Test with ForwardOnlyStream. RewindableStream shouldn't corrupt a ForwardOnlyStream (#161)

src/SharpCompress/Common/Zip/StreamingZipHeaderFactory.cs

@@ -31,7 +31,7 @@ namespace SharpCompress.Common.Zip
                     FlagUtility.HasFlag(lastEntryHeader.Flags, HeaderFlags.UsePostDataDescriptor))
                 {
                     reader = (lastEntryHeader.Part as StreamingZipFilePart).FixStreamedFileLocation(ref rewindableStream);
-                    long pos = rewindableStream.Position;
+                    long? pos = rewindableStream.CanSeek ? (long?)rewindableStream.Position : null;
                     uint crc = reader.ReadUInt32();
                     if (crc == POST_DATA_DESCRIPTOR)
                     {
@@ -40,7 +40,10 @@ namespace SharpCompress.Common.Zip
                     lastEntryHeader.Crc = crc;
                     lastEntryHeader.CompressedSize = reader.ReadUInt32();
                     lastEntryHeader.UncompressedSize = reader.ReadUInt32();
-                    lastEntryHeader.DataStartPosition = pos - lastEntryHeader.CompressedSize;
+                    if (pos.HasValue)
+                    {
+                        lastEntryHeader.DataStartPosition = pos - lastEntryHeader.CompressedSize;
+                    }
                 }
                 lastEntryHeader = null;
                 uint headerBytes = reader.ReadUInt32();

src/SharpCompress/IO/RewindableStream.cs

@@ -72,10 +72,7 @@ namespace SharpCompress.IO
             get { return true; }
         }
 
-        public override bool CanSeek
-        {
-            get { return false; }
-        }
+        public override bool CanSeek => stream.CanSeek;
 
         public override bool CanWrite
         {

test/SharpCompress.Test/ForwardOnlyStream.cs

@@ -0,0 +1,64 @@
+using System;
+using System.IO;
+
+namespace SharpCompress.Test
+{
+    public class ForwardOnlyStream : Stream
+    {
+        private readonly Stream stream;
+
+        public bool IsDisposed { get; private set; }
+
+        public ForwardOnlyStream(Stream stream)
+        {
+            this.stream = stream;
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            base.Dispose(disposing);
+            stream.Dispose();
+            IsDisposed = true;
+        }
+
+        public override bool CanRead => true;
+
+        public override bool CanSeek => false;
+        public override bool CanWrite => false;
+
+        public override void Flush()
+        {
+            throw new NotSupportedException();
+        }
+
+        public override long Length
+        {
+            get { throw new NotSupportedException(); }
+        }
+
+        public override long Position
+        {
+            get { throw new NotSupportedException(); }
+            set { throw new NotSupportedException(); }
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return stream.Read(buffer, offset, count);
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {throw new NotSupportedException();
+        }
+    }
+}

test/SharpCompress.Test/ReaderTests.cs

@@ -18,7 +18,7 @@ namespace SharpCompress.Test
         {
             foreach (var path in testArchives)
             {
-                using (Stream stream = File.OpenRead(path))
+                using (Stream stream = new ForwardOnlyStream(File.OpenRead(path)))
                 using (IReader reader = ReaderFactory.Open(stream))
                 {
                     UseReader(this, reader, expectedCompression);