Book Image

Boost C++ Application Development Cookbook - Second Edition

By : Anton Polukhin Alekseevic
Book Image

Boost C++ Application Development Cookbook - Second Edition

By: Anton Polukhin Alekseevic

Overview of this book

If you want to take advantage of the real power of Boost and C++ and avoid the confusion about which library to use in which situation, then this book is for you. Beginning with the basics of Boost C++, you will move on to learn how the Boost libraries simplify application development. You will learn to convert data such as string to numbers, numbers to string, numbers to numbers and more. Managing resources will become a piece of cake. You’ll see what kind of work can be done at compile time and what Boost containers can do. You will learn everything for the development of high quality fast and portable applications. Write a program once and then you can use it on Linux, Windows, MacOS, Android operating systems. From manipulating images to graphs, directories, timers, files, networking – everyone will find an interesting topic. Be sure that knowledge from this book won’t get outdated, as more and more Boost libraries become part of the C++ Standard.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Using pointers in a shared memory


It is hard to imagine writing some low-level C++ core classes without pointers. Pointers and references are everywhere in C++, and they do not work in shared memory! So, if we have a structure like this in shared memory and assign the address of some integer variable in shared memory to pointer_, the pointer_ would be invalid in other process:

struct with_pointer { 
    int* pointer_; 
    // ... 
    int value_holder_; 
}; 

How can we fix that?

Getting ready

The previous recipe is required for understanding this one. The example requires linking against the runtime system library rt on some platforms.

How to do it...

Fixing it is very simple; we need only to replace the pointer with offset_ptr<>:

#include <boost/interprocess/offset_ptr.hpp> 

struct correct_struct { 
    boost::interprocess::offset_ptr<int> pointer_; 
    // ... 
    int value_holder_; 
}; 

Now, we are free to use it like a usual pointer:

int main() {
    boost::interprocess::managed_shared_memory...