package super_block import ( "google.golang.org/protobuf/proto" "github.com/seaweedfs/seaweedfs/weed/glog" "github.com/seaweedfs/seaweedfs/weed/pb/master_pb" "github.com/seaweedfs/seaweedfs/weed/storage/needle" "github.com/seaweedfs/seaweedfs/weed/util" ) const ( SuperBlockSize = 8 ) /* * Super block currently has 8 bytes allocated for each volume. * Byte 0: version, 1 or 2 * Byte 1: Replica Placement strategy, 000, 001, 002, 010, etc * Byte 2 and byte 3: Time to live. See TTL for definition * Byte 4 and byte 5: The number of times the volume has been compacted. * Rest bytes: Reserved */ type SuperBlock struct { Version needle.Version ReplicaPlacement *ReplicaPlacement Ttl *needle.TTL CompactionRevision uint16 Extra *master_pb.SuperBlockExtra ExtraSize uint16 } func (s *SuperBlock) BlockSize() int { switch s.Version { case needle.Version2, needle.Version3: return SuperBlockSize + int(s.ExtraSize) } return SuperBlockSize } func (s *SuperBlock) Bytes() []byte { header := make([]byte, SuperBlockSize) header[0] = byte(s.Version) header[1] = s.ReplicaPlacement.Byte() s.Ttl.ToBytes(header[2:4]) util.Uint16toBytes(header[4:6], s.CompactionRevision) if s.Extra != nil { extraData, err := proto.Marshal(s.Extra) if err != nil { glog.Fatalf("cannot marshal super block extra %+v: %v", s.Extra, err) } extraSize := len(extraData) if extraSize > 256*256-2 { // reserve a couple of bits for future extension glog.Fatalf("super block extra size is %d bigger than %d", extraSize, 256*256-2) } s.ExtraSize = uint16(extraSize) util.Uint16toBytes(header[6:8], s.ExtraSize) header = append(header, extraData...) } return header } func (s *SuperBlock) Initialized() bool { return s.ReplicaPlacement != nil && s.Ttl != nil }