Boost的Serialization和SmartPoint搭配使用

         准确来说，这篇博文并不是译文，而是一篇某个网页中代码改写而来。原文章中的代码存在几处严重错误，网页又不提供留言功能（不是没有而是一个没有留言功能的留言板）。4年过去了，作者对这些错误不更正让人无法接受。遂在此“翻译”之。原网址：点击打开链接

        此代码是用来解决Boost库中持久化内存问题（主要是内存泄露）。代码如下:

#include <fstream>#include <boost/archive/text_oarchive.hpp>#include <boost/archive/text_iarchive.hpp>#include <cstdlib>#include <boost/tr1/memory.hpp>#include <vector>#include <map>#include <boost/tr1/unordered_map.hpp>#include <memory>#include <boost/serialization/shared_ptr.hpp>#include <boost/serialization/split_free.hpp>using namespace std;using namespace boost::serialization;namespace boost{    namespace serialization{//implement serialization for auto_ptr<T>//note: this must be added to the boost namesapce in order to//be called by the libarytemplate< typename Archive, typename T>inline void save( Archive &ar, const std::auto_ptr<T> &t, const unsigned int file_version){//only the raw pointer has to be savedcont T *const tx = t->get();ar << tx;}template <typename Archive, typename T>inline void load(Archive &ar, std::auto_ptr<T> &t, const unsigned int file_version){T *pTarget;ar >> pTarget;  //note that the reset automagically maintains the reference count#if BOOST_WORKAROUND (BOOST_DINKUMWARE_STDLIB, ==1)t->release();t = std::auto_ptr<T>(pTarget);#elset->reset(pTarget);#endif}//split non-instrusive serialization function member into sparate//non intrusive asve/load member functionstemplate<typename Archive, typename T>inline void serialize(Archive &ar, std::auto_ptr<T> &t, const unsigned int file_version){boost::serialization::split_free(ar, t, file_version);}}// namespace serialization}//namespace boost//举例说明简单类型的序列化class gps_position{private:friend class boost::serialization::access;template<typename Archive>void serialize(Archive &ar, const unsigned int version){ar & degrees;ar & minutes;ar & seconds;}int degrees;int minutes;float seconds;public:gps_position(){degrees = 0;minutes = 0;seconds = 0.0f;}gps_position(int d, int m, float s):     degrees(d),minutes(m),seconds(s) { }}; class bus_stop{friend class boost::serialization::access;template <typename Archive>void serialize( Archive &ar, const unsigned int version ){ar & latitude;ar & longitude;}gps_position latitude;gps_position longitude;public:bus_stop()  {  }bus_stop(const gps_position &lat_, const gps_position &long_):     latitude(lat_), longitude(long_)  {   }virtual ~bus_stop()  {   }};class bus_stop_corner:public bus_stop{friend class boost::serialization::access;template<class Archive>void serialize(Archive & ar, const unsigned int version){// 序列化基类信息ar & boost::serialization::base_object<bus_stop>(*this);ar & street1;ar & street2;}std::string street1;std::string street2;public:bus_stop_corner() {   }bus_stop_corner(const gps_position & lat_, const gps_position & long_,            const std::string & s1_, const std::string & s2_) :                     bus_stop(lat_, long_), street1(s1_), street2(s2_) {    }virtual std::string description() const{return street1 + " and " + street2;}~bus_stop_corner() {  }};class bus_route{friend class boost::serialization::access;    //相对于BoostLearn03，此处改写是为了减少代码量并显示更清楚boost::shared_ptr<bus_stop_corner> msptrBusStop;boost::shared_ptr<bus_stop_corner> maptrBusStop;template<class Archive>void serialize(Archive & ar, const unsigned int version){ar & msptrBusStop;ar & maptrBusStop;}public:bus_route(bus_stop_corner *apStop1, bus_stop_corner *apStop2):msptrBusStop(apStop1/*new bus_stop_corner(apStop1)*/), maptrBusStop(apStop2/*new bus_stop_corner(apStop2)*/){}bus_route()  {}~bus_route(){}};int main(void){std::ofstream ofs("bus_route");//创建类实例const gps_position latitude(1, 2, 3.3f);const gps_position longitude(4, 5, 6.6f);        //注解1：bus_stop_corner *lpStop1 = new bus_stop_corner(latitude, longitude, "corn1", "corn2");bus_stop_corner *lpStop2 = new bus_stop_corner(latitude, longitude, "corn3", "corn4");        //注解2：bus_route route(lpStop1, lpStop2);{boost::archive::text_oarchive oa(ofs);oa << route;}bus_route new_route;{std::ifstream ifs("bus_route", std::ios::binary);boost::archive::text_iarchive ia(ifs);ia >> new_route;}//当智能指针的引用计数为0时，内存会被释放.return 0;}

在修改原来的代码是发现一个弄不明白的地方,如进行下面的更改后便出现 “Expression:_BLOCK_TYPE_IS_VALID (pHead->nBlockUse)”错误.

1.代码中"注解①"处若换成如下两行代码

    bus_stop_corner lpStop1 (latitude, longitude, "corn1", "corn2");    bus_stop_corner lpStop2 (latitude, longitude, "corn3", "corn4");

2."注解②"处换成

bus_route route(&lpStop1, &lpStop2);

3.运行时出现"“Expression:_BLOCK_TYPE_IS_VALID (pHead->nBlockUse)”错误".

        为什么出现如此现象我也不能可定。猜测：

         对比发现，一个是构造函数构造出来的，另一个是用new运算符分配的内存。构造函数构造对象时分配的内存由析构函数负责完成内存释放，new运算符分配的内存通过delete运算或是通过智能指针的引用计数来释放。

        这个猜测还需验证，现记录在此，以后有能力证明这个猜测再来完善。 2013-11-15

更新

2015-04-21      第一次更新

         上面1，2，3的疑惑根源在class bus_route类中使用了shared_ptr引用计数智能指针，其中msptrBusStop、maptrBusStop属性都属于shared_ptr智能指针。shared_ptr智能指针智能封装由new分配出来的指针，所以使用构造函数生成的对象用bus_route route(&lpStop1, &lpStop2);传入由shared_ptr进行封装是不允许的。所以出现以上的疑惑之处。

        对于C++智能指针的详细解析可以参看《C++智能指针使用总结》文章。