doc_move_containers.cpp

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//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006-2007. 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/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
//[doc_move_containers
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <cassert>

int main ()
{
   using namespace boost::interprocess;

   //Typedefs
   typedef managed_shared_memory::segment_manager     SegmentManager;
   typedef allocator<char, SegmentManager>            CharAllocator;
   typedef basic_string<char, std::char_traits<char>
                        ,CharAllocator>                MyShmString;
   typedef allocator<MyShmString, SegmentManager>     StringAllocator;      
   typedef vector<MyShmString, StringAllocator>       MyShmStringVector;

   //Remove old shared memory and create new one
   shared_memory_object::remove("myshm");
   try{
      managed_shared_memory shm(create_only, "myshm", 10000);

      //Create allocators
      CharAllocator     charallocator  (shm.get_segment_manager());
      StringAllocator   stringallocator(shm.get_segment_manager());

      //Create a vector of strings in shared memory.
      MyShmStringVector *myshmvector = 
         shm.construct<MyShmStringVector>("myshmvector")(stringallocator);

      //Insert 50 strings in shared memory. The strings will be allocated
      //only once and no string copy-constructor will be called when inserting
      //strings, leading to a great performance.
      MyShmString string_to_compare(charallocator);
      string_to_compare = "this is a long, long, long, long, long, long, string...";
      
      myshmvector->reserve(50);
      for(int i = 0; i < 50; ++i){
         MyShmString move_me(string_to_compare);
         //In the following line, no string copy-constructor will be called.
         //"move_me"'s contents will be transferred to the string created in
         //the vector
         myshmvector->push_back(boost::interprocess::move(move_me));

         //The source string is in default constructed state
         assert(move_me.empty());

         //The newly created string will be equal to the "move_me"'s old contents
         assert(myshmvector->back() == string_to_compare);
      }

      //Now erase a string...
      myshmvector->pop_back();

      //...And insert one in the first position.
      //No string copy-constructor or assignments will be called, but
      //move constructors and move-assignments. No memory allocation 
      //function will be called in this operations!!
      myshmvector->insert(myshmvector->begin(), boost::interprocess::move(string_to_compare));

      //Destroy vector. This will free all strings that the vector contains
      shm.destroy_ptr(myshmvector);
   }
   catch(...){
      shared_memory_object::remove("myshmvector");
      throw;
   }
   shared_memory_object::remove("myshmvector");
   return 0;
}
//]
#include <boost/interprocess/detail/config_end.hpp>