- Boost-users - lists.boost.org

Re: [Boost-users] XML library?
by Andrej van der Zee 26 Jul '08

26 Jul '08

I would definitely prefer libxml2/libxml++ over xerces-c (its too big and awkward in usage - prepare to type alot). For simple and basic usage you could also use tinyxml/ticpp or rapidxml. And yes, its a pitty that Boost does not provide some basic XML parser/generator. In so many projects you end up needing just a simpel parser... Cheers, Andrej ----- Original Message ---- From: Michiel Helvensteijn <m.helvensteijn(a)gmail.com> To: boost-users(a)lists.boost.org Sent: Saturday, 26 July, 2008 10:44:54 PM Subject: [Boost-users] XML library? I was surprised not to find an XML parser/generator library in boost. Or is it hidden somewhere? Is it planned for a future release, perhaps? In the meantime, can anyone recommend another open source C++ XML library I can use (with DOM parser)? Thanks! -- Michiel Helvensteijn _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users __________________________________________________________ Not happy with your email address?. Get the one you really want - millions of new email addresses available now at Yahoo! http://uk.docs.yahoo.com/ymail/new.html

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(A dynamic) Singleton using weak_ptr and shared_ptr
by Martin Trappel 26 Jul '08

26 Jul '08

Hi all. I was faced with the requirement for a singleton class where the object has to be constructed dynamically and where I wanted to assure that the object is destructed automatically when no longer needed. A solution using shared_ptr and weak_ptr immediately came to mind and after a short google I found http://lists.boost.org/boost-users/2002/10/2014.php. However, if you have to assure that construction and destruction never overlap if you have multiple (sequential) initializations/destructions it gets a bit more complicated :) Well. Here follows what I have come up with and it seems to work pretty well. Any comments welcome. br, Martin Singleton using boost weak_ptr and shared_ptr --------------------------------------------- Requirement: Singleton that is constructed on first use (not on process start) and destroyed after the last "client-code" has finished with it. Note: It is therefore possible that more that one Singleton instances exist within a process's lifetime, BUT there must only be at most one Object active at any given time (Construction must not run before destruction has finished. Starting point: http://lists.boost.org/boost-users/2002/10/2014.php Problem of the simple solution: No protection against multiple initialization and against simultaneous deletion and construction. Solution: The construction and destruction of the singleton instance(s) has to be protected additionally. [CODE:dynamic_singleton.h] #pragma once ////////////////////////////////////////////////////////////////////// #include <boost/noncopyable.hpp> #include <boost/shared_ptr.hpp> #include <boost/scoped_ptr.hpp> ////////////////////////////////////////////////////////////////////// class dynamic_singleton : private boost::noncopyable { public: typedef boost::shared_ptr<dynamic_singleton> shared_t; static shared_t get_instance(); // Interface: void example(int cookie); // ... private: dynamic_singleton(); virtual ~dynamic_singleton(); struct impl; typedef boost::scoped_ptr<impl> impl_t; impl_t pimpl; struct deleter; friend struct deleter; }; [/CODE] [CODE:dynamic_singleton.cpp] #include "dynamic_singleton.h" #include <boost/weak_ptr.hpp> #include <boost/thread/recursive_mutex.hpp> #include <boost/thread.hpp> ////////////////////////////////////////////////////////////////////// #define MESG(msg) \ printf("%s\n", msg); \ /**/ ////////////////////////////////////////////////////////////////////// class atomic_bool : protected boost::noncopyable { public: atomic_bool() : b_(false) {} explicit atomic_bool(bool b) : b_(b) {} inline operator bool() const { boost::recursive_mutex::scoped_lock lock(sync_); return b_; } inline bool operator=(bool b) { boost::recursive_mutex::scoped_lock lock(sync_); b_ = b; return b_; } private: bool b_; mutable boost::recursive_mutex sync_; }; ////////////////////////////////////////////////////////////////////// struct dynamic_singleton::impl : private boost::noncopyable { impl() {} ~impl() {} static void start_construction() { boost::xtime spin_time; spin_time.sec = 1; while(the_object_exists) { boost::thread::sleep(spin_time); } } static void finish_construction() { assert(!the_object_exists); the_object_exists = true; } static void finish_destruction() { assert(the_object_exists); the_object_exists = false; } typedef boost::weak_ptr<dynamic_singleton> internal_shared_t; static internal_shared_t the_object; static boost::recursive_mutex sync_init; static atomic_bool the_object_exists; }; ////////////////////////////////////////////////////////////////////// dynamic_singleton::impl::internal_shared_t dynamic_singleton::impl::the_object; boost::recursive_mutex dynamic_singleton::impl::sync_init; atomic_bool dynamic_singleton::impl::the_object_exists; ////////////////////////////////////////////////////////////////////// struct dynamic_singleton::deleter { void operator() (dynamic_singleton* p) { assert(p); delete p; impl::finish_destruction(); } }; ////////////////////////////////////////////////////////////////////// dynamic_singleton::shared_t dynamic_singleton::get_instance() { // Syncronise Initialization: boost::recursive_mutex::scoped_lock lock(impl::sync_init); MESG(__FUNCTION__); // Acquire singleton pointer: shared_t object_ptr = impl::the_object.lock(); if(!object_ptr.use_count()) { impl::start_construction(); object_ptr.reset(new dynamic_singleton(), dynamic_singleton::deleter()); impl::the_object = object_ptr; impl::finish_construction(); } return object_ptr; } ////////////////////////////////////////////////////////////////////// dynamic_singleton::dynamic_singleton() { pimpl.reset(new impl()); MESG(__FUNCTION__); // For example open a unique system or process global resource printf(" >> Singleton opens the global resouce.\n"); } ////////////////////////////////////////////////////////////////////// dynamic_singleton::~dynamic_singleton() { MESG(__FUNCTION__); // For example close a unique system or process global resource printf(" << Singleton closes the global resouce.\n"); } ////////////////////////////////////////////////////////////////////// void dynamic_singleton::example(int cookie) { printf("%s(%d)\n", __FUNCTION__, cookie); } [/CODE] [CODE:main.cpp] #include "dynamic_singleton.h" #include <iostream> #include <boost/thread.hpp> struct singleton_user { explicit singleton_user(int num) : num_(num) { } void operator()() { using namespace std; printf("%d uses singleton ...\n", num_); dynamic_singleton::shared_t s = dynamic_singleton::get_instance(); s->example(num_); } int num_; }; int main(int argc, char* argv[]) { boost::thread t1( singleton_user(1) ); boost::thread t2( singleton_user(2) ); boost::thread t3( singleton_user(3) ); boost::thread t4( singleton_user(4) ); boost::thread t5( singleton_user(5) ); t1.join(); t2.join(); t3.join(); t4.join(); t5.join(); return 0; } [/CODE]

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[interprocess]Named mutex question
by Eugen Stoianovici 26 Jul '08

26 Jul '08

Is there a way to free a mutex which was locked by a process that died? I'm using a named mutex to synchronize access for some processes on a windows machine. One of those processes died while holding the mutex and now i can't get access to it (not even after killing every process that had any access to it). Is there a way to handle this situation through code?

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Re: [Boost-users] Boost.Date_Time - How to measure time elapsed?
by Tan, Tom (Shanghai) 26 Jul '08

26 Jul '08

>I've been struggling with how to use the Date_Time library to measure >time elapsed (like to measure how long code takes to execute). >Could somebody provide me with an example? Resolution should be around >msec. I could not find any in the reference that particularly >addresses this. I would suggest using boost::timer instead. It's quite simple: #include <boost/timer.hpp> boost::timer t; // code to be measured.... Double e = t.elapsed(); t.restart(); // code to be measured.... e = t.elapsed();

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MPL and Fusion ADL problem
by Joel FALCOU 26 Jul '08

26 Jul '08

Hi, I wanted to know how large can be the "fixing" of MPL/Fusion ADL for function and/or meta-function with somehow common name (length,size etc) ? Not sure if I am alone but I feel clumsy to "hide" fusion types from template argument list just so my own size() function don't conflicts with boost one. Considering the task, if it' sdoable but long, I can help by doing some of it myself. Of course, if there is smarter way to do so, let me know :) Thanks in advance -- Joel FALCOU Research Engineer @ Institut d'Electronique Fondamentale Université PARIS SUD XI France

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[Serialization, Signals?] Memory leaks while deserializing derived type
by Brad Anderson 26 Jul '08

26 Jul '08

I'm getting memory leaks when deserializing objects and I can't figure out what I'm doing wrong. I'm using VC++ 2005. I've boiled it down to the following code: #include <fstream> // include headers that implement a archive in simple text format #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/shared_ptr.hpp> #include <boost/shared_ptr.hpp> #include <boost/signal.hpp> // memory leak detection #ifdef _MSC_VER # include <valarray> // doesn't like the free() replacement macro # define _CRTDBG_MAP_ALLOC # include <stdlib.h> # include <crtdbg.h> #endif using boost::signal; class Base : public boost::enable_shared_from_this<Base> { public: typedef boost::shared_ptr<Base> sptr; //virtual ~Base() { } // uncommmenting this causes leaks to disappear private: virtual int virt() = 0; // commenting this line causes leaks to disappear friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { } }; class Derived : public Base { private: int virt() { return 0; } friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & boost::serialization::base_object<Base>(*this); } signal<void (int, const Base::sptr&)> m_derivedSignal1; }; int main(int argc, const char* argv[]) { #ifdef _MSC_VER _CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF ); #endif { Base::sptr loose_derived(new Derived()); } // no leak // create and open a character archive for output std::ofstream ofs("temp_serialize_file"); Base::sptr d_instance(new Derived()); // no leak std::vector<Base::sptr> d_list; d_list.push_back(d_instance); // save data to archive { boost::archive::text_oarchive oa(ofs); oa.register_type<Derived>(); // write class instance to archive oa & d_list; // archive and stream closed when destructors are called } // load data from archive std::vector<Base::sptr> loaded_d; { std::ifstream ifs("temp_serialize_file", std::ios::binary); boost::archive::text_iarchive ia(ifs); ia.register_type<Derived>(); // read class state from archive ia & loaded_d; // archive and stream closed when destructors are called // loaded instance has leak in memory allocated in boost signals } return 0; } Any ideas would be very appreciated. Brad Anderson

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bundled graph property access?
by Jeffrey Trull 26 Jul '08

26 Jul '08

Hi all, I've found very few references to the use of bundled properties for graph properties, as opposed to edge and vertex properties. Are these supported? I find that I can supply a bundled property type name for the adjacency_list constructor, but cannot use "get_property" to access individual field values. This type of syntax works: adjlist.m_property.fieldname = whatever; but this does not: get_property(adjlist, &graphproptype::fieldname) = whatever; although it seems like the second form would be proper (for data hiding, and also the documentation suggests this is right - at least for old-style internal properties). To be specific, the following code does not compile: // test case for bundled graph properties #include <boost/graph/adjacency_list.hpp> #include <iostream> using namespace std; using namespace boost; /// circuit graph vertex properties struct VertexProps { }; /// circuit graph edge props struct EdgeProps { }; /// graph properties struct GraphProps { int blah; }; typedef adjacency_list<vecS, // storage for vertices vecS, // storage for edges directedS, // edges are directed VertexProps, EdgeProps, GraphProps> TestGraph; int main(int argc, char **argv) { TestGraph mygraph; set_property(mygraph, &GraphProps::blah, 1); } /usr/include/boost/graph/adjacency_list.hpp: In function void boost::set_property(boost::adjacency_list<OutEdgeListS, VertexListS, DirectedS, VertexProperty, EdgeProperty, GraphProperty, EdgeListS>&, Tag, const Value&) [with OEL = boost::vecS, VL = boost::vecS, DirS = boost::directedS, VP = VertexProps, EP = EdgeProps, GP = GraphProps, EL = boost::listS, Tag = int GraphProps::*, Value = int]: test_graphprops.cpp:29: instantiated from here /usr/include/boost/graph/adjacency_list.hpp:433: error: no matching function for call to get_property_value(GraphProps&, int GraphProps::*) Any suggestions? Thanks and Regards, Jeff Trull

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Problem including boost/shared_ptr.hpp
by Marcelo Tomim 25 Jul '08

25 Jul '08

Hello Everyone, I have been trying to include boost/shared_ptr.hpp in a project I am working on, but the compiler keeps giving me the following errors: /usr/include/boost/shared_ptr.hpp:341: error: expected unqualified-id before string constant /usr/include/boost/shared_ptr.hpp:346: error: expected unqualified-id before string constant /usr/include/boost/shared_ptr.hpp:352: error: expected unqualified-id before string constant /usr/include/boost/shared_ptr.hpp:357: error: expected unqualified-id before string constant /usr/include/boost/shared_ptr.hpp:362: error: expected unqualified-id before string constant However, the most mind-boggling part is that if I include the same header file in a program by itself (i.e., outside my project) it compiles fine. Can anybody help me? I really appreciate any suggestion. Regards, Marcelo Aroca Tomim

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Re: [Boost-users] Asio - Errors (Igor R)
by Brian T Crowder 25 Jul '08

25 Jul '08

-----Original Message----- From: Igor R <boost.lists(a)gmail.com> Sent: Friday, July 25, 2008 10:20 AM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Asio - Errors (Igor R) > I guess this means the socket itself is invalid but if i put the local end > point into the constructor for the socket_ as below it works fine. > > socket_(io_service, udp::endpoint( udp::v4(), port ) ) According to the ASIO reference: http://www.boost.org/doc/libs/1_35_0/doc/html/boost_asio/reference/basic_da… "This constructor creates a datagram socket and automatically opens it bound to the specified endpoint on the local machine. " In your example, the socket was created but it's not "open" yet, (so it doesn't have a valid handle). So before you bind() it, you have to open() it: http://www.boost.org/doc/libs/1_35_0/doc/html/boost_asio/reference/basic_da… _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Re: [Boost-users] Asio - Errors (Igor R)
by Tim Pynegar 25 Jul '08

25 Jul '08

Hi, This is the code i'm trying to run. server(boost::asio::io_service& io_service, short port) : io_service_(io_service), socket_(io_service) { try { udp::endpoint localEndpoint( udp::v4(), port ); socket_.bind( localEndpoint ); } catch( boost::system::system_error & error ) { std::cerr << "Exception: " << error.what() << "\n"; } socket_.async_receive_from( boost::asio::buffer(data_, max_length), sender_endpoint_, boost::bind(&server::handle_receive_from, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred) ); } and the error i get is "The file handle supplied is not valid" I guess this means the socket itself is invalid but if i put the local end point into the constructor for the socket_ as below it works fine. socket_(io_service, udp::endpoint( udp::v4(), port ) ) Thanks, Tim. > What message and the code of the system_error you've got? Probably, it > will explain the reason of the error. > By the way, most of the asio functions have no-throw version that gets > error_code& as a paramter and fills it in case of error. > >

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