upb_stream: all callbacks registered ahead-of-time.

This is a significant change to the upb_stream
protocol, and should hopefully be the last
significant change.

All callbacks are now registered ahead-of-time
instead of having delegated callbacks registered
at runtime, which makes it much easier to
aggressively optimize ahead-of-time (like with a
JIT).

Other impacts of this change:

- You no longer need to have loaded descriptor.proto
  as a upb_def to load other descriptors!  This means
  the special-case code we used for bootstrapping is
  no longer necessary, and we no longer need to link
  the descriptor for descriptor.proto into upb.

- A client can now register any upb_value as what
  will be delivered to their value callback, not
  just a upb_fielddef*.  This should allow for other
  clients to get more bang out of the streaming
  decoder.

This change unfortunately causes a bit of a performance
regression -- I think largely due to highly
suboptimal code that GCC generates when structs
are returned by value.  See:
  http://blog.reverberate.org/2011/03/19/when-a-compilers-slow-code-actually-bites-you/

On the other hand, once we have a JIT this should
no longer matter.

Performance numbers:

plain.parsestream_googlemessage1.upb_table: 374 -> 396 (5.88)
plain.parsestream_googlemessage2.upb_table: 616 -> 449 (-27.11)
plain.parsetostruct_googlemessage1.upb_table_byref: 268 -> 269 (0.37)
plain.parsetostruct_googlemessage1.upb_table_byval: 215 -> 204 (-5.12)
plain.parsetostruct_googlemessage2.upb_table_byref: 307 -> 281 (-8.47)
plain.parsetostruct_googlemessage2.upb_table_byval: 297 -> 272 (-8.42)
omitfp.parsestream_googlemessage1.upb_table: 423 -> 410 (-3.07)
omitfp.parsestream_googlemessage2.upb_table: 679 -> 483 (-28.87)
omitfp.parsetostruct_googlemessage1.upb_table_byref: 287 -> 282 (-1.74)
omitfp.parsetostruct_googlemessage1.upb_table_byval: 226 -> 219 (-3.10)
omitfp.parsetostruct_googlemessage2.upb_table_byref: 315 -> 298 (-5.40)
omitfp.parsetostruct_googlemessage2.upb_table_byval: 297 -> 287 (-3.37)

1 files changed, 21 insertions, 22 deletions

diff --git a/src/upb_glue.c b/src/upb_glue.c
index 86022d8..8194d4a 100644
--- a/src/upb_glue.c
+++ b/src/upb_glue.c
@@ -16,25 +16,18 @@ void upb_strtomsg(upb_string *str, upb_msg *msg, upb_msgdef *md,
   upb_stringsrc_init(&strsrc);
   upb_stringsrc_reset(&strsrc, str);
 
-  upb_decoder d;
-  upb_decoder_init(&d, md);
-  upb_decoder_reset(&d, upb_stringsrc_bytesrc(&strsrc));
-  upb_src *src = upb_decoder_src(&d);
-
-  upb_msgpopulator p;
-  upb_msgpopulator_init(&p);
-  upb_msgpopulator_reset(&p, msg, md);
-
   upb_handlers h;
-  upb_handlers_init(&h);
-  upb_msgpopulator_register_handlers(&p, &h);
-  upb_src_sethandlers(src, &h);
+  upb_handlers_init(&h, md);
+  upb_msg_regdhandlers(&h);
+
+  upb_decoder d;
+  upb_decoder_init(&d, &h);
+  upb_decoder_reset(&d, upb_stringsrc_bytesrc(&strsrc), msg);
 
-  upb_src_run(src, status);
+  upb_decoder_decode(&d, status);
 
   upb_stringsrc_uninit(&strsrc);
   upb_decoder_uninit(&d);
-  upb_msgpopulator_uninit(&p);
   upb_handlers_uninit(&h);
 }
 
@@ -46,11 +39,12 @@ void upb_msgtotext(upb_string *str, upb_msg *msg, upb_msgdef *md,
 
   upb_textprinter *p = upb_textprinter_new();
   upb_handlers h;
-  upb_handlers_init(&h);
-  upb_textprinter_reset(p, &h, upb_stringsink_bytesink(&strsink), single_line);
+  upb_handlers_init(&h, md);
+  upb_textprinter_reghandlers(&h);
+  upb_textprinter_reset(p, upb_stringsink_bytesink(&strsink), single_line);
 
   upb_status status = UPB_STATUS_INIT;
-  upb_msg_runhandlers(msg, md, &h, &status);
+  upb_msg_runhandlers(msg, md, &h, p, &status);
   // None of {upb_msg_runhandlers, upb_textprinter, upb_stringsink} should be
   // capable of returning an error.
   assert(upb_ok(&status));
@@ -66,13 +60,18 @@ void upb_parsedesc(upb_symtab *symtab, upb_string *str, upb_status *status) {
   upb_stringsrc_init(&strsrc);
   upb_stringsrc_reset(&strsrc, str);
 
+  upb_handlers h;
+  upb_handlers_init(&h, NULL);
+  upb_defbuilder_reghandlers(&h);
+
   upb_decoder d;
-  upb_msgdef *fds_msgdef = upb_getfdsdef();
-  upb_decoder_init(&d, fds_msgdef);
-  upb_decoder_reset(&d, upb_stringsrc_bytesrc(&strsrc));
+  upb_decoder_init(&d, &h);
+  upb_defbuilder *b = upb_defbuilder_new(symtab);
+  upb_decoder_reset(&d, upb_stringsrc_bytesrc(&strsrc), b);
 
-  upb_symtab_addfds(symtab, upb_decoder_src(&d), status);
+  upb_decoder_decode(&d, status);
+
+  upb_handlers_uninit(&h);
   upb_stringsrc_uninit(&strsrc);
   upb_decoder_uninit(&d);
-  upb_def_unref(UPB_UPCAST(fds_msgdef));
 }