Reserve unknown fields in upb

1. For decoding, an unknownfields will be lazily created on message,
which contains bytes of unknown fields.
2. For encoding, if the unknownfields is present on message, all bytes
contained in it will be serialized.

1 files changed, 1 insertions, 0 deletions

diff --git a/upb/def.c b/upb/def.c
index ceaced2..60bbb84 100644
--- a/upb/def.c
+++ b/upb/def.c
@@ -327,6 +327,7 @@ static bool assign_msg_indices(upb_msgdef *m, upb_status *s) {
     v = upb_value_bool(true);
     upb_inttable_insert(&t, UPB_STARTMSG_SELECTOR, v);
     upb_inttable_insert(&t, UPB_ENDMSG_SELECTOR, v);
+    upb_inttable_insert(&t, UPB_UNKNOWN_SELECTOR, v);
     for(upb_msg_field_begin(&j, m);
         !upb_msg_field_done(&j);
         upb_msg_field_next(&j)) {