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Using boost::asio with thousands of concurrent connections
by Gheorghe Marinca 09 Feb '12

09 Feb '12

Hi, I started to use boost::asio some time ago and want to use it for a windows commercial product that does web filtering and handles thousands of connections concurrently (proxy based product) I am wandering if anybody had experience using it at such a large scale, where besides handling many connections you have to handle inside a connection communication with databases, things that potentially incur delaying handling of subsequent requests. What kind of configuration would you advise in such a case (multiple I/O services per n threads, on IO service that handles all incoming connections and a thread pool that handles processing of async handlers - how one would assure in this case a connections is handled in the same thread then ..etc) Thanks for any input -Ghira

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XML and Boost Property Tree
by Boost Users List 09 Feb '12

09 Feb '12

Hey Boost users! I'm iterating over an XML document using boost property tree and storing the results in a struct. The issue I have is that I can only get to the first "item" nodes and can't access the second "item" nodes. I was hoping someone would point out where I've made a mistake. My program output looks like this (you can see items are missing.. there is no cookie2, candy2 or chocolate2 items shown): jar : snAcks snack : coOkie item : cooKie1 snack : canDy item : caNdy1 snack : cHocolate item : choColate1 Here's the xml file: <root> <jar name="snAcks"> <snack name="coOkie"> <item name="cooKie1"></item> <item name="cookIe2"></item> </snack> <snack name="canDy"> <item name="caNdy1"></item> <item name="candY2"></item> </snack> <snack name="cHocolate"> <item name="choColate1"></item> <item name="chocOlate2"></item> </snack> </jar> </root> Here's the source code: void parse_xml( boost::property_tree::iptree const& pt ) { BOOST_FOREACH( boost::property_tree::iptree::value_type const& v, pt.get_child("root.jar") ) { // Show jar if ( boost::iequals( v.first, "<xmlattr>" ) ) { std::cout << "jar : " << v.second.get<std::string>("NaME") << std::endl; } if ( boost::iequals( v.first, "snack" ) ) { // Show snack std::cout << "snack : " << v.second.get<std::string>("<xmlattr>.name") << std::endl; try { BOOST_FOREACH( boost::property_tree::iptree::value_type const& val, v.second.get_child("item") ) { if ( boost::iequals( val.first, "<xmlattr>" ) ) { // Show item std::cout << "item : " << val.second.get<std::string>("nAmE") << std::endl; } } } catch (boost::property_tree::ptree_bad_path& e) { // Show what caused exception std::cout << "Exception: " << e.what() << std::endl; } } } } Thank you for taking time to read this. I think I've made a simple mistake, but cannot understand where.

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[iostreams] multichar_output_filter works only the first time
by Steven Samuel Cole 09 Feb '12

09 Feb '12

hello, to get started with iostreams, i'm trying to write a multichar output filter that adds a string to the beginning and the end of whatever comes through. my code builds with a warning about unused parameter n and works - but only the first time, the second time, i get no output. i thought at first sending '\0' would trigger the stream's fail-bit or so, but out.good() returns true. any chance someone takes a look at my code and hazards a guess where the problem might be ? disclaimer: i was actually born and bred in C++ country long time ago, but i've been coding in python for a couple of years and got back only recently, so there's a good chance what i'm doing wrong is something really simple. guess you can tell from the code, it's been a while. good to be back though... :-) #include <iostream> #include <sstream> #include <boost/iostreams/concepts.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/operations.hpp> using std::cin; using std::cout; using std::endl; using std::streamsize; using std::string; using std::stringstream; class add_string_output_filter : public boost::iostreams::multichar_output_filter { public: template<typename Sink> streamsize write(Sink& sink, const char* s, streamsize n) { // remove trailing '\0' to prevent line break // TODO: there's probably a better way string tmp_string = string(s); string out_string = tmp_string.substr(0, tmp_string.size()-1); string pre_string("prepended string - "); string app_string(" - appended string"); stringstream sstrm; sstrm << pre_string << out_string << app_string << endl; // TODO: char* to string, back to char* ?!? return boost::iostreams::write(sink, sstrm.str().c_str(), sstrm.str().length()); } }; int main() { boost::iostreams::filtering_ostream out; out.push(add_string_output_filter()); out.push(cout); cout << "prompt: "; string str; while (getline(cin, str)) { out << str << endl; cout << "prompt: "; } } # sample session: prompt: some string prepended string - some string - appended string prompt: another string prompt: why no output ? prompt: # ssc

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Compiler wants to link to threading library all of a sudden
by Crispin Cooper 09 Feb '12

09 Feb '12

Hello Boost users I wonder if anyone can help me please. I have just updated my boost install to svn head to take advantage of some bugfixes. Now the compiler complains that it can't find libboost_thread-vc90-mt-sgd-1_49.lib. But I am not trying to use the threading libraries - my boost includes are: #include <boost/shared_ptr.hpp> #include <boost/pool/pool_alloc.hpp> #include <boost/pool/object_pool.hpp> #include <boost/static_assert.hpp> #include <boost/geometry.hpp> #include <boost/geometry/geometries/point_xy.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/multi/geometries/multi_point.hpp> Have any of these changed such that they require prebuilt libraries? Or is including boost from the head revision somehow different to a released version in this manner? Many thanks in advance Crispin -- Dr Crispin Cooper Sustainable Places Research Institute Cardiff University

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retrieving section names from a boost::proper_tree
by Sean Farrow 09 Feb '12

09 Feb '12

Hi All: I have parsed a .ini file in to a boost::property_tree. I now would like to retrieve all the section names and place them in a vector. Am I needing the key_type or the value_type. I am suspecting the former! Also is there a quick way of outputting the section names without having to use a boost_foreach or similar loop construct? Any herlp appreciated. Regards Sean.

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Re: [Boost-users] Linking errors
by Abdo Haji-Ali 09 Feb '12

09 Feb '12

Thank you very much, that solved it. 3 hours of troubleshooting solved with a simple command rewrite :| It's really strange though, because that exact same command worked on my other machine with Fedora on it and same gcc/OpenMPI versions. -- Abdo Haji-Ali

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Linking errors
by Abdo Haji-Ali 09 Feb '12

09 Feb '12

Hello, I downloaded and compiled boost successfully by calling b2 (version 1.47 for various reasons) Then I tried compiling my program (which uses both Boost.MPI and Boost.Serialization) using mpic++ -I/home/abdo/boost/ -L/home/abdo/boost/stage/lib/ -lboost_serialization -lboost_mpi main.cpp But I keep getting linking errors in boost, for example: undefined reference to `boost::mpi::communicator::size() const' undefined reference to `typeinfo for boost::archive::detail::basic_oserialize I have openmpi installed and I'm able to run simple non-boost OpenMPI programs. I'm also sure that the libraries in my stage library are the ones used, since if I remove the -L argument the compiler complains about -lboost_mpi and -lboost_serialization Is there something I'm missing here? I'm using Ubuntu 11.10 -- Abdo Haji-Ali

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[multi_array] Accessing elements via an iterator
by Bill Buklis 08 Feb '12

08 Feb '12

Given this simple definition for multi_array: struct data { int value; }; typedef boost::multi_array<data, 3> array_type; array_type a; Can someone tell me why pointer dereferencing, i.e. operator->, an element does not successfully compile? Normal derefencing does work, i.e. operator*. Am I doing something wrong or is this a problem with multi_array? For example: // Successfully compiles (*a.begin()->begin()->begin()).value = 10; // Does NOT compile a.begin()->begin()->begin()->value = 10; I'm using MSVC 2010 and it returns an error that "pointer to reference is illegal". I'm using multi_array from the trunk section. -- Bill

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property tree case sensitivity
by Brad Tilley 08 Feb '12

08 Feb '12

I'm trying to make all of the strings (xml tags and attributes) contained within a property tree be case insensitive, to make comparison easy and consistent. Here's an example: boost::property_tree::iptree pt; read_xml( file, pt, boost::property_tree::xml_parser::trim_whitespace ); // case insensitive std::string name = v.second.get<std::string>("<xmlattr>.nAmE"); // case insensitive BOOST_FOREACH( boost::property_tree::iptree::value_type const& v, pt.get_child("neTwOrK") ) { // fails comparison because "thing" is case sensitive. if ( v.first == "tHiNg" ) { .... } } Is it possible to make v.first case insensitive as well? Thanks, Brad

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[traits] missing types aligned at 64 and 128 bytes
by Václav Šmilauer 08 Feb '12

08 Feb '12

The header /boost/type_traits/type_with_alignment.hpp specializes the template type_with_alignment only for 1, 2, 4, 8, 10, 16, 32 bytes. Unless there is a reason to not do so, I would like to ask for extension of the alignment to 64 and 128 bytes as well. (In my case, I need it for the cl_double16 vector type in OpenCL) As workaround, I am currently using doing the specialization in my code: > namespace boost { > namespace align { struct __attribute__((__aligned__(128))) a128 {};} > template<> class type_with_alignment<128> { public: typedef > align::a128 type; }; > }; Best regards, Václav Šmilauer

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