September 2006 - Boost-users - lists.preview.boost.org

Re: [Boost-users] Boost serialization : Possible to append to file?
by Robert Ramey 16 Sep '06

16 Sep '06

Daniel F. Savarese wrote: > In message <20060911172413.74527.qmail(a)web57207.mail.re3.yahoo.com>, > smith smit hson writes: >> This is regarding the boost serialization library. Is >> it possible to append to a pre-existing archive file? > > I don't think anyone's answered this yet. The answer is yes. Hmmm - that would surprise me. > > While on the topic of boost serialization, I'll add an unrelated note > that you cannot safely serialize objects from different threads when > using separate archive instances in each thread. Boost serialization > uses local static variables in places like > boost:archive::detail::oserializer::instantiate(), so even though > you're > using separate archive instances, there's only a single serializer for > a given archive type/object type pair. True - but this should be no problem since the the static object never changes. That is all the functions on this static object ar "const" so they should be re-entrant. Therefore, if you concurrently > serialize the same type of object with separate instances of the same > archive type, you can segfault. I don't see this. > The solution of course is to use > critical sections or delegate all serialization to a single thread. > But you wouldn't expect to have to do so when using separate > instances because the global behavior is not obvious to the API user. I don't think this should be necessary. If it is, then it is contraty to my intentation. Robert Ramey

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[boost::serialization] Convert enumeration to string and back again
by Graham Hudspith 16 Sep '06

16 Sep '06

Another "basic" question for the list again, apologies in advance. I have a class with a data member which is an enumeration, e.g.: typedef enum param_choice { PARAM_CHOICE_UINT8, PARAM_CHOICE_UINT16, PARAM_CHOICE_UINT32, PARAM_CHOICE_INT8, PARAM_CHOICE_BOOL } param_choice_e; I can quite happily user the Boost Serialization library to save and restore a class with a data member of this type: class Stuff { friend std::ostream& operator<<(std::ostream& os, const Stuff& stuff friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int file_version) { ar & BOOST_SERIALIZATION_NVP(choice); } param_choice choice; public: Stuff () {} Stuff (param_choice theChoice); }; This is using XML as the file-format. The data member appears in the file as an integer. However, what I would LIKE to do is output the value of "choice" as a string (e.g. instead of outputing <choice>2</choice>, the file contains <choice>UINT32</choice>). And do a conversion when I read it all back in again, of course. Can someone please provide some pointers to where I can find out how to do this? Or an example? Is the solution going to end up along the lines of: * Split the serialize into separate load and save routines * In the save, convert the data member into a string and output this to the archive * In the load, input from the archive into a string and then store this into the data member Best regards in anticipation, Graham.

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Boost serialization : Possible to append to file?
by smith smithson 16 Sep '06

16 Sep '06

Hello, This is regarding the boost serialization library. Is it possible to append to a pre-existing archive file? i.e. Create an archive file, serialize objects to it, close file, and then re-open file and append more serialized objects to it. Is this allowed? -Thanks! __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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unordered map base on how items are inserted.
by chun ping wang 16 Sep '06

16 Sep '06

I have a question on unordered_map. Are there are any boost library containers that acts like an associative array but also have the items base on how the order their inserted in. I.E. first item inserted is first one, second one is second. Thanks.

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program_options : Executing methods required for options_description before methods for command line options.
by Booster Booster 15 Sep '06

15 Sep '06

Hi, I have a list of options that I want to store before parsing the command line option. For example, po::options_description desc; // This has a couple of options. boost::program_options::variable_map options; po::store(po::command_line_parser(command_args).options(desc).run(), options); The problem is I want to execute the methods that correspond to 'desc' before the methods required by 'command_args' . Is there a way to populate the variable_map in a way such that I get the required sequence ? I did some reading of the docs, but couldn't find a way to do it. Any help would be appreciated. Thanks in advance, Sandy.

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calling a member function of a map iterator
by Alexander Shyrokov 15 Sep '06

15 Sep '06

I have a map<int,c*> and I would like to call a member function of the c* and provide a parameter to it. struct c{void f(char*){}}; typedef std::map<int,c*> TMap; TMap a; std::for_each(a.begin(),a.end(),boost::bind(&c::f,boost::bind(&TMap::value_type::second,_1)),NULL); I get "error C2091: function returns function" This is what I would like to replace with the for_each algorithm: for(TMap::iterator i=a.begin();i!=a.end();++i)(*i)->f(NULL); Thanks. -- Regards, Alexander. http://sjcomp.com

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Re: [Boost-users] Comments / Advice on using Boost Test Library
by Sohail Somani 15 Sep '06

15 Sep '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Dave Steffen > > I just wonder: whats the big deal with breaking all the > encapsulation > > rules to do unit tests? > > Do you mean: > "why are people breaking encapsulation rules for unit tests?" > or > "why do people worry about breaking encapsulation rules > for unit tests?" Second one. I was worried for a second there that there was something I hadn't thought about :) Thanks.

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Re: [Boost-users] Comments / Advice on using Boost Test Library
by Sohail Somani 15 Sep '06

15 Sep '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Aubrey, Jason > Note1: I've no idea if a formal name for this pattern exists, > if not it > does now :) > Note2: I recognize the security issues with this; however, if > it's truly > an issue I suppose the pImpl (i.e. pointer to implementation) > idiom can > be used in tandom so things are truly private from the client. I just wonder: whats the big deal with breaking all the encapsulation rules to do unit tests?

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bind, and member function with a parameter
by Alexander Shyrokov 15 Sep '06

15 Sep '06

I want to call a member function with a parameter from within an algorithm. http://boost.org/libs/bind/bind.html#with_algorithms gives an example: void animation::advance(int ms); std::vector<animation> anims; std::for_each(anims.begin(), anims.end(), boost::bind(&animation::advance, _1, ms)); I am using boost::lambda:: before _1. I get an error error C2825: 'F::result_type': cannot form a qualified name I am using MS VC7.1 and boost_1_33_1 Any ideas why this does not work? Thanks.

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Comments / Advice on using Boost Test Library
by Dave Steffen 15 Sep '06

15 Sep '06

Hi Folks, We've been happy Boost Test Library customers for over a year now, slowly building up a set of unit tests for a large legacy code base. There's no question that it's Good Stuff. Specifically, everything we do is some variation on a BOOST_AUTO_UNIT_TEST-y sort of thing; the extremely low amount of "typing overhead" is a big part of why so many people are writing unit tests (these unit tests are cheap, as unit tests should be). What I'd like to ask the Boost community about is this: how to go about unit testing private class methods. One answer is "don't; only unit test the public interface", which is fine as far as it goes. However, most of our work is extremely mathematical, so it's not uncommon to see something like class Base { ... public interface, etc ...}; class Derived : public Base { public: ... goodies in here ... private: double HelperFn1(); bool HelperFn2(int, double, KalmanFilter&); }; where HelperFn1 and HelperFn2 are extremely non-trivial mathematical operations. Yes, exercising the public interface will signal mistakes in the helper functions, but can't do much to poke at them in depth, or help pinpoint exactly what chunk of math isn't right. What we want is to be able to write unit tests that poke and prod such private member functions directly. Another answer is "give your class a friend "tester" class, that uses its frienship to give the unit tests access to the class' guts". We've been doing that for about a year now; not the most elegant, but an effective solution. Unfortunately, it doesn't work for the thing I wrote this afternoon; I'll skip the details. Another horrible, but effective, possibility is to #define private public #include "ClassToTest.h" ... (only in the unit test suites!) and muck about in the class's guts directly. This is the only way I know of to get into the rather complicated template-class-heirarchy-interface-wrapper thing that I just built. What kinds of techniques are you all using out there? Thanks very much for any comments! ---------------------------------------------------------------------- Dave Steffen, Ph.D. Software Engineer IV Disobey this command! Numerica Corporation ph (970) 419-8343 x27 fax (970) 223-6797 - Douglas Hofstadter dgsteffen(a)numerica.us

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