ceph/src/boost/libs/interprocess/example/doc_move_containers.cpp

   1 //////////////////////////////////////////////////////////////////////////////
   2 //
   3 // (C) Copyright Ion Gaztanaga 2006-2012. 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 #include <boost/interprocess/detail/workaround.hpp>
  12 //[doc_move_containers
  13 #include <boost/interprocess/managed_shared_memory.hpp>
  14 #include <boost/interprocess/containers/vector.hpp>
  15 #include <boost/interprocess/containers/string.hpp>
  16 #include <boost/interprocess/allocators/allocator.hpp>
  17 #include <cassert>
  18 //<-
  19 #include "../test/get_process_id_name.hpp"
  20 //->
  21
  22 int main ()
  23 {
  24    using namespace boost::interprocess;
  25
  26    //Typedefs
  27    typedef managed_shared_memory::segment_manager     SegmentManager;
  28    typedef allocator<char, SegmentManager>            CharAllocator;
  29    typedef basic_string<char, std::char_traits<char>
  30                         ,CharAllocator>                MyShmString;
  31    typedef allocator<MyShmString, SegmentManager>     StringAllocator;
  32    typedef vector<MyShmString, StringAllocator>       MyShmStringVector;
  33
  34    //Remove shared memory on construction and destruction
  35    struct shm_remove
  36    {
  37    //<-
  38    #if 1
  39       shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
  40       ~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
  41    #else
  42    //->
  43       shm_remove() { shared_memory_object::remove("MySharedMemory"); }
  44       ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
  45    //<-
  46    #endif
  47    //->
  48    } remover;
  49    //<-
  50    (void)remover;
  51    //->
  52
  53    //<-
  54    #if 1
  55    managed_shared_memory shm(create_only, test::get_process_id_name(), 65536);
  56    #else
  57    //->
  58    managed_shared_memory shm(create_only, "MySharedMemory", 10000);
  59    //<-
  60    #endif
  61    //->
  62
  63    //Create allocators
  64    CharAllocator     charallocator  (shm.get_segment_manager());
  65    StringAllocator   stringallocator(shm.get_segment_manager());
  66
  67    //Create a vector of strings in shared memory.
  68    MyShmStringVector *myshmvector =
  69       shm.construct<MyShmStringVector>("myshmvector")(stringallocator);
  70
  71    //Insert 50 strings in shared memory. The strings will be allocated
  72    //only once and no string copy-constructor will be called when inserting
  73    //strings, leading to a great performance.
  74    MyShmString string_to_compare(charallocator);
  75    string_to_compare = "this is a long, long, long, long, long, long, string...";
  76
  77    myshmvector->reserve(50);
  78    for(int i = 0; i < 50; ++i){
  79       MyShmString move_me(string_to_compare);
  80       //In the following line, no string copy-constructor will be called.
  81       //"move_me"'s contents will be transferred to the string created in
  82       //the vector
  83       myshmvector->push_back(boost::move(move_me));
  84
  85       //The source string is in default constructed state
  86       assert(move_me.empty());
  87
  88       //The newly created string will be equal to the "move_me"'s old contents
  89       assert(myshmvector->back() == string_to_compare);
  90    }
  91
  92    //Now erase a string...
  93    myshmvector->pop_back();
  94
  95    //...And insert one in the first position.
  96    //No string copy-constructor or assignments will be called, but
  97    //move constructors and move-assignments. No memory allocation
  98    //function will be called in this operations!!
  99    myshmvector->insert(myshmvector->begin(), boost::move(string_to_compare));
 100
 101    //Destroy vector. This will free all strings that the vector contains
 102    shm.destroy_ptr(myshmvector);
 103    return 0;
 104 }
 105 //]
 106 #include <boost/interprocess/detail/config_end.hpp>
 107