Small GenerateOperationId optimization

.github/workflows/ci.yml

@@ -11,9 +11,9 @@ jobs:
     steps:
     - uses: actions/checkout@master
     - name: Set up .NET Core
-      uses: actions/setup-dotnet@v4
+      uses: actions/setup-dotnet@v5
       with:
-        dotnet-version: '9.0.x'
+        global-json-file: global.json
 
     - run: dotnet --info
     - name: Build solution and run all tests

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "9.0.200",
+    "version": "10.0.100",
     "allowPrerelease": true,
     "rollForward": "latestFeature"
   }

src/ZiggyCreatures.FusionCache/Internals/FusionCacheInternalUtils.cs

@@ -15,31 +15,39 @@ internal static class FusionCacheInternalUtils
 {
 	internal static class GeneratorUtils
 	{
-		private static readonly char[] _chars = "0123456789ABCDEFGHIJKLMNOPQRSTUV".ToCharArray();
 		private static long _lastId = DateTime.UtcNow.Ticks;
-		private static readonly ThreadLocal<char[]> _buffer = new(() => new char[13]);
 
 		private static string GenerateOperationId(long id)
 		{
 			// SEE: https://nimaara.com/2018/10/10/generating-ids-in-csharp.html
-
-			char[] buffer = _buffer.Value!;
-
-			buffer[0] = _chars[(int)(id >> 60) & 31];
-			buffer[1] = _chars[(int)(id >> 55) & 31];
-			buffer[2] = _chars[(int)(id >> 50) & 31];
-			buffer[3] = _chars[(int)(id >> 45) & 31];
-			buffer[4] = _chars[(int)(id >> 40) & 31];
-			buffer[5] = _chars[(int)(id >> 35) & 31];
-			buffer[6] = _chars[(int)(id >> 30) & 31];
-			buffer[7] = _chars[(int)(id >> 25) & 31];
-			buffer[8] = _chars[(int)(id >> 20) & 31];
-			buffer[9] = _chars[(int)(id >> 15) & 31];
-			buffer[10] = _chars[(int)(id >> 10) & 31];
-			buffer[11] = _chars[(int)(id >> 5) & 31];
-			buffer[12] = _chars[(int)id & 31];
-
-			return new string(buffer, 0, buffer.Length);
+			const string chars = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
+			const int length = 13;
+#if NETSTANDARD2_0
+			Span<char> buffer = stackalloc char[length];
+			WriteTo(buffer, id);
+			return buffer.ToString();
+#else
+			return string.Create(length, id, WriteTo);
+#endif
+
+			[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			static void WriteTo(Span<char> buffer, long id)
+			{
+				// This order (from 12 to 0) eliminates bound checks for all the assignments except the first one.
+				buffer[12] = chars[(int)id & 31];
+				buffer[11] = chars[(int)(id >> 5) & 31];
+				buffer[10] = chars[(int)(id >> 10) & 31];
+				buffer[9] = chars[(int)(id >> 15) & 31];
+				buffer[8] = chars[(int)(id >> 20) & 31];
+				buffer[7] = chars[(int)(id >> 25) & 31];
+				buffer[6] = chars[(int)(id >> 30) & 31];
+				buffer[5] = chars[(int)(id >> 35) & 31];
+				buffer[4] = chars[(int)(id >> 40) & 31];
+				buffer[3] = chars[(int)(id >> 45) & 31];
+				buffer[2] = chars[(int)(id >> 50) & 31];
+				buffer[1] = chars[(int)(id >> 55) & 31];
+				buffer[0] = chars[(int)(id >> 60) & 31];
+			}
 		}
 
 		public static string GenerateOperationId()