February 2010 - Boost-users

Re: [Boost-users] fusion: work of 4 sequences at the same time
by Hicham Mouline 18 Feb '10

18 Feb '10

> -----Original Message----- > From: Hicham Mouline [mailto:hicham@mouline.org] > Sent: 18 February 2010 17:38 > To: 'boost-users(a)lists.boost.org' > Subject: fusion: work of 4 sequences at the same time > > Hi, > > I am trying to apply fusion::for_each on a sequence, but inside the unary > functor applied to each element, I need to know the index of the element in > question, because I need to extract elements with the same index from other > sequences. > > fusion::vector<...> fseq1; > fusion::vector<...> fseq2; > fusion::vector<...> fseq3; > fusion::vector<...> fseq4; > > fusion::for_each( fseq1, functor<...>(fseq2, fseq3, fseq4) ); > > template <typename Seq2, typename Seq3, typename Seq4) > struct functor { > /// ctor > > template <typename T> > void operator()( const T& t) const > { > /// find out index of t in fseq1, > /// use elements from fseq2,3,4 at the same index > } > }; > > I could use boost::fusion::find to get an iterator and then get its index, but > this doesn not look clean, > > Any ideas, > > Rds, > Ah! fusion::zip is my friend. fusion::for_each( fusion::zip(fseq1, fseq2, fseq3, fseq4), functor() ); Could u confirm though that I will be able to modify fseq1, even through the zipping? Rds,

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Transfering the process state to another process
by Lloyd 18 Feb '10

18 Feb '10

Hi, We want to have a program which cannot be terminated by the user (even admin). I think the only way to do this is to write a watchdog process. So there will be a master and a slave process, the master will be the active process, and the slave keep on watching the master. I case if the master is terminated, the slave become master and initiates a new slave process. But we need to transfer (or share) the process state of "old master" with the "new master" (So that the new master can continue form where the old master has stopped). Is this possible with shared memory? Or is there is a better way? Thanks, Lloyd ______________________________________ Scanned and protected by Email scanner

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multichar_input_filter, what I'm doing wrong?
by eial＠cs.bgu.ac.il 18 Feb '10

18 Feb '10

I'm implementing a base64 decoder using multichar_input_filter, it works well but it doesn't seems to stop, after the last char of the testcase string (which is reads from file), it continues to read, I must be missing something, here is the code: http://codepad.org/YvKREpKS the convert funcion does the actual convert and I don't think it is relevant to the code but if someone thinks it is, I'll include it. I'm banging my head against the wall for a couple of days in this issue... thanks.

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fusion: mpl vector as a fusion vector
by Hicham Mouline 18 Feb '10

18 Feb '10

Hello by include <fusion/include/mpl.hpp> if I have a mpl::vector<> and I want to use it as a member of a struct. This member will actually hold runtime data. typedef mpl::vector<......> mplvector_t; can I just define it as struct S { mplvector_t m; }; or do I need to do this: struct S { fusion::result_of::as_vector<mplvector_t>::type m; }; and then I can store data in m? Regards,

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boost::asio - Can't get timeout on accept to work
by Jean-Sebastien Stoezel 18 Feb '10

18 Feb '10

Hello, I would like to implement a timeout while accepting a connection on a TCP socket. I have reviewed the following example: http://www.boost.org/doc/libs/1_42_0/doc/html/boost_asio/example/timeouts/a… And here is my implementation of it, though it does not seem to wait for the given timeout... And I don't seem to see CProtobufSocket::HandleAccept being called. Could anybody tell me what I am missing with this code? Thanks! Jean-Sebastien int CProtobufSocket::Receive( string port, google::protobuf::Message & message, const boost::posix_time::milliseconds timeout ) { int result = -1; boost::asio::io_service ioService; boost::asio::ip::tcp::acceptor acceptor(ioService, boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), atoi(port.data()))); boost::asio::ip::tcp::socket socket(ioService); try { boost::asio::deadline_timer mytimer(ioService); acceptor.async_accept(socket, boost::bind(CProtobufSocket::HandleAccept, boost::asio::placeholders::error, result)); mytimer.expires_from_now(timeout); mytimer.async_wait(boost::bind(CProtobufSocket::Close, &acceptor)); if(0 == result) { // receive on the socket. result = Receive(socket, message, timeout); } else {} } catch (std::exception& e) { // jstoezel 2910208: removes warning C4101: 'e' : unreferenced local variable e; } try { socket.shutdown(socket.shutdown_both); socket.close(); } catch (std::exception& e) { // jstoezel 2910208: removes warning C4101: 'e' : unreferenced local variable e; } return result; } void CProtobufSocket::Close( boost::asio::ip::tcp::acceptor * acceptor ) { acceptor->close(); } void CProtobufSocket::HandleAccept(const boost::system::error_code &err, int & result) { err; if(err) {} else { result = 0; } }

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Re: [Boost-users] Object pools?
by Michele Caini 18 Feb '10

18 Feb '10

Il 17/02/2010 17:18, Ryan McConnehey ha scritto: > michele.caini(a)gmail.com wrote: >> Simply, That's not as a pool have to work. You are looking for >> something that is a pool but working not as a pool does. > Then what is the definition of a pool? Do you mean that I'm looking for > something that is a pool but doesn't work like a Boost.pool? > > Ryan No, sorry. I mean that pool has responsability for manage offered objects, and so it manages them along their life time. Pool will create objects, pool will release and reclaim objects, and pool will delete objects. That's all. You are looking for something that create objects and forbid about them, until you return that objects to the home. Is correct? Really, it's possible but it is not as a pool works, simply. Your idea breaks also raii pattern and you risk to have memory leaks, because not reclaimed objects maybe be lost during their life time. So, in my opinion, it is not a good idea. I think that is better to create a pool of object during pool construction, so delete them during destruction, eventually resizing pool during use. What about a monostate pattern that globally manages objects as a pool and will be destroyed only when program terminates? That's can be a valid alternative, or not?

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[parameter][mpl] How to do a union of ArgumentPacks?
by Jesse Perla 17 Feb '10

17 Feb '10

I would like to call a function using named parameters where I construct the values from two different argument packs. How do I write a function that will generically take the union of all of the named parameters? I am using Intel C++ 11.1 with C++0X features turned on, so 'decltype' and 'auto' are kosher, but not alternative function syntax. Also, the types I might have in the args could be by value or reference or constant reference, so I can't just copy them all by value. Here is a simple example to see what I mean: BOOST_PARAMETER_NAME(name1) BOOST_PARAMETER_NAME(name2) BOOST_PARAMETER_NAME(name3) template<typename ArgPack> double f(const ArgPack& args) { return args[_name1] + args[_name2] + args[_name3]; } //Test using the argpack directly... this works fine. std::cout << f( (_name1 = 1.0, _name2 = 1.0, _name3 = 1.0) ); //Now try to combine them: template<typename ArgPack1, typename ArgPack2> double g(const ArgPack1& args1, const ArgPack2& args2) { return f( parameter_union(args1, args2) ); //HOW DO I WRITE THE parameter_union FUNCTION? } //usage std::cout << g( (_name1 = 1.0, _name2 = 1.0), (_name3 = 1.0) ); Thanks for your help, Jesse

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Re: [Boost-users] [Serialization] unable to fix UNREGISTERED CLASSexception
by David Graf 17 Feb '10

17 Feb '10

Hello Robert Sorry to bother you again, but I am unable to use force_include correctly. I guest the makro BOOST_USED must be used, correct? I wrote BOOST_USED into each function header in the example. But it doesn't change anything. David On Feb 17, 2010, at 5:25 PM, Robert Ramey wrote: > This is likely due to the fact that a static linker will only include > modules which have have been explicitly referred to. The library uses > "force_include" to implement this when it can. You'll just have to figure > out what the linker is excluding and make sure it's included. > > > Robert Ramey > 830 Cathedral Vista Lane > Santa Barbara, CA 93110 > (805)569-3793 > www.rrsd.com > -----Original Message----- > From: David Graf [mailto:davidagraf@gmail.com] On Behalf Of David Graf > Sent: Wednesday, February 17, 2010 8:08 AM > To: boost-users(a)lists.boost.org; Robert Ramey > Subject: Re: [Boost-users] [Serialization] unable to fix UNREGISTERED > CLASSexception > > Hello Robert > > I fixed the example. I had to add somewhere a virtual function. Otherwise, > the polymorphism doesn't work. > > Unfortunately, I have a new problem. If I put the code into a static > library, the serialization from the outside doesn't work anymore. Then, I > get a unregistered class exception. It only works when I put the code to > execute the serialization into the cpp file where the classes are registered > with BOOST_CLASS_EXPORT_GUID. > > Again, I attached the example source code. The library is created with > cmake. Therefore, you need to have cmake installed on your machine to test > the example. The commands to build the example are cd > /path/to/unpacked/testfolder mkdir build cd build cmake .. > make > > Funnily enough, the serialization from the outside (from the main function) > works if the serialization in the cpp file is executed in advance. > > The example works if the library is a dynamic library. If you wanna see > this, you need to replace STATIC in CMakeLists.txt with SHARED. > > David > > >

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[exception] Conditional error_info addition
by Adam Badura 17 Feb '10

17 Feb '10

Is there a way to add error_info to an exception object conditionally? In my use case I throw upon error during Windows Registry manipulation. One of the data attached to the exception object is the path to the registry key on which operation failed. The problem however is that sometimes (while the library is still developed...) the failure is due to internal code error: the handle to the key is no longer valid because it was closed (erroneously) previously. In such case obtaining path to the key will yield an empty string. I don't want to attach an empty string. I would prefer not to attach anything. (Now actually in this particular case it might be even useful to attach an empty string which is then a clear indication that the key handle was invalid. However I hope that my point is clear here.) Currently I would have to do something like: ExceptionType e; std::wstring path = getPath( hKey ); if ( !path.empty() ) e << PathInfo( path ); BOOST_THROW_EXCEPTION( e ); This code however involves more copying with little hopes for optimization. And it is obviously long. If this was to be done for two or three data items the throwing code would become quite long... Can anything be done about it? Can we have some form of conditional error_info insertion? Adam Badura

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[Serialization] unable to fix UNREGISTERED CLASS exception
by David Graf 17 Feb '10

17 Feb '10

Hello Everybody I am using boost serialization heavily in my project to serialize C++ objects. Unfortunately, I have a big problem when I when polymorphic pointers and non intrusive serialize functions are involved in the serialization. Therefore, I made a little project which demonstrates my usage of boost functionality (see attachment). Basically, I have four classes which are derived in the following way: Item <- AtomicItem <- BooleanItem <- SpecialItem. SpecialItem contains an intrusive serialized functions. The other three contain non intrusive serialize functions. In the main function (testing.cpp), I create a SpecialItem and the stack and assign it to a pointer to an Item. Then, I serialize that Item. Unfortunately, it doesn't work. Only the serialize function of the class Item is invoked. Can you please tell me what I did wrong in my example? Note: The example can be compiled with the command: g++ atomic_items_serialization.cpp testing.cpp -o testing -lboost_serialization-mt And the expected result is: serializing Item serializing AtomicItem serializing BooleanItem serializing SpecialItem Thanks in advance David

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