CPP / C++ Notes - Boost Libraries and complementarty libraries

$ git clone --recurse-submodule -b boost-1.70.0  https://github.com/boostorg/boost --depth=1 boost-src 
$ cd boost-src 

$ mkdir -p ~/libs

$ ./bootstrap.sh --prefix=$HOME/libs/boost/1.70.0 
Building Boost.Build engine with toolset gcc... 
... ... ...   ... ... ...   ... ... ...   ... ... ...   ... ... ... 
... ... ...   ... ... ...   ... ... ...   ... ... ...   ... ... ... 

$ ./b2 install --prefix=$HOME/libs --link=static                                        │boost/
Performing configuration checks                                                         │
                                                                                        │mxpkf8@localhost 16:05 ~/libs
    - default address-model    : 64-bit (cached)                                        │$ rm -rf boost 
    - default architecture     : x86 (cached)                                           │
    - symlinks supported       : yes (cached)                                           │mxpkf8@localhost 16:06 ~/libs
    - C++11 mutex              : yes (cached)                                           │$ ls
    - lockfree boost::atomic_flag : no  (cached)            
  ... ... ...   ... ... ...   ... ... ...   ... ... ... 
  ... ... ...   ... ... ...   ... ... ...   ... ... ... 

$ tree -L 3 ~/libs
├── include
│   └── boost
│       ├── aligned_storage.hpp
│       ├── call_traits.hpp
│       ├── compressed_pair.hpp
... ... ...    ... ... ...    ... ... ...    ... ... ... 
... ... ...    ... ... ...    ... ... ...    ... ... ... 
│       ├── variant
│       ├── variant.hpp
│       └── vmd
└── lib
    ├── cmake
    │   ├── boost_fiber-1.70.0
    │   ├── boost_fiber_numa-1.70.0
... ... ...    ... ... ...    ... ... ...    ... ... ... 
... ... ...    ... ... ...    ... ... ...    ... ... ... 
    ├── libboost_filesystem.so.1.70 -> libboost_filesystem.so.1.70.0
    └── libboost_filesystem.so.1.70.0

17 directories, 19 files

#include <iostream>
#include <fstream>
#include <string>
#include <boost/date_time/gregorian/gregorian.hpp>

namespace gr = boost::gregorian;
namespace dt = boost::date_time;

int main()
{
  std::puts("=========== Boost Date Time ===============\n");
  auto d1 = gr::date(2009, 10, 20);
  std::cout << " date1 = " << d1 << std::endl;
  auto mdate = gr::date(2012, 06, 21);
  std::string text = " Date mdate is equal to: " + gr::to_iso_string(mdate) + "\n";
  std::cout << " Text => " << text;
  return 0;
}

$ g++ test-boost.cpp -o test-boost1.elf -g -lboost_date_time -I$HOME/libs/include -L$HOME/libs/lib

 $ ./test-boost1.elf 
 ./test-boost1.elf: error while loading shared libraries
: libboost_date_time.so.1.70.0: cannot open shared object file: No such file or directory

$ ldd test-boost1.elf 
        linux-vdso.so.1 (0x00007fffe5d76000)
        libboost_date_time.so.1.70.0 => not found
        libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f48b78bc000)
        libm.so.6 => /lib64/libm.so.6 (0x00007f48b7776000)
        libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f48b775b000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f48b7591000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f48b7acf000)

$ env LD_LIBRARY_PATH=$HOME/libs/lib ./test-boost1.elf
=========== Boost Date Time ===============

 date1 = 2009-Oct-20
 Text =>  Date mdate is equal to: 20120621

$ cp ~/libs/lib/libboost_date_time.so.1.70.0 .

$ env LD_LIBRARY_PATH=$PWD ldd ./test-boost1.elf
        linux-vdso.so.1 (0x00007ffff9f1b000)
        libboost_date_time.so.1.70.0 => /home/mxpkf8/libboost_date_time.so.1.70.0 (0x00007fad75ba5000)
        libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fad75994000)
  ... .... .... ....   ... .... .... ....   ... .... .... ....   ... .... .... .... 
  ... .... .... ....   ... .... .... ....   ... .... .... ....   ... .... .... .... 

$ env LD_LIBRARY_PATH=$PWD ./test-boost1.elf
=========== Boost Date Time ===============

 date1 = 2009-Oct-20
 Text =>  Date mdate is equal to: 20120621

# Copy shared library to current directory 
$ cp ~/libs/lib/libboost_date_time.so.1.70.0 .

# Compile with dynamic linking, setting the RPATH to the executable's directory 
$ g++ test-boost.cpp -o test-boost3.elf -g -Wl,-rpath='$ORIGIN'  -lboost_date_time -I$HOME/libs/include -L$HOME/libs/lib 

# --- Check Dependencies ------------------#
$ ldd test-boost3.elf 
        linux-vdso.so.1 (0x00007ffe49d83000)
        libboost_date_time.so.1.70.0 => ./libboost_date_time.so.1.70.0 (0x00007f8d96229000)
        libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f8d96018000
   ... ....    ... ....    ... ....    ... ....    ... ....    ... .... 
   ... ....    ... ....    ... ....    ... ....    ... ....    ... .... 

 # ----- Run the application -------------#
 $ ./test-boost3.elf 
 =========== Boost Date Time ===============

  date1 = 2009-Oct-20
  Text =>  Date mdate is equal to: 20120621

 # -------- Move the app to a new directory -------#
 $ mkdir -p app 
 $ mv test-boost3.elf libboost_date_time.so.1.70.0 app

 # ------ Test the application again --------------#
 $ app/test-boost3.elf 
 =========== Boost Date Time ===============

  date1 = 2009-Oct-20
  Text =>  Date mdate is equal to: 20120621

 env LD_DEBUG=libs app/test-boost3.elf                                                                                                                              
    431158:     find library=libboost_date_time.so.1.70.0 [0]; searching                                                                                             
    431158:      search path=/home/mxpkf8/app/tls/haswell/x86_64:/home/mxpkf8/app/tls/haswell:/home/mxpkf8/app/tls/x86_64:/home/mxpkf8/app/tls:/home/mxpkf8/app/haswe
ll/x86_64:/home/mxpkf8/app/haswell:/home/mxpkf8/app/x86_64:/home/mxpkf8/app             (RPATH from file app/test-boost3.elf)
    431158:       trying file=/home/mxpkf8/app/tls/haswell/x86_64/libboost_date_time.so.1.70.0

 ... ... ....  ... ... ....  ... ... ....  ... ... .... 
  ... ... ....  ... ... ....  ... ... ....  ... ... .... 

    431158:     find library=libstdc++.so.6 [0]; searching                                                                                                           
    431158:      search path=/home/mxpkf8/app           (RPATH from file app/test-boost3.elf)
    431158:       trying file=/home/mxpkf8/app/libstdc++.so.6
    431158:      search cache=/etc/ld.so.cache
    431158:       trying file=/lib64/libstdc++.so.6
    431158:
    431158:     find library=libm.so.6 [0]; searching
    431158:      search path=/home/mxpkf8/app           (RPATH from file app/test-boost3.elf)
    431158:       trying file=/home/mxpkf8/app/libm.so.6
    431158:      search cache=/etc/ld.so.cache
    431158:       trying file=/lib64/libm.so.6
 ... ... ....  ... ... ....  ... ... ....  ... ... .... 

$ g++ test-boost.cpp -o test-boost2.elf -g \
    $HOME/libs/lib/libboost_date_time.a \
    -I$HOME/libs/include \
    -L$HOME/libs/lib 

$ ./test-boost2.elf 
=========== Boost Date Time ===============

 date1 = 2009-Oct-20
 Text =>  Date mdate is equal to: 20120621

cmake_minimum_required(VERSION 2.8)
project(boost-manually)

#========================================#
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_VERBOSE_MAKEFILE ON)

#=========== Find-Package =============#
set(Boost_USE_STATIC_LIBS ON)
set(Boost_NO_SYSTEM_PATHS TRUE)

find_package(Boost REQUIRED date_time serialization )

#=========== Targets ======================#
add_executable(test-boost-app test-boost.cpp)
target_link_libraries(test-boost-app Boost::date_time)

# Configure 
#--------------------------------------------
$ cmake -H. -B_build -DCMAKE_BUILD_TYPE=Debug \
            -DBoost_NO_BOOST_CMAKE=TRUE \
            -DBoost_NO_SYSTEM_PATHS=TRUE \
            -DBOOST_ROOT:PATHNAME=$HOME/libs \
            -DBoost_LIBRARY_DIR:FILEPATH=$HOME/libs/lib

# Compile 
#--------------------------------------------
$ cmake --build _build --target 

# Run 
#--------------------------------------------
$ _build/test-boost-app 
=========== Boost Date Time ===============

 date1 = 2009-Oct-20
 Text =>  Date mdate is equal to: 20120621

cmake_minimum_required(VERSION 2.8)
project(boost-manually)
#========================================#

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_VERBOSE_MAKEFILE ON)

#=========== Find-Package =============#

set(Boost_USE_STATIC_LIBS      ON)
set(Boost_NO_SYSTEM_PATHS      TRUE)
set(BOOST_ROOT        $ENV{HOME}/libs)
set(BOOST_LIBRARY_DIR $ENV{HOME}/libs)

message([TRACE] " BOOST_LIBRARY_DIR = ${BOOST_LIBRARY_DIR}")

find_package(Boost REQUIRED date_time serialization )

#=========== Targets ======================#

add_executable(test-boost-app test-boost.cpp)
target_link_libraries(test-boost-app Boost::date_time)

#--------- Configure -----------#
$ cmake -H. -B_build 
[TRACE] BOOST_LIBRARY_DIR = /home/mxpkf8/libs
-- Configuring done
-- Generating done
-- Build files have been written to: /home/mxpkf8/_build

#--------- Build / Compile -----#
$ cmake --build _build --target

#--------- Run -----------------#
$ _build/test-boost-app 
=========== Boost Date Time ===============

 date1 = 2009-Oct-20
 Text =>  Date mdate is equal to: 20120621

# Compile 
$ clang++ boost-operator.cpp -o boost-operator.bin -std=c++1z -g -O0 -Wall
# Run 
$ ./boost-operator.bin

#include <iostream>
#include <cmath>
#include <cassert>
#include <boost/operators.hpp>

class Vec3D: public boost::less_than_comparable<Vec3D>
           , public boost::addable<Vec3D, double>
{
private:
    double m_x, m_y, m_z;
public:
    Vec3D(double x, double y, double z);
    double norm() const;

    // Stream insertion operator => Make class printable 
    friend std::ostream& operator<<(std::ostream& os, Vec3D const& vec);    

    // Required by: boost::less_than_comparable<Vec3D>
    // From this operator, boost implements the operators (<=), (>), (>=)
    friend bool operator<(Vec3D const& lhs, Vec3D const& rhs);

    // Required by: boost::addable<Vec3D, double>
    // Boost implements: operator+(Vec3D, double) and operator+(double, Vec3D)
    friend Vec3D& operator+=(Vec3D& lhs, double rhs);   
};

friend bool operator<(Vec3D const& lhs, Vec3D const& rhs);

// Implementation: 
bool
operator<(Vec3D const& lhs, Vec3D const& rhs)
{
   return lhs.norm() < rhs.norm();
}

friend bool operator<=(Vec3D const& lhs, Vec3D const& rhs);
friend bool operator>(Vec3D const& lhs, Vec3D const& rhs);
friend bool operator>=(Vec3D const& lhs, Vec3D const& rhs);

friend Vec3D& operator+=(Vec3D& lhs, double rhs);   

// Implementation or definition:
Vec3D&
operator+=(Vec3D& lhs, double rhs)
{
    double  d = rhs;
    lhs = {lhs.m_x + d, lhs.m_y + d, lhs.m_z + d};
    return lhs;
}

friend Vec3D operator+(Vec3D const& lhs, double rhs);   
friend Vec3D operator+(double rhs, Vec3D const& lhs);   

template<typename variable_t>
void disp(const char* variableName, variable_t const& value)
{
   std::cout << " =>> " << variableName << " = " << value << "\n";
}

Vec3D v1 = {3, 5, 6};
Vec3D v2 = {12, 5, 9};
std::cout << std::boolalpha;
disp("v1", v1); disp("v2", v2);
disp("v1.norm()", v1.norm());
disp("v2.norm()", v2.norm());

=>> v1 = Vec3D{  x = 3 ; y = 5 ; z = 6 } 
=>> v2 = Vec3D{  x = 12 ; y = 5 ; z = 9 } 
=>> v1.norm() = 8.3666
=>> v2.norm() = 15.8114

std::cout << "\n EXPERIMENT 1 boost::less_than_comparable<Vec3D>" << "\n";
std::cout << "--------------------------------------------------" << "\n";

std::cout << "[a] v1 <  v2 = " << (v1 < v2) << "\n";
std::cout << "[b] v1 <  v2 = " << operator<(v1, v2) << "\n\n";   

std::cout << "[a] v1 <= v2 = " << (v1 <= v2) << "\n";
std::cout << "[b] v1 <= v2 = " << operator<=(v1, v2) << "\n\n";

std::cout << "[a] v1 >  v2 = " << (v1 > v2) << "\n";
std::cout << "[b] v1 >  v2 = " << operator>(v1, v2) << "\n\n";

std::cout << "[a] v1 >=  v2 = " << (v1 >= v2) << "\n";
std::cout << "[b] v1 >=  v2 = " << operator>=(v1, v2) << "\n\n";

 EXPERIMENT 1 boost::less_than_comparable<Vec3D>
--------------------------------------------------
[a] v1 <  v2 = true
[b] v1 <  v2 = true

[a] v1 <= v2 = true
[b] v1 <= v2 = true

[a] v1 >  v2 = false
[b] v1 >  v2 = false

[a] v1 >=  v2 = false
[b] v1 >=  v2 = false

std::cout << "\n EXPERIMENT 2 boost::less_than_comparable<Vec3D>" << "\n";
std::cout << "--------------------------------------------------" << "\n";
disp("v1 + 5.0", v1 + 5.0);
disp("operator+(v1, 5.0)", operator+(v1, 5.0));
disp("5.0 + v1", 5.0 + v1);
disp("operator+(5.0, v1", operator+(5.0, v1));
disp("v1", v1);

 EXPERIMENT 2 boost::less_than_comparable<Vec3D>
--------------------------------------------------
 =>> v1 + 5.0 = Vec3D{  x = 8 ; y = 10 ; z = 11 } 
 =>> operator+(v1, 5.0) = Vec3D{  x = 8 ; y = 10 ; z = 11 } 
 =>> 5.0 + v1 = Vec3D{  x = 8 ; y = 10 ; z = 11 } 
 =>> operator+(5.0, v1 = Vec3D{  x = 8 ; y = 10 ; z = 11 } 
 =>> v1 = Vec3D{  x = 3 ; y = 5 ; z = 6 } 

#include <iostream>
#include <cassert>
#include <map>
#include <functional>
#include <vector>

#include <boost/interprocess/mapped_region.hpp>
#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/sync/named_mutex.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/segment_manager.hpp>

namespace bi = boost::interprocess;

/** Generic Shared Memory Allocator */
template<typename T>
using ShmemAllocator = bi::allocator<T, bi::managed_shared_memory::segment_manager> ;

/** Generic STL vector allocated in shared memory */
template<typename T>
using ShmemVector = std::vector<T, ShmemAllocator<T>> ;

/** RAII Object for removing shared memory segment. */
struct SharedMemoryCleaner
{   
   std::string m_name;
   SharedMemoryCleaner(std::string name): m_name(name){ }

   ~SharedMemoryCleaner(){
        namespace bi = boost::interprocess;
        std::cerr << " [INFO] Remove shared memory segment { name = " << m_name << " }" << "\n";
        bi::shared_memory_object::remove(m_name.c_str());
   }
};

int serverA();
int clientA();

int serverB();
int clientB();

int serverC();
int clientC();

int main(int argc, char** argv){
     using DispatchTable = std::map<std::string, std::function<int ()>>;
     DispatchTable table = {
         {"serverA", &serverA},
         {"clientA", &clientA},
         {"serverB", &serverB},
         {"clientB", &clientB},
         {"serverC", &serverC},
         {"clientC", &clientC}
     };

     if(argc < 2) {
         std::cout << " Error: invalid arguments." << std::endl;
         return EXIT_SUCCESS;
     }
     auto it = table.find(argv[1]);
     if(it == table.end()){
         std::cout << " Error: invalid command." << std::endl;
         return EXIT_FAILURE;       
     }
     // Execute function 
     return it->second();           
}

// Print string (char array) to shared memory 
int serverA()
{   
    // Create shared memory wrapper object 
    auto shm = bi::shared_memory_object{
                 // Creates shared memory segment if it does not exist 
                 bi::open_or_create,
                 "shared_memory_segment",
                 bi::read_write
               };
    // RAII object that removes the segment when out of scope 
    auto shm_remove = SharedMemoryCleaner("shared_memory_segment"); 
    // Set size of the shared memory segment in Kb (kbytes = 1024 bytes)
    shm.truncate(1024); // 1kb (kbytes)
    // Map the shared memory segment to current process
    auto region = bi::mapped_region{shm, bi::read_write};
    // Pointer to shared memory 
    void* pMem = region.get_address();

    // Print to shared memory
    char* pChar = static_cast<char*>(pMem);
    std::sprintf(pChar, " ==> String written to shared memory segment");

    // Keep the server Alive as the shared memory segment is not 
    // persistent on Windows. 
    std::cout << "Enter RETURN to EXIT " << "\n";
    std::cin.get();
    return EXIT_SUCCESS;
}

// Print string (char array) to shared memory 
int clientA()
{   
    // Create shared memory wrapper object 
    auto shm = bi::shared_memory_object{
       // Creates shared memory segment if it does not exist 
       bi::open_only,
       "shared_memory_segment",
       bi::read_only
       };
    auto region = bi::mapped_region{shm, bi::read_only};
    void* pMem = region.get_address();

    // Interpret shared memory as a pointer to char* 
    char* pMessage = static_cast<char*>(pMem);
    std::cout << " Content of shared memory = " << pMessage << "\n";    
    return EXIT_SUCCESS;
}

/** Allocate double[] array in shared memory */
int serverB()
{
     auto shm = bi::shared_memory_object{   
     bi::open_or_create,
     "shared_memory_segment",
     bi::read_write
     };
     auto shm_remove = SharedMemoryCleaner("shared_memory_segment");
     shm.truncate(1024); // 1kb (kbytes)
     auto region = bi::mapped_region{shm, bi::read_write};
     void* pMem = region.get_address();

     // Allocate array of 5 doubles in the shared memory 
     double* arr = new (pMem) double [5];
     arr[0] = 100.34;
     arr[1] = 200.5;
     arr[2] = -5.6;
     arr[3] = 9.10;
     arr[4] = 10.5;

     // Keep the server Alive as the shared memory segment is not 
     // persistent on Windows. 
     std::cout << "Enter RETURN to EXIT " << "\n";
     std::cin.get();
     return EXIT_SUCCESS;
}

/** Retrieve double[] array from shared memory */
int clientB(){
     auto shm = bi::shared_memory_object{
          bi::open_only, 
         "shared_memory_segment",
          bi::read_only 
     };
     auto region = bi::mapped_region{shm, bi::read_only};

     void* pMem = region.get_address();
     double* arr = static_cast<double*>(pMem);

     std::cout << "arr[0] = " << arr[0] << "\n";
     std::cout << "arr[1] = " << arr[1] << "\n";
     std::cout << "arr[2] = " << *(arr + 2) << "\n";
     std::cout << "arr[3] = " << *(arr + 3) << "\n";
     std::cout << "arr[4] = " << arr[4] << "\n";
     return EXIT_SUCCESS;
}

// Allocate STL container in shared memory  
int serverC(){
     // Remove shared memory segment if it already exists 
     bi::shared_memory_object::remove("shared_seg");

     auto segment = bi::managed_shared_memory(
             bi::open_or_create,
             "shared_seg", // segment name 
             4096              // 4 kbytes 
             );
     auto shm_remove = SharedMemoryCleaner("shared_seg");

     // Segment manager pointer 
     // Type: managed_shared_memory::segment_manage* 
     auto segmgr = segment.get_segment_manager();
     segmgr->construct<const char*>("text")("'Hello world shared memory'");
     segmgr->construct<double>("speed")(10.50);
     segmgr->construct<int>("nodes")(100);

     // === Allocate STL Vector in Shared Memory === // 
     // Build shared memory allocator 
     auto aloc = ShmemAllocator<double>(segmgr);

     // Instantiate vector in shared memory 
     ShmemVector<double>* pVector = segmgr->construct<ShmemVector<double>>("avector")(aloc);
     pVector->reserve(50);
     pVector->push_back(4.5);
     pVector->push_back(10.3);
     pVector->push_back(100.50);
     pVector->push_back(20.0);

     std::cout << "Enter RETURN to EXIT " << "\n";
     std::cin.get();
     return EXIT_SUCCESS;
};

int clientC(){
      auto segment = bi::managed_shared_memory(
              bi::open_or_create,
              "shared_seg", // segment name 
              4096          // 4 kbytes 
            );  

      auto segmgr = segment.get_segment_manager();
      std::pair<double*, size_t> p1 = segmgr->find<double>("speed");
      std::cout << "Speed = " << *p1.first << "\n";

      auto pairNodes = segmgr->find<int>("nodes");
      std::cout << "Nodes = " << *pairNodes.first << "\n";

      auto pairText = segmgr->find<const char*>("text");
      std::cout << "Text = " << *pairText.first << "\n";

      // C++17 - Structured Binding
      auto [pVector, _] = segmgr->find<ShmemVector<double>>("avector");

      std::cout << " => pVector->size() = " << pVector->size() << std::endl;
      std::cout << " => pVector[0] = " << pVector->operator[](0) << std::endl;
      std::cout << " => pVector[1] = " << (*pVector)[1] << std::endl;
      size_t idx = 0;
      for(auto const& x: *pVector)
          std::cout << "pVector[" << idx++ << "] = " <<  x << "\n";

      double speed;
      std::cout << "Enter new speed: ";
      std::cin >> speed;
      *p1.first = speed;

      pVector->push_back(speed);

      return EXIT_SUCCESS;
};

# GCC  
$ g++ boost-shared-memory1.cpp -o boost-shared-memory1.bin -std=c++1z -Wall -lpthread -lrt

# Clang 
$ clang++ boost-shared-memory1.cpp -o boost-shared-memory1.bin -std=c++1z -Wall -lpthread -lrt

$ cl.exe boost-shared-memory1.cpp /Fe:boost-shared-memory1.exe /EHsc /std:c++17 ...
  /GA /MDd /nologo /I C:\boost\boost_1_69_0 /link /LIBPATH:C:\boost\lib

$ g++ boost-shared-memory1.cpp -o boost-shared-memory1.exe -std=c++1z -I C:\boost\boost_1_69_0

F:\boost> boost-shared-memory1.exe serverA
Enter RETURN to EXIT

F:\boost> boost-shared-memory1.exe clientA
 Content of shared memory =  ==> String written to shared memory segment

F:\boost>
F:\boost> boost-shared-memory1.exe serverB
Enter RETURN to EXIT

F:\boost>boost-shared-memory1.exe clientB
arr[0] = 100.34
arr[1] = 200.5
arr[2] = -5.6
arr[3] = 9.1
arr[4] = 10.5

F:\boost> boost-shared-memory1.exe serverC
Enter RETURN to EXIT

F:\boost> boost-shared-memory1.exe clientC
Speed = 100.665
Nodes = 100
Text = 'Hello world shared memory'
 => pVector->size() = 5
 => pVector[0] = 4.5
 => pVector[1] = 10.3
pVector[0] = 4.5
pVector[1] = 10.3
pVector[2] = 100.5
pVector[3] = 20
pVector[4] = 100.665
Enter new speed: 40.51

F:\boost> boost-shared-memory1.exe clientC
Speed = 40.51
Nodes = 100
Text = 'Hello world shared memory'
 => pVector->size() = 6
 => pVector[0] = 4.5
 => pVector[1] = 10.3
pVector[0] = 4.5
pVector[1] = 10.3
pVector[2] = 100.5
pVector[3] = 20
pVector[4] = 100.665
pVector[5] = 40.51
Enter new speed: ^C

#include <iostream>
#include <string>
#include <sstream>

#include <cstring> // strok 
#include <ctime>
#include <chrono>

#include <boost/interprocess/mapped_region.hpp>
#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/sync/named_mutex.hpp>
#include <boost/interprocess/sync/scoped_lock.hpp>

namespace bi = boost::interprocess;

// Create shared memory wrapper object 
auto shm = bi::shared_memory_object{
        bi::open_or_create,  
        "logger_shm",
        bi::read_write
};
// Set size of the shared memory segment in Kb (kbytes = 1024 bytes)
shm.truncate(4096); // 4kb (kbytes)
// Map the shared memory segment to current process
auto region = bi::mapped_region{shm, bi::read_write};
// Pointer to shared memory 
void* pMem = region.get_address();

// Create mutex Object 
bi::named_mutex amutex(bi::open_or_create, "logger_mutex");

if(argc < 2){
    std::cout << "$ " << argv[0] << " [-client|-server]" << "\n";
    return EXIT_SUCCESS;
}

std::string cmd = argv[1];

if(cmd == "-server"){
    char* pMessage = (char*) pMem;
    while(true)
    {
         std::cerr << " [TRACE] Waiting logging message " << std::endl;
         // Acquire mutex lock blocking this thread 
         amutex.lock();
         // Print logging memssage from shared memory 
         std::cout << pMessage << std::endl;
    }
    return EXIT_SUCCESS;
}

if(cmd == "-client")
{
    // Interpret shared memory as a pointer an null-terminated
    // array of characters 
    char* pMessage = (char*) pMem;
    std::string line;
    while(true)
    {
        std::cout << " => Enter line: ";
        std::getline(std::cin, line);           
        std::stringstream ss;
        auto now = std::chrono::system_clock::now();
        std::time_t ttp = std::chrono::system_clock::to_time_t(now);
        ss << " [INFO] " << strtok(std::ctime(&ttp), "\n") << " - " << line;
        // Print to shared memory (pointer by pMessage)
        std::sprintf(pMessage, "%s", ss.str().c_str());
        // Release mutex lock 
        amutex.unlock();
    }      
    return EXIT_SUCCESS;
}

# Clang 
$ clang++ boost-shared-memory-logger.cpp -o logger.bin -std=c++1z -g -O0 -Wall -lpthread -lrt  
# GCC
$ gcc++ boost-shared-memory-logger.cpp -o logger.bin -std=c++1z -g -O0 -Wall -lpthread -lrt  

$ g++ boost-logger.cpp -o boost-logger.exe -IC:\boost\boost_1_69_0

$ cl.exe boost-logger.cpp /Fe:boost-logger1.exe /EHsc /GA /MDd /nologo /I C:\boost\boost_1_69_0 /link /LIBPATH:C:\boost\lib

$ ./logger.bin -server
 [TRACE] Waiting logging message 
 [INFO] Sun Mar 17 08:13:26 2019 - price 10% up
 [TRACE] Waiting logging message 
 [INFO] Sun Mar 17 08:13:38 2019 - price change 4.5 down
 [TRACE] Waiting logging message 
 [INFO] Sun Mar 17 08:14:07 2019 - new forecast arriving soon
 [TRACE] Waiting logging message 
 [INFO] Sun Mar 17 08:14:11 2019 - new data
 [TRACE] Waiting logging message 
 ... ...  ... ...  ... ...  ... ... 

$ ./logger.bin -client
 => Enter line: price 10% up
 => Enter line: price change 4.5 down
 => Enter line: new forecast arriving soon
 => Enter line: new data
 => Enter line: ^C

#include <iostream>
#include <functional>
#include <string>
#include <fstream>
#include <vector>

#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/file_mapping.hpp>
#include <boost/interprocess/mapped_region.hpp>

namespace bi = boost::interprocess; 

/** Generic Memory-mapped file allocator */
template<typename T>
using MMFAllocator = bi::allocator<T, bi::managed_mapped_file::segment_manager> ;

/** Generic STL vector allocated in memory-mapped file */
template<typename T>
using MMFVector = std::vector<T, MMFAllocator<T>> ;

constexpr const char* fileName = "memory-dump.dat";
constexpr size_t      fileSize = 4096; // 4 kbytes
bool flagFileExists            = fileExists(fileName);

// Manged file mapping object => Creates the file if it does not exists 
auto mf = bi::managed_mapped_file{bi::open_or_create, fileName, fileSize};

if(!flagFileExists){
     // Executed when the file did not exist 
     std::cout << " [INFO] Setting file data" << std::endl;
     mf.construct<int>("NumberOfNodes")(100);   
     mf.construct<double>("Speed")(200.0);
     mf.construct<const char*>("Text")("'Allocated text in memory mapped file'");

     // Allocate std::vector<double>
     MMFAllocator<double> aloc1(mf.get_segment_manager());
     MMFVector<double>* pVector = mf.construct<MMFVector<double>>("AVector")(aloc1);
     pVector->reserve(20);
     pVector->push_back(40.5);
     pVector->push_back(98.10);
     pVector->push_back(-50.45);
     pVector->push_back(10);        

     return EXIT_SUCCESS;
}

// ======= Executed when file already exists =========// 

std::cout << " [INFO] Retrieving objects from memory mapped file" << std::endl;

// Retrieve variable NumberOfNodes with very explicitly and verbose notation 
std::pair<int*, size_t> pairResult1 =  mf.find<int>("NumberOfNodes");
if(pairResult1.first == nullptr){
        std::cerr << " [ERROR] I cannot find the object 'NumberOfNodes'" << std::endl;
        return EXIT_FAILURE;
}
std::cout << "Number of nodes = " << *pairResult1.first  << "\n";
(*pairResult1.first)++;

// Retrieve variable text
auto [pText, _size1 ] = mf.find<const char*>("Text");
assert(pText != nullptr);
std::cout << "Text = " << *pText << "\n";

// Retrieve variable speed
auto [pSpeed, _size2 ] = mf.find<double>("Speed");
assert(pSpeed != nullptr);
std::cout << "Speed = " << *pSpeed << "\n";
std::cout << " => Set new speed := ";
std::cin >> *pSpeed;

// Rerieve vector
auto [pVector, _size3] = mf.find<MMFVector<double>>("AVector");
assert(pVector != nullptr);
std::cout << "\n pVector->size() = " << pVector->size() << std::endl;
size_t idx = 0;
for(auto const& x: *pVector)
   std::cout << " pVector[" << idx++ << "] = " << x << std::endl ;  

pVector->push_back(*pSpeed);    
return 0;

# Clang 
$ clang++ boost-memory-mapped-file.cpp -o boost-memory-mapped-file.bin -std=c++1z -g -O0 -Wall -lpthread -lrt 
# GCC
$ g++ boost-memory-mapped-file.cpp -o boost-memory-mapped-file.bin -std=c++1z -g -O0 -Wall -lpthread -lrt 

$ cl.exe boost-memory-mapped-file.cpp /Fe:boost-memory-mapped-file.exe /EHsc /std:c++17 ...
   /GA /MDd /nologo /I C:\boost\boost_1_69_0 /link /LIBPATH:C:\boost\lib

$ g++ boost-memory-mapped-file.cpp -o boost-memory-mapped-file.exe -std=c++1z -I C:\boost\boost_1_69_0

F:\boost> boost-memory-mapped-file.exe

 [INFO] Setting file data

F:\boost> boost-memory-mapped-file.exe

 [INFO] Retrieving objects from memory mapped file
Number of nodes = 100
Text = 'Allocated text in memory mapped file'
Speed = 200
 => Set new speed := 4.51

 pVector->size() = 4
 pVector[0] = 40.5
 pVector[1] = 98.1
 pVector[2] = -50.45
 pVector[3] = 10

F:\boost> boost-memory-mapped-file.exe
 [INFO] Retrieving objects from memory mapped file
Number of nodes = 101
Text = 'Allocated text in memory mapped file'
Speed = 4.51
 => Set new speed := 125.75

 pVector->size() = 5
 pVector[0] = 40.5
 pVector[1] = 98.1
 pVector[2] = -50.45
 pVector[3] = 10
 pVector[4] = 4.51

typedef struct {
    unsigned char e_ident[EI_NIDENT];
    uint16_t      e_type;
    uint16_t      e_machine;
    uint32_t      e_version;
    ElfN_Addr     e_entry;
    ElfN_Off      e_phoff;
    ElfN_Off      e_shoff;
    uint32_t      e_flags;
    uint16_t      e_ehsize;
    uint16_t      e_phentsize;
    uint16_t      e_phnum;
    uint16_t      e_shentsize;
    uint16_t      e_shnum;
    uint16_t      e_shstrndx;
} ElfN_Ehdr;

#include <iostream>
#include <iomanip>
#include <cassert>
#include <map>

#include <boost/interprocess/file_mapping.hpp>
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/mapped_region.hpp>

namespace bi = boost::interprocess;

#define EI_NIDENT 16

using uintN_t = uint64_t;
using ElfN_Addr = uintN_t;
using ElfN_Off  = uintN_t;

// ELF Header extracted from:
//  =>> http://man7.org/linux/man-pages/man5/elf.5.html
typedef struct {
    unsigned char e_ident[EI_NIDENT];
    uint16_t      e_type;
    uint16_t      e_machine;
    uint32_t      e_version;
    ElfN_Addr     e_entry;
    ElfN_Off      e_phoff;
    ElfN_Off      e_shoff;
    uint32_t      e_flags;
    uint16_t      e_ehsize;
    uint16_t      e_phentsize;
    uint16_t      e_phnum;
    uint16_t      e_shentsize;
    uint16_t      e_shnum;
    uint16_t      e_shstrndx;
} ElfN_Ehdr;

// Instruction set ISA type database
static 
std::map<uint8_t, const char*> isa_type_database =
            {
                {0x00, "No specified"}
                ,{0x02, "Sparc"}
                ,{0x03, "x86"}
                ,{0x08, "MIPS"}
                ,{0x14, "Power PC"}
                ,{0x16, "S390"}
                ,{0x28, "ARM"}
                ,{0x2A, "SuperH"}
                ,{0x3E, "x86-64"}
                ,{0xB7, "AArch64"}
                ,{0xF3, "RISC-V"}
};

static std::ostream&
operator<<(std::ostream& os, const std::vector<std::uint8_t>& byte_array)
{
    for(const auto& ch: byte_array)
    {
        if(std::isprint(ch))
            os << ch << "";
        else
            os << "\\0x" << std::hex << std::setw(2) << std::setfill('0')
               << static_cast<int>(ch) << " "
               << std::dec;
    }
    return os;
}


int main(int argc, const char* argv[])
{
    std::puts(" ===========>>> Parsing ELF Header <<==================");

    if(argc < 2) {
        std::perror("Error: missing ELF file name as first argument.");
        return EXIT_FAILURE;
    }

    auto fileName = std::string(argv[1]);   
        // Create file mapping (mf)
    auto mf = bi::file_mapping(fileName.c_str(), bi::read_only);
    // Map whole file to process virtual memory 
        auto region = bi::mapped_region(mf, bi::read_only);

    void* addr = region.get_address();
    if(addr == nullptr){
        std::perror(" Failed to map file.");
        return EXIT_FAILURE;
    }

    // Read ELF header file
    ElfN_Ehdr* elf_header = static_cast<ElfN_Ehdr*>(addr);
    auto machine_id = elf_header->e_machine;

    auto magic_bytes = std::vector<std::uint8_t>( elf_header->e_ident
                                                 ,elf_header->e_ident + 4);

    //std::printf("\n       Magic number = %s ", elf_header->e_ident);
    std::cout << "             Magic Bytes = " << magic_bytes << "\n";
    std::printf("\n            Version     = %d", elf_header->e_version);
    std::printf("\n               Type     = %d", elf_header->e_type);
    std::printf("\n            Machine     = %d / %s", machine_id , isa_type_database.at(machine_id));
    std::printf("\n  Number of sections    = %d", elf_header->e_shnum);
    std::printf("\n        Entry Point     = 0x%zX", elf_header->e_entry);      

    return EXIT_SUCCESS;
}

$ g++ read-elf.cpp -o read-elf.bin -std=c++1z -g -Wall -Wextra 

$ ./read-elf.bin /usr/bin/echo
 ===========>>> Parsing ELF Header <<==================
             Magic Bytes = \0x7f ELF

            Version     = 1
               Type     = 3
            Machine     = 62 / x86-64
  Number of sections    = 30
        Entry Point     = 0x1C90

$ readelf -h /usr/bin/echo 
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x1c90
  Start of program headers:          64 (bytes into file)
  Start of section headers:          40072 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         11
  Size of section headers:           64 (bytes)
  Number of section headers:         30
  Section header string table index: 29

$ ls /lib/ | grep -i date
kconf_update_bin/
libboost_date_time.a
libboost_date_time.so@
libboost_date_time.so.1.67.0*

#include <boost/date_time/gregorian/gregorian.hpp>

// Load shared library 
gSystem->Load("/lib/libboost_date_time.so")

namespace g = boost::gregorian;
namespace dt = boost::date_time;

>> auto d1 = g::date(2009, 10, 20)
(boost::gregorian::date &) @0x7fd6d7647050

>> stg::cout << "d1 = " << d1 << "\n";
d1 = 2009-Oct-20

>> auto today = g::day_clock::local_day()
(boost::gregorian::date &) @0x7fd6d7647030

>> stg::cout << "today = " << today << "\n";
today = 2019-Apr-02
>> 

>> auto mdate = g::date(2012, 06, 21)
(boost::gregorian::date &) @0x7f83a2ba70a8

>> g::to_simple_string(mdate)
(std::string) "2012-Jun-21"

>> g::to_iso_string(mdate)
(std::string) "20120621"

>> g::to_iso_extended_string(mdate)
(std::string) "2012-06-21"

>> auto p = gr::from_undelimited_string("20100921")
(boost::gregorian::date &) @0x7f83a2ba7014

>> std::cout << " p = " << p << "\n";
 p = 2010-Sep-21

g::from_simple_string("2001-10-11")

>> auto s1 = g::from_simple_string("2001-10-11")
(boost::gregorian::date &) @0x7fd6d7647010

// ========= Parse Date =============
>> stg::cout << "s1 = " << s1 << "\n";
s1 = 2001-Oct-11

>> s1.year()
(boost::date_time::date<boost::gregorian::date, boost::gregorian::gregorian_calendar, 
 boost::gregorian::date_duration>::year_type) @0x79588b0
>> 

>> (int) s1.year()
(int) 2001

>> static_cast<int>(s1.year())
(int) 2001
>> 

>> s1.month()
(boost::date_time::date<boost::gregorian::date, boost::gregorian::gregorian_calendar, 
boost::gregorian::date_duration>::month_type) @0x7d69550

>> (int) s1.month()
(int) 10

>> static_cast<int>(s1.month())
(int) 10
>> 

>> s1.day()
(boost::date_time::date<boost::gregorian::date, boost::gregorian::gregorian_calendar, 
boost::gregorian::date_duration>::day_type) @0x7f9bfc0

>> (int) s1.day()
(int) 11

>> stg::cout << s1.day() << "\n";
11

>> auto dw = s1.day_of_week()
(boost::gregorian::greg_weekday &) @0x7fd6d764702e

>> (int) dw
(int) 4

>> (int) s1.day_of_week()
(int) 4

>> static_cast<int>(dw)
(int) 4

>> auto dw = s1.day_of_week()
(boost::gregorian::greg_weekday &) @0x7fd6d764702e

>> dw.as_enum()
(boost::gregorian::greg_weekday::weekday_enum) (boost::date_time::weekdays::Thursday) : (unsigned int) 4

>> dw.as_enum() == dt::weekdays::Thursday
(bool) true  

>> dw.as_short_string()
(const char *) "Thu"

>> dw.as_long_string()
(const char *) "Thursday"

>> s1.day_of_year()
(boost::gregorian::date::day_of_year_type) @0x8000e30

>> (int) s1.day_of_year()
(int) 284

>> static_cast<int>(s1.day_of_year())
(int) 284

>> auto date_a = g::date(2009, 10, 20)
(boost::gregorian::date &) @0x7fd6d7647068

>> auto date_b = g::date(2011, 1, 1)
(boost::gregorian::date &) @0x7fd6d764706c

>> auto diff = date_b - date_a
(boost::gregorian::date_duration &) @0x7fd6d7647070

>> diff.days()
(long) 438

>> auto date_a = g::date(2005, 9, 25)
(boost::gregorian::date &) @0x7f83a2ba7048

>> std::cout << "date_a = " << date_a << "\n";
date_a = 2005-Sep-25

// Create a new date object = date_a + 200 days 
>> auto date_b = date_a + g::days(200)
(boost::gregorian::date &) @0x7f83a2ba7060

>> std::cout << "date_b = " << date_b << "\n";
date_b = 2006-Apr-13

>> std::cout << "date_a + 200 days = " << date_a + g::days(200) << "\n";
date_a + 200 days = 2006-Apr-13

>> std::cout << "date_a + 1200 days = " << date_a + g::days(1200) << "\n";
date_a + 1200 days = 2009-Jan-07

>> auto date_a = g::date(2005, 9, 25)
(boost::gregorian::date &) @0x7f83a2ba7048

>> std::cout << "date_a + 5 months  = " << date_a + g::months(5) << "\n";
date_a + 5 months  = 2006-Feb-25