Reduce heap allocation of the default log message formatting logic in the FileLogger.Log

src/NReco.Logging.File/Extensions/DateTimeExtensions.cs

@@ -0,0 +1,80 @@
+using System;
+
+#nullable enable
+
+namespace NReco.Logging.File.Extensions {
+	public static class DateTimeExtensions {
+		public static int GetFormattedLength(this DateTime dateTime) {
+			const int BaseCharCountInFormatO = 27;
+
+			return BaseCharCountInFormatO + dateTime.Kind switch {
+				DateTimeKind.Local => 6,
+				DateTimeKind.Utc => 1,
+				_ => 0
+			};
+		}
+
+#if NETSTANDARD2_0
+		public static bool TryFormatO(this DateTime dateTime, Span<char> destination, out int charsWritten) {
+			var charsRequired = dateTime.GetFormattedLength();
+
+			if (destination.Length < charsRequired) {
+				charsWritten = 0;
+				return false;
+			}
+
+			charsWritten = charsRequired;
+
+			var year = (uint)dateTime.Year;
+			var month = (uint)dateTime.Month;
+			var day = (uint)dateTime.Day;
+			var hour = (uint)dateTime.Hour;
+			var minute = (uint)dateTime.Minute;
+			var second = (uint)dateTime.Second;
+			var tick = (uint)(dateTime.Ticks - (dateTime.Ticks / TimeSpan.TicksPerSecond * TimeSpan.TicksPerSecond));
+
+			year.WriteDigits(destination, 4);
+			destination[4] = '-';
+			month.WriteDigits(destination.Slice(5), 2);
+			destination[7] = '-';
+			day.WriteDigits(destination.Slice(8), 2);
+			destination[10] = 'T';
+			hour.WriteDigits(destination.Slice(11), 2);
+			destination[13] = ':';
+			minute.WriteDigits(destination.Slice(14), 2);
+			destination[16] = ':';
+			second.WriteDigits(destination.Slice(17), 2);
+			destination[19] = '.';
+			tick.WriteDigits(destination.Slice(20), 7);
+
+			var kind = dateTime.Kind;
+			if (kind == DateTimeKind.Local) {
+				var offset = TimeZoneInfo.Local.GetUtcOffset(dateTime);
+				var offsetTotalMinutes = (int)(offset.Ticks / TimeSpan.TicksPerMinute);
+
+				var sign = '+';
+				if (offsetTotalMinutes < 0) {
+					sign = '-';
+					offsetTotalMinutes = -offsetTotalMinutes;
+				}
+
+				var offsetHours = Math.DivRem(offsetTotalMinutes, 60, out var offsetMinutes);
+
+				destination[27] = sign;
+				((uint)offsetHours).WriteDigits(destination.Slice(28), 2);
+				destination[30] = ':';
+				((uint)offsetMinutes).WriteDigits(destination.Slice(31), 2);
+			}
+			else if (kind == DateTimeKind.Utc) {
+				destination[27] = 'Z';
+			}
+
+			return true;
+		}
+#else
+		public static bool TryFormatO(this DateTime dateTime, Span<char> destination, out int charsWritten) {
+			return dateTime.TryFormat(destination, out charsWritten, format: "O");
+		}
+#endif
+	}
+}

src/NReco.Logging.File/Extensions/IntExtensions.cs

@@ -0,0 +1,41 @@
+using System;
+
+#nullable enable
+
+namespace NReco.Logging.File.Extensions {
+	public static class IntExtensions {
+		public static int GetFormattedLength(this int value) {
+			return value == 0 ? 1 : (int)Math.Floor(Math.Log10(Math.Abs((double)value))) + (value > 0 ? 1 : 2);
+		}
+
+#if NETSTANDARD2_0
+		public static bool TryFormat(this int value, Span<char> destination, out int charsWritten) {
+			charsWritten = value.GetFormattedLength();
+			if (destination.Length < charsWritten) {
+				charsWritten = 0;
+				return false;
+			}
+
+			var dst = destination.Slice(0, charsWritten);
+
+			if (value < 0) {
+				dst[0] = '-';
+				dst = dst.Slice(1);
+			}
+
+			((uint)Math.Abs((long)value)).WriteDigits(dst, dst.Length);
+			return true;
+		}
+
+		internal static void WriteDigits(this uint value, Span<char> destination, int count) {
+			for (var cur = count - 1; cur > 0; cur--) {
+				uint temp = '0' + value;
+				value /= 10;
+				destination[cur] = (char)(temp - (value * 10));
+			}
+
+			destination[0] = (char)('0' + value);
+		}
+#endif
+	}
+}

src/NReco.Logging.File/FileLogger.cs

@@ -3,7 +3,7 @@
  * NReco file logging provider (https://github.com/nreco/logging)
  * Copyright 2017 Vitaliy Fedorchenko
  * Distributed under the MIT license
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -13,16 +13,11 @@
 #endregion
 
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-using System.IO;
-using System.Collections.Concurrent;
+using System.Buffers;
 using System.Text;
 
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Configuration;
-
+using NReco.Logging.File.Extensions;
 namespace NReco.Logging.File {
 
 	/// <summary>
@@ -33,37 +28,32 @@
 		private readonly string logName;
 		private readonly FileLoggerProvider LoggerPrv;
 
 		public FileLogger(string logName, FileLoggerProvider loggerPrv) {
 			this.logName = logName;
 			this.LoggerPrv = loggerPrv;
 		}
 		public IDisposable BeginScope<TState>(TState state) {
 			return null;
 		}
 
 		public bool IsEnabled(LogLevel logLevel) {
 			return logLevel>=LoggerPrv.MinLevel;
 		}
 
 		string GetShortLogLevel(LogLevel logLevel) {
-			switch (logLevel) {
-				case LogLevel.Trace:
-					return "TRCE";
-				case LogLevel.Debug:
-					return "DBUG";
-				case LogLevel.Information:
-					return "INFO";
-				case LogLevel.Warning:
-					return "WARN";
-				case LogLevel.Error:
-					return "FAIL";
-				case LogLevel.Critical:
-					return "CRIT";
-			}
-			return logLevel.ToString().ToUpper();
+			return logLevel switch {
+				LogLevel.Trace => "TRCE",
+				LogLevel.Debug => "DBUG",
+				LogLevel.Information => "INFO",
+				LogLevel.Warning => "WARN",
+				LogLevel.Error => "FAIL",
+				LogLevel.Critical => "CRIT",
+				LogLevel.None => "NONE",
+				_ => logLevel.ToString().ToUpper(),
+			};
 		}
 
 		public void Log<TState>(LogLevel logLevel, EventId eventId, TState state,
 			Exception exception, Func<TState, Exception, string> formatter) {
 			if (!IsEnabled(logLevel)) {
 				return;
@@ -79,34 +69,71 @@
 				if (!LoggerPrv.Options.FilterLogEntry(new LogMessage(logName, logLevel, eventId, message, exception)))
 					return;
 
-			if (LoggerPrv.FormatLogEntry!=null) {
+			if (LoggerPrv.FormatLogEntry != null) {
 				LoggerPrv.WriteEntry(LoggerPrv.FormatLogEntry(
 					new LogMessage(logName, logLevel, eventId, message, exception)));
-			} else {
-				// default formatting logic
-				var logBuilder = new StringBuilder();
-				if (!string.IsNullOrEmpty(message)) {
-					DateTime timeStamp = LoggerPrv.UseUtcTimestamp ? DateTime.UtcNow : DateTime.Now;
-					logBuilder.Append(timeStamp.ToString("o"));
-					logBuilder.Append('\t');
-					logBuilder.Append(GetShortLogLevel(logLevel));
-					logBuilder.Append("\t[");
-					logBuilder.Append(logName);
-					logBuilder.Append("]");
-					logBuilder.Append("\t[");
-					logBuilder.Append(eventId);
-					logBuilder.Append("]\t");
-					logBuilder.Append(message);
+			}
+			else {
+				const int MaxStackAllocatedBufferLength = 256;
+				DateTime timeStamp = LoggerPrv.UseUtcTimestamp ? DateTime.UtcNow : DateTime.Now;
+				var logMessageLength = CalculateLogMessageLength(timeStamp, eventId, message);
+				char[] charBuffer = null;
+				try {
+					Span<char> buffer = logMessageLength <= MaxStackAllocatedBufferLength
+						? stackalloc char[MaxStackAllocatedBufferLength]
+						: (charBuffer = ArrayPool<char>.Shared.Rent(logMessageLength));
+
+					FormatLogEntryDefault(buffer, timeStamp, message, logLevel, eventId, exception);
 				}
-
-				if (exception != null) {
-					// exception message
-					logBuilder.AppendLine(exception.ToString());
+				finally {
+					if (charBuffer is not null) {
+						ArrayPool<char>.Shared.Return(charBuffer);
+					}
 				}
-				LoggerPrv.WriteEntry(logBuilder.ToString());
 			}
 		}
-	}
 
+		private void FormatLogEntryDefault(Span<char> buffer, DateTime timeStamp, string message,
+			LogLevel logLevel, EventId eventId, Exception exception) {
+			// default formatting logic
+			using var logBuilder = new ValueStringBuilder(buffer);
+			if (!string.IsNullOrEmpty(message)) {
+				timeStamp.TryFormatO(logBuilder.RemainingRawChars, out var charsWritten);
+				logBuilder.AppendSpan(charsWritten);
+				logBuilder.Append('\t');
+				logBuilder.Append(GetShortLogLevel(logLevel));
+				logBuilder.Append("\t[");
+				logBuilder.Append(logName);
+				logBuilder.Append("]\t[");
+				if (eventId.Name is not null) {
+					logBuilder.Append(eventId.Name);
+				}
+				else {
+					eventId.Id.TryFormat(logBuilder.RemainingRawChars, out charsWritten);
+					logBuilder.AppendSpan(charsWritten);
+				}
+				logBuilder.Append("]\t");
+				logBuilder.Append(message);
+			}
+
+			if (exception != null) {
+				// exception message
+				logBuilder.Append(exception.ToString());
+				logBuilder.Append(Environment.NewLine);
+			}
+			LoggerPrv.WriteEntry(logBuilder.ToString());
+		}
 
+		private int CalculateLogMessageLength(DateTime timeStamp, EventId eventId, string message) {
+			return timeStamp.GetFormattedLength()
+				+ 1 /* '\t' */
+				+ 4 /* GetShortLogLevel */
+				+ 2 /* "\t[" */
+				+ (logName?.Length ?? 0)
+				+ 3 /* "]\t[" */
+				+ (eventId.Name?.Length ?? eventId.Id.GetFormattedLength())
+				+ 2 /* "]\t" */
+				+ (message?.Length ?? 0);
+		}
+	}
 }

src/NReco.Logging.File/LogMessage.cs

@@ -3,7 +3,7 @@
  * NReco file logging provider (https://github.com/nreco/logging)
  * Copyright 2017 Vitaliy Fedorchenko
  * Distributed under the MIT license
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -13,13 +13,11 @@
 #endregion
 
 using System;
-using System.Collections.Generic;
-using System.Text;
 using Microsoft.Extensions.Logging;
 
 namespace NReco.Logging.File {
 
-	public struct LogMessage {
+	public readonly struct LogMessage {
 		public readonly string LogName;
 		public readonly string Message;
 		public readonly LogLevel LogLevel;

src/NReco.Logging.File/NReco.Logging.File.csproj

@@ -2,12 +2,12 @@
 
   <PropertyGroup>
     <Description>Lightweight file logging provider implementation for NET6 / NET8+ / .NET Core without dependencies on logging frameworks.
-	
+
 How to use:
 
 using NReco.Logging.File;
 
-services.AddLogging(loggingBuilder => {
+services.AddLogging(loggingBuilder =&gt; {
 	loggingBuilder.AddFile("app.log", append:true);
 });
 
@@ -19,6 +19,7 @@ More details and examples: https://github.com/nreco/logging
     <VersionPrefix>1.2.1</VersionPrefix>
     <Authors>Vitalii Fedorchenko</Authors>
     <TargetFrameworks>netstandard2.0;net6.0;net8.0</TargetFrameworks>
+    <LangVersion>12.0</LangVersion>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AssemblyName>NReco.Logging.File</AssemblyName>
     <PackageId>NReco.Logging.File</PackageId>
@@ -27,10 +28,10 @@ More details and examples: https://github.com/nreco/logging
     <PackageProjectUrl>https://github.com/nreco/logging</PackageProjectUrl>
     <PackageLicenseUrl>https://raw.githubusercontent.com/nreco/logging/master/LICENSE</PackageLicenseUrl>
 	<PackageReleaseNotes>How to use: https://github.com/nreco/logging
-	
+
 Version 1.2.1 changes:
  - Added different rolling name conventions #66 (unix-style is supported with 'Descending' convention)
-	
+
 Version 1.2.0 changes:
  - NReco's FileLoggerExtensions should NOT be in the Microsoft.Extensions.Logging namespace #61
  - Added net6 and net8 builds to reference appropriate Microsoft.Logging.Extensions versions
@@ -65,7 +66,7 @@ Version 1.1.0 changes:
 Version 1.0.5 changes:
  - log file folder is created automatically if not exists
  - environment variables are expanded in the file path
-	
+
 Version 1.0.4 changes:
  - added "File" provider alias for MVC Core 2 filtering rules
  - added 'rolling file' behaviour controlled with new FileLoggerProvider properties (FileSizeLimitBytes and MaxRollingFiles)</PackageReleaseNotes>
@@ -81,11 +82,11 @@ Version 1.0.4 changes:
     <SignAssembly>false</SignAssembly>
     <AssemblyOriginatorKeyFile>NReco.Logging.File.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
-  
+
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
-    <PackageReference Include="Microsoft.Extensions.Logging" Version="3.*" />
-    <PackageReference Include="Microsoft.Extensions.Logging.Configuration" Version="3.*" />
-    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="3.*" /> 
+    <PackageReference Include="Microsoft.Extensions.Logging" Version="8.0.*" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Configuration" Version="8.0.*" />
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="8.0.*" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net6.0'">
@@ -97,7 +98,7 @@ Version 1.0.4 changes:
   <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
     <PackageReference Include="Microsoft.Extensions.Logging" Version="8.0.*" />
     <PackageReference Include="Microsoft.Extensions.Logging.Configuration" Version="8.0.*" />
-    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="8.0.*" />  
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="8.0.*" />
   </ItemGroup>
-    
+
 </Project>