PluginLoader

Description

Agnostic plugin loader.

Introduction to plugins in C++

Todo:

Handle (multiple git repos in) MetaInfo (#99)

Introduction to plugins in C++

Todo:

Handle (multiple git repos in) MetaInfo (#99)

#include <PluginLoader.h>

Collaboration diagram for PluginLoader:

Public Member Functions
	PluginLoader (const std::filesystem::path &file, int steering=none)
	PluginLoader (PluginLoader &&other)
	~PluginLoader () noexcept
std::filesystem::path	Which () const
template<Plugin P>
auto	Get () const
	PluginLoader (const std::filesystem::path &file, int steering=none)
	PluginLoader (PluginLoader &&other)
	~PluginLoader () noexcept
std::filesystem::path	Which () const
template<Plugin P>
auto	Get () const

Private Attributes
std::filesystem::path	file
std::vector< std::unique_ptr< IPlugin > >	plugins
void *	handle
int	steering

Constructor & Destructor Documentation

PluginLoader() [1/4]

PluginLoader ( const std::filesystem::path &  file, int  steering = none  )

inline

Standard constructor.

Runs dlopen() and dlsym(), creates T, and throws if anything looks bad.

Note

Use the DARWIN_EXPORT_PLUGIN() macro to provide the function used by dlsym to instantiate the plugin.

Note

dlopen checks that the plugin exists.

Parameters

file	path to .so or .dylib file

        : file(file)
        , handle(nullptr)
        , steering(steering)
    {
        using namespace std;
 
        if (steering & verbose)
            cout << "PluginLoader: Loading plugin from " << file << endl;
 
        handle = dlopen(file.c_str(), RTLD_LAZY);
        if (!handle) {
            string what = file.string() + " could not be loaded"s;
            const char * error = dlerror();
            if (error != nullptr)
                what += ": "s + error;
            BOOST_THROW_EXCEPTION( invalid_argument(what) );
        }
 
        typedef vector<unique_ptr<IPlugin>> * create_t();
        auto CreatePlugin = (create_t *) dlsym(handle, "CreatePlugin");
        if (!CreatePlugin) {
            string what = "`CreatePlugin` could not be found"s;
            const char * error = dlerror();
            if (error != nullptr)
                what += ": "s + error;
            BOOST_THROW_EXCEPTION( runtime_error(what) );
        }
        vector<unique_ptr<IPlugin>> * iplugins = CreatePlugin();
        if (iplugins == nullptr)
            BOOST_THROW_EXCEPTION( runtime_error("`CreatePlugin` returns a nullptr") );
        plugins = std::move(*iplugins);
        ranges::for_each(plugins, [file](unique_ptr<IPlugin>& p) { p->SetPath(file); });
    }
    catch (boost::exception& e) {
        namespace DE = Darwin::Exceptions;
        BOOST_THROW_EXCEPTION( DE::PluginException(file, e) );
    }

PluginLoader() [2/4]

PluginLoader ( PluginLoader &&  other )

inline

Move constructor.

        : file(other.file)
        , plugins(std::move(other.plugins))
        , handle(std::move(other.handle))
    {
        using namespace std;
 
        if (steering & verbose)
            cout << "PluginLoader: Moving plugin from " << file << endl;
 
        other.file.clear();
        other.plugins.clear();
        other.handle = nullptr;
    }

~PluginLoader() [1/2]

~PluginLoader ( )

inlinenoexcept

Closes the plugin handle.

    {
        using namespace std;
 
        if (steering & verbose)
            cout << "PluginLoader: Closing plugin from " << file << endl;
 
        plugins.clear(); // Delete plugins _before_ closing the handle.
 
        if (!handle) return;
        int code = dlclose(handle);
        if (code != 0)
            cerr << orange << "The plugin(s) loaded from " << file
                 << " closed with error " << code << def << '\n';
    }

PluginLoader() [3/4]

PluginLoader ( const std::filesystem::path &  file, int  steering = none  )

inline

Standard constructor.

Runs dlopen() and dlsym(), creates T, and throws if anything looks bad.

Note

Use the DARWIN_EXPORT_PLUGIN() macro to provide the function used by dlsym to instantiate the plugin.

Note

dlopen checks that the plugin exists.

Parameters

file	path to .so or .dylib file

        : file(file)
        , handle(nullptr)
        , steering(steering)
    {
        using namespace std;
 
        if (steering & verbose)
            cout << "PluginLoader: Loading plugin from " << file << endl;
 
        handle = dlopen(file.c_str(), RTLD_LAZY);
        if (!handle) {
            string what = file.string() + " could not be loaded"s;
            const char * error = dlerror();
            if (error != nullptr)
                what += ": "s + error;
            BOOST_THROW_EXCEPTION( invalid_argument(what) );
        }
 
        typedef vector<unique_ptr<IPlugin>> * create_t();
        auto CreatePlugin = (create_t *) dlsym(handle, "CreatePlugin");
        if (!CreatePlugin) {
            string what = "`CreatePlugin` could not be found"s;
            const char * error = dlerror();
            if (error != nullptr)
                what += ": "s + error;
            BOOST_THROW_EXCEPTION( runtime_error(what) );
        }
        vector<unique_ptr<IPlugin>> * iplugins = CreatePlugin();
        if (iplugins == nullptr)
            BOOST_THROW_EXCEPTION( runtime_error("`CreatePlugin` returns a nullptr") );
        plugins = std::move(*iplugins);
        ranges::for_each(plugins, [file](unique_ptr<IPlugin>& p) { p->SetPath(file); });
    }
    catch (boost::exception& e) {
        namespace DE = Darwin::Exceptions;
        BOOST_THROW_EXCEPTION( DE::PluginException(file, e) );
    }

PluginLoader() [4/4]

PluginLoader ( PluginLoader &&  other )

inline

Move constructor.

        : file(other.file)
        , plugins(std::move(other.plugins))
        , handle(std::move(other.handle))
    {
        using namespace std;
 
        if (steering & verbose)
            cout << "PluginLoader: Moving plugin from " << file << endl;
 
        other.file.clear();
        other.plugins.clear();
        other.handle = nullptr;
    }

~PluginLoader() [2/2]

~PluginLoader ( )

inlinenoexcept

Closes the plugin handle.

    {
        using namespace std;
 
        if (steering & verbose)
            cout << "PluginLoader: Closing plugin from " << file << endl;
 
        plugins.clear(); // Delete plugins _before_ closing the handle.
 
        if (!handle) return;
        int code = dlclose(handle);
        if (code != 0)
            cerr << orange << "The plugin(s) loaded from " << file
                 << " closed with error " << code << def << '\n';
    }

Member Function Documentation

Get() [1/2]

auto Get ( ) const

inline

Access to plugin's raw pointers.

    {
        using namespace std;
        auto convert = [this](IPlugin * plugin) -> P * {
            auto ptr = dynamic_cast<P*>(plugin);
            if (ptr == nullptr) {
                string what = "Invalid plugin type for ";
                what += file;
                BOOST_THROW_EXCEPTION( logic_error(what) );
            }
            return ptr;
        };
        return plugins | views::transform(&unique_ptr<IPlugin>::get)
                       | views::transform(convert);
    }

Get() [2/2]

auto Get ( ) const

inline

Access to plugin's raw pointers.

    {
        using namespace std;
        auto convert = [this](IPlugin * plugin) -> P * {
            auto ptr = dynamic_cast<P*>(plugin);
            if (ptr == nullptr) {
                string what = "Invalid plugin type for ";
                what += file;
                BOOST_THROW_EXCEPTION( logic_error(what) );
            }
            return ptr;
        };
        return plugins | views::transform(&unique_ptr<IPlugin>::get)
                       | views::transform(convert);
    }

Which() [1/2]

std::filesystem::path Which ( ) const

inline

Get plugin location.

{ return file; }

Which() [2/2]

std::filesystem::path Which ( ) const

inline

Get plugin location.

{ return file; }

Member Data Documentation

file

std::filesystem::path file

private

plugin location

handle

void * handle

private

pointer to object return by dlopen()

plugins

std::vector< std::unique_ptr< IPlugin > > plugins

private

pointers to function return from the function called by dlopen

steering

int steering

private

See also

Darwin::Tools::Mode

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The documentation for this class was generated from the following file:

• /builds/cms-analysis/general/DasAnalysisSystem/Core/Installer/Darwin/interface/PluginLoader.h