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, 34 insertions, 4 deletions

diff --git a/tests/test_def.c b/tests/test_def.c
index 52d780b..6f3fb8f 100644
--- a/tests/test_def.c
+++ b/tests/test_def.c
@@ -38,15 +38,45 @@ static void test_noreftracking() {
   upb_msgdef_unref(md, &md);
 }
 
+static char *upb_readfile(const char *filename, size_t *len) {
+  long size;
+  char *buf;
+  FILE *f = fopen(filename, "rb");
+  if(!f) return NULL;
+  if(fseek(f, 0, SEEK_END) != 0) goto error;
+  size = ftell(f);
+  if(size < 0) goto error;
+  if(fseek(f, 0, SEEK_SET) != 0) goto error;
+  buf = malloc(size + 1);
+  if(size && fread(buf, size, 1, f) != 1) goto error;
+  fclose(f);
+  if (len) *len = size;
+  return buf;
+
+error:
+  fclose(f);
+  return NULL;
+}
+
 static upb_symtab *load_test_proto(void *owner) {
   upb_symtab *s = upb_symtab_new(owner);
   upb_status status = UPB_STATUS_INIT;
+  size_t len;
+  char *data = upb_readfile(descriptor_file, &len);
+  upb_filedef **files;
   ASSERT(s);
-  if (!upb_load_descriptor_file_into_symtab(s, descriptor_file, &status)) {
-    fprintf(stderr, "Error loading descriptor file: %s\n",
-            upb_status_errmsg(&status));
-    ASSERT(false);
+  ASSERT(data);
+  files = upb_loaddescriptor(data, len, &files, &status);
+  ASSERT(files);
+  free(data);
+
+  while (*files) {
+    bool ok = upb_symtab_addfile(s, *files, &status);
+    ASSERT(ok);
+    upb_filedef_unref(*files, &files);
+    files++;
   }
+
   ASSERT(!upb_symtab_isfrozen(s));
   upb_symtab_freeze(s);
   ASSERT(upb_symtab_isfrozen(s));