Add startseq/endseq handlers.

Startseq/endseq handlers are called at the beginning
and end of a sequence of repeated values.  Protobuf
does not really have direct support for this (repeated
primitive fields do not delimit "begin" and "end" of
the sequence) but we can infer them from the bytestream.

The benefit of supporting them explicitly is that they
get their own stack frame and closure, so we can avoid
having to find the array's address over and over and
deciding if we need to initialize it.

This will also pave the way for better support of JSON,
which does have explicit "startseq/endseq" markers: [].

1 files changed, 21 insertions, 3 deletions

diff --git a/src/upb_decoder_x86.dasc b/src/upb_decoder_x86.dasc
index b7195c2..1780c98 100644
--- a/src/upb_decoder_x86.dasc
+++ b/src/upb_decoder_x86.dasc
@@ -285,6 +285,18 @@ static void upb_decoder_jit_field(upb_decoder *d, uint32_t tag, uint32_t next_ta
   |  cmp  edx, (tag & 0x7)
   |  jne  ->exit_jit     // In the future: could be an unknown field or packed.
   |=>f->jit_pclabel_notypecheck:
+  if (f->repeated) {
+    if (f->startseq != upb_startfield_nop) {
+      |  mov   ARG1_64, CLOSURE
+      |  loadfval f
+      |  callp f->startseq
+    } else {
+      |  mov   rdx, CLOSURE
+    }
+    |  mov   esi, FRAME->end_offset
+    |  pushframe  f, rdx, esi, true
+  }
+
   |1:  // Label for repeating this field.
 
   // Decode the value into arg 3 for the callback.
@@ -382,7 +394,7 @@ static void upb_decoder_jit_field(upb_decoder *d, uint32_t tag, uint32_t next_ta
   // Call callbacks.
   if (upb_issubmsgtype(f->type)) {
     // Call startsubmsg handler (if any).
-    if (f->startsubmsg != upb_startsubmsg_nop) {
+    if (f->startsubmsg != upb_startfield_nop) {
       // upb_sflow_t startsubmsg(void *closure, upb_value fval)
       |  mov   r12d, ARG3_32
       |  callp f->startsubmsg
@@ -396,7 +408,7 @@ static void upb_decoder_jit_field(upb_decoder *d, uint32_t tag, uint32_t next_ta
       |   add   esi, r12d   // = (d->ptr - d->buf) + delim_len
     } else {
       assert(f->type == UPB_TYPE(GROUP));
-      |   mov   esi, -1U
+      |   mov   esi, UPB_NONDELIMITED
     }
     |  pushframe  f, rdx, esi, false
 
@@ -411,7 +423,7 @@ static void upb_decoder_jit_field(upb_decoder *d, uint32_t tag, uint32_t next_ta
     |   popframe
 
     // Call endsubmsg handler (if any).
-    if (f->endsubmsg != upb_endsubmsg_nop) {
+    if (f->endsubmsg != upb_endfield_nop) {
       // upb_flow_t endsubmsg(void *closure, upb_value fval);
       |  mov   ARG1_64, CLOSURE
       |  loadfval  f
@@ -428,6 +440,12 @@ static void upb_decoder_jit_field(upb_decoder *d, uint32_t tag, uint32_t next_ta
   if (f->repeated) {
     |  checktag  tag
     |  je  <1
+    |  popframe
+    if (f->endseq != upb_endfield_nop) {
+      |  mov   ARG1_64, CLOSURE
+      |  loadfval f
+      |  callp f->endseq
+    }
   }
   if (next_tag != 0) {
     |  checktag  next_tag