen
{
/// <summary>Provides a frozen set implementation where strings are grouped by their lengths.</summary>
internal sealed partial class LengthBucketsFrozenSet : FrozenSetInternalBase<string, LengthBucketsFrozenSet.GSW>
{
private readonly int[] _lengthBuckets;
private readonly int _minLength;
private readonly string[] _items;
private readonly bool _ignoreCase;
private LengthBucketsFrozenSet(
string[] items, int[] lengthBuckets, int minLength, IEqualityComparer<string> comparer)
: base(comparer)
{
Debug.Assert(comparer == EqualityComparer<string>.Default || comparer == StringComparer.Ordinal || comparer == StringComparer.OrdinalIgnoreCase);
_items = items;
_lengthBuckets = lengthBuckets;
_minLength = minLength;
_ignoreCase = ReferenceEquals(comparer, StringComparer.OrdinalIgnoreCase);
}
internal static LengthBucketsFrozenSet? CreateLengthBucketsFrozenSetIfAppropriate(
string[] items, IEqualityComparer<string> comparer, int minLength, int maxLength)
{
Debug.Assert(items.Length != 0);
int[]? lengthBuckets = LengthBuckets.CreateLengthBucketsArrayIfAppropriate(items, comparer, minLength, maxLength);
if (lengthBuckets is null)
{
return null;
}
return new LengthBucketsFrozenSet(items, lengthBuckets, minLength, comparer);
}
/// <inheritdoc />
private protected override string[] ItemsCore => _items;
/// <inheritdoc />
private protected override Enumerator GetEnumeratorCore() => new Enumerator(_items);
/// <inheritdoc />
private protected override int CountCore => _items.Length;
/// <inheritdoc />
private protected override int FindItemIndex(string? item)
{
if (item is not null) // this implementation won't be constructed from null values, but Contains may still be called with one
{
// If the length doesn't have an associated bucket, the key isn't in the dictionary.
int bucketIndex = (item.Length - _minLength) * LengthBuckets.MaxPerLength;
int bucketEndIndex = bucketIndex + LengthBuckets.MaxPerLength;
int[] lengthBuckets = _lengthBuckets;
if (bucketIndex >= 0 && bucketEndIndex <= lengthBuckets.Length)
{
string[] items = _items;
if (!_ignoreCase)
{
for (; bucketIndex < bucketEndIndex; bucketIndex++)
{
int index = lengthBuckets[bucketIndex];
if ((uint)index < (uint)items.Length)
{
if (item == items[index])
{
return index;
}
}
else
{
// -1 is used to indicate a null, when it's casted to uint it becomes > items.Length
break;
}
}
}
else
{
for (; bucketIndex < bucketEndIndex; bucketIndex++)
{
int index = lengthBuckets[bucketIndex];
if ((uint)index < (uint)items.Length)
{
if (StringComparer.OrdinalIgnoreCase.Equals(item, items[index]))
{
return index;
}
}
else
{
// -1 is used to indicate a null, when it's casted to unit it becomes > items.Length
break;
}
}
}
}
}
return -1;
}
internal struct GSW : IGenericSpecializedWrapper
{
private LengthBucketsFrozenSet _set;
public void Store(FrozenSet<string> set) => _set = (LengthBucketsFrozenSet)set;
public int Count => _set.Count;
public IEqualityComparer<string> Comparer => _set.Comparer;
public int FindItemIndex(string item) => _set.FindItemIndex(item);
public Enumerator GetEnumerator() => _set.GetEnumerator();
}
}
}
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