NameTable.cs

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namespace System.Xml;
 
public class NameTable : XmlNameTable
{
    private sealed class Entry
    {
        internal string str;
 
        internal int hashCode;
 
        internal Entry next;
 
        internal Entry(string str, int hashCode, Entry next)
        {
            this.str = str;
            this.hashCode = hashCode;
            this.next = next;
        }
    }
 
    private Entry[] _entries;
 
    private int _count;
 
    private int _mask;
 
    public NameTable()
    {
        _mask = 31;
        _entries = new Entry[_mask + 1];
    }
 
    public override string Add(string key)
    {
        if (key == null)
        {
            throw new ArgumentNullException("key");
        }
        if (key.Length == 0)
        {
            return string.Empty;
        }
        int num = ComputeHash32(key);
        for (Entry entry = _entries[num & _mask]; entry != null; entry = entry.next)
        {
            if (entry.hashCode == num && entry.str.Equals(key))
            {
                return entry.str;
            }
        }
        return AddEntry(key, num);
    }
 
    public override string Add(char[] key, int start, int len)
    {
        if (len == 0)
        {
            return string.Empty;
        }
        if (start >= key.Length || start < 0 || (long)start + (long)len > key.Length)
        {
            throw new IndexOutOfRangeException();
        }
        if (len < 0)
        {
            throw new ArgumentOutOfRangeException("len");
        }
        int hashCode = string.GetHashCode(key.AsSpan(start, len));
        for (Entry entry = _entries[hashCode & _mask]; entry != null; entry = entry.next)
        {
            if (entry.hashCode == hashCode && entry.str.AsSpan().SequenceEqual(key.AsSpan(start, len)))
            {
                return entry.str;
            }
        }
        return AddEntry(new string(key, start, len), hashCode);
    }
 
    public override string? Get(string value)
    {
        if (value == null)
        {
            throw new ArgumentNullException("value");
        }
        if (value.Length == 0)
        {
            return string.Empty;
        }
        int num = ComputeHash32(value);
        for (Entry entry = _entries[num & _mask]; entry != null; entry = entry.next)
        {
            if (entry.hashCode == num && entry.str.Equals(value))
            {
                return entry.str;
            }
        }
        return null;
    }
 
    public override string? Get(char[] key, int start, int len)
    {
        if (len == 0)
        {
            return string.Empty;
        }
        if (start >= key.Length || start < 0 || (long)start + (long)len > key.Length)
        {
            throw new IndexOutOfRangeException();
        }
        if (len < 0)
        {
            return null;
        }
        int hashCode = string.GetHashCode(key.AsSpan(start, len));
        for (Entry entry = _entries[hashCode & _mask]; entry != null; entry = entry.next)
        {
            if (entry.hashCode == hashCode && entry.str.AsSpan().SequenceEqual(key.AsSpan(start, len)))
            {
                return entry.str;
            }
        }
        return null;
    }
 
    internal string GetOrAddEntry(string str, int hashCode)
    {
        for (Entry entry = _entries[hashCode & _mask]; entry != null; entry = entry.next)
        {
            if (entry.hashCode == hashCode && entry.str.Equals(str))
            {
                return entry.str;
            }
        }
        return AddEntry(str, hashCode);
    }
 
    internal static int ComputeHash32(string key)
    {
        return string.GetHashCode(key.AsSpan());
    }
 
    private string AddEntry(string str, int hashCode)
    {
        int num = hashCode & _mask;
        Entry entry = new Entry(str, hashCode, _entries[num]);
        _entries[num] = entry;
        if (_count++ == _mask)
        {
            Grow();
        }
        return entry.str;
    }
 
    private void Grow()
    {
        int num = _mask * 2 + 1;
        Entry[] entries = _entries;
        Entry[] array = new Entry[num + 1];
        for (int i = 0; i < entries.Length; i++)
        {
            Entry entry = entries[i];
            while (entry != null)
            {
                int num2 = entry.hashCode & num;
                Entry next = entry.next;
                entry.next = array[num2];
                array[num2] = entry;
                entry = next;
            }
        }
        _entries = array;
        _mask = num;
    }
}