Add a TcParseTable pointer in `ClassData` and change the default

`_InternalParse` implementation to use it.
For LITE messages, populate the entry in `ClassData` and remove the override for
`_InternalParse`.

PiperOrigin-RevId: 606364791

src/google/protobuf/compiler/cpp/message.cc

@@ -3649,6 +3649,7 @@ void MessageGenerator::GenerateClassData(io::Printer* p) {
             PROTOBUF_CONSTINIT static const ClassDataLite<$type_size$> _data_ =
                 {
                     {
+                        &_table_.header,
                         $on_demand_register_arena_dtor$,
                         PROTOBUF_FIELD_OFFSET($classname$, $cached_size$),
                         true,

src/google/protobuf/compiler/cpp/parse_function_generator.cc

@@ -116,7 +116,14 @@ ParseFunctionGenerator::ParseFunctionGenerator(
   variables_["classname"] = ClassName(descriptor, false);
 }
 
+static bool ShouldGenerateInternalParse(const Descriptor* descriptor,
+                                        const Options& options) {
+  return HasGeneratedMethods(descriptor->file(), options) &&
+         HasDescriptorMethods(descriptor->file(), options);
+}
+
 void ParseFunctionGenerator::GenerateMethodDecls(io::Printer* printer) {
+  if (!ShouldGenerateInternalParse(descriptor_, options_)) return;
   Formatter format(printer, variables_);
   format(
       "const char* _InternalParse(const char* ptr, "
@@ -124,6 +131,7 @@ void ParseFunctionGenerator::GenerateMethodDecls(io::Printer* printer) {
 }
 
 void ParseFunctionGenerator::GenerateMethodImpls(io::Printer* printer) {
+  if (!ShouldGenerateInternalParse(descriptor_, options_)) return;
   printer->Emit(R"cc(
     const char* $classname$::_InternalParse(const char* ptr,
                                             ::_pbi::ParseContext* ctx) {

src/google/protobuf/message_lite.cc

@@ -31,6 +31,7 @@
 #include "absl/synchronization/mutex.h"
 #include "absl/types/optional.h"
 #include "google/protobuf/arena.h"
+#include "google/protobuf/generated_message_tctable_impl.h"
 #include "google/protobuf/io/coded_stream.h"
 #include "google/protobuf/io/zero_copy_stream.h"
 #include "google/protobuf/io/zero_copy_stream_impl.h"
@@ -44,6 +45,17 @@
 namespace google {
 namespace protobuf {
 
+const char* MessageLite::_InternalParse(const char* ptr,
+                                        internal::ParseContext* ctx) {
+  auto* data = GetClassData();
+  ABSL_DCHECK(data != nullptr);
+
+  if (data->tc_table != nullptr) {
+    return internal::TcParser::ParseLoop(this, ptr, ctx, data->tc_table);
+  }
+  return nullptr;
+}
+
 std::string MessageLite::GetTypeName() const {
   auto* data = GetClassData();
   ABSL_DCHECK(data != nullptr);

src/google/protobuf/message_lite.h

@@ -130,6 +130,7 @@ class ExtensionSet;
 class LazyField;
 class RepeatedPtrFieldBase;
 class TcParser;
+struct TcParseTableBase;
 class WireFormatLite;
 class WeakFieldMap;
 
@@ -494,10 +495,8 @@ class PROTOBUF_EXPORT MessageLite {
   // method.)
   int GetCachedSize() const;
 
-  virtual const char* _InternalParse(const char* /*ptr*/,
-                                     internal::ParseContext* /*ctx*/) {
-    return nullptr;
-  }
+  virtual const char* _InternalParse(const char* ptr,
+                                     internal::ParseContext* ctx);
 
   void OnDemandRegisterArenaDtor(Arena* arena);
 
@@ -536,6 +535,7 @@ class PROTOBUF_EXPORT MessageLite {
   // otherwise be null. We can have some metadata in ClassData telling us if we
   // have them and their offset.
   struct ClassData {
+    const internal::TcParseTableBase* tc_table;
     void (*on_demand_register_arena_dtor)(MessageLite& msg, Arena& arena);
 
     // Offset of the CachedSize member.
@@ -544,10 +544,22 @@ class PROTOBUF_EXPORT MessageLite {
     // char[] just beyond the ClassData.
     bool is_lite;
 
+    // Temporary constructor while we migrate existing classes to populate the
+    // `tc_table` field.
     constexpr ClassData(void (*on_demand_register_arena_dtor)(MessageLite&,
                                                               Arena&),
                         uint32_t cached_size_offset, bool is_lite)
-        : on_demand_register_arena_dtor(on_demand_register_arena_dtor),
+        : tc_table(),
+          on_demand_register_arena_dtor(on_demand_register_arena_dtor),
+          cached_size_offset(cached_size_offset),
+          is_lite(is_lite) {}
+
+    constexpr ClassData(const internal::TcParseTableBase* tc_table,
+                        void (*on_demand_register_arena_dtor)(MessageLite&,
+                                                              Arena&),
+                        uint32_t cached_size_offset, bool is_lite)
+        : tc_table(tc_table),
+          on_demand_register_arena_dtor(on_demand_register_arena_dtor),
           cached_size_offset(cached_size_offset),
           is_lite(is_lite) {}