libs/interprocess/example/doc_managed_aligned_allocation.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 //[doc_managed_aligned_allocation
  12 #include <boost/interprocess/managed_shared_memory.hpp>
  13 #include <cassert>
  14 //<-
  15 #include "../test/get_process_id_name.hpp"
  16 //->
  17
  18 int main()
  19 {
  20    using namespace boost::interprocess;
  21
  22    //Remove shared memory on construction and destruction
  23    struct shm_remove
  24    {
  25    //<-
  26    #if 1
  27       shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
  28       ~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
  29    #else
  30    //->
  31       shm_remove() { shared_memory_object::remove("MySharedMemory"); }
  32       ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
  33    //<-
  34    #endif
  35    //->
  36    } remover;
  37    //<-
  38    (void)remover;
  39    //->
  40
  41    //Managed memory segment that allocates portions of a shared memory
  42    //segment with the default management algorithm
  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    const std::size_t Alignment = 128;
  54
  55    //Allocate 100 bytes aligned to Alignment from segment, throwing version
  56    void *ptr = managed_shm.allocate_aligned(100, Alignment);
  57
  58    //Check alignment
  59    assert((static_cast<char*>(ptr)-static_cast<char*>(0)) % Alignment == 0);
  60
  61    //Deallocate it
  62    managed_shm.deallocate(ptr);
  63
  64    //Non throwing version
  65    ptr = managed_shm.allocate_aligned(100, Alignment, std::nothrow);
  66
  67    //Check alignment
  68    assert((static_cast<char*>(ptr)-static_cast<char*>(0)) % Alignment == 0);
  69
  70    //Deallocate it
  71    managed_shm.deallocate(ptr);
  72
  73    //If we want to efficiently allocate aligned blocks of memory
  74    //use managed_shared_memory::PayloadPerAllocation value
  75    assert(Alignment > managed_shared_memory::PayloadPerAllocation);
  76
  77    //This allocation will maximize the size of the aligned memory
  78    //and will increase the possibility of finding more aligned memory
  79    ptr = managed_shm.allocate_aligned
  80       (3*Alignment - managed_shared_memory::PayloadPerAllocation, Alignment);
  81
  82    //Check alignment
  83    assert((static_cast<char*>(ptr)-static_cast<char*>(0)) % Alignment == 0);
  84
  85    //Deallocate it
  86    managed_shm.deallocate(ptr);
  87
  88    return 0;
  89 }
  90 //]
  91 /*
  92
  93 #include <vector>
  94 #include <boost/interprocess/managed_windows_shared_memory.hpp>
  95
  96 int main()
  97 {
  98    using namespace boost::interprocess;
  99    typedef boost::interprocess::
 100       managed_windows_shared_memory  shared_segment;
 101
 102    std::vector<void *> ptrs;
 103    shared_segment m_segment(create_only, "shmem", 4096*16);
 104    try{
 105       while(1){
 106          //Now I have several allocate_aligned operations:
 107          ptrs.push_back(m_segment.allocate_aligned(128, 128));
 108       }
 109    }
 110    catch(...){
 111       m_segment.deallocate(ptrs.back());
 112       ptrs.pop_back();
 113       ptrs.push_back(m_segment.allocate_aligned(128, 128));
 114    }
 115    return 0;
 116 }
 117 */
 118 #include <boost/interprocess/detail/config_end.hpp>