add async implementations to readonlysubstream

src/SharpCompress/IO/ReadOnlySubStream.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Diagnostics;
 using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
 
 namespace SharpCompress.IO;
 
@@ -93,6 +95,47 @@ internal class ReadOnlySubStream : SharpCompressStream, IStreamStack
     }
 #endif
 
+    public override async Task<int> ReadAsync(
+        byte[] buffer,
+        int offset,
+        int count,
+        CancellationToken cancellationToken
+    )
+    {
+        if (BytesLeftToRead < count)
+        {
+            count = (int)BytesLeftToRead;
+        }
+        var read = await Stream
+            .ReadAsync(buffer, offset, count, cancellationToken)
+            .ConfigureAwait(false);
+        if (read > 0)
+        {
+            BytesLeftToRead -= read;
+            _position += read;
+        }
+        return read;
+    }
+
+#if !NETFRAMEWORK && !NETSTANDARD2_0
+    public override async ValueTask<int> ReadAsync(
+        Memory<byte> buffer,
+        CancellationToken cancellationToken = default
+    )
+    {
+        var sliceLen = BytesLeftToRead < buffer.Length ? BytesLeftToRead : buffer.Length;
+        var read = await Stream
+            .ReadAsync(buffer.Slice(0, (int)sliceLen), cancellationToken)
+            .ConfigureAwait(false);
+        if (read > 0)
+        {
+            BytesLeftToRead -= read;
+            _position += read;
+        }
+        return read;
+    }
+#endif
+
     public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
 
     public override void SetLength(long value) => throw new NotSupportedException();