class_loader.hpp

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#ifndef CLASS_LOADER__CLASS_LOADER_HPP_
#define CLASS_LOADER__CLASS_LOADER_HPP_
 
#include <boost/bind/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread/recursive_mutex.hpp>
#include <cstddef>
#include <functional>
#include <memory>
#include <string>
#include <vector>
 
#include "console_bridge/console.h"
 
#include "class_loader/class_loader_core.hpp"
#include "class_loader/register_macro.hpp"
#include "class_loader/visibility_control.hpp"
 
namespace class_loader
{
 
CLASS_LOADER_PUBLIC
std::string systemLibraryPrefix();
 
CLASS_LOADER_PUBLIC
std::string systemLibrarySuffix();
 
CLASS_LOADER_PUBLIC
std::string systemLibraryFormat(const std::string & library_name);
 
class ClassLoader
{
public:
  template<typename Base>
  using DeleterType = std::function<void(Base *)>;
 
  template<typename Base>
  using UniquePtr = std::unique_ptr<Base, DeleterType<Base>>;
 
  CLASS_LOADER_PUBLIC
  explicit ClassLoader(const std::string & library_path, bool ondemand_load_unload = false);
 
  CLASS_LOADER_PUBLIC
  virtual ~ClassLoader();
 
  template<class Base>
  std::vector<std::string> getAvailableClasses()
  {
    return class_loader::impl::getAvailableClasses<Base>(this);
  }
 
  CLASS_LOADER_PUBLIC
  std::string getLibraryPath() {return library_path_;}
 
  template<class Base>
  std::shared_ptr<Base> createSharedInstance(const std::string & derived_class_name)
  {
    return std::shared_ptr<Base>(
      createRawInstance<Base>(derived_class_name, true),
      boost::bind(&ClassLoader::onPluginDeletion<Base>, this, boost::placeholders::_1));
  }
 
  template<class Base>
  boost::shared_ptr<Base> createInstance(const std::string & derived_class_name)
  {
    return boost::shared_ptr<Base>(
      createRawInstance<Base>(derived_class_name, true),
      boost::bind(&ClassLoader::onPluginDeletion<Base>, this, boost::placeholders::_1));
  }
 
  template<class Base>
  UniquePtr<Base> createUniqueInstance(const std::string & derived_class_name)
  {
    Base * raw = createRawInstance<Base>(derived_class_name, true);
    return std::unique_ptr<Base, DeleterType<Base>>(
      raw,
      boost::bind(&ClassLoader::onPluginDeletion<Base>, this, boost::placeholders::_1));
  }
 
  template<class Base>
  Base * createUnmanagedInstance(const std::string & derived_class_name)
  {
    return createRawInstance<Base>(derived_class_name, false);
  }
 
  template<class Base>
  bool isClassAvailable(const std::string & class_name)
  {
    std::vector<std::string> available_classes = getAvailableClasses<Base>();
    return std::find(
      available_classes.begin(), available_classes.end(), class_name) != available_classes.end();
  }
 
  CLASS_LOADER_PUBLIC
  bool isLibraryLoaded();
 
  CLASS_LOADER_PUBLIC
  bool isLibraryLoadedByAnyClassloader();
 
  CLASS_LOADER_PUBLIC
  bool isOnDemandLoadUnloadEnabled() {return ondemand_load_unload_;}
 
  CLASS_LOADER_PUBLIC
  void loadLibrary();
 
  CLASS_LOADER_PUBLIC
  int unloadLibrary();
 
private:
  template<class Base>
  void onPluginDeletion(Base * obj)
  {
    CONSOLE_BRIDGE_logDebug(
      "class_loader::ClassLoader: Calling onPluginDeletion() for obj ptr = %p.\n",
      reinterpret_cast<void *>(obj));
    if (nullptr == obj) {
      return;
    }
    boost::recursive_mutex::scoped_lock lock(plugin_ref_count_mutex_);
    delete (obj);
    plugin_ref_count_ = plugin_ref_count_ - 1;
    assert(plugin_ref_count_ >= 0);
    if (0 == plugin_ref_count_ && isOnDemandLoadUnloadEnabled()) {
      if (!ClassLoader::hasUnmanagedInstanceBeenCreated()) {
        unloadLibraryInternal(false);
      } else {
        CONSOLE_BRIDGE_logWarn(
          "class_loader::ClassLoader: "
          "Cannot unload library %s even though last shared pointer went out of scope. "
          "This is because createUnmanagedInstance was used within the scope of this process,"
          " perhaps by a different ClassLoader. Library will NOT be closed.",
          getLibraryPath().c_str());
      }
    }
  }
 
  template<class Base>
  Base * createRawInstance(const std::string & derived_class_name, bool managed)
  {
    if (!managed) {
      has_unmananged_instance_been_created_ = true;
    }
 
    if (
      managed &&
      ClassLoader::hasUnmanagedInstanceBeenCreated() &&
      isOnDemandLoadUnloadEnabled())
    {
      CONSOLE_BRIDGE_logInform("%s",
        "class_loader::ClassLoader: "
        "An attempt is being made to create a managed plugin instance (i.e. boost::shared_ptr), "
        "however an unmanaged instance was created within this process address space. "
        "This means libraries for the managed instances will not be shutdown automatically on "
        "final plugin destruction if on demand (lazy) loading/unloading mode is used."
      );
    }
    if (!isLibraryLoaded()) {
      loadLibrary();
    }
 
    Base * obj = class_loader::impl::createInstance<Base>(derived_class_name, this);
    assert(obj != nullptr);  // Unreachable assertion if createInstance() throws on failure
 
    if (managed) {
      boost::recursive_mutex::scoped_lock lock(plugin_ref_count_mutex_);
      ++plugin_ref_count_;
    }
 
    return obj;
  }
 
  CLASS_LOADER_PUBLIC
  static bool hasUnmanagedInstanceBeenCreated();
 
  CLASS_LOADER_PUBLIC
  int unloadLibraryInternal(bool lock_plugin_ref_count);
 
private:
  bool ondemand_load_unload_;
  std::string library_path_;
  int load_ref_count_;
  boost::recursive_mutex load_ref_count_mutex_;
  int plugin_ref_count_;
  boost::recursive_mutex plugin_ref_count_mutex_;
 
  CLASS_LOADER_PUBLIC
  static bool has_unmananged_instance_been_created_;
};
 
}  // namespace class_loader
 
 
#endif  // CLASS_LOADER__CLASS_LOADER_HPP_