libs/interprocess/example/doc_managed_multiple_allocation.cpp

   1 //////////////////////////////////////////////////////////////////////////////
   2 //
   3 // (C) Copyright Ion Gaztanaga 2006-2009. Distributed under the Boost
   4 // Software License, Version 1.0. (See accompanying file
   5 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // See http://www.boost.org/libs/interprocess for documentation.
   8 //
   9 //////////////////////////////////////////////////////////////////////////////
  10 #include <boost/interprocess/detail/config_begin.hpp>
  11 //[doc_managed_multiple_allocation
  12 #include <boost/interprocess/managed_shared_memory.hpp>
  13 #include <boost/interprocess/detail/move.hpp> //boost::interprocess::move
  14 #include <cassert>//assert
  15 #include <cstring>//std::memset
  16 #include <new>    //std::nothrow
  17 #include <vector> //std::vector
  18 //<-
  19 #include "../test/get_process_id_name.hpp"
  20 //->
  21
  22 int main()
  23 {
  24    using namespace boost::interprocess;
  25    typedef managed_shared_memory::multiallocation_chain multiallocation_chain;
  26
  27    //Remove shared memory on construction and destruction
  28    struct shm_remove
  29    {
  30    //<-
  31    #if 1
  32       shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
  33       ~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
  34    #else
  35    //->
  36       shm_remove() { shared_memory_object::remove("MySharedMemory"); }
  37       ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
  38    //<-
  39    #endif
  40    //->
  41    } remover;
  42
  43    //<-
  44    #if 1
  45    managed_shared_memory managed_shm(create_only,test::get_process_id_name(), 65536);
  46    #else
  47    //->
  48    managed_shared_memory managed_shm(create_only,"MySharedMemory", 65536);
  49    //<-
  50    #endif
  51    //->
  52
  53    //Allocate 16 elements of 100 bytes in a single call. Non-throwing version.
  54    multiallocation_chain chain(managed_shm.allocate_many(100, 16, std::nothrow));
  55
  56    //Check if the memory allocation was successful
  57    if(chain.empty()) return 1;
  58
  59    //Allocated buffers
  60    std::vector<void*> allocated_buffers;
  61
  62    //Initialize our data
  63    while(!chain.empty()){
  64       void *buf = chain.front();
  65       chain.pop_front();
  66       allocated_buffers.push_back(buf);
  67       //The iterator must be incremented before overwriting memory
  68       //because otherwise, the iterator is invalidated.
  69       std::memset(buf, 0, 100);
  70    }
  71
  72    //Now deallocate
  73    while(!allocated_buffers.empty()){
  74       managed_shm.deallocate(allocated_buffers.back());
  75       allocated_buffers.pop_back();
  76    }
  77
  78    //Allocate 10 buffers of different sizes in a single call. Throwing version
  79    std::size_t sizes[10];
  80    for(std::size_t i = 0; i < 10; ++i)
  81       sizes[i] = i*3;
  82
  83    chain = managed_shm.allocate_many(sizes, 10);
  84    managed_shm.deallocate_many(boost::interprocess::move(chain));
  85    return 0;
  86 }
  87 //]
  88 #include <boost/interprocess/detail/config_end.hpp>