Read message type from fix string without regex

BenchmarkDotNet v0.14.0, NixOS 24.11 (Vicuna) 11th Gen Intel Core i7-1165G7 2.80GHz, 1 CPU, 8 logical and 4 physical cores .NET SDK 8.0.307 [Host] : .NET 8.0.11 (8.0.1124.51707), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI DefaultJob : .NET 8.0.11 (8.0.1124.51707), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI | Method | Mean | Error | StdDev | Gen0 | Allocated | |------- |----------:|---------:|----------:|-------:|----------:| | Manual | 35.33 ns | 2.754 ns | 8.122 ns | 0.0038 | 24 B | | Regex | 322.38 ns | 9.405 ns | 25.265 ns | 0.0648 | 408 B |
connamara · Dec 17, 2024 · ee47ce9 · ee47ce9
1 parent 72facb6
commit ee47ce9
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Showing 3 changed files with 42 additions and 15 deletions.
diff --git a/QuickFIXn/Message/Message.cs b/QuickFIXn/Message/Message.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Text;
 using QuickFix.Fields;
-using System.Text.RegularExpressions;
 using System.Text.Json;
 using System.Collections.Generic;
 using QuickFix.DataDictionary;
@@ -256,11 +255,31 @@ public static SessionID GetReverseSessionId(string msg)
         /// <exception cref="MessageParseError">if 35 tag is missing or malformed</exception>
         public static string GetMsgType(string fixstring)
         {
-            Match match = Regex.Match(fixstring, SOH + "35=([^" + SOH + "]*)" + SOH);
-            if (match.Success)
-                return match.Groups[1].Value;
+            // Note: This is faster than regex.  See stats from https://github.com/connamara/quickfixn/pull/910
+            ReadOnlySpan<char> chars = fixstring.AsSpan();
+            int l = 0;
+            int r = 1;
 
-            throw new MessageParseError("missing or malformed tag 35 in msg: " + fixstring);
+            if (chars.Length > 0 && chars[0] == SOH) l = 1;
+            while (r < chars.Length)
+            {
+                if (chars[r] == SOH)
+                {
+                    if (r - l >= 4 &&
+                        chars[l] == '3' &&
+                        chars[l + 1] == '5' &&
+                        chars[l + 2] == '=')
+                    {
+                        return new string(chars[(l + 3)..r]);
+                    }
+
+                    l = r + 1;
+                }
+
+                r++;
+            }
+
+            throw new MessageParseError("Missing or malformed tag 35 in msg: " + fixstring);
         }
 
         public static ApplVerID GetApplVerID(string beginString)

diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
@@ -46,6 +46,7 @@ What's New
 * #891 - make NonSessionLog implement IDisposable and fix the IOException (VAllens)
 * #893 - Upgrade the unit testing framework to the latest version and remove obsolete Assert methods (VAllens)
 * #907 - A fix to make body-less messages work, specifically 35=n aka XMLnonFIX (gbirchmeier)
+* #910 - faster Message.GetMsgType that doesn't use Regex (jkulubya)
 
 ### v1.12.0
 

diff --git a/UnitTests/MessageTests.cs b/UnitTests/MessageTests.cs
@@ -580,16 +580,23 @@ public void TestGetSetSessionId()
             Assert.That(getSessionId.TargetLocationID, Is.EqualTo(""));
         }
 
-        [Test]
-        public void GetMsgTypeTest() {
-            string msgStr = ("8=FIX.4.4|9=104|35=W|34=3|49=sender|52=20110909-09:09:09.999|56=target"
-                             + "55=sym|268=1|269=0|272=20111012|273=22:15:30.444|10=19|").Replace('|', Message.SOH);
-            Assert.That(Message.GetMsgType(msgStr), Is.EqualTo("W"));
-
-            // invalid 35 value, let it ride
-            string msgStr2 = ("8=FIX.4.4|9=68|35=*|34=3|49=sender|52=20110909-09:09:09.999|56=target"
-                              + "55=sym|268=0|10=9|").Replace('|', Message.SOH);
-            Assert.That(Message.GetMsgType(msgStr2), Is.EqualTo("*"));
+        [TestCase("8=FIX.4.4|9=104|35=W|34=3|49=sender|52=20110909-09:09:09.999|56=target|55=sym|268=1|269=0|272=20111012|273=22:15:30.444|10=19|", "W")]
+        [TestCase("8=FIX.4.4|9=104|35=AW|34=3|49=sender|52=20110909-09:09:09.999|56=target|55=sym|268=1|269=0|272=20111012|273=22:15:30.444|10=19|", "AW")]
+        [TestCase("8=FIX.4.4|9=68|35=*|34=3|49=sender|52=20110909-09:09:09.999|56=target|55=sym|268=0|10=9|", "*")]
+        public void GetMsgTypeTest(string message, string expectedMessageType)
+        {
+            var msgStr = message.Replace('|', Message.SOH);
+            Assert.That(Message.GetMsgType(msgStr), Is.EqualTo(expectedMessageType));
+        }
+
+        [TestCase("")]
+        [TestCase("8=FIX.4.4|9=68|34=3|49=sender|52=20110909-09:09:09.999|56=target|55=sym|268=0|10=9|")]
+        [TestCase("8=FIX.4.4|9=68|35=|34=3|49=sender|52=20110909-09:09:09.999|56=target|55=sym|268=0|10=9|")]
+        [TestCase("8=FIX.4.4|9=68|35=")]
+        public void GetInvalidMsgTypeTest(string message)
+        {
+            var msgStr = message.Replace('|', Message.SOH);
+            Assert.Throws<MessageParseError>(() => Message.GetMsgType(msgStr));
         }
 
         [Test]