Use explicit enum, add comments

src/SharpCompress/Common/ArchiveEncoding.cs

@@ -9,5 +9,5 @@ public class ArchiveEncoding : IArchiveEncoding
     public Encoding Password { get; set; } = Encoding.Default;
     public Encoding UTF8 { get; set; } = Encoding.UTF8;
     public Encoding? Forced { get; set; }
-    public Func<byte[], int, int, string>? CustomDecoder { get; set; }
+    public Func<byte[], int, int, EncodingType, string>? CustomDecoder { get; set; }
 }

src/SharpCompress/Common/ArchiveEncodingExtensions.cs

@@ -3,26 +3,85 @@ using System.Text;
 
 namespace SharpCompress.Common;
 
+/// <summary>
+/// Specifies the type of encoding to use.
+/// </summary>
+public enum EncodingType
+{
+    /// <summary>
+    /// Uses the default encoding.
+    /// </summary>
+    Default,
+    /// <summary>
+    /// Uses UTF-8 encoding.
+    /// </summary>
+    UTF8,
+}
+
+/// <summary>
+/// Provides extension methods for archive encoding.
+/// </summary>
 public static class ArchiveEncodingExtensions
 {
+#if !NETFRAMEWORK
+    /// <summary>
+    /// Registers the code pages encoding provider.
+    /// </summary>
+    static ArchiveEncodingExtensions() =>
+        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+#endif
+
+    /// <summary>
+    /// Gets the encoding based on the archive encoding settings.
+    /// </summary>
+    /// <param name="useUtf8">Whether to use UTF-8.</param>
+    /// <returns>The encoding.</returns>
+    /// <param name="encoding">The archive encoding instance.</param>
     extension(IArchiveEncoding encoding)
     {
         public Encoding GetEncoding(bool useUtf8 = false) =>
             encoding.Forced ?? (useUtf8 ? encoding.UTF8 : encoding.Default);
 
-        public Func<byte[], int, int, string> GetDecoder(bool useUtf8) =>
+        /// <summary>
+        /// Gets the decoder function for the archive encoding.
+        /// </summary>
+        /// <returns>The decoder function.</returns>
+        public Func<byte[], int, int, EncodingType, string> GetDecoder() =>
             encoding.CustomDecoder
             ?? (
-                (bytes, index, count) =>
-                    encoding.GetEncoding(useUtf8).GetString(bytes, index, count)
+                (bytes, index, count, type) =>
+                    encoding.GetEncoding(type == EncodingType.UTF8).GetString(bytes, index, count)
             );
 
+        /// <summary>
+        /// Encodes a string using the default encoding.
+        /// </summary>
+        /// <param name="str">The string to encode.</param>
+        /// <returns>The encoded bytes.</returns>
         public byte[] Encode(string str) => encoding.Default.GetBytes(str);
 
-        public string Decode(byte[] bytes, bool useUtf8 = false) =>
-            encoding.Decode(bytes, 0, bytes.Length, useUtf8);
+        /// <summary>
+        /// Decodes bytes using the specified encoding type.
+        /// </summary>
+        /// <param name="bytes">The bytes to decode.</param>
+        /// <param name="type">The encoding type.</param>
+        /// <returns>The decoded string.</returns>
+        public string Decode(byte[] bytes, EncodingType type = EncodingType.Default) =>
+            encoding.Decode(bytes, 0, bytes.Length, type);
 
-        public string Decode(byte[] bytes, int start, int length, bool useUtf8 = false) =>
-            encoding.GetDecoder(useUtf8)(bytes, start, length);
+        /// <summary>
+        /// Decodes a portion of bytes using the specified encoding type.
+        /// </summary>
+        /// <param name="bytes">The bytes to decode.</param>
+        /// <param name="start">The start index.</param>
+        /// <param name="length">The length.</param>
+        /// <param name="type">The encoding type.</param>
+        /// <returns>The decoded string.</returns>
+        public string Decode(
+            byte[] bytes,
+            int start,
+            int length,
+            EncodingType type = EncodingType.Default
+        ) => encoding.GetDecoder()(bytes, start, length, type);
     }
 }

src/SharpCompress/Common/IArchiveEncoding.cs

@@ -3,20 +3,23 @@ using System.Text;
 
 namespace SharpCompress.Common;
 
+/// <summary>
+/// Defines the encoding settings for archives.
+/// </summary>
 public interface IArchiveEncoding
 {
     /// <summary>
-    /// Default encoding to use when archive format doesn't specify one.
+    /// Default encoding to use when archive format doesn't specify one.  Required and defaults to Encoding.Default.
     /// </summary>
     public Encoding Default { get; set; }
 
     /// <summary>
-    /// ArchiveEncoding used by encryption schemes which don't comply with RFC 2898.
+    /// ArchiveEncoding used by encryption schemes which don't comply with RFC 2898. Required and defaults to Encoding.Default.
     /// </summary>
     public Encoding Password { get; set; }
 
     /// <summary>
-    /// Default encoding to use when archive format specifies UTF-8 encoding.
+    /// Default encoding to use when archive format specifies UTF-8 encoding. Required and defaults to Encoding.UTF8.
     /// </summary>
     public Encoding UTF8 { get; set; }
 
@@ -28,6 +31,6 @@ public interface IArchiveEncoding
     /// <summary>
     /// Set this when you want to use a custom method for all decoding operations.
     /// </summary>
-    /// <returns>string Func(bytes, index, length)</returns>
-    public Func<byte[], int, int, string>? CustomDecoder { get; set; }
+    /// <returns>string Func(bytes, index, length, EncodingType)</returns>
+    public Func<byte[], int, int, EncodingType, string>? CustomDecoder { get; set; }
 }

src/SharpCompress/Common/Zip/Headers/DirectoryEntryHeader.cs

@@ -41,8 +41,8 @@ internal class DirectoryEntryHeader : ZipFileEntry
 
         if (Flags.HasFlag(HeaderFlags.Efs))
         {
-            Name = ArchiveEncoding.Decode(name, true);
-            Comment = ArchiveEncoding.Decode(comment, true);
+            Name = ArchiveEncoding.Decode(name, EncodingType.UTF8);
+            Comment = ArchiveEncoding.Decode(comment, EncodingType.UTF8);
         }
         else
         {

src/SharpCompress/Common/Zip/Headers/LocalEntryHeader.cs

@@ -33,7 +33,7 @@ internal class LocalEntryHeader : ZipFileEntry
 
         if (Flags.HasFlag(HeaderFlags.Efs))
         {
-            Name = ArchiveEncoding.Decode(name, true);
+            Name = ArchiveEncoding.Decode(name, EncodingType.UTF8);
         }
         else
         {