Remove code duplication in TarHeader class (dotnet#72501)

* Missing ConfigureAwait(false) in await using.

* Remove argument from TarSizeFieldNegative exception resource string.

* TarHeader.TryGetNextHeaderAsync: Reduce duplication.

* TarHeader.ReadExtendedAttributesBlockAsync: reduce duplication.

* TarHeader.ReadGnuLongPathDataBlockAsync: reduce duplication.

* TarHeader.ReadExtendedAttributesFromBuffer: reduce duplication.

* TarHeader.WriteAsV7Async: Reduce duplication.

* TarHeader.WriteAsUstarAsync: reduce duplication.

* TarHeader.*Pax*Async: reduce duplication.

* TarHeader.WriteAsGnuAsync: reduce duplication.

* Use pretty switch for async writing. Move the sync version to its own method, to keep similar logic close by.

* checksum => tmpChecksum for consistency with other similar methods.

* Add ExtendedAttributes non-nullable property that initializes private nullable property if needed.

* Remove unnecessary buffer cleaning call.

Co-authored-by: carlossanlop <carlossanlop@users.noreply.github.com>

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

@@ -232,7 +232,7 @@
     <value>A POSIX format was expected (Ustar or PAX), but could not be reliably determined for entry '{0}'.</value>
   </data>
   <data name="TarSizeFieldNegative" xml:space="preserve">
-    <value>The size field is negative in the tar entry '{0}'.</value>
+    <value>The size field is negative in a tar entry.</value>
   </data>
   <data name="TarSizeFieldTooLargeForEntryType" xml:space="preserve">
     <value>The value of the size field for the current entry of type '{0}' is beyond the expected length.</value>

src/libraries/System.Formats.Tar/src/System/Formats/Tar/GnuTarEntry.cs

@@ -54,13 +54,13 @@ public GnuTarEntry(TarEntry other)
 
                 if (other is PaxTarEntry paxOther)
                 {
-                    changedATime = TarHelpers.TryGetDateTimeOffsetFromTimestampString(paxOther._header._extendedAttributes, TarHeader.PaxEaATime, out DateTimeOffset aTime);
+                    changedATime = TarHelpers.TryGetDateTimeOffsetFromTimestampString(paxOther._header.ExtendedAttributes, TarHeader.PaxEaATime, out DateTimeOffset aTime);
                     if (changedATime)
                     {
                         _header._aTime = aTime;
                     }
 
-                    changedCTime = TarHelpers.TryGetDateTimeOffsetFromTimestampString(paxOther._header._extendedAttributes, TarHeader.PaxEaCTime, out DateTimeOffset cTime);
+                    changedCTime = TarHelpers.TryGetDateTimeOffsetFromTimestampString(paxOther._header.ExtendedAttributes, TarHeader.PaxEaCTime, out DateTimeOffset cTime);
                     if (changedCTime)
                     {
                         _header._cTime = cTime;

src/libraries/System.Formats.Tar/src/System/Formats/Tar/PaxGlobalExtendedAttributesTarEntry.cs

@@ -29,20 +29,13 @@ public PaxGlobalExtendedAttributesTarEntry(IEnumerable<KeyValuePair<string, stri
             : base(TarEntryType.GlobalExtendedAttributes, TarHeader.GlobalHeadFormatPrefix, TarEntryFormat.Pax, isGea: true)
         {
             ArgumentNullException.ThrowIfNull(globalExtendedAttributes);
-            _header._extendedAttributes = new Dictionary<string, string>(globalExtendedAttributes);
+            _header.InitializeExtendedAttributesWithExisting(globalExtendedAttributes);
         }
 
         /// <summary>
         /// Returns the global extended attributes stored in this entry.
         /// </summary>
-        public IReadOnlyDictionary<string, string> GlobalExtendedAttributes
-        {
-            get
-            {
-                _header._extendedAttributes ??= new Dictionary<string, string>();
-                return _readOnlyGlobalExtendedAttributes ??= _header._extendedAttributes.AsReadOnly();
-            }
-        }
+        public IReadOnlyDictionary<string, string> GlobalExtendedAttributes => _readOnlyGlobalExtendedAttributes ??= _header.ExtendedAttributes.AsReadOnly();
 
         // Determines if the current instance's entry type supports setting a data stream.
         internal override bool IsDataStreamSetterSupported() => false;

src/libraries/System.Formats.Tar/src/System/Formats/Tar/PaxTarEntry.cs

@@ -51,7 +51,6 @@ public PaxTarEntry(TarEntryType entryType, string entryName)
             : base(entryType, entryName, TarEntryFormat.Pax, isGea: false)
         {
             _header._prefix = string.Empty;
-            _header._extendedAttributes = new Dictionary<string, string>();
 
             Debug.Assert(_header._mTime != default);
             AddNewAccessAndChangeTimestampsIfNotExist(useMTime: true);
@@ -92,7 +91,7 @@ public PaxTarEntry(TarEntryType entryType, string entryName, IEnumerable<KeyValu
             ArgumentNullException.ThrowIfNull(extendedAttributes);
 
             _header._prefix = string.Empty;
-            _header._extendedAttributes = new Dictionary<string, string>(extendedAttributes);
+            _header.InitializeExtendedAttributesWithExisting(extendedAttributes);
 
             Debug.Assert(_header._mTime != default);
             AddNewAccessAndChangeTimestampsIfNotExist(useMTime: true);
@@ -111,15 +110,14 @@ public PaxTarEntry(TarEntry other)
 
             if (other is PaxTarEntry paxOther)
             {
-                _header._extendedAttributes = new Dictionary<string, string>(paxOther.ExtendedAttributes);
+                _header.InitializeExtendedAttributesWithExisting(paxOther.ExtendedAttributes);
             }
             else
             {
-                _header._extendedAttributes = new Dictionary<string, string>();
                 if (other is GnuTarEntry gnuOther)
                 {
-                    _header._extendedAttributes[TarHeader.PaxEaATime] = TarHelpers.GetTimestampStringFromDateTimeOffset(gnuOther.AccessTime);
-                    _header._extendedAttributes[TarHeader.PaxEaCTime] = TarHelpers.GetTimestampStringFromDateTimeOffset(gnuOther.ChangeTime);
+                    _header.ExtendedAttributes[TarHeader.PaxEaATime] = TarHelpers.GetTimestampStringFromDateTimeOffset(gnuOther.AccessTime);
+                    _header.ExtendedAttributes[TarHeader.PaxEaCTime] = TarHelpers.GetTimestampStringFromDateTimeOffset(gnuOther.ChangeTime);
                 }
             }
 
@@ -144,14 +142,7 @@ public PaxTarEntry(TarEntry other)
         /// <item>File length, under the name <c>size</c>, as an <see cref="int"/>, if the string representation of the number is larger than 12 bytes.</item>
         /// </list>
         /// </remarks>
-        public IReadOnlyDictionary<string, string> ExtendedAttributes
-        {
-            get
-            {
-                _header._extendedAttributes ??= new Dictionary<string, string>();
-                return _readOnlyExtendedAttributes ??= _header._extendedAttributes.AsReadOnly();
-            }
-        }
+        public IReadOnlyDictionary<string, string> ExtendedAttributes => _readOnlyExtendedAttributes ??= _header.ExtendedAttributes.AsReadOnly();
 
         // Determines if the current instance's entry type supports setting a data stream.
         internal override bool IsDataStreamSetterSupported() => EntryType == TarEntryType.RegularFile;
@@ -162,22 +153,21 @@ public IReadOnlyDictionary<string, string> ExtendedAttributes
         private void AddNewAccessAndChangeTimestampsIfNotExist(bool useMTime)
         {
             Debug.Assert(!useMTime || (useMTime && _header._mTime != default));
-            Debug.Assert(_header._extendedAttributes != null);
-            bool containsATime = _header._extendedAttributes.ContainsKey(TarHeader.PaxEaATime);
-            bool containsCTime = _header._extendedAttributes.ContainsKey(TarHeader.PaxEaCTime);
+            bool containsATime = _header.ExtendedAttributes.ContainsKey(TarHeader.PaxEaATime);
+            bool containsCTime = _header.ExtendedAttributes.ContainsKey(TarHeader.PaxEaCTime);
 
             if (!containsATime || !containsCTime)
             {
                 string secondsFromEpochString = TarHelpers.GetTimestampStringFromDateTimeOffset(useMTime ? _header._mTime : DateTimeOffset.UtcNow);
 
                 if (!containsATime)
                 {
-                    _header._extendedAttributes[TarHeader.PaxEaATime] = secondsFromEpochString;
+                    _header.ExtendedAttributes[TarHeader.PaxEaATime] = secondsFromEpochString;
                 }
 
                 if (!containsCTime)
                 {
-                    _header._extendedAttributes[TarHeader.PaxEaCTime] = secondsFromEpochString;
+                    _header.ExtendedAttributes[TarHeader.PaxEaCTime] = secondsFromEpochString;
                 }
             }
         }

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarEntry.cs

@@ -529,7 +529,7 @@ private async Task ExtractAsRegularFileAsync(string destinationFileName, Cancell
 
             // Rely on FileStream's ctor for further checking destinationFileName parameter
             FileStream fs = new FileStream(destinationFileName, CreateFileStreamOptions(isAsync: true));
-            await using (fs)
+            await using (fs.ConfigureAwait(false))
             {
                 if (DataStream != null)
                 {