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Boost.Filesystem: question about code conversion for char16_t with version 3
by Yasuhiro Hara 01 Sep '10

01 Sep '10

Hello, I am studying Boost.Filesystem version 3, but I got a couple of questions. I am wondering if someone helps me to understand version 3. I saw the reference document and path.hpp header file, I am not sure how to specify a code conversion API for char16_t or char32_t. It looks like only code conversion API between wchar_t and char can be specified. Since version 3 tries to support char16_t and char32_t, I am a little puzzled. I would appreciate if someone helps me to understand how I can use char16_t with version 3. Best regrads, /yasu

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compressed fusion::vector?
by Cory Nelson 01 Sep '10

01 Sep '10

Hello, Is there a compressed fusion::vector that minimizes the size if the types passed in are empty, like compressed_pair? Thanks! -- Cory Nelson http://int64.org

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[iostreams] filtering_ostream does not flush std::cout.
by Duncan Smith 01 Sep '10

01 Sep '10

I'm using Boost 1.43.0, and I've found that filtering_ostream does not flush "std::cout". I found a relevant (and recent) ticket against Boost 1.44.0, but my issue is slightly different. https://svn.boost.org/trac/boost/ticket/4590 I'm using GCC 4.3.4 on Gentoo Linux. I'm hoping that I'm just doing something wrong, but if you think there's a bug, I'll add my testcase to the ticket. The basic recipe: filtering_ostream out; out.push(any_filter_at_all()); out.push(std::cout); out << "Hello World!" << std::flush; sleep(10); // Observe an empty console. std::cout << std::flush; sleep(10); // Observe printed text on console. This problem is quite bad for me when doing the following on the command-line (for a more complicated program): ./program 2>&1 | tee some-file.log Because stdout is not getting flushed, the stdout and stderr get intermingled strangely. However, disabling buffering on stdout works around the problem: stdbuf --output=0 ./program 2>&1 | tee some-file.log Please tell me if you think there's a bug in my code. If it's a bug in Boost.Iostreams (or I'm expecting the wrong behaviour), I would appreciate any ideas for workarounds (I tried cout.setf(unitbuf), and that doesn't seem to do the trick). Here's the full text of my code: ------------------ // Test case for flushing a filtering_ostream based on the // boost_iostreams_filtering_ostream.cpp attached to ticket #4950: // https://svn.boost.org/trac/boost/ticket/4590 // https://svn.boost.org/trac/boost/attachment/ticket/4590/boost_iostreams_fil… // changed to use "cout" as the sink. // // Flushing a filtering_ostream using the flush() global function does not work // in Boost 1.43. I suspect it also does not work in Boost 1.44. // // Using GCC-4.3.4 on Gentoo Linux. // #include <cassert> #include <string> #include <boost/iostreams/categories.hpp> #include <boost/iostreams/operations.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <iostream> // Included for "sleep()" call below. #include <unistd.h> namespace io = boost::iostreams; // Simple output filter forwarding just forwarding the put chars to // the sink. struct transparent_output_filter { typedef char char_type; typedef io::output_filter_tag category; template <typename Sink> bool put(Sink& snk, char c) { return io::put(snk, c); } }; int main(int argc, char *argv[]) { using namespace std; io::filtering_stream<io::output> out; // Transparent filter just forward the characters to the sink. // // Note: I observe this behaviour with and without this line. out.push(transparent_output_filter()); // Sink appends characters to "cout". out.push(cout); // Write test string to filtering_ostream. out << "Hello World!"; // On my system, this will flush the buffer iff I'm on an // interactive console. "\n" and endl have the same effect. I believe // that my shell sets "stdout" to be line-buffered if it's interactive. // out << "\n"; bool wasFlushed = false; // The flush does *not* work in Boost 1.43. wasFlushed = io::flush(out); // This assertion does not go off, though. assert(wasFlushed); // This also doesn't work. wasFlushed = out.flush(); assert(wasFlushed); // This also doesn't work. out << std::flush; // Demonstrate that none of the above flush calls had any effect on "cout". sleep(10); // Now we finally get the characters on the console. cout << flush; // Demonstrate that the direct flush call works when called directly on // "cout". sleep(10); return 0; }

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Can I use both filesystem versions v2 and v3 in a program ?
by Timothy Madden 01 Sep '10

01 Sep '10

Hello Can I include <boost/filesystem.hpp> but use the BOOST_FILESYSTEM_V... macro to include one version in on of my cpps and another version in another cpp ? Do both versions get compiled when boost is built ? Thank you, Timothy Madden

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Re: [Boost-users] Boost.Serialization: Restoringobjectstate(preventcreation of a new object)?
by ray＠maya-studio.com 01 Sep '10

01 Sep '10

I've ended up with the following solution: #include <fstream> #include <iostream> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/serialization/export.hpp> #include <boost/foreach.hpp> #define _SERIALIZATION_FUNC(CLASS_NAME, ARCH_TYPE) \ public: \ virtual void Serialize(ARCH_TYPE& ar) \ { \ CLASS_NAME& x = *static_cast<CLASS_NAME*>(this); \ ar & BOOST_SERIALIZATION_NVP(x); \ } #define SERIALIZATION(CLASS_NAME) \ public: \ _SERIALIZATION_FUNC(CLASS_NAME, boost::archive::text_iarchive) \ _SERIALIZATION_FUNC(CLASS_NAME, boost::archive::text_oarchive) \ _SERIALIZATION_FUNC(CLASS_NAME, boost::archive::xml_iarchive) \ _SERIALIZATION_FUNC(CLASS_NAME, boost::archive::xml_oarchive) \ private: \ friend class boost::serialization::access; \ template<typename TArchive> \ void serialize(TArchive & ar, const unsigned int version /*file_version*/) class A { public: A() : m_a(0) {} protected: int m_a; private: SERIALIZATION(A) { ar & BOOST_SERIALIZATION_NVP(m_a); } }; class B : public A { public: B() : m_b(0) {} protected: int m_b; private: SERIALIZATION(B) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(A); ar & BOOST_SERIALIZATION_NVP(m_b); } }; BOOST_CLASS_EXPORT(B) int main(int argc, char* argv[]) { // ... A a; B b; std::list<A*> lst; // List of A* pointers lst.push_back(&a); // Base class lst.push_back(&b); // Derived //... // Save { std::ofstream ofs("c:/test.xml"); boost::archive::xml_oarchive oa(ofs); BOOST_FOREACH(A* pA, lst) { pA->Serialize(oa); } } //... // Restore { std::ifstream is("c:/test.xml"); boost::archive::xml_iarchive ia(is); BOOST_FOREACH(A* pA, lst ) { pA->Serialize(ia); } } //... } Everything works as expected (my classes can live with a few additional virtual functions :). And thank you for creating this excellent serialization library! Ray

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Using Boost.MPI with gather , data becomes overwritten after gather operation
by hgc-01134＠hkedcity.net wong 01 Sep '10

01 Sep '10

Hi, I am trying to use Boost.MPI to do a very simple program that 1. Processes from different ranks do a gather operation 2. The gather operation will gather the CoProcessInfo ( which is just a data structure of rank# and hostname) into a vector 3. After the gather operation, Rank 0 will print the CoProcessInfo one by one in the vector. ------------------------------------------------------------------------------------------------------------------------------------------------------ My testing environment consists of TWO virtual machine ( each of the machine has two cores ): Centos 5.5 mpich2 Boost.mpich2 Boost 1.41 mpiexec ------------------------------------------------------------------------------------------------------------------------------------------------------ The expected output of the program should be something like ( just an example order of ranks ): Host VM1, Rank 0 Host VM1, Rank 1 Host VM2, Rank 2 Host VM2, Rank 3 ---------------------------------------------------------------------------------------------------------------------------------------------------------- However, I got something like: ( just an example order of ranks ), the hostname is incorrect after gather operation ( three VM2 appears!) Host VM1, Rank 0 Host VM2, Rank 1 Host VM2, Rank 2 Host VM2, Rank 3 I found that each process CAN correctly found out the hostname and rank#, however, the data will become a bit like overwritten, after the gather operation. Thank you very much. ------------------------------------------- Source Code ------------------------------------------------------------------- #include <boost/asio/ip/host_name.hpp> #include <iostream> #include <vector> #include <string> #include <boost/mpi/environment.hpp> #include <boost/mpi/communicator.hpp> #include <boost/mpi.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <sstream> #include <fstream> using namespace std; namespace mpi = boost::mpi; class CoProcessInfo { private: string hostname; int rank; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* version */) { ar & hostname & rank; } public: CoProcessInfo() { hostname = boost::asio::ip::host_name(); rank = 0; } void setRank(int _rank) { rank = _rank; } string getHostname() const { return hostname; } int getRank() const { return rank; } }; int main(int argc, char* argv[]) { int myrank; mpi::environment env(argc, argv); mpi::communicator world; myrank = world.rank(); CoProcessInfo localInfo; localInfo.setRank( myrank ); std::vector<CoProcessInfo> coProcInfo; mpi::gather(world, localInfo, coProcInfo, 0); if( myrank == 0 ){ for (std::vector<CoProcessInfo>::const_iterator it = coProcInfo.begin(); it !=coProcInfo.end(); ++it) { cout << endl << " Host : " << it->getHostname() << " , Rank : " << it->getRank() << endl; } } return 0; } ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Regards, Joseph

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boost::addressof
by Stanisław Findeisen 31 Aug '10

31 Aug '10

Hi! In the latest boost release (1.44) boost::addressof is defined as follows (boost/utility/addressof.hpp): namespace detail { template<class T> struct addr_impl_ref { T & v_; inline addr_impl_ref( T & v ): v_( v ) {} inline operator T& () const { return v_; } private: addr_impl_ref & operator=(const addr_impl_ref &); }; template<class T> struct addressof_impl { static inline T * f( T & v, long ) { return reinterpret_cast<T*>( &const_cast<char&>(reinterpret_cast<const volatile char &>(v))); } static inline T * f( T * v, int ) { return v; } }; } // namespace detail template<class T> T * addressof( T & v ) { #if defined( __BORLANDC__ ) && BOOST_WORKAROUND( __BORLANDC__, BOOST_TESTED_AT( 0x610 ) ) return boost::detail::addressof_impl<T>::f( v, 0 ); #else return boost::detail::addressof_impl<T>::f( boost::detail::addr_impl_ref<T>( v ), 0 ); #endif } Q1: What is volatile in the cast needed for? Q2: Could anyone please explain to me what are the 2nd parameters in each of the f functions in struct addressof_impl for? Q3: What is struct addr_impl_ref::operator T& () const ??! I understand it is there to get called when passing addr_impl_ref<T>(v) instead of v to addressof_impl<T>::f, but I've never seen such a thing before. I would understand T& struct addr_impl_ref::operator(), or something, but this one is different. Sorry if this is a newbie question. Q4: I can see that in 1.34.1 boost::addressof was much more simple: // VC7 strips const from nested classes unless we add indirection here # if BOOST_WORKAROUND(BOOST_MSVC, == 1300) template<class T> struct _addp { typedef T * type; }; template <typename T> typename _addp<T>::type # else template <typename T> T* # endif addressof(T& v) { return reinterpret_cast<T*>( &const_cast<char&>(reinterpret_cast<const volatile char &>(v))); } so I wonder what was the problem with this design?... -- http://eisenbits.homelinux.net/~stf/ OpenPGP: DFD9 0146 3794 9CF6 17EA D63F DBF5 8AA8 3B31 FE8A Like Hardship, Risk & Challenge? --- Follow Jesus!!

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Creating a thread and blocking its execution
by Jean-Sebastien Stoezel 31 Aug '10

31 Aug '10

Hello, I use boost::thread as follow: mp_Thread = new boost::thread(boost::bind(CSubsystem::TaskWrapper, this)); to create a thread in an initialization method. I observe that this thread gets to run before my initialization method has completed its execution. I would like to create a thread from this initialization method, and wait for it to execute until the whole initialization process it done. Is it possible to create a thread in suspended mode, and then release it once the system is ready? Or do I need to use a synchronization mechanism like a semaphore to release it? Jean-Sebastien

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Does BOOST ASIO HTTP support 1.1
by Manna Patri 31 Aug '10

31 Aug '10

Hi, Looking at the boost::asio:: http server I am very much interested to have it in my application server.However before proceeding further I would like to know does HTTP server implmentation supports HTTP 1.1 ? Looking at the example available under HTTP client it seems "HTTP 1.0" is sent across in header as part of HTTP message. And to my curoisity when I modifeid the client code to send "HTTP 1.1" that also worked. Reply in this regard is appreciated. Thanks. Manna

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Re: [Boost-users] Boost.Serialization: Restoring object state(preventcreation of a new object)?
by ray＠maya-studio.com 31 Aug '10

31 Aug '10

> That's likely something else entirely. We'd have to see more code. Forget my previous post, the exception was due to mixed up ofstream and ifstream... Just to resume - if I have a list of pointers to the objects (all derived from the same base class) and I'd like to serialize them through a reference, a code like this would be needed: // List of pointers A a; B b; // Derived from A C c; // Derived from C std::list<A*> list; list.push_back(&a); // Base list.push_back(&b); // Derived list.push_back(&c); // Derived ... // Save std::ofstream ofs("c:/test.xml"); boost::archive::xml_oarchive oa(ofs); BOOST_FOREACH(A* pA, list) { if (dynamic_cast<B*>(pA)) { B& b = *static_cast<B*>(pA); oa & BOOST_SERIALIZATION_NVP(b); } else if (dynamic_cast<C*>(pA)) { C& c = *pA; BOOST_SERIALIZATION_NVP(c); } else { A& a = *pA; BOOST_SERIALIZATION_NVP(a); } } Am I right?

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