boost_1_45_0/libs/interprocess/example/doc_move_containers.cpp

//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006-2009. 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>
//<-
#include "../test/get_process_id_name.hpp"
//->

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 shared memory on construction and destruction
   struct shm_remove
   {
   //<-
   #if 1
      shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
      ~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
   #else 
   //->
      shm_remove() { shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
   //<-
   #endif
   //->
   } remover;

   //<-
   #if 1
   managed_shared_memory shm(create_only, test::get_process_id_name(), 65536);
   #else
   //->
   managed_shared_memory shm(create_only, "MySharedMemory", 10000);
   //<-
   #endif
   //->

   //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);
   return 0;
}
//]
#include <boost/interprocess/detail/config_end.hpp>