April 2008 - Boost-users - lists.preview.boost.org

How to set a search mask with wild card for directory_iterator ?
by Silvio Reis Junior 04 Apr '08

04 Apr '08

Hi all! I'm trying to learn how to use boost and for a first exercise I chose to create a class to perform files enumeration. The code below works fine but I didn't find a way to set a search mask with wild card, example: *.jpeg or test???.* How can I do it? //------------------------------------------------------------------- VOID CFileSearch::InternalSearch( path RootDir, string Mask ) { directory_iterator EndDirItr; string OutPut; for ( directory_iterator DirItr( RootDir ); DirItr != EndDirItr; ++DirItr ) { if ( is_regular( DirItr->status() ) ) { m_FileCount++; OutPut = "FILE: " + DirItr->path().string(); _tprintf( _T( "%s\n" ), OutPut.c_str() ); } else { InternalSearch( DirItr->path(), Mask ); } } } //------------------------------------------------------------------- VOID CFileSearch::Search( string RootDir, string Mask ) { path TempRootDir = system_complete( path( RootDir, native ) ); if ( exists( TempRootDir ) == true ) { InternalSearch( TempRootDir, Mask ); _tprintf( _T( "%d files found\n" ), m_FileCount ); } }

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[boost::function] Getting base class pointer of functor ?
by Johannes Stallkamp 04 Apr '08

04 Apr '08

Hello there, Short version: Are there any reasons, why base class access is currently not allowed/implemented in boost::function (via target() function)? Long version/explanation/scenario: I have a class using boost::any which I use for data exchange between different modules of my program. Some modules are able to process the data if it contains "numbers" (in contrast to other arbitrary data structures), ie. basically POD. These modules do not necessarily bother what _exact_ type the provided number is (some do, some don't) and might just use it as, e.g. double, so they don't care what type was originally inserted into the boost::any as long as they get a double-converted value out of it. As boost::any only allows to get the original type out of it with any_cast<T>, the class provides a set of conversion functions like boost::function< int () > toInt; boost::function< short () > toShort; ... ... struct Converter_base { Converter_base( const boost::any* a ) : m_any(a) {}; public: const boost::any* m_any; }; template< typename Target, typename Source > struct Converter : public Converter_base{ Converter( const boost::any* a ) : Converter_base(a) {}; T operator()() const { return boost::numeric_cast<Target>( * boost::any_cast<Source>( Converter_base::m_any ) ); }; }; template< typename SourceType > void setValue ( SourceType& value ) { m_value = value // this is boost::any toInt = Converter< int, SourceType > ( &m_value ); toShort = Converter< short, SourceType > ( &m_value ); ...... } This allows me to ask for the value converted to my desired type and receiving an exception if the conversion is not possible (or produces overflows). The problem is that the functor Converter is not copy-constructible because of the pointer to boost::any. So I have to take care of setting the correct pointer in the copy constructor of my data exchange class. In order to get the pointer to the converter functor and thus to the mep_any, I need to know SourceType. But since the module that provides the data and the module that consumes the data don't know about each other, the consumer doesn't know SourceType and cannot compile the appropriate copy constructor. Since mep_any is independent from the template arguments, I moved it to a base class Converter_base and let Converter inherit from it. Now, I want to access the functor via toInt.target<Converter_base>() in order to access/update the mep_any. But target() returns 0 .... I checked function/function_base.hpp and found: // DPG TBD: Since we're only storing a pointer, it's // possible that the user could ask for a base class or // derived class. Is that okay? Are there any reasons, why base class access is currently not allowed/implemented? Sorry that the post got a bit long, but I hope at leas my intention got somehow clear... Johannes

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Re: [Boost-users] serialization, 1.34/1.35 difference: serializing a vector
by Filip Peters 04 Apr '08

04 Apr '08

Huh? I just got the whole trunk, and built it. Still the same problem: it can't read in std::vector<int> created with 1.34.1 Anyway how would a fix in trunk help? -I can't use the released version 1.35, as it can't read in older files. -I can't use trunk in our program, only released/tested versions. I just tried compiling with trunk, seems there are some other issues in other libraries that would take some work. (something went missing in the signals library) Yes, I can add item_version into the optimised versions of vector.hpp, but how is it going to work in 1.36? If you'd tell how you would fix it in the 1.35 version, I could use just that fix in our version, untill 1.35.1 or 1.36 comes out. Without ending up with our own branched version that's always incompatible with the released versions. thanks, Filip Peters ----- Original Message ---- From: Robert Ramey <ramey(a)rrsd.com> To: boost-users(a)lists.boost.org Sent: Thursday, April 3, 2008 8:32:52 AM Subject: Re: [Boost-users] serialization, 1.34/1.35 difference: serializing a vector Looks like the trunk version is already fixed. Robert Ramey "Filip Peters" <filippeters(a)yahoo.com> wrote in message news:753101.4971.qm@web30701.mail.mud.yahoo.com... I looked a bit deeper into the code and found this: in 1.34.1, a vector would use the code from collections_save_imp.hpp, which contains the following: unsigned int count = s.size(); ar << BOOST_SERIALIZATION_NVP(count); if(3 < ar.get_library_version()){ const unsigned int item_version = version< BOOST_DEDUCED_TYPENAME Container::value_type >::value; ar << BOOST_SERIALIZATION_NVP(item_version); } in 1.35.0, there is an "optimized" version in vector.hpp, const collection_size_type count(t.size()); ar << BOOST_SERIALIZATION_NVP(count); if (!t.empty()) ar << make_array(detail::get_data(t),t.size()); without the item_version. Loading a vector of a type like int or double, created in 1.34 won't work in 1.35. Filip Peters. Haven't used boost's trac before, but I'll enter it tomorrow. In the meantime, adding item_version into the optimized versions seems to solve my problem, except I have to make sure it doesn't break in the next version. ----- Original Message ---- From: Robert Ramey <ramey(a)rrsd.com> To: boost-users(a)lists.boost.org Sent: Wednesday, April 2, 2008 6:30:01 PM Subject: Re: [Boost-users] serialization, 1.34/1.35 difference: serializing a vector Hmm I don't recal where that might have come from. Open a TRAK item. Robert Ramey "Filip Peters" <filippeters(a)yahoo.com> wrote in message news:859190.51711.qm@web30705.mail.mud.yahoo.com... I just tried serializing a simple vector, std::vector<unsigned int> vectortest; If I serialize out in 1.34, I can't read it in in 1.35. xml result from 1.35: <vectortest> <count>3</count> <item>1</item> <item>2</item> <item>3< /item> </vectortest> from 1.34: <vectortest> <count>3</count> <item_version>0</item_version> <item>1</item> &n bsp; <item>2</item> <item>3</item> </vectortest> Notice the item_version, this causes an exception when reading it in with 1.35.... I need a way to get the behavior from 1.34 back.... Otherwise my files aren't readable anymore. small testprogram: #include <boost/config.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/archive/xml_iarchive.hpp> //#include <boost/archive/binary_iarchive.hpp> //#include <boost/archive/binary_oarchive.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/export.hpp> #include <fstream> #include <iomanip> int _tmain(int argc, _TCHAR* argv[]) { std::vector<unsigned int> testvector; testvector.push_back(1.); testvector.push_back (2.); testvector.push_back(3.); //this in 1.34 std::ofstream ofs( "testing2.txt", std::ios::binary ) ; boost::archive::xml_oarchive oa(ofs); oa << boost::serialization::make_nvp("vectortest", testvector); ofs.close(); //do this in 1.35 try{ std::ifstream ofs( "testing2.txt", std::ios::binary ) ; boost::archive::xml_iarchive ia(ofs); ia >> boost::serialization::make_nvp("vectortest", testvector2); &nb sp; ofs.close(); } catch(boost::archi ve::archive_exception testexception){ //reading a file from 1.34, will end up here std::string error = testexception.what(); } return 0; } ____________________________________________________________________________________ You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access, No Cost. http://tc.deals.yahoo.com/tc/blockbuster/text5.com

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[StringAlgo] Need help to use find_format()
by Bruno Lalande 04 Apr '08

04 Apr '08

Hi, I'm having a hard time trying to use the find_format() function provided in the Algorithm/String library. In the examples provided in the Concepts page, 2 examples of finder and formatter are provided: simple_finder and simple_formatter. The first problem is a typing error in simple_finder that prevents it form compiling, I've opened a ticket to fix this (#1761). The second problem is that simple_finder uses a function called make_range that I can't find anywhere in the Boost headers. What is this function? Am I supposed to write it myself? The third problem is that I can't find any example of actual use of those classes. I thought that this: find_format(string("foobar"), simple_finder(), simple_formatter()); would compile and run (basically replacing the whole string by the same string), but after having tried to get rid of the second problem by de-templatizing the simple_finder to adapt it to string, it doesn't compile. But maybe I'm wrong in the way I did that: struct simple_finder { template<typename ForwardIteratorT> boost::iterator_range<ForwardIteratorT> operator()( ForwardIteratorT Begin, ForwardIteratorT End ) { return string( Begin, End ); } }; Can anyone help me? Bruno

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Boost Visualizers for MSVC 8/9 updated
by Filip Konvička 04 Apr '08

04 Apr '08

Hi Boost, a new visualizer for boost::optional was just added to http://svn.boost.org/trac/boost/wiki/DebuggerVisualizers#NativeCDebuggerVis… As always, the current visualizers can be checked out from the following url: https://svn.boost.org/svn/boost/sandbox/boost_docs/subprojects/DebuggerVisu… Thanks to Daniel Krügler for this one, and my apologies for the delay. Cheers, Filip

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[1.35] configuring for 'complete'
by Christoph Duelli 04 Apr '08

04 Apr '08

bjam has the option --build-type=complete Is it somehow possible (other than manually editing the Makefile) to specify this option when calling configure? (I'm asking because I'd like to script the build of Boost; and so far it only builds in release mode. I'd like to avoid to edit Makefile on any machine I need to build Boost on.) And: when I am using the (non-)multi-threaded boost libs, do I need to #define a variable so that the header-only libs are thread-safe too? Thank you, best regards Christoph

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[GIL] Default constructing pixels??
by John Femiani 04 Apr '08

04 Apr '08

I am used to explicitly invoking the default constructor to initialize values to 'zero', but that does not seem to work with GIL. In the following code: template<class View> void do_something(View const& img){ typedef typename View::value_type pixel_type; pixel_type black = pixel_type(); //I expect zero, I guess this may not always be black... //..... } The value held in 'black' turns out to be 205 (I think it is acting like uninitialized stack data). Is this the intended behavior? I have a slew of code that used to work this way and somehow now it does not - did this behavior change recently? In the meantime I just made a struct named black with a typecast operator enabled for gil pixels. -- John

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unordered_map memory footprint
by Robert Dailey 03 Apr '08

03 Apr '08

Hey guys, Hash tables are new to me since they have never been part of the C++ standard template library, and having started C++ as my first language I have never been exposed to them. Ever since unordered_map appeared in the Boost library, I've been trying to understand how they function in terms of functionality, memory, and performance. A major source of information has been from Wikipedia, specifically this page<http://en.wikipedia.org/wiki/Hash_table>. Below I have outlined a few questions concerning boost::unordered_map: 1. From what I've read, the performance of a hash table is O(1), however it mentions that depending on specific situations it may be O(n). Is this true with unordered map? If so, what conditions would force it to maintain O(n) complexity? 2. What is the memory footprint of an unordered_map? From my research, hash tables seem to be a simple wrapper over an array in that the size of the "internal array" in the hash table will contain as many elements as the largest hash value generated by one of the key elements. So if I put two elements in my hash table and the generated keys are 200 and then 1,000,000, then the hash table would be 1,000,000 elements in size (which is at least a megabyte of memory in the most optimistic scenario). This logic is rather ridiculous and impractical, so I am pretty sure I'm misunderstanding how the memory mechanics work under the hood for an unordered_map. Those are the biggest questions I have now and if I think of more I'll most certainly be providing follow-up posts. I thank everyone in advance for reading and helping.

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[iostreams] newline_filter problem
by Soren Soe 03 Apr '08

03 Apr '08

Hi, It appears boost::iostreams::newline_filter(posix) converts all CRs into LFs rather than just converting the sequence CRLF. In other words: "\rtext\r\r\n" is converted to "\ntext\n\n" when I would have expected "\rtext\r\n". Indeed the latter is what dos2unix does on my linux system. Is this a bug in the newline_filter? Thanks, Soren Soe

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[lexical_cast] for user type extensions.
by Balasubramanyam, Shivakumar 03 Apr '08

03 Apr '08

Hi, I need conversion from strings to integers. But the strings could also be hex numbers. So example is, typedef unsigned long hexType; hexType value; lexical_cast<HexType>("0xAABBCCDD"); How do we extend the boost::lexical_cast to support casting user defined types? I can perform this by specialization but those would need to be in boost namespace which does not seem to be a recommended way to add customizations. Thanks, Shiva

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