boost_1_45_0/libs/interprocess/example/doc_vectorstream.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_vectorstream
#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/streams/vectorstream.hpp>
#include <iterator>
//<-
#include "../test/get_process_id_name.hpp"
//->

using namespace boost::interprocess;

typedef allocator<int, managed_shared_memory::segment_manager> 
   IntAllocator;
typedef allocator<char, managed_shared_memory::segment_manager> 
   CharAllocator;
typedef vector<int, IntAllocator>   MyVector;
typedef basic_string
   <char, std::char_traits<char>, CharAllocator>   MyString;
typedef basic_vectorstream<MyString>               MyVectorStream;

int main ()
{
   //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 segment(
      create_only, 
      test::get_process_id_name(), //segment name
      65536);           //segment size in bytes
   #else
   //->
   managed_shared_memory segment(
      create_only, 
      "MySharedMemory", //segment name
      65536);           //segment size in bytes
   //<-
   #endif
   //->

   //Construct shared memory vector
   MyVector *myvector = 
      segment.construct<MyVector>("MyVector")
      (IntAllocator(segment.get_segment_manager()));

   //Fill vector
   myvector->reserve(100);
   for(int i = 0; i < 100; ++i){
      myvector->push_back(i);
   }

   //Create the vectorstream. To create the internal shared memory
   //basic_string we need to pass the shared memory allocator as
   //a constructor argument
   MyVectorStream myvectorstream(CharAllocator(segment.get_segment_manager()));

   //Reserve the internal string
   myvectorstream.reserve(100*5);

   //Write all vector elements as text in the internal string
   //Data will be directly written in shared memory, because
   //internal string's allocator is a shared memory allocator
   for(std::size_t i = 0, max = myvector->size(); i < max; ++i){
      myvectorstream << (*myvector)[i] << std::endl;
   }

   //Auxiliary vector to compare original data
   MyVector *myvector2 =
      segment.construct<MyVector>("MyVector2")
      (IntAllocator(segment.get_segment_manager()));

   //Avoid reallocations
   myvector2->reserve(100);

   //Extract all values from the internal 
   //string directly to a shared memory vector.
   std::istream_iterator<int> it(myvectorstream), itend;
   std::copy(it, itend, std::back_inserter(*myvector2));

   //Compare vectors
   assert(std::equal(myvector->begin(), myvector->end(), myvector2->begin()));

   //Create a copy of the internal string
   MyString stringcopy (myvectorstream.vector());

   //Now we create a new empty shared memory string...
   MyString *mystring = 
      segment.construct<MyString>("MyString")
      (CharAllocator(segment.get_segment_manager()));

   //...and we swap vectorstream's internal string
   //with the new one: after this statement mystring
   //will be the owner of the formatted data.
   //No reallocations, no data copies
   myvectorstream.swap_vector(*mystring);

   //Let's compare both strings
   assert(stringcopy == *mystring);

   //Done, destroy and delete vectors and string from the segment
   segment.destroy_ptr(myvector2);
   segment.destroy_ptr(myvector);
   segment.destroy_ptr(mystring);
   return 0;
}
//]
#include <boost/interprocess/detail/config_end.hpp>