|
// 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;
using System.Runtime.CompilerServices;
namespace System.Collections.Frozen
{
/// <summary>Provides a frozen dictionary implementation where strings are grouped by their lengths.</summary>
internal sealed partial class LengthBucketsFrozenDictionary<TValue> : FrozenDictionary<string, TValue>
{
private readonly int[] _lengthBuckets;
private readonly int _minLength;
private readonly string[] _keys;
private readonly TValue[] _values;
private readonly bool _ignoreCase;
private LengthBucketsFrozenDictionary(
string[] keys, TValue[] values, int[] lengthBuckets, int minLength, IEqualityComparer<string> comparer)
: base(comparer)
{
Debug.Assert(comparer == EqualityComparer<string>.Default || comparer == StringComparer.Ordinal || comparer == StringComparer.OrdinalIgnoreCase);
_keys = keys;
_values = values;
_lengthBuckets = lengthBuckets;
_minLength = minLength;
_ignoreCase = ReferenceEquals(comparer, StringComparer.OrdinalIgnoreCase);
}
internal static LengthBucketsFrozenDictionary<TValue>? CreateLengthBucketsFrozenDictionaryIfAppropriate(
string[] keys, TValue[] values, IEqualityComparer<string> comparer, int minLength, int maxLength)
{
Debug.Assert(keys.Length != 0 && keys.Length == values.Length);
int[]? lengthBuckets = LengthBuckets.CreateLengthBucketsArrayIfAppropriate(keys, comparer, minLength, maxLength);
if (lengthBuckets is null)
{
return null;
}
return new LengthBucketsFrozenDictionary<TValue>(keys, values, lengthBuckets, minLength, comparer);
}
/// <inheritdoc />
private protected override string[] KeysCore => _keys;
/// <inheritdoc />
private protected override TValue[] ValuesCore => _values;
/// <inheritdoc />
private protected override Enumerator GetEnumeratorCore() => new Enumerator(_keys, _values);
/// <inheritdoc />
private protected override int CountCore => _keys.Length;
/// <inheritdoc />
private protected override ref readonly TValue GetValueRefOrNullRefCore(string key)
{
// If the length doesn't have an associated bucket, the key isn't in the dictionary.
int bucketIndex = (key.Length - _minLength) * LengthBuckets.MaxPerLength;
int bucketEndIndex = bucketIndex + LengthBuckets.MaxPerLength;
int[] lengthBuckets = _lengthBuckets;
if (bucketIndex >= 0 && bucketEndIndex <= lengthBuckets.Length)
{
string[] keys = _keys;
TValue[] values = _values;
if (!_ignoreCase)
{
for (; bucketIndex < bucketEndIndex; bucketIndex++)
{
int index = lengthBuckets[bucketIndex];
if ((uint)index < (uint)keys.Length)
{
if (key == keys[index])
{
return ref values[index];
}
}
else
{
// -1 is used to indicate a null, when it's casted to unit it becomes > keys.Length
break;
}
}
}
else
{
for (; bucketIndex < bucketEndIndex; bucketIndex++)
{
int index = lengthBuckets[bucketIndex];
if ((uint)index < (uint)keys.Length)
{
if (StringComparer.OrdinalIgnoreCase.Equals(key, keys[index]))
{
return ref values[index];
}
}
else
{
// -1 is used to indicate a null, when it's casted to unit it becomes > keys.Length
break;
}
}
}
}
return ref Unsafe.NullRef<TValue>();
}
}
}
|