class_loader_imp.hpp

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#ifndef PLUGINLIB__CLASS_LOADER_IMP_HPP_
#define PLUGINLIB__CLASS_LOADER_IMP_HPP_

#include <cstdlib>
#include <list>
#include <map>
#include <memory>
#include <sstream>
#include <stdexcept>
#include <string>
#include <utility>
#include <vector>

#include "boost/algorithm/string.hpp"
#include "boost/bind.hpp"
#include "boost/filesystem.hpp"
#include "boost/foreach.hpp"
#include "class_loader/class_loader.hpp"

#include "ros/package.h"

#include "./class_loader.hpp"

#ifdef _WIN32
const std::string os_pathsep(";");  // NOLINT
#else
const std::string os_pathsep(":");  // NOLINT
#endif

namespace pluginlib
{
template<class T>
ClassLoader<T>::ClassLoader(
  std::string package, std::string base_class, std::string attrib_name,
  std::vector<std::string> plugin_xml_paths)
: plugin_xml_paths_(plugin_xml_paths),
  package_(package),
  base_class_(base_class),
  attrib_name_(attrib_name),
  // NOTE: The parameter to the class loader enables/disables on-demand class
  // loading/unloading.
  // Leaving it off for now... libraries will be loaded immediately and won't
  // be unloaded until class loader is destroyed or force unload.
  lowlevel_class_loader_(false)
  /***************************************************************************/
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Creating ClassLoader, base = %s, address = %p",
    base_class.c_str(), this);
  if (ros::package::getPath(package_).empty()) {
    throw pluginlib::ClassLoaderException("Unable to find package: " + package_);
  }

  if (0 == plugin_xml_paths_.size()) {
    plugin_xml_paths_ = getPluginXmlPaths(package_, attrib_name_);
  }
  classes_available_ = determineAvailableClasses(plugin_xml_paths_);
  ROS_DEBUG_NAMED("pluginlib.ClassLoader",
    "Finished constructring ClassLoader, base = %s, address = %p",
    base_class.c_str(), this);
}

template<class T>
ClassLoader<T>::~ClassLoader()
/***************************************************************************/
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Destroying ClassLoader, base = %s, address = %p",
    getBaseClassType().c_str(), this);
}


template<class T>
T * ClassLoader<T>::createClassInstance(const std::string & lookup_name, bool auto_load)
/***************************************************************************/
{
  // Note: This method is deprecated
  ROS_DEBUG_NAMED("pluginlib.ClassLoader",
    "In deprecated call createClassInstance(), lookup_name = %s, auto_load = %i.",
    (lookup_name.c_str()), auto_load);

  if (auto_load && !isClassLoaded(lookup_name)) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader",
      "Autoloading class library before attempting to create instance.");
    loadLibraryForClass(lookup_name);
  }

  try {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader",
      "Attempting to create instance through low-level MultiLibraryClassLoader...");
    T * obj = lowlevel_class_loader_.createUnmanagedInstance<T>(getClassType(lookup_name));
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Instance created with object pointer = %p", obj);

    return obj;
  } catch (const class_loader::CreateClassException & ex) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "CreateClassException about to be raised for class %s",
      lookup_name.c_str());
    throw pluginlib::CreateClassException(ex.what());
  }
}

template<class T>
boost::shared_ptr<T> ClassLoader<T>::createInstance(const std::string & lookup_name)
/***************************************************************************/
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Attempting to create managed instance for class %s.",
    lookup_name.c_str());

  if (!isClassLoaded(lookup_name)) {
    loadLibraryForClass(lookup_name);
  }

  try {
    std::string class_type = getClassType(lookup_name);
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "%s maps to real class type %s",
      lookup_name.c_str(), class_type.c_str());

    boost::shared_ptr<T> obj = lowlevel_class_loader_.createInstance<T>(class_type);

    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "boost::shared_ptr to object of real type %s created.",
      class_type.c_str());

    return obj;
  } catch (const class_loader::CreateClassException & ex) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader",
      "Exception raised by low-level multi-library class loader when attempting "
      "to create instance of class %s.",
      lookup_name.c_str());
    throw pluginlib::CreateClassException(ex.what());
  }
}

#if __cplusplus >= 201103L
template<class T>
UniquePtr<T> ClassLoader<T>::createUniqueInstance(const std::string & lookup_name)
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader",
    "Attempting to create managed (unique) instance for class %s.",
    lookup_name.c_str());

  if (!isClassLoaded(lookup_name)) {
    loadLibraryForClass(lookup_name);
  }

  try {
    std::string class_type = getClassType(lookup_name);
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "%s maps to real class type %s",
      lookup_name.c_str(), class_type.c_str());

    UniquePtr<T> obj = lowlevel_class_loader_.createUniqueInstance<T>(class_type);

    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "std::unique_ptr to object of real type %s created.",
      class_type.c_str());

    return obj;
  } catch (const class_loader::CreateClassException & ex) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader",
      "Exception raised by low-level multi-library class loader when attempting "
      "to create instance of class %s.",
      lookup_name.c_str());
    throw pluginlib::CreateClassException(ex.what());
  }
}
#endif

template<class T>
T * ClassLoader<T>::createUnmanagedInstance(const std::string & lookup_name)
/***************************************************************************/
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Attempting to create UNMANAGED instance for class %s.",
    lookup_name.c_str());

  if (!isClassLoaded(lookup_name)) {
    loadLibraryForClass(lookup_name);
  }

  T * instance = 0;
  try {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader",
      "Attempting to create instance through low level multi-library class loader.");
    std::string class_type = getClassType(lookup_name);
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "%s maps to real class type %s",
      lookup_name.c_str(), class_type.c_str());
    instance = lowlevel_class_loader_.createUnmanagedInstance<T>(class_type);
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Instance of type %s created.", class_type.c_str());
  } catch (const class_loader::CreateClassException & ex) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader",
      "Exception raised by low-level multi-library class loader when attempting "
      "to create UNMANAGED instance of class %s.",
      lookup_name.c_str());
    throw pluginlib::CreateClassException(ex.what());
  }
  return instance;
}

template<class T>
std::vector<std::string> ClassLoader<T>::getPluginXmlPaths(
  const std::string & package,
  const std::string & attrib_name,
  bool force_recrawl)
/***************************************************************************/
{
  // Pull possible files from manifests of packages which depend on this package and export class
  std::vector<std::string> paths;
  ros::package::getPlugins(package, attrib_name, paths, force_recrawl);
  return paths;
}

template<class T>
std::map<std::string, ClassDesc> ClassLoader<T>::determineAvailableClasses(
  const std::vector<std::string> & plugin_xml_paths)
/***************************************************************************/
{
  // mas - This method requires major refactoring...
  // not only is it really long and confusing but a lot of the comments do not
  // seem to be correct.
  // With time I keep correcting small things, but a good rewrite is needed.

  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Entering determineAvailableClasses()...");
  std::map<std::string, ClassDesc> classes_available;

  // Walk the list of all plugin XML files (variable "paths") that are exported by the build system
  for (std::vector<std::string>::const_iterator it = plugin_xml_paths.begin();
    it != plugin_xml_paths.end(); ++it)
  {
    try {
      processSingleXMLPluginFile(*it, classes_available);
    } catch (const pluginlib::InvalidXMLException & e) {
      ROS_ERROR_NAMED("pluginlib.ClassLoader",
        "Skipped loading plugin with error: %s.",
        e.what());
    }
  }

  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Exiting determineAvailableClasses()...");
  return classes_available;
}

template<class T>
std::string ClassLoader<T>::extractPackageNameFromPackageXML(const std::string & package_xml_path)
/***************************************************************************/
{
  tinyxml2::XMLDocument document;
  document.LoadFile(package_xml_path.c_str());
  tinyxml2::XMLElement * doc_root_node = document.FirstChildElement("package");
  if (NULL == doc_root_node) {
    ROS_ERROR_NAMED("pluginlib.ClassLoader",
      "Could not find a root element for package manifest at %s.",
      package_xml_path.c_str());
    return "";
  }

  assert(document.RootElement() == doc_root_node);

  tinyxml2::XMLElement * package_name_node = doc_root_node->FirstChildElement("name");
  if (NULL == package_name_node) {
    ROS_ERROR_NAMED("pluginlib.ClassLoader",
      "package.xml at %s does not have a <name> tag! Cannot determine package "
      "which exports plugin.",
      package_xml_path.c_str());
    return "";
  }

  const char* package_name_node_txt = package_name_node->GetText();
  if (NULL == package_name_node_txt) {
    ROS_ERROR_NAMED("pluginlib.ClassLoader",
      "package.xml at %s has an invalid <name> tag! Cannot determine package "
      "which exports plugin.",
      package_xml_path.c_str());
    return "";
  }

  return package_name_node_txt;
}

template<class T>
std::vector<std::string> ClassLoader<T>::getCatkinLibraryPaths()
/***************************************************************************/
{
  std::vector<std::string> lib_paths;
  const char * env = std::getenv("CMAKE_PREFIX_PATH");
  if (env) {
    std::string env_catkin_prefix_paths(env);
    std::vector<std::string> catkin_prefix_paths;
    boost::split(catkin_prefix_paths, env_catkin_prefix_paths, boost::is_any_of(os_pathsep));
    BOOST_FOREACH(std::string catkin_prefix_path, catkin_prefix_paths) {
      boost::filesystem::path path(catkin_prefix_path);
#if _WIN32
      boost::filesystem::path bin("bin");
      lib_paths.push_back((path / bin).string());
#endif
      boost::filesystem::path lib("lib");
      lib_paths.push_back((path / lib).string());
    }
  }
  return lib_paths;
}

template<class T>
std::vector<std::string> ClassLoader<T>::getAllLibraryPathsToTry(
  const std::string & library_name,
  const std::string & exporting_package_name)
/***************************************************************************/
{
  // Catkin-rosbuild Backwards Compatability Rules - Note library_name may be prefixed with
  // relative path (e.g. "/lib/libFoo")
  // 1. Try catkin library paths (catkin_find --libs) + library_name + extension
  // 2. Try catkin library paths
  //   (catkin_find -- libs) + stripAllButFileFromPath(library_name) + extension
  // 3. Try export_pkg/library_name + extension

  std::vector<std::string> all_paths;
  std::vector<std::string> all_paths_without_extension = getCatkinLibraryPaths();
  all_paths_without_extension.push_back(getROSBuildLibraryPath(exporting_package_name));
  bool debug_library_suffix = (0 == class_loader::systemLibrarySuffix().compare(0, 1, "d"));
  std::string non_debug_suffix;
  if (debug_library_suffix) {
    non_debug_suffix = class_loader::systemLibrarySuffix().substr(1);
  } else {
    non_debug_suffix = class_loader::systemLibrarySuffix();
  }
  std::string library_name_with_extension = library_name + non_debug_suffix;
  std::string stripped_library_name = stripAllButFileFromPath(library_name);
  std::string stripped_library_name_with_extension = stripped_library_name + non_debug_suffix;

  const std::string path_separator = getPathSeparator();

  for (unsigned int c = 0; c < all_paths_without_extension.size(); c++) {
    std::string current_path = all_paths_without_extension.at(c);
    all_paths.push_back(current_path + path_separator + library_name_with_extension);
    all_paths.push_back(current_path + path_separator + stripped_library_name_with_extension);
    // We're in debug mode, try debug libraries as well
    if (debug_library_suffix) {
      all_paths.push_back(
        current_path + path_separator + library_name + class_loader::systemLibrarySuffix());
      all_paths.push_back(
        current_path + path_separator + stripped_library_name +
        class_loader::systemLibrarySuffix());
    }
  }

  return all_paths;
}

template<class T>
bool ClassLoader<T>::isClassLoaded(const std::string & lookup_name)
/***************************************************************************/
{
  return lowlevel_class_loader_.isClassAvailable<T>(getClassType(lookup_name));
}

template<class T>
std::string ClassLoader<T>::getBaseClassType() const
/***************************************************************************/
{
  return base_class_;
}

template<class T>
std::string ClassLoader<T>::getClassDescription(const std::string & lookup_name)
/***************************************************************************/
{
  ClassMapIterator it = classes_available_.find(lookup_name);
  if (it != classes_available_.end()) {
    return it->second.description_;
  }
  return "";
}

template<class T>
std::string ClassLoader<T>::getClassType(const std::string & lookup_name)
/***************************************************************************/
{
  ClassMapIterator it = classes_available_.find(lookup_name);
  if (it != classes_available_.end()) {
    return it->second.derived_class_;
  }
  return "";
}

template<class T>
std::string ClassLoader<T>::getClassLibraryPath(const std::string & lookup_name)
/***************************************************************************/
{
  if (classes_available_.find(lookup_name) == classes_available_.end()) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Class %s has no mapping in classes_available_.",
      lookup_name.c_str());
    return "";
  }
  ClassMapIterator it = classes_available_.find(lookup_name);
  std::string library_name = it->second.library_name_;
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Class %s maps to library %s in classes_available_.",
    lookup_name.c_str(), library_name.c_str());

  std::vector<std::string> paths_to_try =
    getAllLibraryPathsToTry(library_name, it->second.package_);

  ROS_DEBUG_NAMED("pluginlib.ClassLoader",
    "Iterating through all possible paths where %s could be located...",
    library_name.c_str());
  for (std::vector<std::string>::const_iterator it = paths_to_try.begin(); it != paths_to_try.end();
    it++)
  {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Checking path %s ", it->c_str());
    if (boost::filesystem::exists(*it)) {
      ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Library %s found at explicit path %s.",
        library_name.c_str(), it->c_str());
      return *it;
    }
  }
  return "";
}

template<class T>
std::string ClassLoader<T>::getClassPackage(const std::string & lookup_name)
/***************************************************************************/
{
  ClassMapIterator it = classes_available_.find(lookup_name);
  if (it != classes_available_.end()) {
    return it->second.package_;
  }
  return "";
}

template<class T>
std::vector<std::string> ClassLoader<T>::getPluginXmlPaths()
/***************************************************************************/
{
  return plugin_xml_paths_;
}

template<class T>
std::vector<std::string> ClassLoader<T>::getDeclaredClasses()
/***************************************************************************/
{
  std::vector<std::string> lookup_names;
  for (ClassMapIterator it = classes_available_.begin(); it != classes_available_.end(); ++it) {
    lookup_names.push_back(it->first);
  }

  return lookup_names;
}

template<class T>
std::string ClassLoader<T>::getErrorStringForUnknownClass(const std::string & lookup_name)
/***************************************************************************/
{
  std::string declared_types;
  std::vector<std::string> types = getDeclaredClasses();
  for (unsigned int i = 0; i < types.size(); i++) {
    declared_types = declared_types + std::string(" ") + types[i];
  }
  return "According to the loaded plugin descriptions the class " + lookup_name +
         " with base class type " + base_class_ + " does not exist. Declared types are " +
         declared_types;
}

template<class T>
std::string ClassLoader<T>::getName(const std::string & lookup_name)
/***************************************************************************/
{
  // remove the package name to get the raw plugin name
  std::vector<std::string> split;
  boost::split(split, lookup_name, boost::is_any_of("/:"));
  return split.back();
}

template<class T>
std::string
ClassLoader<T>::getPackageFromPluginXMLFilePath(const std::string & plugin_xml_file_path)
/***************************************************************************/
{
  // Note: This method takes an input a path to a plugin xml file and must determine which
  // package the XML file came from. This is not necessariliy the same thing as the member
  // variable "package_". The plugin xml file can be located anywhere in the source tree for a
  // package

  // rosbuild:
  // 1. Find nearest encasing manifest.xml
  // 2. Once found, the name of the folder containg the manifest should be the
  //   package name we are looking for
  // 3. Confirm package is findable with rospack

  // catkin:
  // 1. Find nearest encasing package.xml
  // 2. Extract name of package from package.xml

  std::string package_name;
  boost::filesystem::path p(plugin_xml_file_path);
  boost::filesystem::path parent = p.parent_path();

  // Figure out exactly which package the passed XML file is exported by.
  while (true) {
    if (boost::filesystem::exists(parent / "package.xml")) {
      std::string package_file_path = (boost::filesystem::path(parent / "package.xml")).string();
      return extractPackageNameFromPackageXML(package_file_path);
    } else if (boost::filesystem::exists(parent / "manifest.xml")) {
#if BOOST_FILESYSTEM_VERSION >= 3
      std::string package = parent.filename().string();
#else
      std::string package = parent.filename();
#endif
      std::string package_path = ros::package::getPath(package);

      // package_path is a substr of passed plugin xml path
      if (0 == plugin_xml_file_path.find(package_path)) {
        package_name = package;
        break;
      }
    }

    // Recursive case - hop one folder up
    parent = parent.parent_path().string();

    // Base case - reached root and cannot find what we're looking for
    if (parent.string().empty()) {
      return "";
    }
  }

  return package_name;
}

template<class T>
std::string ClassLoader<T>::getPathSeparator()
/***************************************************************************/
{
#if BOOST_FILESYSTEM_VERSION >= 3
#  ifdef _WIN32
     return boost::filesystem::path("/").string();
#  else
     return boost::filesystem::path("/").native();
#  endif
#else
  return boost::filesystem::path("/").external_file_string();
#endif
}


template<class T>
std::string ClassLoader<T>::getPluginManifestPath(const std::string & lookup_name)
/***************************************************************************/
{
  ClassMapIterator it = classes_available_.find(lookup_name);
  if (it != classes_available_.end()) {
    return it->second.plugin_manifest_path_;
  }
  return "";
}


template<class T>
std::vector<std::string> ClassLoader<T>::getRegisteredLibraries()
/***************************************************************************/
{
  return lowlevel_class_loader_.getRegisteredLibraries();
}

template<class T>
std::string ClassLoader<T>::getROSBuildLibraryPath(const std::string & exporting_package_name)
/***************************************************************************/
{
  return ros::package::getPath(exporting_package_name);
}

template<class T>
bool ClassLoader<T>::isClassAvailable(const std::string & lookup_name)
/***************************************************************************/
{
  return classes_available_.find(lookup_name) != classes_available_.end();
}

template<class T>
std::string ClassLoader<T>::joinPaths(const std::string & path1, const std::string & path2)
/***************************************************************************/
{
  boost::filesystem::path p1(path1);
  return (p1 / path2).string();
}

template<class T>
void ClassLoader<T>::loadLibraryForClass(const std::string & lookup_name)
/***************************************************************************/
{
  ClassMapIterator it = classes_available_.find(lookup_name);
  if (it == classes_available_.end()) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Class %s has no mapping in classes_available_.",
      lookup_name.c_str());
    throw pluginlib::LibraryLoadException(getErrorStringForUnknownClass(lookup_name));
  }

  std::string library_path = getClassLibraryPath(lookup_name);
  if ("" == library_path) {
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "No path could be found to the library containing %s.",
      lookup_name.c_str());
    std::ostringstream error_msg;
    error_msg << "Could not find library corresponding to plugin " << lookup_name <<
      ". Make sure the plugin description XML file has the correct name of the "
      "library and that the library actually exists.";
    throw pluginlib::LibraryLoadException(error_msg.str());
  }

  try {
    lowlevel_class_loader_.loadLibrary(library_path);
    it->second.resolved_library_path_ = library_path;
  } catch (const class_loader::LibraryLoadException & ex) {
    std::string error_string =
      "Failed to load library " + library_path + ". "
      "Make sure that you are calling the PLUGINLIB_EXPORT_CLASS macro in the "
      "library code, and that names are consistent between this macro and your XML. "
      "Error string: " + ex.what();
    throw pluginlib::LibraryLoadException(error_string);
  }
}

template<class T>
void ClassLoader<T>::processSingleXMLPluginFile(
  const std::string & xml_file, std::map<std::string,
  ClassDesc> & classes_available)
/***************************************************************************/
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Processing xml file %s...", xml_file.c_str());
  tinyxml2::XMLDocument document;
  document.LoadFile(xml_file.c_str());
  tinyxml2::XMLElement * config = document.RootElement();
  if (NULL == config) {
    throw pluginlib::InvalidXMLException(
            "XML Document '" + xml_file +
            "' has no Root Element. This likely means the XML is malformed or missing.");
    return;
  }
  const char* config_value = config->Value();
  if (NULL == config_value) {
      throw pluginlib::InvalidXMLException(
              "XML Document '" + xml_file +
              "' has an invalid Root Element. This likely means the XML is malformed or missing.");
      return;
  }
  if (!(strcmp(config_value, "library") == 0 ||
    strcmp(config_value, "class_libraries") == 0))
  {
    throw pluginlib::InvalidXMLException(
            "The XML document '" + xml_file + "' given to add must have either \"library\" or "
            "\"class_libraries\" as the root tag");
    return;
  }
  // Step into the filter list if necessary
  if (strcmp(config_value, "class_libraries") == 0) {
    config = config->FirstChildElement("library");
  }

  tinyxml2::XMLElement * library = config;
  while (library != NULL) {
    const char* path = library->Attribute("path");
    if (NULL == path) {
      ROS_ERROR_NAMED("pluginlib.ClassLoader",
        "Attribute 'path' in 'library' tag is missing in %s.", xml_file.c_str());
      continue;
    }
    std::string library_path(path);
    if (0 == library_path.size()) {
      ROS_ERROR_NAMED("pluginlib.ClassLoader",
        "Attribute 'path' in 'library' tag is missing in %s.", xml_file.c_str());
      continue;
    }

    std::string package_name = getPackageFromPluginXMLFilePath(xml_file);
    if ("" == package_name) {
      ROS_ERROR_NAMED("pluginlib.ClassLoader",
        "Could not find package manifest (neither package.xml or deprecated "
        "manifest.xml) at same directory level as the plugin XML file %s. "
        "Plugins will likely not be exported properly.\n)",
        xml_file.c_str());
    }

    tinyxml2::XMLElement * class_element = library->FirstChildElement("class");
    while (class_element) {
      std::string derived_class;
      if (class_element->Attribute("type") != NULL) {
        derived_class = std::string(class_element->Attribute("type"));
      } else {
        throw pluginlib::ClassLoaderException(
                "Class could not be loaded. Attribute 'type' in class tag is missing.");
      }

      std::string base_class_type;
      if (class_element->Attribute("base_class_type") != NULL) {
        base_class_type = std::string(class_element->Attribute("base_class_type"));
      } else {
        throw pluginlib::ClassLoaderException(
                "Class could not be loaded. Attribute 'base_class_type' in class tag is missing.");
      }

      std::string lookup_name;
      if (class_element->Attribute("name") != NULL) {
        lookup_name = class_element->Attribute("name");
        ROS_DEBUG_NAMED("pluginlib.ClassLoader",
          "XML file specifies lookup name (i.e. magic name) = %s.",
          lookup_name.c_str());
      } else {
        ROS_DEBUG_NAMED("pluginlib.ClassLoader",
          "XML file has no lookup name (i.e. magic name) for class %s, "
          "assuming lookup_name == real class name.",
          derived_class.c_str());
        lookup_name = derived_class;
      }

      // make sure that this class is of the right type before registering it
      if (base_class_type == base_class_) {
        // register class here
        tinyxml2::XMLElement * description = class_element->FirstChildElement("description");
        std::string description_str;
        if (description) {
          description_str = description->GetText() ? description->GetText() : "";
        } else {
          description_str = "No 'description' tag for this plugin in plugin description file.";
        }

        classes_available.insert(std::pair<std::string, ClassDesc>(lookup_name,
          ClassDesc(lookup_name, derived_class, base_class_type, package_name, description_str,
          library_path, xml_file)));
      }

      // step to next class_element
      class_element = class_element->NextSiblingElement("class");
    }
    library = library->NextSiblingElement("library");
  }
}

template<class T>
void ClassLoader<T>::refreshDeclaredClasses()
/***************************************************************************/
{
  ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Refreshing declared classes.");
  // determine classes not currently loaded for removal
  std::list<std::string> remove_classes;
  for (std::map<std::string, ClassDesc>::const_iterator it = classes_available_.begin();
    it != classes_available_.end(); it++)
  {
    std::string resolved_library_path = it->second.resolved_library_path_;
    std::vector<std::string> open_libs = lowlevel_class_loader_.getRegisteredLibraries();
    if (std::find(open_libs.begin(), open_libs.end(), resolved_library_path) != open_libs.end()) {
      remove_classes.push_back(it->first);
    }
  }

  while (!remove_classes.empty()) {
    classes_available_.erase(remove_classes.front());
    remove_classes.pop_front();
  }

  // add new classes
  plugin_xml_paths_ = getPluginXmlPaths(package_, attrib_name_, true);
  std::map<std::string, ClassDesc> updated_classes = determineAvailableClasses(plugin_xml_paths_);
  for (std::map<std::string, ClassDesc>::const_iterator it = updated_classes.begin();
    it != updated_classes.end(); it++)
  {
    if (classes_available_.find(it->first) == classes_available_.end()) {
      classes_available_.insert(std::pair<std::string, ClassDesc>(it->first, it->second));
    }
  }
}

template<class T>
std::string ClassLoader<T>::stripAllButFileFromPath(const std::string & path)
/***************************************************************************/
{
  std::string only_file;
  size_t c = path.find_last_of(getPathSeparator());
  if (std::string::npos == c) {
    return path;
  } else {
    return path.substr(c, path.size());
  }
}

template<class T>
int ClassLoader<T>::unloadLibraryForClass(const std::string & lookup_name)
/***************************************************************************/
{
  ClassMapIterator it = classes_available_.find(lookup_name);
  if (it != classes_available_.end() && it->second.resolved_library_path_ != "UNRESOLVED") {
    std::string library_path = it->second.resolved_library_path_;
    ROS_DEBUG_NAMED("pluginlib.ClassLoader", "Attempting to unload library %s for class %s",
      library_path.c_str(), lookup_name.c_str());
    return unloadClassLibraryInternal(library_path);
  } else {
    throw pluginlib::LibraryUnloadException(getErrorStringForUnknownClass(lookup_name));
  }
}

template<class T>
int ClassLoader<T>::unloadClassLibraryInternal(const std::string & library_path)
/***************************************************************************/
{
  return lowlevel_class_loader_.unloadLibrary(library_path);
}

}  // namespace pluginlib

#endif  // PLUGINLIB__CLASS_LOADER_IMP_HPP_