Added Utf16Utf8Dictionary.

Author: Bobris

BTDB/Collections/DerivedUtf16Utf8Dictionary.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace BTDB.Collections;
+
+public readonly struct DerivedUtf16Utf8Dictionary<TDerivedValue, TValue>
+{
+    readonly Utf16Utf8Dictionary<TValue> _parent;
+    readonly TDerivedValue[] _values;
+
+    public DerivedUtf16Utf8Dictionary(Utf16Utf8Dictionary<TValue> parent)
+    {
+        _parent = parent;
+        _values = new TDerivedValue[parent.Count];
+    }
+
+    public Utf16Utf8Dictionary<TValue> Parent => _parent;
+
+    public ref TDerivedValue ValueRef(uint index)
+    {
+        return ref _values[index];
+    }
+
+    public ref TDerivedValue GetValueRef(ReadOnlySpan<char> key, out bool found)
+    {
+        var index = _parent.GetIndex(key);
+        if (index >= 0)
+        {
+            found = true;
+            return ref _values[(uint)index];
+        }
+
+        found = false;
+        return ref Unsafe.NullRef<TDerivedValue>();
+    }
+
+    public ref TDerivedValue GetValueRef(ReadOnlySpan<byte> key, out bool found)
+    {
+        var index = _parent.GetIndex(key);
+        if (index >= 0)
+        {
+            found = true;
+            return ref _values[(uint)index];
+        }
+
+        found = false;
+        return ref Unsafe.NullRef<TDerivedValue>();
+    }
+
+    public bool TryGetValue(ReadOnlySpan<char> key, out TDerivedValue value)
+    {
+        var index = _parent.GetIndex(key);
+        if (index >= 0)
+        {
+            value = _values[(uint)index];
+            return true;
+        }
+
+        value = default;
+        return false;
+    }
+
+    public bool TryGetValue(ReadOnlySpan<byte> key, out TDerivedValue value)
+    {
+        var index = _parent.GetIndex(key);
+        if (index >= 0)
+        {
+            value = _values[(uint)index];
+            return true;
+        }
+
+        value = default;
+        return false;
+    }
+}