Introduce upb_ByteSize

Naïve computation of a serialized upb message

PiperOrigin-RevId: 670990379

pkg/BUILD.bazel

@@ -218,6 +218,7 @@ cc_dist_library(
         "//upb/text",
         "//upb/util:def_to_proto",
         "//upb/util:required_fields",
+        "//upb/wire:byte_size",
     ],
 )
 

upb/wire/BUILD

@@ -61,6 +61,35 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "byte_size",
+    srcs = ["byte_size.c"],
+    hdrs = ["byte_size.h"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//upb:mem",
+        "//upb:message",
+        "//upb:mini_table",
+        "//upb:port",
+        "//upb:wire",
+    ],
+)
+
+cc_test(
+    name = "byte_size_test",
+    srcs = ["byte_size_test.cc"],
+    deps = [
+        ":byte_size",
+        "//upb:base",
+        "//upb:mem",
+        "//upb:mini_table",
+        "//upb/test:test_messages_proto2_upb_minitable",
+        "//upb/test:test_messages_proto2_upb_proto",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "eps_copy_input_stream",
     srcs = ["eps_copy_input_stream.c"],

upb/wire/byte_size.c

@@ -0,0 +1,37 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "upb/wire/byte_size.h"
+
+#include <stddef.h>
+
+#include "upb/mem/arena.h"
+#include "upb/message/message.h"
+#include "upb/mini_table/message.h"
+#include "upb/wire/encode.h"
+
+// Must be last.
+#include "upb/port/def.inc"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+size_t upb_ByteSize(const upb_Message* msg, const upb_MiniTable* mt) {
+  upb_Arena* arena = upb_Arena_New();
+  char* buf;
+  size_t res = 0;
+
+  upb_Encode(msg, mt, 0, arena, &buf, &res);
+
+  upb_Arena_Free(arena);
+  return res;
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif

upb/wire/byte_size.h

@@ -0,0 +1,31 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef UPB_WIRE_BYTE_SIZE_H_
+#define UPB_WIRE_BYTE_SIZE_H_
+
+#include <stddef.h>
+
+#include "upb/message/message.h"
+#include "upb/mini_table/message.h"
+
+// Must be last.
+#include "upb/port/def.inc"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+UPB_API size_t upb_ByteSize(const upb_Message* msg, const upb_MiniTable* mt);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#include "upb/port/undef.inc"
+
+#endif  // UPB_WIRE_BYTE_SIZE_H_

upb/wire/byte_size_test.cc

@@ -0,0 +1,40 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "upb/wire/byte_size.h"
+
+#include <gtest/gtest.h>
+#include "google/protobuf/test_messages_proto2.upb.h"
+#include "google/protobuf/test_messages_proto2.upb_minitable.h"
+#include "upb/base/upcast.h"
+#include "upb/mem/arena.h"
+#include "upb/mini_table/message.h"
+
+namespace {
+static const upb_MiniTable* kTestMiniTable =
+    &protobuf_0test_0messages__proto2__TestAllTypesProto2_msg_init;
+
+TEST(ByteSizeTest, UnpopulatedMsg) {
+  upb_Arena* arena = upb_Arena_New();
+  protobuf_test_messages_proto2_TestAllTypesProto2* msg =
+      protobuf_test_messages_proto2_TestAllTypesProto2_new(arena);
+  auto res = upb_ByteSize(UPB_UPCAST(msg), kTestMiniTable);
+  EXPECT_EQ(res, 0);
+  upb_Arena_Free(arena);
+}
+
+TEST(ByteSizeTest, PopulatedMsg) {
+  upb_Arena* arena = upb_Arena_New();
+  protobuf_test_messages_proto2_TestAllTypesProto2* msg =
+      protobuf_test_messages_proto2_TestAllTypesProto2_new(arena);
+  protobuf_test_messages_proto2_TestAllTypesProto2_set_optional_int32(msg, 322);
+  auto res = upb_ByteSize(UPB_UPCAST(msg), kTestMiniTable);
+  EXPECT_EQ(res, 3);
+  upb_Arena_Free(arena);
+}
+
+}  // namespace