add extension methods for checks

src/SharpCompress/StreamValidationExtensions.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace SharpCompress;
+
+internal static class StreamValidationExtensions
+{
+    internal static Stream RequireReadable(this Stream stream)
+    {
+        stream.NotNull(nameof(stream));
+
+        if (!stream.CanRead)
+        {
+            throw new ArgumentException("Stream must be readable", nameof(stream));
+        }
+
+        return stream;
+    }
+
+    internal static Stream RequireSeekable(this Stream stream)
+    {
+        stream.NotNull(nameof(stream));
+
+        if (!stream.CanSeek)
+        {
+            throw new ArgumentException("Stream must be seekable", nameof(stream));
+        }
+
+        return stream;
+    }
+
+    internal static IReadOnlyList<Stream> RequireSeekable(this IReadOnlyList<Stream> streams)
+    {
+        streams.NotNull(nameof(streams));
+
+        foreach (var stream in streams)
+        {
+            stream.RequireSeekable();
+        }
+
+        return streams;
+    }
+
+    internal static IReadOnlyList<Stream> RequireReadable(this IEnumerable<Stream> streams)
+    {
+        streams.NotNull(nameof(streams));
+
+        var streamArray = streams as IReadOnlyList<Stream> ?? streams.ToArray();
+        foreach (var stream in streamArray)
+        {
+            stream.RequireReadable();
+        }
+
+        return streamArray;
+    }
+}