GZipFIle - Support Header / Footer / WriteBom

snakefoot · snakefoot · commit e9422fc4e648 · 2026-03-28T10:24:44.000+01:00
diff --git a/src/NLog/Targets/FileTarget.cs b/src/NLog/Targets/FileTarget.cs
@@ -1296,7 +1296,7 @@ private Stream OpenNewFileStream(string filePath, int bufferSize, bool initialFi
 
                 if (WriteBom)
                 {
-                    fileWasEmpty = ReplaceFileContentsOnEachWrite || fileStream.Length == 0;
+                    fileWasEmpty = IsNewFileEmpty(initialFileOpen, fileStream);
                     if (fileWasEmpty == true)
                     {
                         InternalLogger.Trace("{0}: Write byte order mark from encoding={1}", this, Encoding);
@@ -1310,7 +1310,7 @@ private Stream OpenNewFileStream(string filePath, int bufferSize, bool initialFi
 
                 if (Header != null)
                 {
-                    bool writeHeader = (initialFileOpen && WriteHeaderWhenInitialFileNotEmpty) || ReplaceFileContentsOnEachWrite || (fileWasEmpty ?? fileStream.Length == 0);
+                    bool writeHeader = (initialFileOpen && WriteHeaderWhenInitialFileNotEmpty) || (fileWasEmpty ?? IsNewFileEmpty(initialFileOpen, fileStream));
                     if (writeHeader)
                     {
                         InternalLogger.Trace("{0}: Write header", this);
@@ -1328,6 +1328,15 @@ private Stream OpenNewFileStream(string filePath, int bufferSize, bool initialFi
             }
         }
 
+        private bool IsNewFileEmpty(bool initialFileOpen, Stream fileStream)
+        {
+            if (ReplaceFileContentsOnEachWrite)
+                return true;
+            if (initialFileOpen && ArchiveOldFileOnStartup && !typeof(FileStream).Equals(fileStream.GetType()))
+                return true;
+            return fileStream.Length == 0;
+        }
+
         /// <summary>
         /// Creates stream for appending to the specified <paramref name="filePath"/>
         /// </summary>
diff --git a/tests/NLog.Targets.GZipFile.Tests/GZipFileTests.cs b/tests/NLog.Targets.GZipFile.Tests/GZipFileTests.cs
@@ -40,6 +40,11 @@ namespace NLog.Targets.GZipFile.Tests
 {
     public class GZipFileTests
     {
+        public GZipFileTests()
+        {
+            LogManager.ThrowExceptions = true;
+        }
+
         [Fact]
         public void SimpleFileGZipStream()
         {
@@ -102,6 +107,45 @@ public void SimpleFileGZipStream_AutoFlush_False()
             }
         }
 
+        [Fact]
+        public void SimpleFileGZipStream_HeaderFooterBom()
+        {
+            var tempDir = Path.Combine(Path.GetTempPath(), "nlog_" + Guid.NewGuid().ToString());
+            var logFileName = Path.Combine(tempDir, "log.gzip");
+
+            try
+            {
+                var logFactory = new LogFactory().Setup().LoadConfiguration(cfg =>
+                {
+                    cfg.ForLogger().WriteTo(new GZipFileTarget()
+                    {
+                        FileName = logFileName,
+                        Layout = "${message}",
+                        LineEnding = LineEndingMode.LF,
+                        Header = "Hello World",
+                        Footer = "Goodbye World",
+                        WriteBom = true,
+                    });
+                }).LogFactory;
+
+                logFactory.GetCurrentClassLogger().Info("There was light");
+                logFactory.Shutdown();
+
+                using (var logFile = new StreamReader(new GZipStream(new FileStream(logFileName, FileMode.Open), CompressionMode.Decompress)))
+                {
+                    Assert.Equal("Hello World", logFile.ReadLine());
+                    Assert.Equal("There was light", logFile.ReadLine());
+                    Assert.Equal("Goodbye World", logFile.ReadLine());
+                    Assert.Null(logFile.ReadLine());
+                }
+            }
+            finally
+            {
+                if (Directory.Exists(tempDir))
+                    Directory.Delete(tempDir, true);
+            }
+        }
+
         [Fact]
         public void SimpleFileGZipStream_ArchiveAboveSize()
         {

Original file line number	Diff line number	Diff line change
`@@ -1296,7 +1296,7 @@ private Stream OpenNewFileStream(string filePath, int bufferSize, bool initialFi`
`1296`	`1296`
`1297`	`1297`	`if (WriteBom)`
`1298`	`1298`	`{`
`1299`		`- fileWasEmpty = ReplaceFileContentsOnEachWrite \|\| fileStream.Length == 0;`
	`1299`	`+ fileWasEmpty = IsNewFileEmpty(initialFileOpen, fileStream);`
`1300`	`1300`	`if (fileWasEmpty == true)`
`1301`	`1301`	`{`
`1302`	`1302`	`InternalLogger.Trace("{0}: Write byte order mark from encoding={1}", this, Encoding);`
`@@ -1310,7 +1310,7 @@ private Stream OpenNewFileStream(string filePath, int bufferSize, bool initialFi`
`1310`	`1310`
`1311`	`1311`	`if (Header != null)`
`1312`	`1312`	`{`
`1313`		`- bool writeHeader = (initialFileOpen && WriteHeaderWhenInitialFileNotEmpty) \|\| ReplaceFileContentsOnEachWrite \|\| (fileWasEmpty ?? fileStream.Length == 0);`
	`1313`	`+ bool writeHeader = (initialFileOpen && WriteHeaderWhenInitialFileNotEmpty) \|\| (fileWasEmpty ?? IsNewFileEmpty(initialFileOpen, fileStream));`
`1314`	`1314`	`if (writeHeader)`
`1315`	`1315`	`{`
`1316`	`1316`	`InternalLogger.Trace("{0}: Write header", this);`
`@@ -1328,6 +1328,15 @@ private Stream OpenNewFileStream(string filePath, int bufferSize, bool initialFi`
`1328`	`1328`	`}`
`1329`	`1329`	`}`
`1330`	`1330`
	`1331`	`+ private bool IsNewFileEmpty(bool initialFileOpen, Stream fileStream)`
	`1332`	`+ {`
	`1333`	`+ if (ReplaceFileContentsOnEachWrite)`
	`1334`	`+ return true;`
	`1335`	`+ if (initialFileOpen && ArchiveOldFileOnStartup && !typeof(FileStream).Equals(fileStream.GetType()))`
	`1336`	`+ return true;`
	`1337`	`+ return fileStream.Length == 0;`
	`1338`	`+ }`
	`1339`	`+`
`1331`	`1340`	`/// <summary>`
`1332`	`1341`	`/// Creates stream for appending to the specified <paramref name="filePath"/>`
`1333`	`1342`	`/// </summary>`