From 0abfe473322a8824a2889854763f5249781d715a Mon Sep 17 00:00:00 2001
From: Hong Shin <hongshin@google.com>
Date: Thu, 1 May 2025 13:20:17 -0700
Subject: [PATCH] hpb: skeleton impl for hpb(cpp) to plumb ::Serialize

PiperOrigin-RevId: 753703483
---
 hpb_generator/context.h         | 28 ++++++++++----------
 hpb_generator/protoc-gen-hpb.cc | 46 ++++++++++++++++++++++++++++-----
 2 files changed, 54 insertions(+), 20 deletions(-)

diff --git a/hpb_generator/context.h b/hpb_generator/context.h
index 5c1ee3130526a..9dbc4a05ed43d 100644
--- a/hpb_generator/context.h
+++ b/hpb_generator/context.h
@@ -103,20 +103,22 @@ inline std::string ToPreproc(absl::string_view str) {
   return absl::AsciiStrToUpper(ToCIdent(str));
 }
 
+inline std::string StringifiedBackend(Context& ctx) {
+  return ctx.options().backend == Backend::UPB ? "upb" : "cpp";
+}
+
 inline void EmitFileWarning(const google::protobuf::FileDescriptor* file, Context& ctx) {
-  ctx.EmitLegacy(
-      R"cc(
-        /* This file was generated by hpb_generator (Handle Protobuf) "
-        from the input
-         * file:
-         *
-         *     $0
-         *
-         * Do not edit -- your changes will be discarded when the file is
-         * regenerated. */
-      )cc",
-      file->name());
-  ctx.Emit("\n");
+  ctx.Emit({{"file_name", file->name()}, {"backend", StringifiedBackend(ctx)}},
+           R"cc(
+             /* This file was generated by hpb ($backend$) "
+             from the input
+              * file:
+              *
+              *     $file_name$
+              *
+              * Do not edit -- your changes will be discarded when the file is
+              * regenerated. */
+           )cc");
 }
 
 // TODO: b/346865271 append ::hpb instead of ::protos after namespace swap
diff --git a/hpb_generator/protoc-gen-hpb.cc b/hpb_generator/protoc-gen-hpb.cc
index 8266d8750568c..4d658f437f7c5 100644
--- a/hpb_generator/protoc-gen-hpb.cc
+++ b/hpb_generator/protoc-gen-hpb.cc
@@ -30,8 +30,8 @@ namespace protobuf = ::proto2;
 using FileDescriptor = ::google::protobuf::FileDescriptor;
 using google::protobuf::Edition;
 
-void WriteSource(const protobuf::FileDescriptor* file, Context& ctx);
 void WriteHeader(const protobuf::FileDescriptor* file, Context& ctx);
+void WriteSource(const protobuf::FileDescriptor* file, Context& ctx);
 void WriteMessageImplementations(const protobuf::FileDescriptor* file,
                                  Context& ctx);
 void WriteTypedefForwardingHeader(
@@ -103,10 +103,42 @@ void WriteForwardDecls(const protobuf::FileDescriptor* file, Context& ctx) {
 }
 
 void WriteHeader(const protobuf::FileDescriptor* file, Context& ctx) {
-  if (ctx.options().backend == Backend::CPP) {
-    abort();
-  }
   EmitFileWarning(file, ctx);
+
+  if (ctx.options().backend == Backend::CPP || true) {
+    const auto msgs = SortedMessages(file);
+    auto ns = absl::StrCat(absl::StrReplaceAll(file->package(), {{".", "::"}}),
+                           "::hpb");
+    for (auto message : msgs) {
+      ctx.Emit({{"class_name", ClassName(message)}, {"namespace", ns}},
+               R"cc(
+
+                 namespace $namespace$ {
+
+                 class $class_name$ {
+                  public:
+                   using CProxy = bool;
+                   using Proxy = bool;
+                   using Access = bool;
+
+                   $class_name$() = default;
+
+                   $class_name$(void* msg) : msg_(msg) {}
+
+                   void* msg() const { return msg_; }
+
+                   // $class_name$::$class_name$(int x): x_(x) {
+                   //  }
+
+                   // friend class hpb::internal::backend::cpp::Shim;
+                   // friend struct hpb::internal::PrivateAccess;
+                  private:
+                   void* msg_;
+                 };
+                 }  // namespace $namespace$
+               )cc");
+    }
+  }
   ctx.EmitLegacy(
       R"cc(
 #ifndef $0_HPB_PROTO_H_
@@ -171,10 +203,10 @@ void WriteHeader(const protobuf::FileDescriptor* file, Context& ctx) {
 
 // Writes a .hpb.cc source file.
 void WriteSource(const protobuf::FileDescriptor* file, Context& ctx) {
-  if (ctx.options().backend == Backend::CPP) {
-    abort();
-  }
   EmitFileWarning(file, ctx);
+  if (ctx.options().backend == Backend::CPP || true) {
+    return;
+  }
 
   ctx.EmitLegacy(
       R"cc(