improved GetSchemaVer

Author: wickedmachinator

LightWeight/DataTypeInfo.cs

@@ -45,7 +45,10 @@ public override string ToString()
         return Name + ", " + ClrTypeName + ", " + DataTypeName + (Precision != null && Scale != null ? " (" + Precision.Value.ToString(CultureInfo.InvariantCulture) + ", " + Scale.Value.ToString(CultureInfo.InvariantCulture) + ")" : "");
     }
 
-    public static string GetSchemaVer(List<DataTypeInfo> columns, string[] keyColumns)
+    /// <summary>
+    /// Use .ToString("X16") to convert to a more compact form.
+    /// </summary>
+    public static ulong GetSchemaVer(List<DataTypeInfo> columns, string[] keyColumns)
     {
         var keySet = keyColumns?.ToHashSet(StringComparer.InvariantCultureIgnoreCase);
 
@@ -68,22 +71,13 @@ public static string GetSchemaVer(List<DataTypeInfo> columns, string[] keyColumn
         var content = sb.ToString();
         var data = Encoding.UTF8.GetBytes(content);
 
-        var hash1 = 0x811C9DC5;
-        var hash2 = 0x811C9DC5;
-
+        var hash = 0xCBF29CE484222325;
         for (var i = 0; i < data.Length; i++)
         {
-            hash1 ^= data[i];
-            hash1 *= 0x01000193;
-        }
-
-        for (var i = data.Length - 1; i >= 0; i--)
-        {
-            hash2 ^= data[i];
-            hash2 *= 0x01000193;
+            hash ^= data[i];
+            hash *= 0x100000001B3u;
         }
 
-        var hashStr = (columns.Count % 256).ToString("X2") + hash1.ToString("X8") + (hash2 % 256).ToString("X2");
-        return hashStr;
+        return hash;
     }
 }