fix merger to convert legacy blocks

merger/merger_io.go

@@ -1,11 +1,11 @@
 package merger
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"sort"
 	"strconv"
 	"strings"
@@ -174,6 +174,34 @@ func (s *DStoreIO) WalkOneBlockFiles(ctx context.Context, lowestBlock uint64, ca
 
 }
 
+// fixLegacyBlock reads the header and looks for "Version 0", rewriting to Version 1 on the fly if needed
+func fixLegacyBlock(in []byte) ([]byte, error) {
+	dbinReader, err := bstream.NewDBinBlockReader(bytes.NewReader(in))
+	if err != nil {
+		return nil, fmt.Errorf("creating block reader in fixLegacyBlock: %w", err)
+	}
+
+	if dbinReader.Header.Version != 0 {
+		return in, nil
+	}
+
+	blk, err := dbinReader.Read()
+	if err != nil {
+		return nil, err
+	}
+
+	out := new(bytes.Buffer)
+	writer, err := bstream.NewDBinBlockWriter(out)
+	if err != nil {
+		return nil, err
+	}
+	if err := writer.Write(blk); err != nil {
+		return nil, err
+	}
+	return out.Bytes(), nil
+
+}
+
 func (s *DStoreIO) DownloadOneBlockFile(ctx context.Context, oneBlockFile *bstream.OneBlockFile) (data []byte, err error) {
 	for filename := range oneBlockFile.Filenames { // will try to get MemoizeData from any of those files
 		var out io.ReadCloser
@@ -190,9 +218,14 @@ func (s *DStoreIO) DownloadOneBlockFile(ctx context.Context, oneBlockFile *bstre
 		default:
 		}
 
-		data, err = ioutil.ReadAll(out)
+		data, err = io.ReadAll(out)
+		if err != nil {
+			continue
+		}
+
+		data, err = fixLegacyBlock(data)
 		if err == nil {
-			return data, nil
+			break
 		}
 	}