func (r *Reader) AddNonTrailingChecksum(cs *Checksum, ignoreValue bool) error {
	if cs == nil {
		return nil
	}
	r.contentHash = *cs
	if ignoreValue {
		// Do not validate, but allow for transfer
		return nil
	}

	r.contentHasher = cs.Type.Hasher()
	if r.contentHasher == nil {
		return ErrInvalidChecksum
	}
	return nil
}

func (r *Reader) Read(p []byte) (int, error) {

func parsePAX(r io.Reader) (map[string]string, error) {
	buf, err := readSpecialFile(r)
	if err != nil {
		return nil, err
	}
	sbuf := string(buf)

	// For GNU PAX sparse format 0.0 support.
	// This function transforms the sparse format 0.0 headers into format 0.1
	// headers since 0.0 headers were not PAX compliant.
	var sparseMap []string

	paxHdrs := make(map[string]string)
	for len(sbuf) > 0 {