func calcHash()

in image/create.go [419:474]
46 lines of code
13 McCabe index (conditional complexity)

func calcHash(initialHash []byte, hdr ImageHdr, pad []byte,
	plainBody []byte, protTlvs []ImageTlv) ([]byte, error) {

	hash := sha256.New()

	add := func(itf interface{}) error {
		b := &bytes.Buffer{}
		if err := binary.Write(b, binary.LittleEndian, itf); err != nil {
			return err
		}
		if err := binary.Write(hash, binary.LittleEndian, itf); err != nil {
			return errors.Wrapf(err, "failed to hash data")
		}

		return nil
	}

	if initialHash != nil {
		if err := add(initialHash); err != nil {
			return nil, err
		}
	}

	if err := add(hdr); err != nil {
		return nil, err
	}

	if err := add(pad); err != nil {
		return nil, err
	}

	if err := add(plainBody); err != nil {
		return nil, err
	}

	if len(protTlvs) > 0 {
		trailer := ImageTrailer{
			Magic:     IMAGE_PROT_TRAILER_MAGIC,
			TlvTotLen: hdr.ProtSz,
		}
		if err := add(trailer); err != nil {
			return nil, err
		}

		for _, tlv := range protTlvs {
			if err := add(tlv.Header); err != nil {
				return nil, err
			}
			if err := add(tlv.Data); err != nil {
				return nil, err
			}
		}
	}

	return hash.Sum(nil), nil
}