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Boost-enabled loosely coupled ORM serialization
by Michael Powell 05 Apr '13

05 Apr '13

Hello, I am coming up on a decision in the architecture I am working on. I want to serialize some domain data to a data store. I'm aware boost has serialization features, which I'd like to explore further. I'm coming at this first from a boost standpoint because I am successfully building upon it for other parts of the engine and domain model, so boost is available right now. I am expecting I might go with a third-party library like ODB, Wt::Dbo, or something like that. Also, background, I am no stranger to ORM concepts. I was first exposed to them through Java, C# .NET, and have dealt with Hibernate, NHibernate, Fluent NHibernate, and so on. So vocabulary-wise, grammar-wise, we're talking the same language. Also, I'll defer backend decisions until later. Probably that will be somewhat determined by target platform support and so on: landing on ArchLinux ARM. For now, my focus for now is on keeping ORM intersection with my domain as loosely coupled as possible. For anyone versed in ORM nuances, for obvious reasons, I want for the ORM to be as transparent through the domain model as possible. I want to steer clear of the active record anti-pattern whenever possible. I'd like to gear up for a repository pattern whenever feasible. No time to get into that discussion why I believe these are patterns or anti-patterns. That's a separate blog for another time. Wrappers like smart pointers, smart collections, are understandable, and may be the way to go, but put opaqueness layers between end-users of the domain objects and the rest of the model. Will use them if I must, but I'd like to avoid them if possible. Additionally, given some language "features", perhaps "limitations" if you will, of C++11, as contrasted with a C# let's say, I also want for any ORM code, whether meta-programmed or not, to be as non-intrusive to the domain model as possible. I've seen a ton of code that have persist methods, friend access, macros, and such. Sounds like a tall order I know. Call me spoiled on the "niceness" of .NET, Reflection, and so on. More likely I'm getting reacquainted with the practicalities of using a paradigm-rich language like C++11. Now back to the "real world" what the rest of us deal with. Realistically, a sober look at it, I believe there will be tradeoffs: SOLID is my goal, sufficiently extensible to meet the seams we'll need to meet, yet maintainable at the end of the day. Regards, Michael Powell

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Signals2 event broker framework
by Michael Powell 05 Apr '13

05 Apr '13

Hello, I am interested to put an event broker system into practice in our architecture. Since we're using boost successfully already, Signals2 seems like the most likely candidate. At the moment, this is intra-process, most likely inter-thread but for now that's not the concern. Just getting event signals from point A to points B, C, D in pub/sub manner, however, is. http://www.boost.org/doc/libs/1_53_0/doc/html/signals2.html If I can abstract that out further, for instance I noticed there was an C# event-like abstraction someone published as an add-on feature to boost a little while back, handled subscriptions through +=, -= operator overloads, that sort of thing, would be helpful, but probably not completely necessary. If I can loosely couple subscribers from publishers is also desired. Something like bbv EventBroker ( http://code.google.com/p/bbvcommon/wiki/EventBroker) is to C#. That'll keep things nice and loosely coupled, so that if we ever need to get more distributed (i.e. via a CORBA or ZeroC) we can potentially do so. Regards, Michael Powell

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dynamic_bitset get block_type not ulong
by Michael Powell 05 Apr '13

05 Apr '13

Hello, How do I get at the block_type value itself, not an unsigned long, from a dynamic_bitset (or std::bitset for that matter). For instance, can I do something like this? typedef unsigned char byte; boost::dynamic_bitset<byte> my_bitset(static_cast<byte>(0x00)); //Do some bit twiddling... byte my_value = static_cast<byte>(my_bitset); Or something like that. Basically I want to avoid any to_ulong() mumbo jumbo if I can just get at the underlying block_type value. Thank you... Regards, Michael Powell

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Problem with Serialization: invalid signature
by Alexander Striffeler 04 Apr '13

04 Apr '13

Hi all I have some trouble with the serialization of objects in C++ using boost. Since there was some strange behaviour in the code, I tried to serialize and deserialize a sample object isolated trying two versions: |deSerialize(Packet p1, Packet p2){ // Version 1 using stringstreams std::ostringstream *serialized = new std::ostringstream[2];|| ||serialized[0]=std::ostringstream(std::ios_base::binary);|| ||serialized[1]=std::ostringstream(std::ios_base::binary);|| || || boost::archive::text_oarchive oa(serialized[0]);|| || oa << p1;|| || || boost::archive::text_oarchive oa2(serialized[1]);|| || oa2 << p2;|| || || std::string s1, s2;|| || || s1 = serialized[0].str();|| || s2 = serialized[1].str();|| || || //deserialize CCNDataPkt newPacket; std::istringstream inputStream(s2, std::ios_base::binary); boost::archive::text_iarchive ia(inputStream); | | ia >> newPacket;| // throws boost::archive::archive_exception: invalid signature. } and |deSerialize(Packet p1, Packet p2){ // Version 2 using ofstreams ||std::ofstream of("deleteme",std::ios_base::binary);|| || boost::archive::binary_oarchive oa(of);|| || oa << p1;|| || || std::ifstream ifstr("deleteme", std::ios_base::binary);|| || CCNDataPkt newp;|| || boost::archive::binary_iarchive ia(ifstr);|| | | ia >> newp;| // boost::archive::archive_exception: invalid signature. } However, both variants returned an invalid signature exception even though I haven't changed anything on the serialized data. Does anyone know what is wrong in either of the examples above? The methods for serializing the custom object 'Packet' are implemented according to the boost serialization tutorial (non-intrusive version splitted) Any hints are very much appreciated - TIA! Cheers, Alex

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[Parallel BGL] Error during building library
by Nikos Kyrtatas 04 Apr '13

04 Apr '13

In order to build Parallel BGL 0.7.0 beta, I first used cmake: ~/project/lib> cmake parallel-bgl-0.7.0/ -- The C compiler identification is GNU -- The CXX compiler identification is GNU -- Check for working C compiler: /usr/bin/cc -- Check for working C compiler: /usr/bin/cc -- works -- Detecting C compiler ABI info -- Detecting C compiler ABI info - done -- Check for working CXX compiler: /usr/bin/c++ -- Check for working CXX compiler: /usr/bin/c++ -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Configuring done -- Generating done -- Build files have been written to: /home/nkyrtata/project/lib and then make: ~/project/lib> make -- Configuring done -- Generating done -- Build files have been written to: /home/nkyrtata/project/lib Scanning dependencies of target boost_graph_mpi [ 2%] Building CXX object libs/graph_parallel/src/CMakeFiles/boost_graph_mpi.dir/mpi_process_group.cpp.o [ 5%] Building CXX object libs/graph_parallel/src/CMakeFiles/boost_graph_mpi.dir/tag_allocator.cpp.o Linking CXX static library ../../../lib/libboost_graph_mpi.a [ 5%] Built target boost_graph_mpi Scanning dependencies of target adjlist_build_test [ 8%] Building CXX object libs/graph_parallel/test/CMakeFiles/adjlist_build_test.dir/adjlist_build_test.cpp.o In file included from /home/nkyrtata/project/lib/parallel-bgl-0.7.0/boost/graph/distributed/adjacency_list.hpp:3961:0, from /home/nkyrtata/project/lib/parallel-bgl-0.7.0/libs/graph_parallel/test/adjlist_build_test.cpp:10: /home/nkyrtata/project/lib/parallel-bgl-0.7.0/boost/graph/distributed/adjlist/serialization.hpp: In function ‘std::vector<int> boost::detail::parallel::available_process_files(const string&)’: /home/nkyrtata/project/lib/parallel-bgl-0.7.0/boost/graph/distributed/adjlist/serialization.hpp:97:61: error: conversion from ‘boost::filesystem3::path’ to non-scalar type ‘std::string {aka std::basic_string<char>}’ requested make[2]: *** [libs/graph_parallel/test/CMakeFiles/adjlist_build_test.dir/adjlist_build_test.cpp.o] Error 1 make[1]: *** [libs/graph_parallel/test/CMakeFiles/adjlist_build_test.dir/all] Error 2 make: *** [all] Error 2 I am using Ubuntu 11.10, gcc 4.6.1 and boost 1.52. Any help would be greatly appreciated.

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[program options] compile error if BOOST_NO_EXCEPTIONS defined
by Olaf Krzikalla 04 Apr '13

04 Apr '13

Hi, MSVC 2008, program_options/variables_map.cpp: try without catch error, if BOOST_NO_EXCEPTIONS is defined. Fixable by wrapping the try on line 46: + #ifndef BOOST_NO_EXCEPTIONS try + #endif Best Olaf

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[Boost.Coroutine] Problem compiling simple code with c++98 compiler
by Lukas Czaja 03 Apr '13

03 Apr '13

Hi, i was checking if my code is compatible with c++98 standard and i've encounterd compile error. With -std c++11 option everything works fine. Below i've written code causing same problem. #include <boost/coroutine/coroutine.hpp> #include <boost/coroutine/attributes.hpp> typedef boost::coroutines::coroutine<void( boost::system::error_code , std::size_t)> coro_t; struct coro_test{ coro_test() {} void coro_fun(typename coro_t::caller_type& ca)const{ boost::system::error_code ec; boost::tie(ec, boost::tuples::ignore) = ca.get(); ca(); } coro_t coro; }; int main(int argc, char *argv[]) { { boost::system::error_code ec; coro_t coro2; //default construction is ok coro_test ctest; //compile error , why ??? coro_t coro( boost::bind(&coro_test::coro_fun, &ctest, _1),coro_t::arguments( ec, 7)); coro = coro_t(boost::bind(&coro_test::coro_fun, &ctest, _1),coro_t::arguments( ec, 7)); } ... /usr/local/include/boost/type_traits/is_function.hpp:50: błąd:forming pointer to reference type 'boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&' /usr/local/include/boost/type_traits/is_function.hpp:102: błąd:'value' is not a member of 'boost::detail::is_function_impl<boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&>' /usr/local/include/boost/type_traits/is_convertible.hpp:354: błąd:'value' is not a member of 'boost::is_function<boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&>' /usr/local/include/boost/utility/enable_if.hpp:59: błąd:'value' is not a member of 'boost::is_convertible<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)>&, boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&>' I work with Qt, g++ compiler on ubuntu 12.10 Is this library bug ?

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[serialization] serializing a pointer without causing object tracking
by Stefan Strasser 02 Apr '13

02 Apr '13

Hi everyone, Hi Robert, in case you'd like to answer this one, because I have a rather specific question about your library. Thank you in advance! I'd like to serialize an object and later reconstruct it from the serialized data: void save(T const &t){ ar << t; } T* load(){ T *t=new T(); //error ar >> *t; } T might not have a default constructor. so load_construct_data should be used. apparently the way to do this is to serialize through a pointer: void save(T const *t){ ar << t; } T *load(){ T *t; ar >> t; } this works, but it causes the type T to be tracked, if its object tracking is set to track_selectively. I don't want that. but I can't set it to track_never either, because if the type is serialized at another point in the program through a pointer, the type should be tracked. is there a solution to this? is there a serialization wrapper that says "don't track this type just because of this pointer"? what comes to mind as a solution is serializing as an object, and calling load/save_construct_data manually. but then there is another problem: void save(T const &t){ save_construct_data(t,version<T>::value); ar << t; } void load(T *unconstructed_t){ load_construct_data(unconstructed_t, ??? ); ar >> *t; } if the implementation level of T is object_class_info, the object version is loaded from the preamble when the object itself is loaded. there is no in between loading the version and loading the object, it's entirely handled in the non-header part of the library. so basically I have a solution when the implementation level is object_serializable (no version info, call load_construct_data manually), and when tracking is set to track_never (serialize as a pointer). but not for the default case, object_class_info with track_selectively. am I missing something? Stefan

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Problems with stl::map
by Michael Powell 02 Apr '13

02 Apr '13

Hello, Perhaps there is a boost answer for this, I don't know. I have a typedef unsigned char byte defined in global scope. Then a typedef byte address_type defined in the scope of a class. I'd like to setup a std::map<address_type, byte> if at all possible. Or just in general, use std::map, but it doesn't seem to like anything I give it. I am building using GCC 4.7.2 cross compiling to ARM through Sourcery CodeBench for ARM. Kind of at a loss. Regards, Michael Powell

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safe check if lockfree::queue is empty
by niXman 02 Apr '13

02 Apr '13

Hi, I read the docs about lockfree::queue::empty() and understang what this way is not safe in multithreaded program. The question is, how can I verify that the queue is empty? Will it be correct the following code? bool empty() { T *tmp = 0; if ( queue.pop(tmp) ) { queue.push(tmp); return false; } return true; } Thanks. -- Regards, niXman ___________________________________________________ Dual-target(32 & 64-bit) MinGW compilers for 32 and 64-bit Windows: http://sourceforge.net/projects/mingwbuilds/ ___________________________________________________ Another online IDE: http://liveworkspace.org/

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