preloading_class_loader.hpp

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#pragma once

#include <string>

#include <class_loader/class_loader.hpp>
#include <pluginlib/class_loader.hpp>

#include <cras_cpp_common/type_utils.hpp>

/*
 * In the classes where you need to use this classloader, insert the following code at the very beginning of the CPP
 * file:
 *
// HACK: we need to alter the private lowlever_class_loader_ of pluginlib::ClassLoader
#define private public
#include <pluginlib/class_loader.hpp>
#undef private
 *
 */

template <typename Impl, typename Base>
class PreloadingClassLoader : public class_loader::ClassLoader
{
protected:
  PreloadingClassLoader() : ClassLoader("", true)
  {
    const auto implType = cras::getTypeName<Impl>();
    const auto baseType = cras::getTypeName<Base>();
    auto metaObject = new class_loader::impl::MetaObject<Impl, Base>(implType, baseType);
    metaObject->addOwningClassLoader(this);
    class_loader::impl::getFactoryMapForBaseClass<Base>()[implType] = metaObject;
  }

public:
  ~PreloadingClassLoader() override
  {
    const auto implType = cras::getTypeName<Impl>();
    auto metaObject = class_loader::impl::getFactoryMapForBaseClass<Base>()[implType];
    metaObject->removeOwningClassLoader(this);
    class_loader::impl::getFactoryMapForBaseClass<Base>().erase(implType);
    delete metaObject;
  }

  static void preload(const std::string& pluginlibType, pluginlib::ClassLoader<Base>& loader)
  {
    const auto implType = cras::getTypeName<Impl>();
    const auto baseType = cras::getTypeName<Base>();
    loader.lowlevel_class_loader_.active_class_loaders_[implType] = new PreloadingClassLoader<Impl, Base>();
    loader.classes_available_.insert({pluginlibType, {pluginlibType, implType, baseType, "", "", "", ""}});
    loader.classes_available_.at(pluginlibType).resolved_library_path_ = implType;
  }

  static void unPreload(const std::string& pluginlibType, pluginlib::ClassLoader<Base>& loader)
  {
    loader.unloadLibraryForClass(pluginlibType);
  }
};