April 2011 - Boost-users - lists.boost.org

[iostreams] Flushing problems with :filtering_ostream
by Bo Jensen 02 May '11

02 May '11

I had some older code which used to work before, but seem to have flushing problems now. The problem is I can not make boost::iostreams::filtering_ostream flush properly. Here is a snippet of my code, which is not compilable in the current form, since I just pulled it out of my own code. Here it goes : /* Helper class for writing gzipped files */ class gzip_sink { public: typedef char char_type; typedef boost::iostreams::sink_tag category; Log &Logger_; /* Logger */ boost::iostreams::filtering_ostream sink_; /* Sink used to push filters */ SlmOfstream outifstr_; /* Write stream to be pushed into sink */ std::wstring name_; /* Store name of attached file */ /* Constructor */ gzip_sink(const wchar_t *filename,Log &logger) SlmExcStartConstructor : Logger_(logger), name_(filename) { /* Open for write */ SlmOpenWriteFile(Logger_, name_.c_str(), outifstr_); /* Push gzip compressor */ sink_.push(boost::iostreams::gzip_compressor()); } SlmExcStopConstructor gzip_sink(const gzip_sink &rhs) SlmExcStartConstructor : Logger_(rhs.Logger_), name_(rhs.name_) { /* Open for write */ SlmOpenWriteFile(Logger_, name_.c_str(), outifstr_); /* Push gzip compressor */ sink_.push(boost::iostreams::gzip_compressor()); } SlmExcStopConstructor void Close() { sink_.reset(); } ~gzip_sink() { sink_.reset(); } /* Write function */ std::streamsize write( const char * s, std::streamsize n ) { /* Push write stream */ /* THIS IS THE HACK !!! WE NEED TO PUSH AND POP EACH TIME OTHERWISE SOME FLUSH IS NOT DONE!! */ sink_.push(outifstr_); sink_.write(s,n); sink_.pop(); return n; } }; I have to push and pop the stream on to the sink each time I write, which should only be done once in the constructor. It is clearly some flushing issue, but I have tried flushing in all places and no luck, any help ? If you think it looks a bit odd, it's because I use it together with boost::iostreams::code_converter<gzip_sink> to be able to use gzip with wide streams.

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[Spirit] Semantic actions (binary parser) - user error or bug?
by Vitaly Budovski 01 May '11

01 May '11

Hi, I've come across some behaviour with semantic actions that seems strange. I'm not sure if this is intended or if it is indeed a bug. Please see the attached test case.

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Boost deserialization of a derived class problem
by adrien.barral＠robopec.com 30 Apr '11

30 Apr '11

Hello, I have got a problem serializing data via TCP/IP. My application is highly inspired of the asio example on serialization. I have a server (my class "Recepteur"), and a client (my class "Logger"). I try to serialize two kine of data : - Loggable - HumanReadable. Loggable is a public base of HumanReadable, later I will have other Loggable class to serialize (OneDPlotable etc...). Look at my two serializable classes : [code] // file Loggable.hpp #ifndef LOGGABLE_HPP #define LOGGABLE_HPP #include #include #include #include #include class Loggable { protected : friend class boost::serialization::access; template void serialize(Archive& _archive, const unsigned int _version) { std::cout

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[Multi-Index] Categorised Container
by Hossein Haeri 30 Apr '11

30 Apr '11

Dear all, I have an application where something we call a "categorised container" with colleagues comes very hand. We do currently have a working version and I am looking to see whether it's possible to do some refactoring on that using Multi-Index. Here is an exemplified explanation of what constitutes a decision-making point for me. I would be pleased if anyone here could tell me whether this facility is available under Multi-Index: multi_index_container< T hashed_non_unique<...>, ordered_non_unique<...>> my_container; Now, is there anyway I can get all elements of my_container which have a certain hash and sorted according to the second index? In our own local terminology, we call that retrieving all the elements of a given CATEGORY in a sorted manner. (Sorry I'm not still fluent in the MultiIndex syntax to make that more formal with actual code.) TIA,--Hossein

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[Review] Boost.Convert library, last 3 days
by Edward Diener 30 Apr '11

30 Apr '11

This is a reminder that formal review of the Boost.Convert library by Vladimir Batov has 3 more days and ends on May 2. There have only been a small number of reviews and this is the last weekend to review the library. I am hoping that programmers who may have been busy during the week in their work will find time this weekend for a review. The review period ends on Monday at midnight, so please get your review in before the review period ends. If you intend to do a review of the library but feel you would be late in doing so, please contact me about it. *************** * Its Purpose * *************** The library builds on the past boost::lexical_cast experience, then takes those conversion-related ideas further to suit better today's applications and programing needs. It still offers simple, minimal interface, familiar conversion behavior and additionally provides: * throwing and non-throwing conversion-failure behavior; * support for the default/fallback value to be returned when conversion fails; * two types of the conversion-failure check - basic/simple and better/safe; * formatting support based on the standard std::streams and std::stream-based manipulators (like std::hex, std::scientific, etc.); * support for different locales; * support for boost::range-compliant char and wchar_t-based containers; * no DefaultConstructibility requirement for the Target/Destination type; * consistent framework to uniformly incorporate any type-to-type conversions, extensibility and additional room to grow. With its present support for string-to-type and type-to-string conversions it is an essential tool for applications making extensive use of configuration or MS-Windows-Registry-style files or having to process/prepare considerable amounts of data in, say, XML, etc. More so, it is easily extendable to accommodate, specialize and uniformly deploy new user-defined type-to-type conversions. ******************* * Where to get it * ******************* You can get the library, using Subversion, from https://svn.boost.org/svn/boost/sandbox/convert. The HTML documentation is part of the distribution and can be found at libs/convert/index.html in the distribution above. ******************** * Writing a review * ******************** The reviews and all comments should be submitted to the developers list, and the email should have "[convert] Review" at the beginning of the subject line to make sure it's not missed. Please explicitly state in your review whether the library should be accepted. The general review checklist: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Edward Diener, Review Manager

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[units][phoenix] static physical constants don't play well with phoenix?
by alfC 30 Apr '11

30 Apr '11

Hi, This post is just to point out a deficiency of either boost.phoenix or boost.units and see if there are workarounds. Phoenix 3 now plays well with Boos.units quantities out of the box but for some reason it does not play well with boost.units static physical constants. Like in the following example. This is because the constant 'hbar' is not a normal quantity type but a boost::units::constant< ... hbar_t > type. do you think physical constants could be defined as normal quantities in the future so it can play well with phoenix? #include<iostream> #include<boost/units/systems/si/io.hpp> #include<boost/units/systems/si/codata_constants.hpp> #include<boost/phoenix/phoenix.hpp> int main(){ using namespace boost::units; using namespace boost::phoenix; using namespace boost::phoenix::arg_names; quantity<si::action> const hbarvar = boost::units::si::constants::codata::hbar; std::clog << (arg1 * hbarvar)(5.) << std::endl; // works std::clog << (arg1 * boost::units::si::constants::codata::hbar)(5.) << std::endl; //doesn't work return 0; }

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Re: [Boost-users] [Multi-Index] Categorised Container
by Hossein Haeri 29 Apr '11

29 Apr '11

Hi Marsh, multi_index_container < T hashed_non_unique<...>, ordered_non_unique<...> > my_container; > So are you expecting hash collisions and doing something useful with > them? This is interesting, can you explain more about the problem and > why this is useful? Sure. Take T = pair<TimeStamp, shared_ptr<B> > where B is some base class for a hierarchy in my application. B has a pure virtual member function called id() which returns the same string for any instance of a class D, where D is derived from B. I will need to have all the instances the dynamic type of the second element of which is of D, but sorted according to TimeStamp's operator <. My idea was to get the first index in my_container to be this id() member function and the second index to be operator < (const TimeStamp&, const TimeStamp&). Is that doable in Multi-Index? > I think you're on the right track by calling them 'categories' and > suggest you not try to overload it with the hash value used to index the > collection (even if they happen to be the same). Sorry but I'm not sure I can follow your English here. Would you mind paraphrasing it if the issue is still important? > If you didn't want to store redundant data in T, you could define a key > extractor which runs your preferred hash function to calculate the > category on the fly. This much redundancy is not a matter for me. But, I'd rather not calculate the category on-the-fly for this container is going to be heavily accessed (and also populated/garbage-collected) for every D which derives from B. Does that make it easier to answer my questions? TIA, --Hossein

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ning Boost Regression Tests
by Ted Byers 29 Apr '11

29 Apr '11

I have been using boost for quite a while (for years I used boost without running any tests other than those I wrote myself), and am now looking at running the regression tests. I found the statement: "To run every library's regression tests, run bjam from Boost's /status directory." What I haven't found is how to view the results of that testing on my own machine. I don't know if that is a catastrophic failure of the test script, or if I just didn't invoke bjam correctly. I ran bjam (in cygwin's bash, on Windows 7), without any arguments, in boost's status directory, and it executed a lot of tests. Obviously, that produced a lot more output than can be copied here, but the last few lines of output (after many many hundreds of lines of output) were: 1 [main] bjam 9280 fhandler_dev_zero::fixup_mmap_after_fork: requested 0x772B0000 != 0x0 mem alloc base 0x772B0000, state 0x1000, size 8192, Win32 error 487 263 [main] bjam 9280 C:\cygwin\home\Ted\boost_1_46_1\bjam.exe: *** fatal error - recreate_mmaps_after_fork_failed Stack trace: Frame Function Args 0028E5D0 6102796B (0028E5D0, 00000000, 00000000, 74C98458) 0028E8C0 6102796B (6117EC60, 00008000, 00000000, 61180977) 0028F8F0 61004F1B (61180DAC, 00000000, 61180DA6, 0041A000) 0028F930 610061B1 (00000060, 02000000, 6116A724, 6116A720) 0028F960 610064C0 (00000000, 00000002, 00000000, 75053480) 0028FA20 6106FC15 (61000000, 00000001, 0028FD24, 00000001) 0028FA40 77169960 (6106F960, 61000000, 00000001, 0028FD24) 0028FB34 7716D8C9 (0028FD24, 7EFDD000, 7EFDE000, 7723206C) 0028FCB0 771837EE (0028FD24, 77130000, 77AB63F9, 00000000) 0028FD00 77182187 (0028FD24, 77130000, 00000000, 00000000) 0028FD10 77169E89 (0028FD24, 77130000, 00000000, 0001002F) End of stack trace 0 [main] bjam 8628 fork: child -1 - died waiting for longjmp before initialization, retry 0, exit code 0x100, errno 11 vfork: Resource temporarily unavailable Obviously the last test executed failed, but I found no summary of the results, nothing to indicate whether or not most of the built library was built correctly. Did the regression test script abort without producing the summary, or do I need to pass some argument to tell it to display a summary (I had in mind the kind of output you get when building gcc, and you execute 'make check' before executing 'make install', as one doesn't want to install a library or anything else that didn't get built correctly)? Thanks Ted

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Boost in an MFC app on WinNT4
by tangleman＠secules.net 29 Apr '11

29 Apr '11

I am trying to modify a current MFC application running on Windows NT4 to use boost libraries for ethernet communcications (originally, it used CommX for serial) and general increased performance, effieciency, and clarity of code. I started out modifying it in VS2010, but I found that I was unable to produce a valid NT4 app with VS2010. I googled the issue and found that VS2005 was the last version able to create an NT4 app. I got everything to compile in VS2005, but found that I had to change certain #define statements in stdafx.h in order to get the app to run on NT4. However, even after doing that, when I execute the program on NT4, it immediately quits with no error. It doesn't show anything. I even checked the Task Manager processes while executing it. It is like it never executed at all. I got desperate and tried compiling the app in VS2003, but I got so many errors that I gave that up. My last attempt was VC6, but again, I got 262 errors and started wondering whether it was even possible for boost to run in VB6 or on an NT4 machine. This is a very tight-schedule project, so any (prompt) help would be very appreciated! Thank you!

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[boost::fusion] map or set uniqueness guarantees
by Ovanes Markarian 29 Apr '11

29 Apr '11

Hello *, I am wondering if I should expect some uniqueness guarantees on contained element from fusion set or map containers? In this example: struct print_value { template<class T> void operator()(T& v)const { cout << typeid(T).name() << " has value: " << v << endl; } }; boost::fusion::set<int, int, int> s; boost::fusion::for_each(s, print_value()); I get 3 lines - one for each int I put in. I would expect only one line. What are my expectations for at_key? Which int would it return? Which type is going to be returned after I inserted the same type again? May be the better question would be, is the new type inserted as the head element or at the end of the underlying list? Many thanks for the anserws? With Kind Regards, Ovanes

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