fix(tar): enable unix paths in tar RootPath

src/ICSharpCode.SharpZipLib/Tar/TarArchive.cs

@@ -356,8 +356,7 @@ public string RootPath
 				{
 					throw new ObjectDisposedException("TarArchive");
 				}
-				// Convert to forward slashes for matching. Trim trailing / for correct final path
-				rootPath = value.Replace('\\', '/').TrimEnd('/');
+				rootPath = value.ClearTarPath().TrimEnd('/');
 			}
 		}
 

src/ICSharpCode.SharpZipLib/Tar/TarEntry.cs

@@ -418,15 +418,10 @@ public void GetFileTarHeader(TarHeader header, string file)
 						}
 			*/
 
-			name = name.Replace(Path.DirectorySeparatorChar, '/');
-
 			// No absolute pathnames
 			// Windows (and Posix?) paths can start with UNC style "\\NetworkDrive\",
 			// so we loop on starting /'s.
-			while (name.StartsWith("/", StringComparison.Ordinal))
-			{
-				name = name.Substring(1);
-			}
+			name = name.ClearTarPath();
 
 			header.LinkName = String.Empty;
 			header.Name = name;

src/ICSharpCode.SharpZipLib/Tar/TarStringExtension.cs

@@ -0,0 +1,17 @@
+using System.IO;
+
+namespace ICSharpCode.SharpZipLib.Tar
+{
+	internal static class TarStringExtension
+	{
+		public static string ClearTarPath(this string s)
+		{
+			var pathRoot = Path.GetPathRoot(s);
+			if (!string.IsNullOrEmpty(pathRoot))
+			{
+				s = s.Substring(pathRoot.Length);
+			}
+			return s.Replace(Path.DirectorySeparatorChar, '/');
+		}
+	}
+}

test/ICSharpCode.SharpZipLib.Tests/Tar/TarTests.cs

@@ -859,7 +859,7 @@ public void ParseHeaderWithEncoding(int length, string encodingName)
 			reparseHeader.ParseBuffer(headerbytes, enc);
 			Assert.AreEqual(name, reparseHeader.Name);
 			// top 100 bytes are name field in tar header
-			for (int i = 0;i < encodedName.Length;i++)
+			for (int i = 0; i < encodedName.Length; i++)
 			{
 				Assert.AreEqual(encodedName[i], headerbytes[i]);
 			}
@@ -878,17 +878,17 @@ public void StreamWithJapaneseName(int length, string encodingName)
 			var entryName = new string((char)0x3042, length);
 			var data = new byte[32];
 			var encoding = Encoding.GetEncoding(encodingName);
-			using(var memoryStream = new MemoryStream())
+			using (var memoryStream = new MemoryStream())
 			{
-				using(var tarOutput = new TarOutputStream(memoryStream, encoding))
+				using (var tarOutput = new TarOutputStream(memoryStream, encoding))
 				{
 					var entry = TarEntry.CreateTarEntry(entryName);
 					entry.Size = 32;
 					tarOutput.PutNextEntry(entry);
 					tarOutput.Write(data, 0, data.Length);
 				}
-				using(var memInput = new MemoryStream(memoryStream.ToArray()))
-				using(var inputStream = new TarInputStream(memInput, encoding))
+				using (var memInput = new MemoryStream(memoryStream.ToArray()))
+				using (var inputStream = new TarInputStream(memInput, encoding))
 				{
 					var buf = new byte[64];
 					var entry = inputStream.GetNextEntry();
@@ -899,5 +899,77 @@ public void StreamWithJapaneseName(int length, string encodingName)
 				File.WriteAllBytes(Path.Combine(Path.GetTempPath(), $"jpnametest_{length}_{encodingName}.tar"), memoryStream.ToArray());
 			}
 		}
+		/// <summary>
+		/// This test could be considered integration test. it creates a tar archive with the root directory specified
+		/// Then extracts it and compares the two folders. This used to fail on unix due to issues with root folder handling
+		/// in the tar archive.
+		/// </summary>
+		[Test]
+		[Category("Tar")]
+		public void rootPathIsRespected()
+		{
+			// create dummy folder structure
+			var tempDirectory = Path.Combine(Path.GetTempPath(), "sharpziplib_tar_test_folder");
+			CreateAndClearDirectory(tempDirectory);
+			using (var dummyfile = File.Create(Path.Combine(tempDirectory, "dummyfile"))) 
+			{
+				using (var randomStream = new ChaosStream())
+				{
+					randomStream.CopyTo(dummyfile);
+				}
+			}
+
+			var tarFileName = Path.Combine(Path.GetTempPath(), "sharpziplib_tar_test_folder_archive.tar");
+
+			using (var tarFile = File.Open(tarFileName, FileMode.Create))
+			{
+				using (var tarOutputStream = TarArchive.CreateOutputTarArchive(tarFile))
+				{
+					tarOutputStream.RootPath = tempDirectory;
+					var entry = TarEntry.CreateEntryFromFile(tempDirectory);
+					tarOutputStream.WriteEntry(entry, true);
+				}
+			}
+
+			var extractDirectory = Path.Combine(Path.GetTempPath(), "sharpziplib_tar_extract_folder");
+			CreateAndClearDirectory(extractDirectory);
+			using (var file = File.OpenRead(tarFileName))
+			{
+				using (var archive = TarArchive.CreateInputTarArchive(file, Encoding.UTF8))
+				{
+					archive.ExtractContents(extractDirectory);
+				}
+			}
+
+			var expectationDirectory = new DirectoryInfo(tempDirectory);
+			foreach (var checkFile in expectationDirectory.GetFiles("", SearchOption.AllDirectories))
+			{
+				var relativePath = checkFile.FullName.Substring(expectationDirectory.FullName.Length + 1);
+				FileAssert.Exists(Path.Combine(extractDirectory, relativePath));
+				FileAssert.AreEqual(checkFile.FullName, Path.Combine(extractDirectory, relativePath));
+			}
+		}
+
+		private void CreateAndClearDirectory(string path)
+		{
+			if (Directory.Exists(path))
+			{
+				Directory.Delete(path, true);
+			}
+			Directory.CreateDirectory(path);
+		}
+
+		public class ChaosStream : MemoryStream
+		{
+			private readonly int length = new Random().Next() % 500000 + 200;
+
+			// Create constructors as needed to match desired MemoryStream construction
+
+			public override int Read(byte[] buffer, int offset, int count)
+			{
+				int readCount = Math.Max(0, Math.Min(length - offset, count));
+				return base.Read(buffer, offset, readCount);
+			}
+		}
 	}
 }