next (#5)

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

mfer/deserialize.go

@@ -0,0 +1,89 @@
+package mfer
+
+import (
+	"bytes"
+	"compress/gzip"
+	"errors"
+	"io"
+
+	"git.eeqj.de/sneak/mfer/internal/bork"
+	"git.eeqj.de/sneak/mfer/internal/log"
+	"google.golang.org/protobuf/proto"
+)
+
+func (m *manifest) validateProtoOuter() error {
+	if m.pbOuter.Version != MFFileOuter_VERSION_ONE {
+		return errors.New("unknown version")
+	}
+	if m.pbOuter.CompressionType != MFFileOuter_COMPRESSION_GZIP {
+		return errors.New("unknown compression type")
+	}
+
+	bb := bytes.NewBuffer(m.pbOuter.InnerMessage)
+
+	gzr, err := gzip.NewReader(bb)
+	if err != nil {
+		return err
+	}
+
+	dat, err := io.ReadAll(gzr)
+	defer gzr.Close()
+
+	if err != nil {
+		return err
+	}
+
+	isize := len(dat)
+	if int64(isize) != m.pbOuter.Size {
+		log.Debugf("truncated data, got %d expected %d", isize, m.pbOuter.Size)
+		return bork.ErrFileTruncated
+	}
+	log.Debugf("inner data size is %d", isize)
+	log.Dump(dat)
+	log.Dump(m.pbOuter.Sha256)
+	return nil
+}
+
+func validateMagic(dat []byte) bool {
+	ml := len([]byte(MAGIC))
+	if len(dat) < ml {
+		return false
+	}
+	got := dat[0:ml]
+	expected := []byte(MAGIC)
+	return bytes.Equal(got, expected)
+}
+
+func NewFromProto(input io.Reader) (*manifest, error) {
+	m := New()
+	dat, err := io.ReadAll(input)
+	if err != nil {
+		return nil, err
+	}
+	if !validateMagic(dat) {
+		return nil, errors.New("invalid file format")
+	}
+
+	// remove magic bytes prefix:
+	ml := len([]byte(MAGIC))
+	bb := bytes.NewBuffer(dat[ml:])
+	dat = bb.Bytes()
+
+	log.Dump(dat)
+
+	// deserialize:
+	m.pbOuter = new(MFFileOuter)
+	err = proto.Unmarshal(dat, m.pbOuter)
+
+	if err != nil {
+		return nil, err
+	}
+
+	ve := m.validateProtoOuter()
+	if ve != nil {
+		return nil, ve
+	}
+
+	// FIXME TODO deserialize inner
+	return m, nil
+}