From fe27a0577895b0f5e831988ea4485cd2fabff83f Mon Sep 17 00:00:00 2001
From: "COMBINATION\\ano" <alexander.nordh@combination.se>
Date: Wed, 15 Feb 2023 13:38:09 +0100
Subject: [PATCH] Use bytes for hash code generation instead of creating string
 and calculate hash code from string object

---
 src/Combination.StringPools/PooledUtf8String.cs |  2 +-
 src/Combination.StringPools/Utf8StringPool.cs   | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/Combination.StringPools/PooledUtf8String.cs b/src/Combination.StringPools/PooledUtf8String.cs
index 5f878a1..bfaf80f 100644
--- a/src/Combination.StringPools/PooledUtf8String.cs
+++ b/src/Combination.StringPools/PooledUtf8String.cs
@@ -39,7 +39,7 @@ public override bool Equals(object? obj)
     }
 
     public override int GetHashCode()
-        => unchecked((int)StringHash.Compute(Utf8StringPool.Get(handle)));
+        => unchecked((int)StringHash.Compute(Utf8StringPool.GetBytes(handle)));
 
     public override string ToString() => Utf8StringPool.Get(handle);
 
diff --git a/src/Combination.StringPools/Utf8StringPool.cs b/src/Combination.StringPools/Utf8StringPool.cs
index d486cdf..99f8f75 100644
--- a/src/Combination.StringPools/Utf8StringPool.cs
+++ b/src/Combination.StringPools/Utf8StringPool.cs
@@ -267,6 +267,16 @@ public static string Get(ulong handle)
             return string.Empty;
         }
 
+        return Encoding.UTF8.GetString(GetBytes(handle));
+    }
+
+    public static ReadOnlySpan<byte> GetBytes(ulong handle)
+    {
+        if (handle == ulong.MaxValue)
+        {
+            return Array.Empty<byte>();
+        }
+
         var poolIndex = handle >> (64 - PoolIndexBits);
         if (poolIndex >= (ulong)Pools.Count)
         {
@@ -283,7 +293,7 @@ public static string Get(ulong handle)
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-    private string GetFromPool(ulong handle)
+    private ReadOnlySpan<byte> GetFromPool(ulong handle)
     {
         using (disposeLock.PreventDispose())
         {
@@ -296,7 +306,7 @@ private string GetFromPool(ulong handle)
                 throw new InvalidOperationException($"Internal error: Deduplicated string pool mismatch ({index} != {poolIndex})");
             }
 #endif
-            return Encoding.UTF8.GetString(GetStringBytes(offset));
+            return GetStringBytes(offset);
         }
     }