export snapshot CID

Author: hanabi1224

certstore/snapshot.go

@@ -6,49 +6,76 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"hash"
 	"io"
 
 	"github.com/filecoin-project/go-f3/certs"
 	"github.com/filecoin-project/go-f3/gpbft"
 	"github.com/filecoin-project/go-state-types/cbor"
+	cid "github.com/ipfs/go-cid"
 	"github.com/ipfs/go-datastore"
+	"github.com/multiformats/go-multihash"
+	"golang.org/x/crypto/blake2b"
 )
 
 var ErrUnknownLatestCertificate = errors.New("latest certificate is not known")
 
 // ExportLatestSnapshot exports an F3 snapshot that includes the finality certificate chain until the current `latestCertificate`.
 //
 // Checkout the snapshot format specification at <https://github.com/filecoin-project/FIPs/blob/master/FRCs/frc-0108.md>
-func (cs *Store) ExportLatestSnapshot(ctx context.Context, writer io.Writer) error {
+func (cs *Store) ExportLatestSnapshot(ctx context.Context, writer io.Writer) (cid.Cid, error) {
 	if cs.latestCertificate == nil {
-		return ErrUnknownLatestCertificate
+		return cid.Undef, ErrUnknownLatestCertificate
 	}
 	return cs.ExportSnapshot(ctx, cs.latestCertificate.GPBFTInstance, writer)
 }
 
 // ExportSnapshot exports an F3 snapshot that includes the finality certificate chain from the `Store.firstInstance` to the specified `lastInstance`.
 //
 // Checkout the snapshot format specification at <https://github.com/filecoin-project/FIPs/blob/master/FRCs/frc-0108.md>
-func (cs *Store) ExportSnapshot(ctx context.Context, latestInstance uint64, writer io.Writer) error {
+func (cs *Store) ExportSnapshot(ctx context.Context, latestInstance uint64, writer io.Writer) (cid.Cid, error) {
+	hasher, err := blake2b.New256(nil)
+	if err != nil {
+		return cid.Undef, err
+	}
+	hashWriter := hashWriter{hasher, writer}
 	initialPowerTable, err := cs.GetPowerTable(ctx, cs.firstInstance)
 	if err != nil {
-		return fmt.Errorf("failed to get initial power table at instance %d: %w", cs.firstInstance, err)
+		return cid.Undef, fmt.Errorf("failed to get initial power table at instance %d: %w", cs.firstInstance, err)
 	}
 	header := SnapshotHeader{1, cs.firstInstance, latestInstance, initialPowerTable}
-	if _, err := header.WriteTo(writer); err != nil {
-		return fmt.Errorf("failed to write snapshot header: %w", err)
+	if _, err := header.WriteTo(hashWriter); err != nil {
+		return cid.Undef, fmt.Errorf("failed to write snapshot header: %w", err)
 	}
 	for i := cs.firstInstance; i <= latestInstance; i++ {
 		cert, err := cs.ds.Get(ctx, cs.keyForCert(i))
 		if err != nil {
-			return fmt.Errorf("failed to get certificate at instance %d:: %w", i, err)
+			return cid.Undef, fmt.Errorf("failed to get certificate at instance %d:: %w", i, err)
 		}
 		buffer := bytes.NewBuffer(cert)
-		if _, err := writeSnapshotBlockBytes(writer, buffer); err != nil {
-			return err
+		if _, err := writeSnapshotBlockBytes(hashWriter, buffer); err != nil {
+			return cid.Undef, err
 		}
 	}
-	return nil
+	hash := hashWriter.hasher.Sum(nil)
+	mh, err := multihash.Encode(hash, multihash.BLAKE2B_MIN+31)
+	if err != nil {
+		return cid.Undef, err
+	}
+
+	return cid.NewCidV1(cid.Raw, mh), nil
+}
+
+type hashWriter struct {
+	hasher hash.Hash
+	writer io.Writer
+}
+
+func (w hashWriter) Write(p []byte) (n int, err error) {
+	if _, err := w.hasher.Write(p); err != nil {
+		return 0, err
+	}
+	return w.writer.Write(p)
 }
 
 type SnapshotReader interface {

certstore/snapshot_test.go

@@ -13,9 +13,12 @@ import (
 	"github.com/filecoin-project/go-f3/internal/consensus"
 	"github.com/filecoin-project/go-f3/manifest"
 	"github.com/filecoin-project/go-f3/sim/signing"
+	"github.com/ipfs/go-cid"
 	"github.com/ipfs/go-datastore"
+	"github.com/multiformats/go-multihash"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/zap/buffer"
+	"golang.org/x/crypto/blake2b"
 )
 
 func Test_SnapshotExportImportRoundTrip(t *testing.T) {
@@ -88,8 +91,16 @@ func Test_SnapshotExportImportRoundTrip(t *testing.T) {
 	}
 
 	snapshot := buffer.Buffer{}
-	err = cs.ExportLatestSnapshot(ctx, &snapshot)
+	c, err := cs.ExportLatestSnapshot(ctx, &snapshot)
 	require.NoError(t, err)
+	require.NotEqual(t, c, cid.Undef)
+	require.Equal(t, int(c.Prefix().Version), 1)
+	require.Equal(t, int(c.Prefix().Codec), cid.Raw)
+	require.Equal(t, int(c.Prefix().MhType), 0xb220)
+	hash := blake2b.Sum256(snapshot.Bytes())
+	mh, err := multihash.Encode(hash[:], multihash.BLAKE2B_MIN+31)
+	require.NoError(t, err)
+	require.Equal(t, c.Hash(), multihash.Multihash(mh))
 
 	ds2 := datastore.NewMapDatastore()
 	err = importSnapshotToDatastoreWithTestingPowerTableFrequency(ctx, bytes.NewReader(snapshot.Bytes()), ds2, testingPowerTableFreqency)