kubernetes/vendor/go.etcd.io/etcd/server/v3/etcdserver/snapshot_merge.go

// createMergedSnapshotMessage creates a snapshot message that contains: raft status (term, conf),
// a snapshot of v2 store inside raft.Snapshot as []byte, a snapshot of v3 KV in the top level message
// as ReadCloser.
func (s *EtcdServer) createMergedSnapshotMessage(m raftpb.Message, snapt, snapi uint64, confState raftpb.ConfState) snap.Message { … }

func newSnapshotReaderCloser(lg *zap.Logger, snapshot backend.Snapshot) io.ReadCloser { … }