req.Header.Set("x-amz-decoded-content-length", strconv.FormatInt(dataLength, 10))
	req.Header.Set("content-length", strconv.FormatInt(contentLength, 10))

	// Seek back to beginning.
	body.Seek(0, 0)

	// Add body
	req.Body = io.NopCloser(body)
	req.ContentLength = contentLength

	return req, nil
}

	buf := NewReader(r)
	allocs := testing.AllocsPerRun(100, func() {
		r.Seek(0, io.SeekStart)
		buf.Reset(r)

		_, err := buf.ReadString('\n')
		if err != nil {
			t.Fatal(err)
		}
	})
	if allocs != 1 {
		t.Errorf("Unexpected number of allocations, got %f, want 1", allocs)

	// Verify it is a regular file, otherwise subsequent Seek is
	// undefined.
	if !st.Mode().IsRegular() {
		file.Close()
		return nil, errIsNotRegular
	}

	if st.Size() < offset+length {
		// Expected size cannot be satisfied for
		// requested offset and length
		file.Close()
		return nil, errFileCorrupt
	}

	if offset > 0 {
		if _, err = file.Seek(offset, io.SeekStart); err != nil {