Added upb::FileDef, which represents the file defs are declared in.

It is entirely optional: MessageDef/EnumDef can still exist
on their own.  But this can represent a def's file when it is
desirable to do so (eg. for code generators).

This approach will require that we change the way we handle
extensions.  But I think it will be a good change overall.

Specifically, we previously handled extensions by duplicating
the extended message and then adding the extension as a regular
field to the duplicated message.  This required also duplicating
any messages that could reach the extended message.

In the new world we will need a way of declaring and looking up
extensions separately from the message being extended.

This change also involves some notable changes to the generated
code:

- files are now called foo.upbdefs.h instead of foo.upb.h.
  This reflects the fact that we might possibly generate several
  different output files for a .proto file, and this one is just
  for defs.

- we no longer generate selectors in the .h file.

- the upbdefs.c no longer vends a SymbolTable.  Now it vends the
  individual messages (and possibly a FileDef later).  I think this
  will compose better once we can generate files where one
  generated files imports another.

We also make the descriptor reader vend a list of FileDefs now.
This is the best conceptual match for parsing a FileDescriptorSet.

1 files changed, 14 insertions, 3 deletions

diff --git a/upb/structdefs.int.h b/upb/structdefs.int.h
index 467963b..467374a 100644
--- a/upb/structdefs.int.h
+++ b/upb/structdefs.int.h
@@ -33,6 +33,7 @@ struct upb_def {
   upb_refcounted base;
 
   const char *fullname;
+  const upb_filedef* file;
   char type;  /* A upb_deftype_t (char to save space) */
 
   /* Used as a flag during the def's mutable stage.  Must be false unless
@@ -43,7 +44,7 @@ struct upb_def {
 };
 
 #define UPB_DEF_INIT(name, type, refs, ref2s) \
-    { UPB_REFCOUNT_INIT(refs, ref2s), name, type, false }
+    { UPB_REFCOUNT_INIT(refs, ref2s), name, NULL, type, false }
 
 
 /* upb_fielddef ***************************************************************/
@@ -114,10 +115,10 @@ struct upb_msgdef {
    * descriptor.upb.c. */
   bool map_entry;
 
-  /* Do primitive values in this message have explicit presence or not?
+  /* Whether this message has proto2 or proto3 semantics.
    * TODO: set this flag properly for static descriptors; regenerate
    * descriptor.upb.c. */
-  bool primitives_have_presence;
+  upb_syntax_t syntax;
 
   /* TODO(haberman): proper extension ranges (there can be multiple). */
 };
@@ -173,5 +174,15 @@ struct upb_symtab {
 #define UPB_SYMTAB_INIT(symtab, refs, ref2s) \
   { UPB_REFCOUNT_INIT(refs, ref2s), symtab }
 
+struct upb_filedef {
+  upb_refcounted base;
+
+  const char *name;
+  const char *package;
+  upb_syntax_t syntax;
+
+  upb_inttable defs;
+  upb_inttable deps;
+};
 
 #endif  /* UPB_STATICINIT_H_ */