[Boost-users] Questions about packaged_task , Promise and serialization of a class object and event handling

Hello all again . i have couple of questions again which i would appreciate any kind of help and answer, my first question is about packaged_task and how we can use it , i mean i tried using packaged_task with functions , with parameters , and i got errors doing it . so do we always have to use class or stcucts in order for us to use packaged_task ? how can i send some arguments to a function when im trying to make a package out of ? i have done the packaging with parameterelss functions , but i dont know how im supposed to pass parameters ! : here is my application working with parameterless functions .

//in the name of GOD //Seyyed Hossein Hasan Pour //Learning Boost- How Threading works in Boost //How to pass parameters to functions in packaged_task #define BOOST_THREAD_USE_LIB #include <iostream> #include <cstdlib> #include #include using namespace std;

vector<int> SharedResource; boost::shared_mutex sharedMutex;

int FillSharedResource() { int numberOfItems=10; for (int i = 0; i< numberOfItems; i++) { boost::unique_lockboost::shared_mutex lock(sharedMutex); SharedResource.push_back(i); lock.unlock(); } return 10; }

int Print1() { for (int i = 0; i< SharedResource.size(); i++) { boost::this_thread::sleep(boost::posix_time::seconds(1)); boost::lock_guardboost::shared_mutex locker(sharedMutex); cout<

int Print2() { for (int i = 0; i< SharedResource.size(); i++) { boost::this_thread::sleep(boost::posix_time::seconds(1)); boost::lock_guardboost::shared_mutex locker(sharedMutex); cout<

int main() {

boost::packaged_task<int> pkg0(FillSharedResource), pkg1(Print1), pkg2(Print2);

boost::thread t0(ref(pkg0)), t1(ref(pkg1)), t2(ref(pkg2));

boost::unique_future<int> f0(pkg0.get_future()), f1(pkg1.get_future()), f2(pkg2.get_future());

std::cout<< f0.get()<<"\n"<< f1.get()<< "\n"<< f2.get();

system("pause"); return 0; }

------------------------- can someone show me a simple sample of using Promise in threading ? i mean i already know about future , whats the need for Promise ? ! -------------------------- whats the different between read_some and async_read_some ? in asio ? -------------------------- i know that when i need to send an argument to event handler ( signal ) , i frist should declare sth like this :

*boost::signal2::signal mysignal ;* *mysignal**.connect(myfunc,my-functions-argumant)*; *mysignal**.connect(myfunc2,my-function2s-argumant)*;

now if i have couple of functions with the same signature , doing different jobs with different arguments , how can i give their respective arguments ? i mean at the moment , i can only write : mysignal(5);! and this passes 5 to all functions connected with this signal! do i really have to make one signal for each functions ?so that i can pass different and yet with the same type argument to different functions using one signal . is'nt there any other way around it ? if inside a signal , i run a thread and then i block that signal using signal.block , would that block that thread too ? and then unblocking it would it unblock that thread too ? is it safe doing this ? --------------------------- why do we use function names with const that the end of it ? i mean sth like this :

void operator()() const { } or void boostFunctionName(sth) const { }

what is that const for ? what does it declare ? why is it necessary to use it that way ? -------------------- how do i serialize a class of mine ? i mean i read that if i have vector , i need to use some functions , if i have foo i need another function ! what exactly do you serialize your classes ? i mean maybe i have std::string , char , vectors of some kind , and a self made class or type used in my class to be serialized , how should i go about it . any guidance is greatly appreciated . --------------------- i tired to use boost::container::vector for storing my threads , and it went just fine . but i have a problem in determining which thread is which , i mean i already found out that i can use if-else for this matter , but since i used a vector , and the number of threads being created at run-time is not known , so i need to use a for statement so that i can iterate throuh all of th evectors items and then if i find a match , i do as i wish . the problem is , when i try to have sth like this , it fails :

boost::id id = myvect[0]

i want to pass this id for matching operation ( or declare it as global ) , what am i missing again ? another problem i have in this regard is that , when i store my threads in a lets say vector just like the sample i gave earlier , it is not guaranteed that threads inside that vector actually points to a legal thread of execution by the time i go to check for sth .!( i mean there is a good chance that they already ran and got terminated!) seemingly i can not use joinable to see if i am dealing with an active or lets say legitimate thread ! , my question is , how can i check to see if an object of type thread , actually points to sth real ? how to check that ? --------------------- when i try to compile source codes using Asio using MingW , i get linking errors ! what is the cause and how can i fix that ? i get the errors:

C:\boost_1_49_0\boost\asio\detail\impl\winsock_init.ipp|39|undefined reference to `WSAStartup@8'| C:\boost_1_49_0\boost\asio\detail\impl\winsock_init.ipp|48|undefined reference to `WSACleanup@0'|

Thank you all in advance Seyyed Hossein Hasan Pour