diff --git a/upb/message/accessors.h b/upb/message/accessors.h
index 6a5f49a90c..697b5ed777 100644
--- a/upb/message/accessors.h
+++ b/upb/message/accessors.h
@@ -521,6 +521,17 @@ UPB_API_INLINE upb_Array* upb_Message_GetMutableArray(
   return (upb_Array*)upb_Message_GetArray(msg, field);
 }
 
+UPB_API_INLINE upb_Array* upb_Message_GetOrCreateMutableArray(
+    upb_Message* msg, const upb_MiniTableField* field, upb_CType ctype,
+    upb_Arena* arena) {
+  upb_Array* array = upb_Message_GetMutableArray(msg, field);
+  if (!array) {
+    array = upb_Array_New(arena, ctype);
+    _upb_Message_SetField(msg, field, &array, arena);
+  }
+  return array;
+}
+
 void* upb_Message_ResizeArray(upb_Message* msg, const upb_MiniTableField* field,
                               size_t len, upb_Arena* arena);
 
diff --git a/upbc/BUILD b/upbc/BUILD
index fc06f75f93..c2e7caa5a8 100644
--- a/upbc/BUILD
+++ b/upbc/BUILD
@@ -75,10 +75,12 @@ cc_binary(
     linkstatic = 1,
     visibility = ["//visibility:public"],
     deps = [
+        "//:collections",
         "//:mem",
         "//:message",
         "//:message_accessors",
         "//:mini_table",
+        "//:port",
         "//upbc:upbdev",
     ],
 )
diff --git a/upbc/upbc_so.c b/upbc/upbc_so.c
index ac109e05c6..16df62e7e1 100644
--- a/upbc/upbc_so.c
+++ b/upbc/upbc_so.c
@@ -27,10 +27,72 @@
 
 // This disables inlining and forces all public functions to be exported to the
 // linker. It is used to generate bindings for FFIs from other languages.
+#ifndef UPB_BUILD_API
 #define UPB_BUILD_API
+#endif
 
-#include "upb/mem/arena.h"
+#include "upb/collections/array.h"
 #include "upb/message/accessors.h"
 #include "upb/message/message.h"
 #include "upb/mini_table/decode.h"
 #include "upbc/upbdev.h"
+
+// Must be last.
+#include "upb/port/def.inc"
+
+UPB_API bool upb_Array_AppendBool(upb_Array* array, bool val,
+                                  upb_Arena* arena) {
+  const upb_MessageValue mv = {.bool_val = val};
+  return upb_Array_Append(array, mv, arena);
+}
+
+UPB_API bool upb_Array_AppendDouble(upb_Array* array, double val,
+                                    upb_Arena* arena) {
+  const upb_MessageValue mv = {.double_val = val};
+  return upb_Array_Append(array, mv, arena);
+}
+
+UPB_API bool upb_Array_AppendFloat(upb_Array* array, float val,
+                                   upb_Arena* arena) {
+  const upb_MessageValue mv = {.float_val = val};
+  return upb_Array_Append(array, mv, arena);
+}
+
+UPB_API bool upb_Array_AppendInt32(upb_Array* array, int32_t val,
+                                   upb_Arena* arena) {
+  const upb_MessageValue mv = {.int32_val = val};
+  return upb_Array_Append(array, mv, arena);
+}
+
+UPB_API bool upb_Array_AppendUInt32(upb_Array* array, uint32_t val,
+                                    upb_Arena* arena) {
+  const upb_MessageValue mv = {.uint32_val = val};
+  return upb_Array_Append(array, mv, arena);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+UPB_API void upb_Array_SetBool(upb_Array* array, size_t i, bool val) {
+  const upb_MessageValue mv = {.bool_val = val};
+  upb_Array_Set(array, i, mv);
+}
+
+UPB_API void upb_Array_SetDouble(upb_Array* array, size_t i, double val) {
+  const upb_MessageValue mv = {.double_val = val};
+  upb_Array_Set(array, i, mv);
+}
+
+UPB_API void upb_Array_SetFloat(upb_Array* array, size_t i, float val) {
+  const upb_MessageValue mv = {.float_val = val};
+  upb_Array_Set(array, i, mv);
+}
+
+UPB_API void upb_Array_SetInt32(upb_Array* array, size_t i, int32_t val) {
+  const upb_MessageValue mv = {.int32_val = val};
+  upb_Array_Set(array, i, mv);
+}
+
+UPB_API void upb_Array_SetUInt32(upb_Array* array, size_t i, uint32_t val) {
+  const upb_MessageValue mv = {.uint32_val = val};
+  upb_Array_Set(array, i, mv);
+}