Merge pull request #13 from nblumhardt/f-charcountfix

Revise the method of file size limiting

Author: nblumhardt

example/Sample/Program.cs

@@ -0,0 +1,31 @@
+using System;
+using System.IO;
+using Serilog;
+
+namespace Sample
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            Log.Logger = new LoggerConfiguration()
+                .WriteTo.File("log.txt")
+                .CreateLogger();
+
+            var sw = System.Diagnostics.Stopwatch.StartNew();
+
+            for (var i = 0; i < 1000000; ++i)
+            {
+                Log.Information("Hello, file logger!");
+            }
+
+            Log.CloseAndFlush();
+
+            sw.Stop();
+
+            Console.WriteLine($"Elapsed: {sw.ElapsedMilliseconds} ms");
+
+            File.Delete("log.txt");
+        }
+    }
+}

example/Sample/Properties/AssemblyInfo.cs

@@ -0,0 +1,19 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("Sample")]
+[assembly: AssemblyTrademark("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible
+// to COM components.  If you need to access a type in this assembly from
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("a34235a2-a717-4a1c-bf5c-f4a9e06e1260")]

example/Sample/Sample.xproj

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+
+  <Import Project="$(VSToolsPath)\DotNet\Microsoft.DotNet.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>a34235a2-a717-4a1c-bf5c-f4a9e06e1260</ProjectGuid>
+    <RootNamespace>Sample</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">.\obj</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">.\bin\</OutputPath>
+    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DotNet\Microsoft.DotNet.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

example/Sample/project.json

@@ -0,0 +1,20 @@
+{
+  "version": "1.0.0-*",
+  "buildOptions": {
+    "emitEntryPoint": true
+  },
+
+  "dependencies": {
+    "Serilog.Sinks.File": { "target": "project" },
+    "Microsoft.NETCore.App": {
+      "type": "platform",
+      "version": "1.0.0"
+    }
+  },
+
+  "frameworks": {
+    "netcoreapp1.0": {
+      "imports": "dnxcore50"
+    }
+  }
+}

serilog-sinks-file.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 14
-VisualStudioVersion = 14.0.25123.0
+VisualStudioVersion = 14.0.25420.1
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{037440DE-440B-4129-9F7A-09B42D00397E}"
 EndProject
@@ -21,6 +21,10 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "test", "test", "{7B927378-9
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Serilog.Sinks.File.Tests", "test\Serilog.Sinks.File.Tests\Serilog.Sinks.File.Tests.xproj", "{3C2D8E01-5580-426A-BDD9-EC59CD98E618}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "example", "example", "{196B1544-C617-4D7C-96D1-628713BDD52A}"
+EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Sample", "example\Sample\Sample.xproj", "{A34235A2-A717-4A1C-BF5C-F4A9E06E1260}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -35,12 +39,17 @@ Global
 		{3C2D8E01-5580-426A-BDD9-EC59CD98E618}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{3C2D8E01-5580-426A-BDD9-EC59CD98E618}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{3C2D8E01-5580-426A-BDD9-EC59CD98E618}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A34235A2-A717-4A1C-BF5C-F4A9E06E1260}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A34235A2-A717-4A1C-BF5C-F4A9E06E1260}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A34235A2-A717-4A1C-BF5C-F4A9E06E1260}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A34235A2-A717-4A1C-BF5C-F4A9E06E1260}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{57E0ED0E-0F45-48AB-A73D-6A92B7C32095} = {037440DE-440B-4129-9F7A-09B42D00397E}
 		{3C2D8E01-5580-426A-BDD9-EC59CD98E618} = {7B927378-9F16-4F6F-B3F6-156395136646}
+		{A34235A2-A717-4A1C-BF5C-F4A9E06E1260} = {196B1544-C617-4D7C-96D1-628713BDD52A}
 	EndGlobalSection
 EndGlobal

src/Serilog.Sinks.File/FileLoggerConfigurationExtensions.cs

@@ -42,8 +42,9 @@ public static class FileLoggerConfigurationExtensions
         /// <param name="formatProvider">Supplies culture-specific formatting information, or null.</param>
         /// <param name="outputTemplate">A message template describing the format used to write to the sink.
         /// the default is "{Timestamp} [{Level}] {Message}{NewLine}{Exception}".</param>
-        /// <param name="fileSizeLimitBytes">The maximum size, in bytes, to which a log file will be allowed to grow.
-        /// For unrestricted growth, pass null. The default is 1 GB.</param>
+        /// <param name="fileSizeLimitBytes">The approximate maximum size, in bytes, to which a log file will be allowed to grow.
+        /// For unrestricted growth, pass null. The default is 1 GB. To avoid writing partial events, the last event within the limit
+        /// will be written in full even if it exceeds the limit.</param>
         /// <param name="buffered">Indicates if flushing to the output file can be buffered or not. The default
         /// is false.</param>
         /// <returns>Configuration object allowing method chaining.</returns>
@@ -80,8 +81,9 @@ public static LoggerConfiguration File(
         /// events passed through the sink. Ignored when <paramref name="levelSwitch"/> is specified.</param>
         /// <param name="levelSwitch">A switch allowing the pass-through minimum level
         /// to be changed at runtime.</param>
-        /// <param name="fileSizeLimitBytes">The maximum size, in bytes, to which a log file will be allowed to grow.
-        /// For unrestricted growth, pass null. The default is 1 GB.</param>
+        /// <param name="fileSizeLimitBytes">The approximate maximum size, in bytes, to which a log file will be allowed to grow.
+        /// For unrestricted growth, pass null. The default is 1 GB. To avoid writing partial events, the last event within the limit
+        /// will be written in full even if it exceeds the limit.</param>
         /// <param name="buffered">Indicates if flushing to the output file can be buffered or not. The default
         /// is false.</param>
         /// <returns>Configuration object allowing method chaining.</returns>

src/Serilog.Sinks.File/Sinks/File/CharacterCountLimitedTextWriter.cs

@@ -26,18 +26,20 @@ namespace Serilog.Sinks.File
     /// </summary>
     public sealed class FileSink : ILogEventSink, IDisposable
     {
-        const int BytesPerCharacterApproximate = 1;
         readonly TextWriter _output;
         readonly ITextFormatter _textFormatter;
+        readonly long? _fileSizeLimitBytes;
         readonly bool _buffered;
         readonly object _syncRoot = new object();
+        readonly WriteCountingStream _countingStreamWrapper;
 
         /// <summary>Construct a <see cref="FileSink"/>.</summary>
         /// <param name="path">Path to the file.</param>
         /// <param name="textFormatter">Formatter used to convert log events to text.</param>
-        /// <param name="fileSizeLimitBytes">The maximum size, in bytes, to which a log file will be allowed to grow.
-        /// For unrestricted growth, pass null. The default is 1 GB.</param>
-        /// <param name="encoding">Character encoding used to write the text file. The default is UTF-8.</param>
+        /// <param name="fileSizeLimitBytes">The approximate maximum size, in bytes, to which a log file will be allowed to grow.
+        /// For unrestricted growth, pass null. The default is 1 GB. To avoid writing partial events, the last event within the limit
+        /// will be written in full even if it exceeds the limit.</param>
+        /// <param name="encoding">Character encoding used to write the text file. The default is UTF-8 without BOM.</param>
         /// <param name="buffered">Indicates if flushing to the output file can be buffered or not. The default
         /// is false.</param>
         /// <returns>Configuration object allowing method chaining.</returns>
@@ -50,6 +52,7 @@ public FileSink(string path, ITextFormatter textFormatter, long? fileSizeLimitBy
             if (fileSizeLimitBytes.HasValue && fileSizeLimitBytes < 0) throw new ArgumentException("Negative value provided; file size limit must be non-negative");
 
             _textFormatter = textFormatter;
+            _fileSizeLimitBytes = fileSizeLimitBytes;
             _buffered = buffered;
 
             var directory = Path.GetDirectoryName(path);
@@ -58,18 +61,13 @@ public FileSink(string path, ITextFormatter textFormatter, long? fileSizeLimitBy
                 Directory.CreateDirectory(directory);
             }
 
-            var file = System.IO.File.Open(path, FileMode.Append, FileAccess.Write, FileShare.Read);
-            var outputWriter = new StreamWriter(file, encoding ?? new UTF8Encoding(encoderShouldEmitUTF8Identifier: false));
-            if (fileSizeLimitBytes != null)
+            Stream file = System.IO.File.Open(path, FileMode.Append, FileAccess.Write, FileShare.Read);
+            if (_fileSizeLimitBytes != null)
             {
-                var initialBytes = file.Length;
-                var remainingCharacters = Math.Max(fileSizeLimitBytes.Value - initialBytes, 0L) / BytesPerCharacterApproximate;
-                _output = new CharacterCountLimitedTextWriter(outputWriter, remainingCharacters);
-            }
-            else
-            {
-                _output = outputWriter;
+                file = _countingStreamWrapper = new WriteCountingStream(file);
             }
+
+            _output = new StreamWriter(file, encoding ?? new UTF8Encoding(encoderShouldEmitUTF8Identifier: false));
         }
 
         /// <summary>
@@ -81,6 +79,12 @@ public void Emit(LogEvent logEvent)
             if (logEvent == null) throw new ArgumentNullException(nameof(logEvent));
             lock (_syncRoot)
             {
+                if (_fileSizeLimitBytes != null)
+                {
+                    if (_countingStreamWrapper.CountedLength >= _fileSizeLimitBytes.Value)
+                        return;
+                }
+
                 _textFormatter.Format(logEvent, _output);
                 if (!_buffered)
                     _output.Flush();

src/Serilog.Sinks.File/Sinks/File/FileSink.cs

@@ -0,0 +1,75 @@
+// Copyright 2013-2016 Serilog Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// 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.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System;
+using System.IO;
+
+namespace Serilog.Sinks.File
+{
+    sealed class WriteCountingStream : Stream
+    {
+        readonly Stream _stream;
+        long _countedLength;
+
+        public WriteCountingStream(Stream stream)
+        {
+            if (stream == null) throw new ArgumentNullException(nameof(stream));
+            _stream = stream;
+            _countedLength = stream.Length;
+        }
+
+        public long CountedLength => _countedLength;
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+                _stream.Dispose();
+
+            base.Dispose(disposing);
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            _stream.Write(buffer, offset, count);
+            _countedLength += count;
+        }
+
+        public override void Flush() => _stream.Flush();
+        public override bool CanRead => false;
+        public override bool CanSeek => false;
+        public override bool CanWrite => true;
+        public override long Length => _stream.Length;
+
+        public override long Position
+        {
+            get { return _stream.Position; }
+            set { throw new NotSupportedException(); }
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}