- Boost - lists.boost.org

[fsm review] Not quite a review
by Darryl Green 22 Aug '08

22 Aug '08

I don't know if I will have time to do a proper review of the library. The following are my notes on it so far. I've read the documentation for the libary, but haven't tried to use it. Good points: Simple. Relatively fast at runtime. Docs are quite good, but perhaps lack enough rationale style documentation on how the library models FSM concepts. Would benefit from some "how to" examples of more realistic usage and some "how to" docs on translating FSMs expressed using UML (or Harel) statecharts into a form implementable using FSM. Bad points: Unusual terminology. While there are obvious performance reasons for avoiding the Boost Statechart approach of applying an RAII model to state activation, it is not clear why at least basic concepts and terminology have not been used in FSM - especially as most Statechart terminology and FSM behavioural concepts are straight from UML terminology (it is a standard, you could pick another one, but why not stick with this one)? Note that this is *not* a request that the library include more features - just for some consistent ones. Some idiosyncratic behaviour. The FSM delivers the event to the on_process() handler in the "switched to" state when the transition is specified using the transition map, while delivering it to the on_process() handler in the current state if no transition map entry matches. There are warnings against mixing the transition map and switch_to() approaches to FSM specification, but even so it seems that the 2 uses of the on_process() handler are completely different. Would it not be better to have a model similar to Boost.Statechart where a custom reaction (implemented by a react() method) in a state is used to perform actions within the start state, generally including making a (gated) transition, while any action to occur on a transition is specified as part of the transition? Further, that transition action should be performed after the exit action of the current state and before the entry action of the new state. No event queuing mechanism, so no way to post an event while processing an event - although I see there has been some discussion about adding event deferral - which might be (almost) enough. Slow at compile time. I have not tested as yet, but if it is as slow as the mpl example state machine implementation, this will be a problem (I have previously had to abandon use of the MPL FSM due to compilation time issues on only moderately complex FSMs). Lacks real world use? I don't know if that is true, but I haven't seen anything other than toy examples. I was thinking that in the cases where the performance of Statechart was inadequate for complex augumented FSM implementation I would consider using FSM - but it would mean building a fair bit of additional scaffolding around FSM - maybe this should be part of the library? Or at least some examples of ideomatic use should be included? I found myself wondering if anyone had actually tried to use it in this way? Conversely, I don't find it compelling for implementing something like a lexer or even the terminal emulator example. What is the application domain? Not quite a conclusion: This is a hard one. At one extreme, Boost.Statechart is extremely powerful and well worth using in certain application domains (but there are performance implications), and at the other, as has been illustrated, various hand-rolled solutions of varying degrees of elegance get the job done. There seems to be a lot of space in between, and I'm not sure that the proposed FSM library fills enough of it.

2 3

[lambda][bind] trivial bind fails when lambda and bind are in the same source file
by Michael Marcin 22 Aug '08

22 Aug '08

My environment is VC9 SP1 and Boost 1.35. This problem also occurs in boost 1.36. I had some code using lambda which worked fine for several weeks until today when someone else included my header in his code which used bind. He told me my code was broken but my tests ran fine. It took us a few minutes to find the problem and I've distilled it to this trivial reproducible case. #include <boost/bind.hpp> #include <boost/lambda/bind.hpp> void foo( int ) { } int main() { using namespace boost::lambda; bind( &foo, _1 ); } Compiling this gives: error C2872: '_1' : ambiguous symbol 1> could be 'c:\vfx\third_party\boost\1_35_0\boost\lambda\core.hpp(69) : boost::lambda::placeholder1_type &boost::lambda::`anonymous-namespace'::_1' 1> or 'c:\vfx\third_party\boost\1_35_0\boost\bind\placeholders.hpp(42) : boost::arg<I> `anonymous-namespace'::_1' 1> with 1> [ 1> I=1 1> ] I can make the problem go away by changing main to int main() { using boost::lambda::_1; using boost::lambda::bind; bind( &foo, _1 ); } but the actual code uses a lot more lambda and the amount of using directives I would need makes the code longer than rolling my own functor. I could also alias lambda to make main look something like int main() { namespace bll = boost::lambda; bll::bind( &foo, bll::_1 ); } but this introduces a lot of noise into the lambda expression and makes complex lambdas unreadable. Is this accepted behavior? Thanks, Michael Marcin

4 5

[boost exception]complaint
by Robert Ramey 22 Aug '08

22 Aug '08

In the course of investigating some issues with the serialization library I had occasion to investigate boost/throw exception.hpp . I understood the original purpose of this header was to provide support for throw for both compilers which implemented exceptions and those that didn't (e.g. some embedded systems environment). Looking through this header - it seems that its function has changed completely. It now drags in a lot of machinery that no one who was using it before will need. It seems that the whole purpose of the header has been changed. I did review the documentation for boost exception and indeed, it now seems that boost/throw_exception does implement a different purpose. Besides imposing the requirement for RTTI - I have no idea what else this might break. Should all users of throw_exception be advised to recode? Could we not restore the orginal boost/throw_exception and make a differently named file like boost/exception/???.hpp. This would provide all the benefits of the new library to those who want and require them without requiring changes all over the rest of boost. Robert Ramey

7 15

Documentation Redux (was Re: Boost 1.36.0 release notice)
by Dean Michael Berris 22 Aug '08

22 Aug '08

On Mon, Aug 18, 2008 at 4:17 PM, John Maddock <john(a)johnmaddock.co.uk> wrote: > Robert Ramey wrote: >> >> LOL - of course it does. If regression testing were setup for >> boost tools, they would be demonstrated to be functioning as >> expected before they were used in the actual release process. >> Had this been procedure been in place, the issue raised >> above would not have occurred. > > This is a good point, in fact is there any reason why the doc build > shouldn't be part of the regression tests? > > Ah.... but it requires external tools that might not be available > (especially now that accumulators has introduced a dependency on Latex and > Ghostscript) :-( > I think this may be something that should be solved by policy rather than technical solutions. For instance, libraries follow a certain set of guidelines regarding how the code is organized (namespaces, macro names, type names, directory structure, directory naming, etc.). Why shouldn't there be guidelines regarding the documentation of these libraries? I know the guidelines are minimal by design (for example should be in HTML and/or PDF) but right now it's getting quite unwieldy -- and arguably, the documentation is becoming as important as the actual code is. I understand that documentation is largely an author/maintainer domain, and that currently the choice of documentation tools used is left to the author/maintainer. If we can somehow standardize on a tool set and help authors/maintainers convert their documentation from their current format to another then maybe we can make some progress regarding fixing the documentation-building/generation process and "improvement" of the library documentation. This also allows interested contributors to (more easily) learn the tools required and help out in the "improvement" of the documentation effort. Traditionally, Wiki's have worked well for other projects. Should Boost start doing this too, and just export documentation from the Wiki into properly cross-linked HTML pages in release builds? I understand Trac has the Wiki functionality already available -- should we start using it for documentation? Another option (that I think Dave Abrahams has been doing) is to use RST [0] to make writing/reading the source documentation easier than having to rely on Boostbook+XSLT (which I personally think is a brittle tool-chain). Quickbook is also a nice documentation language to use, but the reliance on Boostbook+XSLT makes it harder to pull-off. I don't know though if Quickbook can be made to generate HTML directly instead of XML. Joel? I understand there's also a Boost Documentation project. Anything happening in that front? [0] - http://docutils.sourceforge.net/rst.html -- Dean Michael C. Berris Software Engineer, Friendster, Inc.

11 17

[md5] Try out optimizations
by Daryle Walker 21 Aug '08

21 Aug '08

In revision 48279 at <http://svn.boost.org/svn/boost/sandbox/md5>, I added a class that will submit bytes to a MD5-processor byte-wise if CHAR_BIT was a factor of the hash block size, 512 bits. (This satisfies most computers since they have CHAR_BIT as 8.) I was wondering if anyone would like to try out the library, both people who have a system with CHAR_BIT == 8 and those who not, including those who have a system with 512 % CHAR_BIT == 0 even when CHAR_BIT isn't 8. I also need help checking little- vs. big-endian systems (if CHAR_BIT == 8). This will test all the optimizations. There are two preprocessor flags controlling optimizations, so try all qualifying combinations of those settings too. I hope this code is as speedy as C-based MD5 code. -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

1 0

wacky async_read?_write behavior!
by Abu Amar 21 Aug '08

21 Aug '08

Hi, I am trying to do a simple POP3S client. I am using the boost::asio sockets and SSL wrapper. Somehow, the output from the sock read is directed to the input of the sock write. Any idea? The code snippet is below, but here is the output of my program first (I replaced the IP with x's) -bash# ./main 209.85.199.111 995 foo.bar(a)gmail.com pass_in_plain_text Got RES (66) bytes +OK Gpop ready for requests from xxx.xxx.xxx.xxx c20pf1156691rvf.3 Sent REQ: APOP foo.bar(a)gmail.com pass_in_plain_text Got RES (36) bytes -ERR bad command c20pf1156691rvf.3 Sent REQ: STAT Read failed: End of file Exception: End of file and here is the code snippet that produced this input enum { max_length = 8192 }; class client { public: client(boost::asio::io_service& io_service, boost::asio::ssl::context& context, boost::asio::ip::tcp::endpoint& endpoint) : socket_(io_service, context) { //connect to the pop3 server socket_.lowest_layer().async_connect(endpoint, boost::bind(&client::handle_connect, this, boost::asio::placeholders::error)); } ~client() { socket_.lowest_layer().close(); } void handle_connect(const boost::system::error_code& error) { if (!error) { //do the SSL handshake socket_.async_handshake(boost::asio::ssl::stream_base::client, boost::bind(&client::handle_handshake, this, boost::asio::placeholders::error)); } else { std::cerr << "Connection failed: " << error << "\n"; boost::asio::detail::throw_error(error); } } void handle_handshake(const boost::system::error_code& error) { if (error) { std::cerr << "SSL Handshaking failed: " << error << "\n"; boost::asio::detail::throw_error(error); } } void write(std::string buffer) { str_req=buffer; boost::asio::async_write(socket_, boost::asio::buffer(str_req), boost::bind(&client::handle_write, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_write(const boost::system::error_code& error, size_t bytes) { if (!error) { std::cout << "Sent REQ: " << str_req <<std::endl; try{ boost::asio::async_read_until(socket_, buff_, "\r\n", boost::bind(&client::handle_read_until, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); }catch(const boost::system::system_error &err){ std::cerr << " code: " << err.code().value() << " :" << err.code().message() << std::endl; } } else { std::cerr << "Write failed: " << error.message() << "\n"; boost::asio::detail::throw_error(error); } } void read() { try{ boost::asio::async_read_until(socket_, buff_, "\r\n", boost::bind(&client::handle_read_until, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); }catch(const boost::system::system_error &err){ std::cerr << " code: " << err.code().value() << " :" << err.code().message() << std::endl; } } void handle_read_until(const boost::system::error_code& error, size_t bytes_transferred) { if (!error) { std::cout << "Got RES (" << bytes_transferred<<") bytes\n"; std::cout << &buff_; std::cout << "\n"; } else { std::cout << "Read failed: " << error.message() << "\n"; boost::asio::detail::throw_error(error); } } private: boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket_; boost::asio::streambuf buff_; //for receiving std::string str_req; //for sending }; int main(int argc, char* argv[]) { try { if (argc != 5) { std::cerr << "Usage: " << argv[0] << " <host> <port> <user> <pass>\n"; return 1; } boost::asio::io_service io_service; boost::asio::ssl::context ctx(io_service, boost::asio::ssl::context::sslv23); ctx.set_verify_mode(boost::asio::ssl::context::verify_none); boost::asio::ip::tcp::endpoint endpoint( boost::asio::ip::address::from_string(argv[1]), atoi(argv[2])); client c(io_service, ctx, endpoint); io_service.run(); //should execute till handshake completes //read the pop3 greeting io_service.reset(); io_service.post(boost::bind(&client::read,&c)); io_service.run(); //send the authentication command std::string str_cmd="APOP " + std::string(argv[3]) + " " + std::string(argv[4]) +"\r\n"; io_service.reset(); io_service.post(boost::bind(&client::write,&c,str_cmd)); io_service.run(); //get how many messages are in the inbox str_cmd="STAT\r\n"; io_service.reset(); io_service.post(boost::bind(&client::write,&c,str_cmd)); io_service.run(); //quit the pop3 session str_cmd="QUIT\r\n"; io_service.reset(); io_service.post(boost::bind(&client::write,&c,str_cmd)); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; }

1 0

[bigint] Integer data type larger than 64 bits?
by Simonson, Lucanus J 21 Aug '08

21 Aug '08

I have encountered the need for an integer data type larger than 64 bits to prevent overflow when doing algebra on 32 bit integer data. I notice that there is mention of a couple proposed boost big int libraries in the archive. Is there a boost library that provides this currently, or is there a library nearing acceptance level quality that I should use? I am not eager to take on a non-boost/non-stl dependency because I intend to submit the geometry library I need this for to boost. Thanks, Luke

2 6

GIL: how to convert an any_image_view to its const equivalent?
by Philipp Reh 21 Aug '08

21 Aug '08

Dear list, I think GIL is not able to convert an any_image_view to its const equivalent or I don't know how to do it. The variant class checks in its constructor if it can hold the given type but it doesn't have a constructor to convert an any_image_view from one to another. Here is a simple piece of code declaring two any_image_views: typedef boost::gil::any_image_view< boost::mpl::vector< boost::gil::rgba8_view_t > > image_view; typedef boost::gil::any_image_view< boost::mpl::vector< boost::gil::rgba8c_view_t > > const_image_view; Now when I try to construct a const_image_view from an image_view I get an std::bad_cast exception. What can I do about it? Cheers, Philipp -- View this message in context: http://www.nabble.com/GIL%3A-how-to-convert-an-any_image_view-to-its-const-… Sent from the Boost - Dev mailing list archive at Nabble.com.

2 2

[1.35] using binary_oarchive instead of text_oarchive
by Alexander Dong Back Kim 21 Aug '08

21 Aug '08

Dear members, I'm trying to use binary_oarchive instead of text_oarchive because I expect using binary may decrease the size of archive compare to using text_oarchive. std::ostreamstream ostr; boost::archive::text_oarvhice oa (ostr); oa & foo; The codes above works fine and I could do deserialization as well without any problem. In this case if I want to use binary_oarchive, what codes should I have to add? Any suggestion or advice will be appreciated. Thank you very much at all time. regards, -- Alexander Dong Back Kim

2 1

[Important] Server outage on Thursday, August 21st
by Doug Gregor 21 Aug '08

21 Aug '08

There will be a server outage on Thursday, August 21st from 8:00AM-9:00AM EDT while we upgrade Boost's Subversion repository to Subversion 1.5. The Boost Subversion repository, Trac, and mailing - Doug

5 5