1 files changed, 38 insertions, 13 deletions

diff --git a/upb/json/printer.c b/upb/json/printer.c
index c7267e0..539f83a 100644
--- a/upb/json/printer.c
+++ b/upb/json/printer.c
@@ -15,6 +15,27 @@
 #include <string.h>
 #include <stdint.h>
 
+struct upb_json_printer {
+  upb_sink input_;
+  // BytesSink closure.
+  void *subc_;
+  upb_bytessink *output_;
+
+  // We track the depth so that we know when to emit startstr/endstr on the
+  // output.
+  int depth_;
+
+  // Have we emitted the first element? This state is necessary to emit commas
+  // without leaving a trailing comma in arrays/maps. We keep this state per
+  // frame depth.
+  //
+  // Why max_depth * 2? UPB_MAX_HANDLER_DEPTH counts depth as nested messages.
+  // We count frames (contexts in which we separate elements by commas) as both
+  // repeated fields and messages (maps), and the worst case is a
+  // message->repeated field->submessage->repeated field->... nesting.
+  bool first_elem_[UPB_MAX_HANDLER_DEPTH * 2];
+};
+
 // StringPiece; a pointer plus a length.
 typedef struct {
   const char *ptr;
@@ -731,25 +752,29 @@ void printer_sethandlers(const void *closure, upb_handlers *h) {
 #undef TYPE
 }
 
-/* Public API *****************************************************************/
-
-void upb_json_printer_init(upb_json_printer *p, const upb_handlers *h) {
-  p->output_ = NULL;
+static void json_printer_reset(upb_json_printer *p) {
   p->depth_ = 0;
-  upb_sink_reset(&p->input_, h, p);
 }
 
-void upb_json_printer_uninit(upb_json_printer *p) {
-  UPB_UNUSED(p);
-}
 
-void upb_json_printer_reset(upb_json_printer *p) {
-  p->depth_ = 0;
-}
+/* Public API *****************************************************************/
+
+upb_json_printer *upb_json_printer_create(upb_env *e, const upb_handlers *h,
+                                          upb_bytessink *output) {
+#ifndef NDEBUG
+  size_t size_before = upb_env_bytesallocated(e);
+#endif
+
+  upb_json_printer *p = upb_env_malloc(e, sizeof(upb_json_printer));
+  if (!p) return NULL;
 
-void upb_json_printer_resetoutput(upb_json_printer *p, upb_bytessink *output) {
-  upb_json_printer_reset(p);
   p->output_ = output;
+  json_printer_reset(p);
+  upb_sink_reset(&p->input_, h, p);
+
+  // If this fails, increase the value in printer.h.
+  assert(upb_env_bytesallocated(e) - size_before <= UPB_JSON_PRINTER_SIZE);
+  return p;
 }
 
 upb_sink *upb_json_printer_input(upb_json_printer *p) {