next (#5)

Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #5

mfer/serialize.go

@@ -0,0 +1,100 @@
+package mfer
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/sha256"
+	"errors"
+	"time"
+
+	"google.golang.org/protobuf/proto"
+)
+
+//go:generate protoc --go_out=. --go_opt=paths=source_relative mf.proto
+
+// rot13("MANIFEST")
+const MAGIC string = "ZNAVSRFG"
+
+func newTimestampFromTime(t time.Time) *Timestamp {
+	out := &Timestamp{
+		Seconds: t.Unix(),
+		Nanos:   int32(t.UnixNano() - (t.Unix() * 1000000000)),
+	}
+	return out
+}
+
+func (m *manifest) generate() error {
+	if m.pbInner == nil {
+		e := m.generateInner()
+		if e != nil {
+			return e
+		}
+	}
+	if m.pbOuter == nil {
+		e := m.generateOuter()
+		if e != nil {
+			return e
+		}
+	}
+	dat, err := proto.MarshalOptions{Deterministic: true}.Marshal(m.pbOuter)
+	if err != nil {
+		return err
+	}
+	m.output = bytes.NewBuffer([]byte(MAGIC))
+	_, err = m.output.Write(dat)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (m *manifest) generateOuter() error {
+	if m.pbInner == nil {
+		return errors.New("internal error")
+	}
+	innerData, err := proto.MarshalOptions{Deterministic: true}.Marshal(m.pbInner)
+	if err != nil {
+		return err
+	}
+
+	h := sha256.New()
+	h.Write(innerData)
+
+	idc := new(bytes.Buffer)
+	gzw, err := gzip.NewWriterLevel(idc, gzip.BestCompression)
+	if err != nil {
+		return err
+	}
+	_, err = gzw.Write(innerData)
+	if err != nil {
+		return err
+	}
+
+	gzw.Close()
+
+	o := &MFFileOuter{
+		InnerMessage:    idc.Bytes(),
+		Size:            int64(len(innerData)),
+		Sha256:          h.Sum(nil),
+		Version:         MFFileOuter_VERSION_ONE,
+		CompressionType: MFFileOuter_COMPRESSION_GZIP,
+	}
+	m.pbOuter = o
+	return nil
+}
+
+func (m *manifest) generateInner() error {
+	m.pbInner = &MFFile{
+		Version:   MFFile_VERSION_ONE,
+		CreatedAt: newTimestampFromTime(time.Now()),
+		Files:     []*MFFilePath{},
+	}
+	for _, f := range m.files {
+		nf := &MFFilePath{
+			Path: f.path,
+			// FIXME add more stuff
+		}
+		m.pbInner.Files = append(m.pbInner.Files, nf)
+	}
+	return nil
+}