return wrapReader{
		Reader: wrapped,
	}
}

// A Reader wraps an io.Reader and computes the
// MD5 checksum of the read content as ETag.
//
// Optionally, a Reader can also verify that
// the computed ETag matches an expected value.
// Therefore, it compares both ETags once the
// underlying io.Reader returns io.EOF.
// If the computed ETag does not match the
// expected ETag then Read returns a VerifyError.
//

		if bytes.Equal(tr.blk[:], zeroBlock[:]) {
			return nil, nil, io.EOF // normal EOF; exactly 2 block of zeros read
		}
		return nil, nil, ErrHeader // Zero block and then non-zero block
	}

	// Verify the header matches a known format.
	format := tr.blk.getFormat()
	if format == FormatUnknown {
		return nil, nil, ErrHeader
	}

	var p parser
	hdr := new(Header)

	// Unpack the V7 header.
	v7 := tr.blk.toV7()