internal_class_registry.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2019, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include "rtti-precomp.h"  // Precompiled headers

#include <mrpt/rtti/CObject.h>

#include <atomic>
#include <cstdarg>
#include <iostream>
#include <map>
#include <mutex>

#include "internal_class_registry.h"

using namespace mrpt::rtti;

/*---------------------------------------------------------------
                    STATIC GLOBAL VARIABLES
 ---------------------------------------------------------------*/
bool mrpt::rtti::pending_class_registers_modified = false;

// Creation on first call pattern:
std::atomic<int>& mrpt::rtti::pending_class_registers_count()
{
    static std::atomic<int> cnt(0);
    return cnt;
}

// Creation on first call pattern:
queue_register_functions_t& mrpt::rtti::pending_class_registers()
{
    pending_class_registers_modified = true;
    static queue_register_functions_t lst;
    return lst;
}

namespace mrpt::rtti
{
using TClassnameToRuntimeId = std::map<std::string, const TRuntimeClassId*>;

/** A singleton with the central registry for CSerializable run-time classes:
 * users do not use this class in any direct way.
 * \note Class is thread-safe.
 */
class CClassRegistry
{
   public:
    /**  The unique access point point to the singleton instance.
     */
    static CClassRegistry& Instance()
    {
        static CClassRegistry obj;
        return obj;
    }

    void Add(const std::string& className, const TRuntimeClassId& id)
    {
        m_being_modified = true;
        {
            std::unique_lock<std::mutex> lk(m_cs);

            // Sanity check: don't allow registering twice the same class name!
            const auto it = registeredClasses.find(className);
            if (it != registeredClasses.cend())
            {
                if (it->second != &id)
                {
                    std::cerr << mrpt::format(
                        "[MRPT class registry] Warning: overwriting already "
                        "registered className=`%s` with different "
                        "`TRuntimeClassId`!\n",
                        className.c_str());
                }
            }
            registeredClasses[className] = &id;
        }
        m_being_modified = false;
    }

    const TRuntimeClassId* Get(const std::string& className)
    {
        // Optimization to avoid the costly lock() in virtually all situations:
        bool has_to_unlock = false;
        if (m_being_modified)
        {
            m_cs.lock();
            has_to_unlock = true;
        }
        const TRuntimeClassId* ret = registeredClasses[className];
        if (has_to_unlock) m_cs.unlock();
        return ret;
    }

    std::vector<const TRuntimeClassId*> getListOfAllRegisteredClasses()
    {
        std::unique_lock<std::mutex> lk(m_cs);

        std::vector<const TRuntimeClassId*> ret;
        for (auto& registeredClasse : registeredClasses)
            ret.push_back(registeredClasse.second);
        return ret;
    }

   private:
    // This must be static since we can be called from C startup
    // functions and it cannot be assured that classesKeeper will be
    // initialized before other classes that call it...
    TClassnameToRuntimeId registeredClasses;
    std::mutex m_cs;
    std::atomic<bool> m_being_modified{false};
};

}  // namespace mrpt::rtti

/** Register all pending classes - to be called just before de-serializing an
 * object, for example.
 */
void mrpt::rtti::registerAllPendingClasses()
{
    if (!pending_class_registers_modified) return;  // Quick return

    while (pending_class_registers_count() != 0)
    {
        TRegisterFunction ptrToPtr = nullptr;
        pending_class_registers().get(ptrToPtr);
        --pending_class_registers_count();

        // Call it:
        if (ptrToPtr != nullptr)
        {
            (*ptrToPtr)();
        }
    }
    pending_class_registers_modified = false;
}

/*---------------------------------------------------------------
                    RegisterClass
 ---------------------------------------------------------------*/
void mrpt::rtti::registerClass(const TRuntimeClassId* pNewClass)
{
    // Register it:
    if (pNewClass && pNewClass->className)
    {
        CClassRegistry::Instance().Add(
            std::string(pNewClass->className), *pNewClass);
    }
    else
    {
        fprintf(
            stderr,
            "[mrpt::rtti::registerClass] Warning: Invoked with a nullptr "
            "classname (?).\n");
    }

    // Automatically register all classes when the first one is registered.
    registerAllPendingClasses();
}

/** For internal use within mrpt sources, and only in exceptional cases
 * (CMultiMetricMaps, CImage,...)
 */
void mrpt::rtti::registerClassCustomName(
    const char* customName, const TRuntimeClassId* pNewClass)
{
    // Register it:
    CClassRegistry::Instance().Add(customName, *pNewClass);

    // Automatically register all classes when the first one is registered.
    registerAllPendingClasses();
}

std::vector<const TRuntimeClassId*> mrpt::rtti::getAllRegisteredClasses()
{
    return CClassRegistry::Instance().getListOfAllRegisteredClasses();
}

std::vector<const TRuntimeClassId*>
    mrpt::rtti::getAllRegisteredClassesChildrenOf(
        const TRuntimeClassId* parent_id)
{
    std::vector<const TRuntimeClassId*> res;
    const auto lst = mrpt::rtti::getAllRegisteredClasses();
    for (const auto& c : lst)
    {
        if (c->derivedFrom(parent_id) && c != parent_id)
        {
            res.push_back(c);
        }
    }
    return res;
}

/*---------------------------------------------------------------
                    findRegisteredClass
 ---------------------------------------------------------------*/
const TRuntimeClassId* mrpt::rtti::findRegisteredClass(
    const std::string& className)
{
    return CClassRegistry::Instance().Get(className);
}