src/google/protobuf/internal_message_util.cc

// Protocol Buffers - Google's data interchange format
// Copyright 2023 Google Inc.  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 "google/protobuf/internal_message_util.h"

#include <vector>

#include "google/protobuf/map_field.h"

namespace google {
namespace protobuf {
namespace internal {

class MessageUtil {
 public:
  static const internal::MapFieldBase* GetMapData(
      const Reflection* reflection, const Message& message,
      const FieldDescriptor* field) {
    return reflection->GetMapData(message, field);
  }

  // Walks the entire message tree and eager parses all lazy fields.
  static void EagerParseLazyField(Message* message);
};

namespace {

// Returns true if the field is a map that contains non-message value.
bool IsNonMessageMap(const FieldDescriptor* field) {
  if (!field->is_map()) {
    return false;
  }
  constexpr int kValueIndex = 1;
  return field->message_type()->field(kValueIndex)->cpp_type() !=
         FieldDescriptor::CPPTYPE_MESSAGE;
}

inline bool UseMapIterator(const Reflection* reflection, const Message& message,
                           const FieldDescriptor* field) {
  return field->is_map() &&
         MessageUtil::GetMapData(reflection, message, field)->IsMapValid();
}

inline bool IsNonMessageField(const FieldDescriptor* field) {
  return field->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE ||
         IsNonMessageMap(field);
}

}  // namespace

// To eagerly parse lazy fields in the entire message tree, mutates all the
// message fields (optional, repeated, extensions).
void MessageUtil::EagerParseLazyField(Message* message) {
  const Reflection* reflection = message->GetReflection();
  std::vector<const FieldDescriptor*> fields;
  reflection->ListFields(*message, &fields);

  for (const auto* field : fields) {
    if (IsNonMessageField(field)) continue;

    if (!field->is_repeated()) {
      EagerParseLazyField(reflection->MutableMessage(message, field));
      continue;
    }

    // Map values cannot be lazy but their child message may be.
    if (UseMapIterator(reflection, *message, field)) {
      auto end = reflection->MapEnd(message, field);
      for (auto it = reflection->MapBegin(message, field); it != end; ++it) {
        EagerParseLazyField(it.MutableValueRef()->MutableMessageValue());
      }
      continue;
    }

    // Repeated messages cannot be lazy but their child messages may be.
    if (field->is_repeated()) {
      for (int i = 0, end = reflection->FieldSize(*message, field); i < end;
           ++i) {
        EagerParseLazyField(
            reflection->MutableRepeatedMessage(message, field, i));
      }
    }
  }
}

void EagerParseLazyField(Message& message) {
  MessageUtil::EagerParseLazyField(&message);
}

}  // namespace internal
}  // namespace protobuf
}  // namespace google