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/* Boost.MultiIndex example of serialization of a MRU list.
*
* Copyright 2003-2005 Joaqun M Lpez Muoz.
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org/libs/multi_index for library home page.
*/
#if !defined(NDEBUG)
#define BOOST_MULTI_INDEX_ENABLE_INVARIANT_CHECKING
#define BOOST_MULTI_INDEX_ENABLE_SAFE_MODE
#endif
#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
#include <algorithm>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/sequenced_index.hpp>
#include <fstream>
#include <iostream>
#include <iterator>
#include <sstream>
#include <string>
using namespace boost::multi_index;
/* An MRU (most recently used) list keeps record of the last n
* inserted items, listing first the newer ones. Care has to be
* taken when a duplicate item is inserted: instead of letting it
* appear twice, the MRU list relocates it to the first position.
*/
template <typename Item>
class mru_list
{
typedef multi_index_container<
Item,
indexed_by<
sequenced<>,
hashed_unique<identity<Item> >
>
> item_list;
public:
typedef Item item_type;
typedef typename item_list::iterator iterator;
mru_list(std::size_t max_num_items):max_num_items(max_num_items){}
void insert(const item_type& item)
{
std::pair<iterator,bool> p=il.push_front(item);
if(!p.second){ /* duplicate item */
il.relocate(il.begin(),p.first); /* put in front */
}
else if(il.size()>max_num_items){ /* keep the length <= max_num_items */
il.pop_back();
}
}
iterator begin(){return il.begin();}
iterator end(){return il.end();}
/* Utilities to save and load the MRU list, internally
* based on Boost.Serialization.
*/
void save_to_file(const char* file_name)const
{
std::ofstream ofs(file_name);
boost::archive::text_oarchive oa(ofs);
oa<<boost::serialization::make_nvp("mru",*this);
}
void load_from_file(const char* file_name)
{
std::ifstream ifs(file_name);
if(ifs){
boost::archive::text_iarchive ia(ifs);
ia>>boost::serialization::make_nvp("mru",*this);
}
}
private:
item_list il;
std::size_t max_num_items;
/* serialization support */
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive& ar,const unsigned int)
{
ar&BOOST_SERIALIZATION_NVP(il);
ar&BOOST_SERIALIZATION_NVP(max_num_items);
}
};
int main()
{
const char* mru_store="mru_store";
/* Construct a MRU limited to 10 items and retrieve its
* previous contents.
*/
mru_list<std::string> mru(10);
mru.load_from_file(mru_store);
/* main loop */
for(;;){
std::cout<<"enter a term: ";
std::string line;
std::getline(std::cin,line);
if(line.empty())break;
std::string term;
std::istringstream iss(line);
iss>>term;
if(term.empty())break;
mru.insert(term);
std::cout<<"most recently entered terms:"<<std::endl;
std::copy(
mru.begin(),mru.end(),
std::ostream_iterator<std::string>(std::cout,"\n"));
}
/* persist the MRU list */
mru.save_to_file(mru_store);
return 0;
}
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