PluginManager.h

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#ifndef FWCore_PluginManager_PluginManager_h
#define FWCore_PluginManager_PluginManager_h
// -*- C++ -*-
//
// Package:     PluginManager
// Class  :     PluginManager
//
//
// Original Author:  Chris Jones
//         Created:  Wed Apr  4 14:28:48 EDT 2007
//

// system include files
#include <filesystem>
#include <map>
#include <memory>
#include <mutex>
#include <string>
#include <vector>

#include "oneapi/tbb/concurrent_unordered_map.h"

// user include files
#include "FWCore/Utilities/interface/Signal.h"
#include "FWCore/PluginManager/interface/SharedLibrary.h"
#include "FWCore/PluginManager/interface/PluginInfo.h"

// forward declarations
namespace edmplugin {
  class DummyFriend;
  class PluginFactoryBase;

  struct PluginManagerPathHasher {
    size_t operator()(std::filesystem::path const& iPath) const { return std::hash<std::string>{}(iPath.native()); }
  };

  class PluginManager {
    friend class DummyFriend;

  public:
    typedef std::vector<std::string> SearchPath;
    typedef std::vector<PluginInfo> Infos;
    typedef std::map<std::string, Infos> CategoryToInfos;

    class Config {
    public:
      Config() {}
      Config& searchPath(const SearchPath& iPath) {
        m_path = iPath;
        return *this;
      }
      const SearchPath& searchPath() const { return m_path; }
      void allowNoCache() { m_mustHaveCache = false; }

      bool mustHaveCache() const { return m_mustHaveCache; }

    private:
      SearchPath m_path;
      bool m_mustHaveCache = true;
    };

    PluginManager(const PluginManager&) = delete;                   // stop default
    const PluginManager& operator=(const PluginManager&) = delete;  // stop default
    ~PluginManager();

    // ---------- const member functions ---------------------
    const SharedLibrary& load(const std::string& iCategory, const std::string& iPlugin);

    const std::filesystem::path& loadableFor(const std::string& iCategory, const std::string& iPlugin);

    const CategoryToInfos& categoryToInfos() const { return categoryToInfos_; }

    //If can not find iPlugin in category iCategory return null pointer, any other failure will cause a throw
    const SharedLibrary* tryToLoad(const std::string& iCategory, const std::string& iPlugin);

    // ---------- static member functions --------------------
    static const std::string& loadingFile() { return loadingLibraryNamed_(); }

    static const std::string& staticallyLinkedLoadingFileName();

    static PluginManager* get();
    static PluginManager& configure(const Config&);

    static bool isAvailable();

    // ---------- member functions ---------------------------
    edm::signalslot::Signal<void(const std::filesystem::path&)> goingToLoad_;
    edm::signalslot::Signal<void(const SharedLibrary&)> justLoaded_;
    edm::signalslot::Signal<void(const std::string&, const std::string&)> askedToLoadCategoryWithPlugin_;

  private:
    PluginManager(const Config&);

    void newFactory(const PluginFactoryBase*);
    static std::string& loadingLibraryNamed_();
    static PluginManager*& singleton();

    std::recursive_mutex& pluginLoadMutex() { return pluginLoadMutex_; }

    const std::filesystem::path& loadableFor_(const std::string& iCategory,
                                              const std::string& iPlugin,
                                              bool& ioThrowIfFailElseSucceedStatus);
    // ---------- member data --------------------------------
    SearchPath searchPath_;
    oneapi::tbb::concurrent_unordered_map<std::filesystem::path, std::shared_ptr<SharedLibrary>, PluginManagerPathHasher>
        loadables_;

    CategoryToInfos categoryToInfos_;
    std::recursive_mutex pluginLoadMutex_;
  };

}  // namespace edmplugin
#endif