June 2007 - Boost-users - lists.boost.org

[asio] http-server example
by Daniel Albuschat 13 Jun '07

13 Jun '07

Hello there, I'm currently building my own, specialized http-server based on the http-server example. I experience crashes for certain types of replies. Here's something I really do not understand: In connection.cpp, after request_parser_.parse() finished and result == true, there is this line: boost::asio::async_write(socket_, reply_.to_buffers(), boost::bind(&connection::handle_write, shared_from_this(), boost::asio::placeholders::error)); It's the last user-code in the stacktrace of the crash that I frequently experience. What bothers me is the reply_.to_buffers() function. It looks like this: std::vector<boost::asio::const_buffer> reply::to_buffers() { std::vector<boost::asio::const_buffer> buffers; buffers.push_back(status_strings::to_buffer(status)); for (std::size_t i = 0; i < headers.size(); ++i) { header& h = headers[i]; buffers.push_back(boost::asio::buffer(h.name)); buffers.push_back(boost::asio::buffer(misc_strings::name_value_separator)); buffers.push_back(boost::asio::buffer(h.value)); buffers.push_back(boost::asio::buffer(misc_strings::crlf)); } buffers.push_back(boost::asio::buffer(misc_strings::crlf)); buffers.push_back(boost::asio::buffer(content)); return buffers; } How can this even work? It adds temporaries (the misc_strings are const char[]s) to a const_buffer-vector and reads them later. Even the references to h.name, etc. seem invalid to me, since the io is asynchronous and there's no guarantee that they don't change. IMHO the whole content needs to be COPIED to new buffers and then, after the async_write finished, deleted. Am I missing something? Was the author of this example not aware of the const_buffer's ownership policy (i.e. it is *not* owner of the data)? I've spent hours and hours in debugging now, but I just can't figure out where it goes wrong. You can see the stacktrace here: http://mandrill.fuxx0r.net/c++/paste:7702 Kind regards, Daniel Albuschat -- eat(this); // delicious suicide

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[asio] file streaming
by Chris Fairles 13 Jun '07

13 Jun '07

I give up! I cannot for the life of me figure out buffers and streams. Any help is greatly appreciated. Here's what I have so far: filesize_ = fs::file_size(filepath_); std::ifstream file(filepath_.file_string().c_str(), std::ios::in ); file.seekg (file_offset_, std::ios::beg); //offset typically 0 unless resuming transfer //just trying this for fun boost::asio::ip::tcp::socket::send_buffer_size option; data_socket_.get_option(option); //tcp socket uint64_t size = option.value(); while (bytes_sent < filesize_) { //i test a file 21200678 bytes long. This tranfers anywhere from 21135097 to 21196000. bytes_sent += data_socket_.send(boost::asio::buffer(file.rdbuf(), std::min(size,filesize_-bytes_sent))); //this always transfers 21204202 bytes_sent += data_socket_.send(boost::asio::buffer(file.rdbuf(), size)); } data_socket_.close(); boost::asio::async_read_until(control_socket_, response_, "\r\n", boost::bind(&FTPClient::handleRead, this, boost::asio::placeholders::error)); write_some vs. send give same results. I've also tried something like: char buf[1024]; socket.write_some(buf, file.readsome(buf, 1024)); which deosnt read all the bytes. Sometimes if I check file.rdbuf()->in_avail(), it reports 0 using above method and bytes_sent stops growing about 99% of the way through. I tired setting the the socket linger option to true. No go. I tried making the data_socket a buffered_write_stream, same results. What am I doing wrong? Sometimes bytes_sent is exactly the file size, but the remote file size is slightly less. Maybe closing the socket stream too early? That sends an eof which the server responds to but it should arrive AFTER the data i would think... no clue. please help :) In the meantime, I'm going to go rip up some FSF ftp client code from source forge heh. Thanks Chris

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[iostreams] Using bzip2_decompressor with text files
by Thomas Trummer 13 Jun '07

13 Jun '07

Hi, I have a text file that is compressed with bzip2 and im trying to read with it the iostream lib and parse it with iostream::operator>>. Unfortunately this doesn't work so I wanted to ask if this is an unsupported scenario or if I'm doing something wrong. filtering_istream in; in.push(bzip2_decompressor()); in.push(file_source("text.bz2")); in >> lineId; // std::string lineId Regards, Thomas

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[postmaster@sina.com: boost-users@sina.com??????????]
by Zeljko Vrba 13 Jun '07

13 Jun '07

Enough is enough. I kindly ask the mailing list manager to remove the offending sender(s) (@sina.com) from the mailing list. I attach the complete mail which I get in response to every mail I send to the boost users mailing list. Thanks in advance.

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math/statistics policy-interface feedback requested.
by John Maddock 13 Jun '07

13 Jun '07

Following the successful review of the math-toolkit of special functions and statistical distributions the main feature request was for a better way of customising the library: both for choosing between precision vs speed tradeoffs, and for determining how errors are best handled. I've been experimenting with various policy-based interfaced based on Boost.Parameter, and I think I now have something useable, so I'd like to know what people think: Policy Defaults ~~~~~~~~~~~~~~~ The library will use a sensible set of defaults (throw on domain errors and internal evaluation errors, favour accuracy over speed etc), which can be changed via the usual macro mechanism, so adding: #define BOOST_MATH_DOMAIN_ERROR_POLICY errno_on_error #define BOOST_MATH_OVERFLOW_ERROR_POLICY ignor_error to a user-config header would do what they say to the default policies. Add Hock Changes: ~~~~~~~~~~~~~~~~~ We can create an ad-hock policy change at the call site by using the make_policy function, for example: using namespace boost::math::policy; using namespace boost::math; quantile( poisson(100), 0.05, make_policy( // 5 dicimal digits precision only digits10<10>(), // don't internally promote double->long double for extra precision: promote_double<false>(), // return integer result, immediately below the "real" value: discrete_quantile<integer_below>() )); Which returns the lower 95% quantile (ie critical value) of a poisson distribution with rate parameter of 100 event's per unit time. The result is calculated using only 10 decimal digits internal precision, truncated to the largest integer that gives a CDF less than 0.05. Predefined Policies ~~~~~~~~~~~~~~~~~~~ Although ad-hock policies are useful for testing, I imagine most sites would want a few carefully controlled (and tested) policies. To achieve that you define a typedef of the policy class: using namespace boost::math::policy; typedef policy< // Set error handling: domain_error<throw_on_error>, pole_error<throw_on_error>, overflow_error<throw_on_error>, evaluation_error<throw_on_error>, denorm_error<ignor_error>, underflow_error<ignor_error>, // calculate to 8 decimal digits internally digits10<8>, // don't promote double->long double for accuracy promote_double<false>, // Integer quantiles return the "outside edge": // below the real value for lower critical values, // above it for upper critical values, so that the // area inside contains *at least* the requested coverage: discrete_quantile<integer_outside_edge> > fast_quantile_policy; static fast_quantile_policy fast_quantile; Then we can just use: quantile( poisson(100), 0.05, fast_quantile); In our actual code. Currently this policy interface is vapourware: I have enough of a prototype implemented to know that it's possible to achieve this syntax (this is revision #3 already !), but there's a lot of hairy meta-programming to convert that into something that the library's internals can make use of... so I'd like to know what folks think before I invest too much time messing about with MPL :-) The main disadvantage I've noticed at present, is that the mangled names of the policy class - and therefore all the special functions etc - are *very* long. This has an impact on error messages: in particular we currently use BOOST_CURRENT_FUNCTION to get a nice formatted name of a function that's about to throw, but with function names a couple of pages long I don't think that will be possible with this interface any more :-( Thanks in advance, John Maddock.

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Re: [Boost-users] Boost 1.34 and VC++ 64
by Yutaka Leon Suematsu 13 Jun '07

13 Jun '07

Hi Chris, Thank you for your help. >> The command I used was: >> >> bjam --build-dir=C:\tmp\build-boost --toolset=msvc address-model=64 >> stage > > Hi, > you have to use the 'Visual Studio x64 Win64 Command Prompt', so > the correct environment variables are set and then use bjam like: > > bjam --build-dir=C:\tmp\build-boost --toolset=msvc-8-0_64 stage > I could compile with the toolset "msvc-8.0_64", I didn't know its existence. bjam --build-dir=C:\tmp\build-boost --toolset=msvc-8.0_64 stage Thanks, Yutaka.

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multi_index and base class
by Andrej van der Zee 13 Jun '07

13 Jun '07

Hi, I'm trying to store these classes in a multi_index: struct Foo { int a; }; struct Bar :Foo { }; typedef multi_index_container< Bar, indexed_by< ordered_unique< member<Foo, int, &Bar::a> > > > Bar_container; Notice I have to use "Foo" in the "member<" line. However, even with this, when trying to do a search: Bar_container bar_container; int function() { Bar_container::nth_index<0>::type& a_index = bar_container.get<0>(); Bar_container::nth_index<0>::type::iterator i = a_index.find(5); if (i != a_index.end()) return -1; return 0; } I get this: /usr/include/boost/multi_index/member.hpp: In member function 'Type& boost::multi_index::detail::non_const_member_base<Class, Type, PtrToMember>::operator()(const ChainedPtr&) const [with ChainedPtr = Bar, Class = Foo, Type = int, Type Class::* PtrToMember = &Foo::a]': /usr/include/boost/multi_index/detail/ord_index_ops.hpp:65: instantiated from 'Node* boost::multi_index::detail::ordered_index_find(Node*, const KeyFromValue&, const CompatibleKey&, const CompatibleCompare&) [with Node = boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::i ndex_node_base<Bar> >, KeyFromValue = boost::multi_index::member<Foo, int, &Foo::a>, CompatibleKey = int, CompatibleCompare = std::less<int>]' /usr/include/boost/multi_index/ordered_index.hpp:376: instantiated from 'boost::multi_index::detail::index_iterator<boost::multi_index::detail::orde red_index_node<typename SuperMeta::type::node_type> > boost::multi_index::detail::ordered_index<KeyFromValue, Compare, SuperMeta, TagList, Category>::find(const CompatibleKey&) const [with CompatibleKey = int, KeyFromValue = boost::multi_index::member<Foo, int, &Foo::a>, Compare = std::less<int>, SuperMeta = boost::multi_index::detail::nth_layer<1, Bar, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::mul ti_index::member<Foo, int, &Foo::a>, mpl_::na, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<Bar> >, TagList = boost::mpl::vector0<mpl_::na>, Category = boost::multi_index::detail::ordered_unique_tag]' multitest2.cc:55: instantiated from here /usr/include/boost/multi_index/member.hpp:84: error: no match for 'operator*' in '*x' I've tried a few alternatives such as providing a custom compare function but I always get this error. It seems to have something to do with the fact that the key is in the base class. If I move the key to the derived class (and change the "member<" line), it works fine. Surely there's a way to do this. Anyone know how ? Using gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21) and libboost 1.33.1. Thanks ___________________________________________________________ New Yahoo! Mail is the ultimate force in competitive emailing. Find out more at the Yahoo! Mail Championships. Plus: play games and win prizes. http://uk.rd.yahoo.com/evt=44106/*http://mail.yahoo.net/uk

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Problems instantiating class Boost Python class
by Phil 13 Jun '07

13 Jun '07

Hi, I'm a newbie having some problems instantiating a class written in C++ in Python using Boost.Python. I can get a very simple example working when I expose a function outside of a class, that returns a string, but the below fails as shown, despite building. The enum in the same library however works fine. I've googled the error returned from Python and I get zero hits - has anyone get any idea what I'm doing wrong? I'm using Python 2.5, GCC 4.0.1 and Boost 1.33 on Mac OS X 10.4.9. I don't think it matters but I'm building the solution as a dynamic C++ bsd library in XCode and the changing the Mac OS X .dylib extention to .so as is required by Python. This all works for simpler examples and the enum in this example. Error: TypeError: __init__() should return None, not 'NoneType' Thanks, Phil. From header file example.h: enum payOffType { CALL, PUT }; class Option { public: //defaults to call Option( double strike, double expiry ); double getPutCallMultiplier(); private: double strike; double expiry; payOffType type; }; From cpp file example.cpp: Option::Option( double strike, double expiry ) : strike( strike ), expiry( expiry ), type( CALL ) { cout << "Option Contructor called"; } double Option::getPutCallMultiplier() { return ( type == CALL ) ? 1 : -1; } BOOST_PYTHON_MODULE(libphil_boost) { class_<Option>("Option", init<double, double>()) .def("getPutCallMultiplier", &Option::getPutCallMultiplier) ; enum_<payOffType>("payOffType") .value("CALL", CALL) .value("PUT", PUT) ; } Using Python on the resulting .so: $ python Python 2.5.1 (r251:54863, Jun 10 2007, 17:57:56) [GCC 4.0.1 (Apple Computer, Inc. build 5250)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import libphil_boost >>> p = libphil_boost.Option( 23, 23 ) Option Contructor calledTraceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: __init__() should return None, not 'NoneType' >>>

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boost::pool issue
by v r 12 Jun '07

12 Jun '07

Hi, I have a main object that allocates many small objects via singleton_pool , and during its operation main obj uses up much memory so i want to release that memory before program termination, because main obj performs only support operations in my program. So upon main obj destruction i make a singleton_pool::purge_memory() call in main obj destructor, the memory is released and i should be quite happy,but when the main obj is constructed again the pool allocates twice as much memory as it used before, and it continues to double every time i construct/destruct the main object, so very soon my program hangs up. I wonder what have i done wrong? It seems like something is not reset on memory purge, or maybe it`s a bug? --------------------------------- Вы уже с Yahoo!? Испытайте обновленную и улучшенную Yahoo! Почту!

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[asio] Receiving non-UDP multicast frames?
by Eric Hill 12 Jun '07

12 Jun '07

I have been requested to write a tiny diagnostic application that will listen for Cisco Discovery Protocol (CDP) messages from Cisco switches on a workstation so that the workstation will "know" what switch port it is plugged into. I have found the following information with my limited google-foo: CDP Packet Format: http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/frames.htm#xtocid… CDP Information: http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note091… The latter link says that CDP uses a destination multicast address 01-00-0c-cc-cc-cc, HDLC protocol type 0x2000 on an Ethernet segment. This is where I get lost. Is that an Ethernet MAC broadcast, or a socket-based broadcast? Can I capture those CDP advertisements with asio? Eric

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