March 2011 - Boost-users - lists.preview.boost.org

[GIL] write gray32fc_view_t to PNG
by Alex Flint 07 Mar '11

07 Mar '11

Hi there, I'm trying to write a grayscale image of 32-bit floats to a file. I understand that I need to construct some kind of color converted view but I can't find much documentation on this. So far I have gray32fc_view_t view = ....; png_write_view(file, view); Which gives me a static assertion failure (I suppose png_write_view can't handle 32-bit float views directly). Cheers, Alex

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GUI creation for boost::graph
by Bastien ROUCARIES 07 Mar '11

07 Mar '11

Hi, I whish to create a boost graph gui using qt However I have a problem I do not know how to link qt to boost graph. If I use bundle property of qt object could I get next and previous node from the qtobject? I am thinking about using a sets indexed by qtobject adress but I seems really painfull for managing memory. Particularly I want my implement my algorigthm on the graph and able to modify the graphical object from the boost::graph but also able to modify the graph from graphical qt object Any ideas? Bastien

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[gil] inverting alpha channel
by Alex Flint 07 Mar '11

07 Mar '11

Hi there, I have RGBA images using alpha=0 as opaque and alpha=255 as transparent. Is there any way that I can get png_write_view to use this convention without actually changing the data? Cheers, Alex

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[GIL] IO Errors
by Szymon Gatner 07 Mar '11

07 Mar '11

Hi, Why calls like png_read_image that take actual filename to load do not throw an exception that carries that filename? cheers, Szymon

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[BGL] depth first search : forcing backtrack
by andreas tanner 07 Mar '11

07 Mar '11

I understand that for early exit from a depth_first_search, I use exceptions thrown in a visitor. Now how can I force not a complete exit, but just an immediate backtrack towards the root node?

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[network] 0.9-devel and BOOST_NETWORK_NO_LIB
by Dean Michael Berris 07 Mar '11

07 Mar '11

Hi Everyone, I just recently finished a consulting project that tied me up good the past three months. Now that I'm pretty much free again to work on cpp-netlib, I went for the things that have been brought up most recently on the list (and the Boost developers mailing list): 1. The server tests that used a different port each, configurable at the command-line with a default. This is already in 0.9-devel. 2. An option to turn off the required external library to be linked with a macro (BOOST_NETWORK_NO_LIB). With this macro defined before any cpp-netlib headers are included (or on the command line) the functions that were made extern or just free functions at namespace level are marked 'inline' and have their definitions pulled in accordingly in each translation unit. This addresses Jeff Garland's and others' concern of the need for an external library when using cpp-netlib when it's always been header-only until 0.9. I'm still wrestling with the thought of making the header-only behavior a default, but I'm not married to the "external library as default" decision either. 3. A consistent look/view between server-side request/response objects and client-side request/response objects. Now they can be dealt with using the same directives and modifiers. 4. Starting to change the library name to Boost.Network (after the suggestions). #2 is still undocumented, but I am going to be including a Doxygen-Sphinx bridge that would allow us to write documentation in-line on the types and have Doxygen invoked when the Sphinx documentation is built. I found a Sphinx extension to do that and it looks like it can be bundled with cpp-netlib as well (because it's under a BSD license) -- it's called "breathe" and can be found here: http://michaeljones.github.com/breathe/ #3 has been in the branch for a while already and it should be doable to back-port some of the things to the 0.8 line. #4 is largely a documentation matter. I have decided that in order for the development of the network library to scale, that I would spear-head a mini-community effort that would be called "The C++ Network Library Project" taking in a diplomatic and consensus-building approach. This way those willing to contribute to the effort can help with setting the direction of the library, the design decisions, etc. with me starting as the "benevolent dictator" and letting more people jump into the fray and becoming co-maintainers and regular contributors. There are already a couple of people (Oleg Malashenko and Emre Turkay) who have recently contributing to the project that I would like to thank, and also give the chance to get a bigger role in the development of the library going forward. So for now the focus is still to get a review-ready library for inclusion in Boost that would be called Boost.Network. I think 0.9 will be ready in a couple of days and will be a the pre-1.0 snapshot that will be submitted for review, getting all the required documentation in place. At this time I'm still looking for able and willing review managers. Feedback would be most definitely appreciated. -- Dean Michael Berris http://about.me/deanberris

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[asio] negating address_configured
by Alexander Lamaison 06 Mar '11

06 Mar '11

What is the correct way to negate the (default) resolver flag, address_configured? On Windows, at least, specifying address_configured (which translates to AI_ADDRCONFIG) has a nasty side effect. If the 'external' network is down, the resolver can no longer resolve the "localhost" address. More here http://src.chromium.org/viewvc/chrome/trunk/src/net/base/host_resolver.cc?r… address_configured is the default flag for ip::basic_resolver_query so I need to specify a flag that turns it off. In the underlying addrinfo struct this would just mean specifying 0 as the flag but that isn't an option with ASIO as far as I can tell. How would I do this? Thanks! Alex -- Easy SFTP for Windows Explorer (http://www.swish-sftp.org)

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Boost::asio, complexity
by Dhaivat Pandya 06 Mar '11

06 Mar '11

Hello everyone. I've been using Boost::Asio recently for tasks that one would often use languages such as Python or Perl for (e.g. sending GET requests), but I use C++ and ASIO since: 1) I need substantial speed 2) I just like C++ However, I notice that even though Asio works wonderfully for larger, asynchronous projects, it gets in the way while doing smaller, more routine tasks. And, asio also is not a miniscule library and when creating binaries, one is often including things he/she wouldn't need. So, I wrote a small library (<500 LOC) that basically lets you pretend that a socket is a stream and you can use it like std::cout and std::cin. Would anyone consider having this included in the Boost repository, or even merged with Asio (the former is preferable because of the binary size reason)? It currently works on Linux, and I'm working on compatibility with Windows. An example of code you can write with it: http://ideone.com/2GHe5 (GETs data from google.com) Right now, all calls are blocking, so that non-blocking can be done with Asio, which is more powerful.

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Help needed to reconnect a socket to a new endpoint with Boost asio in Windows
by Adolfo Jimenez 06 Mar '11

06 Mar '11

I'm having trouble when in Windows XP, try to connect a socket to an endpoint after being connected to another. This is the situation: a) The boost::asio::ip::tcp::socket is connected to a remote host (say pop.remote1.com) b) The transmission ends, and the socket is closed: socket_.shutdown(boost::asio::ip::tcp::socket::shutdown_both, error); socket_.close(error); Then, when trying to connect to another host (say pop.remote2.com) using the same process that in a), the proccess returns without error, but the socket remains closed. Note that when using pop.remote2.com as the first connection, the things run Ok, and the same problem arises if try to connect to pop.remote1.com after closing. In both situations there are not pending processes in the attached io_service. I tried to open the socket before the reconnection, but the result remains the same. That is, the result is the same if after closing the previous connection with. socket_.shutdown(...); socket_.close(...); is used socket_.open(...); socket_.async_connect( ... ); or just socket_.async_connect( ... ); The questions are: Is that reconnection admissible? Is that the supposed correct process? Thanks in advance.

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Boost.fusion 1.42 / Gcc 4.5: what is this error trying to tell me? (Works with Gcc 4.4)
by Joost Kraaijeveld 06 Mar '11

06 Mar '11

Hi, I have code that compiles OK with Gcc 4.4 but fails with 4.5 and I cannot understand what the error I get from the compiler means. Maybe someone here can give me a suggestion? The error: In file included from /usr/include/boost/fusion/algorithm/query/find.hpp:13:0, from /usr/include/boost/fusion/sequence/intrinsic/has_key.hpp:12, from /usr/include/boost/fusion/sequence/intrinsic.hpp:16, from /usr/include/boost/fusion/sequence.hpp:12, from ../../../library/../include/Danu/DanuModelObjects/User.hpp:11, from ../../../library/../include/Danu/DanuViewObjects/UserViewObject.hpp:12, from ../../../library/../include/Danu/DanuViewObjects/UserDialog.hpp:15, from ../../../library/../include/Danu/DanuModelObjectsFactory/UserCreatorFunction.hpp:10, from ../../../library/DanuModelObjectsFactory/UserCreatorFunction.cpp:7: /usr/include/boost/fusion/iterator/key_of.hpp: In instantiation of 'boost::fusion::result_of::key_of<mpl_::arg<1> >': /usr/include/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:85:88: instantiated from 'const int boost::mpl::aux::template_arity_impl<boost::is_same<boost::fusion::result_of::key_of<mpl_::arg<1> >, Danu::UserCreator::objectId>, 1>::value' /usr/include/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:93:261: instantiated from 'const int boost::mpl::aux::template_arity<boost::is_same<boost::fusion::result_of::key_of<mpl_::arg<1> >, Danu::UserCreator::objectId> >::value' /usr/include/boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:98:30: instantiated from 'boost::mpl::aux::template_arity<boost::is_same<boost::fusion::result_of::key_of<mpl_::arg<1> >, Danu::UserCreator::objectId> >' /usr/include/boost/fusion/algorithm/query/detail/find_if.hpp:184:9: instantiated from 'boost::fusion::detail::static_find_if<boost::fusion::basic_iterator<boost::fusion::map_iterator_tag, boost::fusion::map<boost::fusion::pair<Danu::UserCreator::objectId, Danu::ObjectId>, boost::fusion::pair<Danu::UserCreator::userId, int>, boost::fusion::pair<Danu::UserCreator::userName, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::password, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::firstName, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::infix, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::lastName, std::basic_string<char> > >::category, const Danu::UserCreator::UserCreationArguments, 0>, boost::fusion::basic_iterator<boost::fusion::map_iterator_tag, boost::fusion::map<boost::fusion::pair<Danu::UserCreator::objectId, Danu::ObjectId>, boost::fusion::pair<Danu::UserCreator::userId, int>, boost::fusion::pair<Danu::UserCreator::userName, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::password, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::firstName, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::infix, std::basic_string<char> >, boost::fusion::pair<Danu::UserCreator::lastName, std::basic_string<char> > >::category, const Danu::UserCreator::UserCreationArguments, 7>, boost::is_same<boost::fusion::result_of::key_of<mpl_::arg<1> >, Danu::UserCreator::objectId> >' /usr/include/boost/fusion/algorithm/query/find.hpp:46:43: instantiated from 'boost::fusion::result_of::find<const Danu::UserCreator::UserCreationArguments, Danu::UserCreator::objectId>' /usr/include/boost/fusion/sequence/intrinsic/at_key.hpp:37:17: instantiated from 'boost::fusion::extension::at_key_impl<boost::fusion::map_tag>::apply<const Danu::UserCreator::UserCreationArguments, Danu::UserCreator::objectId>' /usr/include/boost/fusion/sequence/intrinsic/at_key.hpp:70:9: instantiated from 'boost::fusion::result_of::at_key<const Danu::UserCreator::UserCreationArguments, Danu::UserCreator::objectId>' ../../../library/DanuModelObjectsFactory/UserCreatorFunction.cpp:40:83: instantiated from here /usr/include/boost/fusion/iterator/key_of.hpp:38:9: error: invalid use of incomplete type 'struct boost::fusion::extension::key_of_impl<boost::fusion::non_fusion_tag>' /usr/include/boost/fusion/iterator/key_of.hpp:20:16: error: declaration of 'struct boost::fusion::extension::key_of_impl<boost::fusion::non_fusion_tag>' Snippets of relevant code (hopefully enough): - the first snipped is how I declare the boost::fusion::map - the second is how I use and where the error is (<--!!!!!!!!) ... namespace UserCreator { struct objectId; struct userId; struct userName; typedef boost::fusion::map < boost::fusion::pair< objectId, ObjectId >, boost::fusion::pair< userId, int >, boost::fusion::pair< userName, std::string > > UserArgs; struct UserCreationArguments : public MOCFunctionParameter, public UserArgs ... ... ModelObject* UserCreatorFunction::createObject( const MOCFunctionParameter* aMOCFunctionParameter /* = NULL */) const { ... if ( (arguments = dynamic_cast< UserCreator::UserCreationArguments* >(const_cast<MOCFunctionParameter*>(aMOCFunctionParameter))) ) { ObjectId& objectId = boost::fusion::at_key< UserCreator::objectId >(*arguments); <--!!!!!!!! int& userId = boost::fusion::at_key< UserCreator::userId >(*arguments); std::string& userName = boost::fusion::at_key< UserCreator::userName >(*arguments); ... TIA -- Met vriendelijke groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 web: www.askesis.nl

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