[release/7.0] backport Tar fixes (#76322)

* Use UTF8 encoding on Tar string fields

* Slice destination on Checksum

* Use Encoding.GetByteCount as fast path

* Use escape sequences on hardcoded UTF8 characters

* Fix ustar prefix logic and throw if name would be truncated

* Address feedback

* Fix truncation and prefix logic

* Fix nits

* Add async tests

* Add tests for unseekable streams

* Address feedback

* Tar: Use indexer setter instead of Add on ExtendedAttributes dictionary (#76404)

* Use indexer setter instead of Add on ExtendedAttributes dictionary

* Add roundtrip tests

* Fix TryAddStringField and always set mtime

Co-authored-by: David Cantu <dacantu@microsoft.com>

src/libraries/Common/src/System/IO/PathInternal.Unix.cs

@@ -17,6 +17,7 @@ internal static partial class PathInternal
         internal const string DirectorySeparatorCharAsString = "/";
         internal const string ParentDirectoryPrefix = @"../";
         internal const string DirectorySeparators = DirectorySeparatorCharAsString;
+        internal static ReadOnlySpan<byte> Utf8DirectorySeparators => "/"u8;
 
         internal static int GetRootLength(ReadOnlySpan<char> path)
         {

src/libraries/Common/src/System/IO/PathInternal.Windows.cs

@@ -55,6 +55,7 @@ internal static partial class PathInternal
         internal const string DevicePathPrefix = @"\\.\";
         internal const string ParentDirectoryPrefix = @"..\";
         internal const string DirectorySeparators = @"\/";
+        internal static ReadOnlySpan<byte> Utf8DirectorySeparators => @"\/"u8;
 
         internal const int MaxShortPath = 260;
         internal const int MaxShortDirectoryPath = 248;

src/libraries/System.Formats.Tar/src/Resources/Strings.resx

@@ -1,17 +1,17 @@
 <?xml version="1.0" encoding="utf-8"?>
 <root>
-  <!--
-    Microsoft ResX Schema
-
+  <!-- 
+    Microsoft ResX Schema 
+    
     Version 2.0
-
-    The primary goals of this format is to allow a simple XML format
-    that is mostly human readable. The generation and parsing of the
-    various data types are done through the TypeConverter classes
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
     associated with the data types.
-
+    
     Example:
-
+    
     ... ado.net/XML headers & schema ...
     <resheader name="resmimetype">text/microsoft-resx</resheader>
     <resheader name="version">2.0</resheader>
@@ -26,36 +26,36 @@
         <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
         <comment>This is a comment</comment>
     </data>
-
-    There are any number of "resheader" rows that contain simple
+                
+    There are any number of "resheader" rows that contain simple 
     name/value pairs.
-
-    Each data row contains a name, and value. The row also contains a
-    type or mimetype. Type corresponds to a .NET class that support
-    text/value conversion through the TypeConverter architecture.
-    Classes that don't support this are serialized and stored with the
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
     mimetype set.
-
-    The mimetype is used for serialized objects, and tells the
-    ResXResourceReader how to depersist the object. This is currently not
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
     extensible. For a given mimetype the value must be set accordingly:
-
-    Note - application/x-microsoft.net.object.binary.base64 is the format
-    that the ResXResourceWriter will generate, however the reader can
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
     read any of the formats listed below.
-
+    
     mimetype: application/x-microsoft.net.object.binary.base64
-    value   : The object must be serialized with
+    value   : The object must be serialized with 
             : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
             : and then encoded with base64 encoding.
-
+    
     mimetype: application/x-microsoft.net.object.soap.base64
-    value   : The object must be serialized with
+    value   : The object must be serialized with 
             : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
             : and then encoded with base64 encoding.
 
     mimetype: application/x-microsoft.net.object.bytearray.base64
-    value   : The object must be serialized into a byte array
+    value   : The object must be serialized into a byte array 
             : using a System.ComponentModel.TypeConverter
             : and then encoded with base64 encoding.
     -->
@@ -261,4 +261,7 @@
   <data name="TarInvalidNumber" xml:space="preserve">
     <value>Unable to parse number.</value>
   </data>
-</root>
+  <data name="TarEntryFieldExceedsMaxLength" xml:space="preserve">
+    <value>The field '{0}' exceeds the maximum allowed length for this format.</value>
+  </data>
+</root>

src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj

@@ -65,6 +65,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.MkFifo.cs" Link="Common\Interop\Unix\System.Native\Interop.MkFifo.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Stat.cs" Link="Common\Interop\Unix\Interop.Stat.cs" />
     <Compile Include="$(CommonPath)System\IO\Archiving.Utils.Unix.cs" Link="Common\System\IO\Archiving.Utils.Unix.cs" />
+    <Compile Include="$(CommonPath)System\IO\PathInternal.Unix.cs" Link="Common\System\IO\PathInternal.Unix.cs" />
   </ItemGroup>
   <ItemGroup>
     <Reference Include="System.Collections" />

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.Read.cs

@@ -517,8 +517,8 @@ private void ReadVersionAttribute(Span<byte> buffer)
         private void ReadPosixAndGnuSharedAttributes(Span<byte> buffer)
         {
             // Convert the byte arrays
-            _uName = TarHelpers.GetTrimmedAsciiString(buffer.Slice(FieldLocations.UName, FieldLengths.UName));
-            _gName = TarHelpers.GetTrimmedAsciiString(buffer.Slice(FieldLocations.GName, FieldLengths.GName));
+            _uName = TarHelpers.GetTrimmedUtf8String(buffer.Slice(FieldLocations.UName, FieldLengths.UName));
+            _gName = TarHelpers.GetTrimmedUtf8String(buffer.Slice(FieldLocations.GName, FieldLengths.GName));
 
             // DevMajor and DevMinor only have values with character devices and block devices.
             // For all other typeflags, the values in these fields are irrelevant.