libs/interprocess/example/doc_intrusive.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
  11 #include <boost/interprocess/detail/config_begin.hpp>
  12 #include <boost/interprocess/detail/workaround.hpp>
  13 //[doc_intrusive
  14 #include <boost/interprocess/managed_shared_memory.hpp>
  15 #include <boost/interprocess/smart_ptr/intrusive_ptr.hpp>
  16 //<-
  17 #include "../test/get_process_id_name.hpp"
  18 //->
  19
  20 using namespace boost::interprocess;
  21
  22 namespace N {
  23
  24 //A class that has an internal reference count
  25 class reference_counted_class
  26 {
  27    private:
  28    //Non-copyable
  29    reference_counted_class(const reference_counted_class  &);
  30    //Non-assignable
  31    reference_counted_class & operator=(const reference_counted_class &);
  32    //A typedef to save typing
  33    typedef managed_shared_memory::segment_manager segment_manager;
  34    //This is the reference count
  35    unsigned int m_use_count;
  36    //The segment manager allows deletion from shared memory segment
  37    offset_ptr<segment_manager> mp_segment_manager;
  38
  39    public:
  40    //Constructor
  41    reference_counted_class(segment_manager *s_mngr)
  42    : m_use_count(0), mp_segment_manager(s_mngr){}
  43    //Destructor
  44    ~reference_counted_class(){}
  45
  46    public:
  47    //Returns the reference count
  48    unsigned int use_count() const
  49    {  return m_use_count;   }
  50
  51    //Adds a reference
  52    inline friend void intrusive_ptr_add_ref(reference_counted_class * p)
  53    {  ++p->m_use_count; }
  54
  55    //Releases a reference
  56    inline friend void intrusive_ptr_release(reference_counted_class * p)
  57    {  if(--p->m_use_count == 0)  p->mp_segment_manager->destroy_ptr(p); }
  58 };
  59
  60 }  //namespace N {
  61
  62 //A class that has an intrusive pointer to reference_counted_class
  63 class intrusive_ptr_owner
  64 {
  65    typedef intrusive_ptr<N::reference_counted_class,
  66                            offset_ptr<void> > intrusive_ptr_t;
  67    intrusive_ptr_t m_intrusive_ptr;
  68
  69    public:
  70    //Takes a pointer to the reference counted class
  71    intrusive_ptr_owner(N::reference_counted_class *ptr)
  72       : m_intrusive_ptr(ptr){}
  73 };
  74
  75 int main()
  76 {
  77    //Remove shared memory on construction and destruction
  78    struct shm_remove
  79    {
  80    //<-
  81    #if 1
  82       shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
  83       ~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
  84    #else
  85    //->
  86       shm_remove() { shared_memory_object::remove("MySharedMemory"); }
  87       ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
  88    //<-
  89    #endif
  90    //->
  91    } remover;
  92
  93    //Create shared memory
  94    //<-
  95    #if 1
  96    managed_shared_memory shmem(create_only, test::get_process_id_name(), 10000);
  97    #else
  98    //->
  99    managed_shared_memory shmem(create_only, "MySharedMemory", 10000);
 100    //<-
 101    #endif
 102    //->
 103
 104    //Create the unique reference counted object in shared memory
 105    N::reference_counted_class *ref_counted =
 106       shmem.construct<N::reference_counted_class>
 107          ("ref_counted")(shmem.get_segment_manager());
 108
 109    //Create an array of ten intrusive pointer owners in shared memory
 110    intrusive_ptr_owner *intrusive_owner_array =
 111       shmem.construct<intrusive_ptr_owner>
 112          (anonymous_instance)[10](ref_counted);
 113
 114    //Now test that reference count is ten
 115    if(ref_counted->use_count() != 10)
 116       return 1;
 117
 118    //Now destroy the array of intrusive pointer owners
 119    //This should destroy every intrusive_ptr and because of
 120    //that reference_counted_class will be destroyed
 121    shmem.destroy_ptr(intrusive_owner_array);
 122
 123    //Now the reference counted object should have been destroyed
 124    if(shmem.find<intrusive_ptr_owner>("ref_counted").first)
 125       return 1;
 126    //Success!
 127    return 0;
 128 }
 129 //]
 130 #include <boost/interprocess/detail/config_end.hpp>