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
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
21int 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(filename: ManagedFile);
46 file_mapping::remove(filename: 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>(name: "MyInt")(0);
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>(name: "MyInt"))
60 throw int(0);
61 managed_file_cow.construct<int>(name: "MyInt2");
62
63 //Check changes
64 if(managed_file_cow.find<int>(name: "MyInt").first && !managed_file_cow.find<int>(name: "MyInt2").first)
65 throw int(0);
66
67 //Check the original is intact
68 if(!managed_file.find<int>(name: "MyInt").first && managed_file.find<int>(name: "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(s: static_cast<const char *>(managed_file_cow.get_address()), n: (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>(name: "MyInt").first && !managed_file_cow2.find<int>(name: "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>(name: "MyInt").first && managed_file_ro.find<int>(name: "MyInt2").first)
89 throw int(0);
90
91 //Check the number of named objects using the iterators
92 if(std::distance(first: managed_file_ro.named_begin(), last: managed_file_ro.named_end()) != 1 &&
93 std::distance(first: managed_file_ro.unique_begin(), last: managed_file_ro.unique_end()) != 0 )
94 throw int(0);
95 }
96 return 0;
97}
98//]
99
100

source code of boost/libs/interprocess/example/doc_managed_copy_on_write.cpp