libs/interprocess/example/doc_scoped_ptr.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 #include <boost/interprocess/detail/workaround.hpp>
  12 //[doc_scoped_ptr
  13 #include <boost/interprocess/managed_shared_memory.hpp>
  14 #include <boost/interprocess/smart_ptr/scoped_ptr.hpp>
  15 //<-
  16 #include "../test/get_process_id_name.hpp"
  17 //->
  18
  19 using namespace boost::interprocess;
  20
  21 class my_class
  22 {};
  23
  24 class my_exception
  25 {};
  26
  27 //A functor that destroys the shared memory object
  28 template<class T>
  29 class my_deleter
  30 {
  31    private:
  32    //A typedef to save typing
  33    typedef managed_shared_memory::segment_manager segment_manager;
  34    //This my_deleter is created in the stack, not in shared memory,
  35    //so we can use raw pointers
  36    segment_manager *mp_segment_manager;
  37
  38    public:
  39    //This typedef will specify the pointer type that
  40    //scoped_ptr will store
  41    typedef T *pointer;
  42    //Constructor
  43    my_deleter(segment_manager *s_mngr)
  44    : mp_segment_manager(s_mngr){}
  45
  46    void operator()(pointer object_to_delete)
  47    {  mp_segment_manager->destroy_ptr(object_to_delete);  }
  48 };
  49
  50 int main ()
  51 {
  52    //Create shared memory
  53    //Remove shared memory on construction and destruction
  54    struct shm_remove
  55    {
  56    //<-
  57    #if 1
  58       shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
  59       ~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
  60    #else
  61    //->
  62       shm_remove() { shared_memory_object::remove("MySharedMemory"); }
  63       ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
  64    //<-
  65    #endif
  66    //->
  67    } remover;
  68
  69    //<-
  70    #if 1
  71    managed_shared_memory shmem(create_only, test::get_process_id_name(), 10000);
  72    #else
  73    //->
  74    managed_shared_memory shmem(create_only, "MySharedMemory", 10000);
  75    //<-
  76    #endif
  77    //->
  78
  79    //In the first try, there will be no exceptions
  80    //in the second try we will throw an exception
  81    for(int i = 0; i < 2; ++i){
  82       //Create an object in shared memory
  83       my_class * my_object = shmem.construct<my_class>("my_object")();
  84       my_class * my_object2 = shmem.construct<my_class>(anonymous_instance)();
  85       shmem.destroy_ptr(my_object2);
  86
  87       //Since the next shared memory allocation can throw
  88       //assign it to a scoped_ptr so that if an exception occurs
  89       //we destroy the object automatically
  90       my_deleter<my_class> d(shmem.get_segment_manager());
  91
  92       try{
  93          scoped_ptr<my_class, my_deleter<my_class> > s_ptr(my_object, d);
  94          //Let's emulate a exception capable operation
  95          //In the second try, throw an exception
  96          if(i == 1){
  97             throw(my_exception());
  98          }
  99          //If we have passed the dangerous zone
 100          //we can release the scoped pointer
 101          //to avoid destruction
 102          s_ptr.release();
 103       }
 104       catch(const my_exception &){}
 105       //Here, scoped_ptr is destroyed
 106       //so it we haven't thrown an exception
 107       //the object should be there, otherwise, destroyed
 108       if(i == 0){
 109          //Make sure the object is alive
 110          if(!shmem.find<my_class>("my_object").first){
 111             return 1;
 112          }
 113          //Now we can use it and delete it manually
 114          shmem.destroy<my_class>("my_object");
 115       }
 116       else{
 117          //Make sure the object has been deleted
 118          if(shmem.find<my_class>("my_object").first){
 119             return 1;
 120          }
 121       }
 122    }
 123    return 0;
 124 }
 125 //]
 126 #include <boost/interprocess/detail/config_end.hpp>