CacheDict.cs

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using System.Diagnostics.CodeAnalysis;
using System.Threading;
 
namespace System.Dynamic.Utils;
 
internal sealed class CacheDict<TKey, TValue>
{
    private sealed class Entry
    {
        internal readonly int _hash;
 
        internal readonly TKey _key;
 
        internal readonly TValue _value;
 
        internal Entry(int hash, TKey key, TValue value)
        {
            _hash = hash;
            _key = key;
            _value = value;
        }
    }
 
    private readonly int _mask;
 
    private readonly Entry[] _entries;
 
    internal TValue this[TKey key]
    {
        set
        {
            Add(key, value);
        }
    }
 
    internal CacheDict(int size)
    {
        int num = AlignSize(size);
        _mask = num - 1;
        _entries = new Entry[num];
    }
 
    private static int AlignSize(int size)
    {
        size--;
        size |= size >> 1;
        size |= size >> 2;
        size |= size >> 4;
        size |= size >> 8;
        size |= size >> 16;
        size++;
        return size;
    }
 
    internal bool TryGetValue(TKey key, [MaybeNullWhen(false)] out TValue value)
    {
        int hashCode = key.GetHashCode();
        int num = hashCode & _mask;
        Entry entry = Volatile.Read(ref _entries[num]);
        if (entry != null && entry._hash == hashCode && entry._key.Equals(key))
        {
            value = entry._value;
            return true;
        }
        value = default(TValue);
        return false;
    }
 
    internal void Add(TKey key, TValue value)
    {
        int hashCode = key.GetHashCode();
        int num = hashCode & _mask;
        Entry entry = Volatile.Read(ref _entries[num]);
        if (entry == null || entry._hash != hashCode || !entry._key.Equals(key))
        {
            Volatile.Write(ref _entries[num], new Entry(hashCode, key, value));
        }
    }
}