Improve MurmurHash string hash memory footprint (#5028)

* Reduce memory footprint

* Fix enumerator, off by 1 error

Author: Arkatufus

src/Akka.sln

@@ -244,7 +244,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Samples.Akka.AspNetCore", "
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SerializationBenchmarks", "benchmark\SerializationBenchmarks\SerializationBenchmarks.csproj", "{2E4B9584-42CC-4D17-B719-9F462B16C94D}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DDataStressTest", "examples\Cluster\DData\DDataStressTest\DDataStressTest.csproj", "{44B3DDD6-6103-4E8F-8AC2-0F4BA3CF6B50}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DDataStressTest", "examples\Cluster\DData\DDataStressTest\DDataStressTest.csproj", "{44B3DDD6-6103-4E8F-8AC2-0F4BA3CF6B50}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

src/contrib/cluster/Akka.DistributedData/ORSet.cs

@@ -712,9 +712,9 @@ private ORSet<T> MergeRemoveDelta(RemoveDeltaOperation delta)
             {
                 while (deleteDots.MoveNext())
                 {
-                    var curr = deleteDots.Current;
-                    deleteDotNodes.Add(curr.Key);
-                    deleteDotsAreGreater &= (thisDot != null && (thisDot.VersionAt(curr.Key) <= curr.Value));
+                    var current = deleteDots.Current;
+                    deleteDotNodes.Add(current.Key);
+                    deleteDotsAreGreater &= (thisDot != null && (thisDot.VersionAt(current.Key) <= current.Value));
                 }
             }
 

src/core/Akka/Actor/Address.cs

@@ -40,7 +40,7 @@ public int Compare(Address x, Address y)
                 if (result != 0) return result;
                 result = string.CompareOrdinal(x.System, y.System);
                 if (result != 0) return result;
-                result = string.CompareOrdinal(x.Host ?? "", y.Host ?? "");
+                result = string.CompareOrdinal(x.Host ?? string.Empty, y.Host ?? string.Empty);
                 if (result != 0) return result;
                 result = (x.Port ?? 0).CompareTo(y.Port ?? 0);
                 return result;

src/core/Akka/Util/MurmurHash.cs

@@ -202,20 +202,20 @@ public static int StringHash(string s)
         {
             unchecked
             {
-                var sChar = s.ToCharArray();
+                var span = s.AsSpan();
                 var h = StartHash((uint)s.Length * StringSeed);
                 var c = HiddenMagicA;
                 var k = HiddenMagicB;
                 var j = 0;
                 while (j + 1 < s.Length)
                 {
-                    var i = (uint)((sChar[j] << 16) + sChar[j + 1]);
+                    var i = (uint)((span[j] << 16) + span[j + 1]);
                     h = ExtendHash(h, i, c, k);
                     c = NextMagicA(c);
                     k = NextMagicB(k);
                     j += 2;
                 }
-                if (j < s.Length) h = ExtendHash(h, sChar[j], c, k);
+                if (j < s.Length) h = ExtendHash(h, span[j], c, k);
                 return (int)FinalizeHash(h);
             }
         }