feat: certstore snapshot export

certstore/snapshot.go

@@ -0,0 +1,90 @@
+package certstore
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"errors"
+	"io"
+
+	"github.com/filecoin-project/go-f3/gpbft"
+	"github.com/ipfs/go-datastore"
+	xerrors "golang.org/x/xerrors"
+)
+
+var ErrlatestCertificateNil = errors.New("latest certificate is not available")
+
+// Exports an F3 snapshot that includes the finality certificate chain until the current `latestCertificate`.
+func (cs *Store) ExportLatestSnapshot(ctx context.Context, writer io.Writer) error {
+	if cs.latestCertificate == nil {
+		return ErrlatestCertificateNil
+	}
+	return cs.ExportSnapshot(ctx, cs.latestCertificate.GPBFTInstance, writer)
+}
+
+// Exports an F3 snapshot that includes the finality certificate chain until the specified `lastInstance`.
+func (cs *Store) ExportSnapshot(ctx context.Context, lastInstance uint64, writer io.Writer) error {
+	initialPowerTable, err := cs.GetPowerTable(ctx, cs.firstInstance)
+	if err != nil {
+		return xerrors.Errorf("failed to get initial power table at instance %d: %w", cs.firstInstance, err)
+	}
+	header := SnapshotHeader{1, cs.firstInstance, lastInstance, initialPowerTable}
+	if err := header.WriteToSnapshot(writer); err != nil {
+		return xerrors.Errorf("failed to write snapshot header: %w", err)
+	}
+	for i := cs.firstInstance; i <= lastInstance; i++ {
+		cert, err := cs.ds.Get(ctx, cs.keyForCert(i))
+		if err != nil {
+			return xerrors.Errorf("failed to get certificate at instance %d:: %w", i, err)
+		}
+		buffer := bytes.NewBuffer(cert)
+		if err := writeSnapshotBlockBytes(writer, buffer); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Imports an F3 snapshot and opens the certificate store.
+//
+// The passed Datastore has to be thread safe.
+func ImportSnapshotAndOpenStore(ctx context.Context, ds datastore.Datastore) error {
+	return xerrors.New("to be implemented")
+}
+
+type SnapshotHeader struct {
+	Version           uint64
+	FirstInstance     uint64
+	LatestInstance    uint64
+	InitialPowerTable gpbft.PowerEntries
+}
+
+func (h *SnapshotHeader) WriteToSnapshot(writer io.Writer) error {
+	return writeSnapshotCborEncodedBlock(writer, h)
+}
+
+// Writes CBOR-encoded header or data block with a varint-encoded length prefix
+func writeSnapshotCborEncodedBlock(writer io.Writer, block MarshalCBOR) error {
+	var buffer bytes.Buffer
+	if err := block.MarshalCBOR(&buffer); err != nil {
+		return err
+	}
+	return writeSnapshotBlockBytes(writer, &buffer)
+}
+
+// Writes header or data block with a varint-encoded length prefix
+func writeSnapshotBlockBytes(writer io.Writer, buffer *bytes.Buffer) error {
+	buf := make([]byte, 8)
+	n := binary.PutUvarint(buf, uint64(buffer.Len()))
+	if _, err := writer.Write(buf[:n]); err != nil {
+		return err
+	}
+	if _, err := buffer.WriteTo(writer); err != nil {
+		return err
+	}
+	return nil
+}
+
+type MarshalCBOR interface {
+	MarshalCBOR(w io.Writer) error
+}

gen/main.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/filecoin-project/go-f3/certexchange"
 	"github.com/filecoin-project/go-f3/certs"
+	"github.com/filecoin-project/go-f3/certstore"
 	"github.com/filecoin-project/go-f3/chainexchange"
 	"github.com/filecoin-project/go-f3/gpbft"
 	gen "github.com/whyrusleeping/cbor-gen"
@@ -47,6 +48,11 @@ func main() {
 			chainexchange.Message{},
 		)
 	})
+	eg.Go(func() error {
+		return gen.WriteTupleEncodersToFile("../certstore/cbor_gen.go", "certstore",
+			certstore.SnapshotHeader{},
+		)
+	})
 	if err := eg.Wait(); err != nil {
 		fmt.Printf("Failed to complete cborg_gen: %v\n", err)
 		os.Exit(1)