Rename because it is ordered

PersistentOrderedMap/KeyStrategies.cs

@@ -0,0 +1,67 @@
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+
+namespace PersistentOrderedMap;
+
+using System;
+using System.Buffers.Binary;
+using System.Runtime.CompilerServices;
+
+public interface IKeyStrategy<K>
+{
+    int Compare(K x, K y);
+    long GetPrefix(K key);
+
+    bool UsesPrefixes => true;
+
+    bool IsLossless => false;
+    bool UseBinarySearch => false;
+}
+
+
+
+
+public struct UnicodeStrategy : IKeyStrategy<string>
+{
+    
+    public bool UsesPrefixes => true;
+    public bool UseBinarySearch => false;
+    public bool IsLossLess => false;
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public int Compare(string? x, string? y) => string.CompareOrdinal(x, y);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public long GetPrefix(string key)
+    {
+        if (string.IsNullOrEmpty(key)) return long.MinValue;
+
+        // 1. Prepare Buffer (8 bytes)
+        // stackalloc is virtually free (pointer bump)
+        Span<byte> utf8Bytes = stackalloc byte[8];
+
+        // 2. Transcode (The "Safe" Magic)
+        // This intrinsic handles ASCII efficiently and converts Surrogates/Chinese 
+        // into bytes that maintain the correct "Magnitude" (Sort Order).
+        // Invalid surrogates become 0xEF (Replacement Char), which sorts > ASCII.
+        System.Text.Unicode.Utf8.FromUtf16(
+            key.AsSpan(0, Math.Min(key.Length, 8)),
+            utf8Bytes,
+            out _,
+            out _,
+            replaceInvalidSequences: true); // True ensures we get 0xEF for broken chars
+
+        // 3. Load as Big Endian Long
+        long packed = BinaryPrimitives.ReadInt64BigEndian(utf8Bytes);
+
+        // 4. Sign Toggle
+        // Maps the byte range 0x00..0xFF to the signed long range Min..Max
+        // Essential for the < and > operators to work correctly.
+        return packed ^ unchecked((long)0x8080808080808080);
+    }
+
+}
+
+
+