if len(SHA256) != 0 {
		h = sha256.New()
	}
	return &Reader{
		src:           src,
		size:          size,
		actualSize:    actualSize,
		checksum:      MD5,
		contentSHA256: SHA256,
		sha256:        h,
		disableMD5:    disableMD5,
	}, nil
}

// ErrInvalidChecksum is returned when an invalid checksum is provided in headers.
var ErrInvalidChecksum = errors.New("invalid checksum")