ceph/src/boost/libs/interprocess/example/doc_managed_copy_on_write.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/os_file_functions.hpp>
  12 //[doc_managed_copy_on_write
  13 #include <boost/interprocess/managed_mapped_file.hpp>
  14 #include <fstream> //std::fstream
  15 #include <iterator>//std::distance
  16
  17 //<-
  18 #include "../test/get_process_id_name.hpp"
  19 //->
  20
  21 int main()
  22 {
  23    using namespace boost::interprocess;
  24
  25    //Define file names
  26    //<-
  27    #if 1
  28    const char *ManagedFile  = 0;
  29    const char *ManagedFile2 = 0;
  30    std::string managed_file_name(boost::interprocess::ipcdetail::get_temporary_path());
  31    managed_file_name += "/"; managed_file_name += test::get_process_id_name();
  32    ManagedFile = managed_file_name.c_str();
  33    std::string managed_file2_name(boost::interprocess::ipcdetail::get_temporary_path());
  34    managed_file2_name += "/"; managed_file2_name += test::get_process_id_name();  managed_file2_name += "_2";
  35    ManagedFile2 = managed_file2_name.c_str();
  36    #else
  37    //->
  38    const char *ManagedFile  = "MyManagedFile";
  39    const char *ManagedFile2 = "MyManagedFile2";
  40    //<-
  41    #endif
  42    //->
  43
  44    //Try to erase any previous managed segment with the same name
  45    file_mapping::remove(ManagedFile);
  46    file_mapping::remove(ManagedFile2);
  47    remove_file_on_destroy destroyer1(ManagedFile);
  48    remove_file_on_destroy destroyer2(ManagedFile2);
  49
  50    {
  51       //Create an named integer in a managed mapped file
  52       managed_mapped_file managed_file(create_only, ManagedFile, 65536);
  53       managed_file.construct<int>("MyInt")(0u);
  54
  55       //Now create a copy on write version
  56       managed_mapped_file managed_file_cow(open_copy_on_write, ManagedFile);
  57
  58       //Erase the int and create a new one
  59       if(!managed_file_cow.destroy<int>("MyInt"))
  60          throw int(0);
  61       managed_file_cow.construct<int>("MyInt2");
  62
  63       //Check changes
  64       if(managed_file_cow.find<int>("MyInt").first && !managed_file_cow.find<int>("MyInt2").first)
  65          throw int(0);
  66
  67       //Check the original is intact
  68       if(!managed_file.find<int>("MyInt").first && managed_file.find<int>("MyInt2").first)
  69          throw int(0);
  70
  71       {  //Dump the modified copy on write segment to a file
  72          std::fstream file(ManagedFile2, std::ios_base::out | std::ios_base::binary);
  73          if(!file)
  74             throw int(0);
  75        file.write(static_cast<const char *>(managed_file_cow.get_address()), (std::streamsize)managed_file_cow.get_size());
  76       }
  77
  78       //Now open the modified file and test changes
  79       managed_mapped_file managed_file_cow2(open_only, ManagedFile2);
  80       if(managed_file_cow2.find<int>("MyInt").first && !managed_file_cow2.find<int>("MyInt2").first)
  81          throw int(0);
  82    }
  83    {
  84       //Now create a read-only version
  85       managed_mapped_file managed_file_ro(open_read_only, ManagedFile);
  86
  87       //Check the original is intact
  88       if(!managed_file_ro.find<int>("MyInt").first && managed_file_ro.find<int>("MyInt2").first)
  89          throw int(0);
  90
  91       //Check the number of named objects using the iterators
  92       if(std::distance(managed_file_ro.named_begin(),  managed_file_ro.named_end())  != 1 &&
  93          std::distance(managed_file_ro.unique_begin(), managed_file_ro.unique_end()) != 0 )
  94          throw int(0);
  95    }
  96    return 0;
  97 }
  98 //]
  99 #include <boost/interprocess/detail/config_end.hpp>