April 2011 - Boost-users - lists.preview.boost.org

[Asio] Socket Read/Write Thread-Safety
by Timothy Liang 06 Apr '11

06 Apr '11

Hi, I'm implementing a full-duplex protocol over TCP/IP using Boost.Asio. Multiple threads will be calling 'io_service::run_one()', so I have to serialize my completion handlers. Since I need to be reading and writing on a socket at the same time, can I use the 'boost::asio::async_read(...)' and 'boost::asio::async_write(...)' functions? The documentation states that these are implemented in terms of calls to the stream's async_read_some and async_write_some functions, and the 'basic_stream_socket' class isn't thread-safe. Thanks, Timothy

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[fusion] Adding to a map (1.42)
by Noah Roberts 05 Apr '11

05 Apr '11

https://svn.boost.org/trac/boost/ticket/4604 I've got 1.42 though. Updating at this point isn't a good option. Is there a way to work around this so that I can add a new pair to an existing fusion map?

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[lambda] Lambda bind and upgrading
by Swerts, Benjamin 05 Apr '11

05 Apr '11

Hello all, In the process of upgrading Boost from 1.39.0 to 1.46.1 I encountered a few problems with Boost.Lambda. Some places where I used bind and operator== are not compiling anymore with Visual Studio 2008 SP1. Here's a self-contained example showing the problem: --------------------- #include <algorithm> #include <vector> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> using boost::lambda::bind; using boost::lambda::_1; struct A { unsigned int id; }; struct B { const A* a; }; int main() { const std::vector<B> vb; std::find_if(vb.begin(), vb.end(), bind(&A::id, bind(&B::a, _1)) == 2); return 0; } --------------------- - This code compiles fine with Boost 1.39.0 - When compiled with Boost 1.46.1 it shows the following error: boost_1_46_1/boost/lambda/detail/function_adaptors.hpp(280) : error C2440: 'return' : cannot convert from 'const unsigned int' to 'unsigned int &' - When removing the 'const' before the vector, this doesn't even compile in 1.39.0 - What's even stranger is that a simpler version doesn't compile under other circumstances. This compiles with 1.46.1: std::vector<A> va; std::find_if(va.begin(), va.end(), bind(&A::id, _1) == 2); but making the vector const doesn't (exact same error message). Both compile fine with 1.39.0. Both examples compile fine when I use Boost.Bind but that's not always a possible backup plan. I do plan on replacing all the bind calls with their Phoenix v3 equivalents but I first need to get Boost upgraded. Many thanks in advance for any insights. Greets, Ben

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Problems creating unit wrappers with StlSoft
by Ryan 05 Apr '11

05 Apr '11

My current project has several coordinate systems. These include Polar(azimuth, elevation, range) and LLA (latitude, longitude, altitude). I've really enjoyed using boost units to allow the user to input the required unit system but converting them behind the scenes to the unit system I need. I'm developing a function overload that lets the user call a single function but based on the coordinate system given the function behaves differently. Unfortunately, the units for Polar and LLA are the same. Both systems use two plane angles and a length. A second problem is two different groups use two different ways of talking about the Polar coordinate system. One group defines Polar as azimuth, elevation and range while the other group defines Polar as range, azimuth and elevation. I want to give both group the ability to call the function with the Polar definition they are used to talking about. I realize I could create a class for Polar and LLA and then pass that class to my overloaded function. This just pushes off the second problem to the newly created classes. Instead of creating classes for the coordinate systems I wanted to differentiate the different boost units from each other. This would let me overload my function without the need to create larger classes for each coordinate system. I ended up modifying the "true_typedef" class from StlSoft that wraps a type so it becomes incompatible with the same types. This allowed me, for example, to wrap a boost unit plane angle into a longitude and latitude that wouldn't be compatible with each other. What I don't like about this process is having to define a structure type and then using it in the typedef. Is there a boost library that would allow me to create this class in one pass without the two step process? Ryan #define STLSOFT_GEN_OPAQUE(type) typedef struct __stlsoft_htype##{ int i; } const* type; using namespace boost::units; template<typename T, typename U> class BoostUnitQuantityWrapper { typedef T unit_type; typedef U unique_type; typedef BoostUnitQuantityWrapper<T, U> class_type; quantity<unit_type> m_Value; public: template<class System> explicit BoostUnitQuantityWrapper ( quantity< unit< typename unit_type::dimension_type, System> > const& value) : m_Value(quantity<unit_type>(value)) {} BoostUnitQuantityWrapper(class_type const& rhs) : m_Value(rhs.m_Value) {} class_type const& operator= (class_type const& rhs) { m_Value = rhs.m_Value; return *this; } operator quantity<unit_type> () const { return m_Value; } }; STLSOFT_GEN_OPAQUE(latitude_type); STLSOFT_GEN_OPAQUE(longitude_type); STLSOFT_GEN_OPAQUE(range_type); STLSOFT_GEN_OPAQUE(altitude_type); typedef BoostUnitQuantityWrapper<si::plane_angle, latitude_type> Latitude; typedef BoostUnitQuantityWrapper<si::plane_angle, longitude_type> Longitude; typedef BoostUnitQuantityWrapper<si::length, range_type> Range; typedef BoostUnitQuantityWrapper<si::length, altitude_type> Altitude;

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Problem with boost::interprocess::ipc::message_queue
by Ming Lu 05 Apr '11

05 Apr '11

Hello Everybody, i used boost::interprocess::ipc::message_queue (boost 1.40) in my project. it works perfect. after upgrade from boost 1.40.0 to 1.46.0 i do have a problem with the message_queue. my usage of message_queue: Receiver: message_queue message_queue(open_or_create, strQueueName.c_str(), nMessagesNumber, nMessageLength); / .... bReceiveSucces = message_queue.try_receive(pchPuffer, m_nMessageLength, nRecievedSize, nPriority);/ Sender: message_queue message_queue(open_only, m_strMessageQueueName.c_str()); message_queue.try_send(strMessage.c_str(), nMessageLength, nPriority); (the Receiver is running before Sender has be started.) i readed the content in the output windows from Visual Studio 2008 (my building envoriment) during start of my application: * 1.40.0:* /'MessageQueueReceiver.exe': Loaded 'C:\data\20_NoBackup\Project\MessageQueueSender\Debug\MessageQueueReceiver.exe', Symbols loaded./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\ntdll.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\kernel32.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\advapi32.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\rpcrt4.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\secur32.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\WinSxS\x86_Microsoft.VC90.DebugCRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww_597c3456\msvcr90d.dll', Symbols loaded./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\WinSxS\x86_Microsoft.VC90.DebugCRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww_597c3456\msvcp90d.dll', Symbols loaded./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\shimeng.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\shimeng.dll'/ the receiver-application loaded these dlls and waiting for the input message from the sender-application.. *1.46.0:* /MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\wbem\wbemprox.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\wbem\wbemcomn.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\ws2_32.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\ws2help.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\wbem\wbemsvc.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\wbem\fastprox.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\msvcp60.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\ntdsapi.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\dnsapi.dll'/ /'MessageQueueReceiver.exe': Loaded 'C:\WINDOWS\system32\wldap32.dll', Symbols loaded (source information stripped)./ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\wbem\fastprox.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\ntdsapi.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\wldap32.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\dnsapi.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\msvcp60.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\wbem\wbemsvc.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\wbem\wbemprox.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\ws2_32.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\ws2help.dll'/ /'MessageQueueReceiver.exe': Unloaded 'C:\WINDOWS\system32\wbem\wbemcomn.dll'/ ...................... ...................... ...................... the receiver-application loaded these complettly different Dlls (in compare with 1.40) and unloaded them repeatly (endless). if man compare the cruise of the message_queue, is 1.46.0 about 4 times slower as 1.40.0. do somebody know? is it a bug or just the sideeffect from the changement? how can i use the message_queue correctly? thanks a lot for any suggestion best regards Ming Lu

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[unit test] problem inside boost UTF
by Bruno Belarte 05 Apr '11

05 Apr '11

Hi, I'm new with boost, and I'm actually experiencing some weird issues... I wrote a class which is basically a wrapper around boost::adjacency_list, and two other nested classes which are wrappers around boost::adjacency_list::vertex_iterator and boost::adjacency_list::out_edge_iterator. I tested theses three classes with the boost unit test framework : everything works fine. Then I wrote a class Tree, which uses boost::shared_/weak_ptr. But when I try to test this class with boost UTF, the test case of the previous graph's out_edge_iterator returns some failures (different depending of the functions from the Tree class called on the test). It's particularly weird considering that these classes share nothing in common except the fact that they use different part of boost. Maybe somebody have a hint on what I am doing wrong !? I used UTF with dynamic lininking, boost1.42 from ubuntu 10.10 package. Thanks, Bruno

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[threads] Deadlock?
by The Novice Coder 05 Apr '11

05 Apr '11

I'm working with boost:threads, and am having what appears to be a deadlock issue. I'm not sure if the lock is something I'm doing, or if it's my lack of understanding of boost::condition_variable. The code deadlocks on this snippit: if( wait) { // lock the condition, add the event, wait for the condition, and get the return value! boost::mutex::scoped_lock lk(serviceMutex_); clearException(); returnValue_ = 0; qApp->postEvent(temp_this, temp_event, Qt::HighEventPriority); serviceCondition_.wait(lk); } Where wait is specified by the caller to wait for the other thread to return. In the service request thread has this snippet: { boost::mutex::scoped_lock lk( serviceMutex_); returnValue_ = qtService(s->getCommand()); serviceCondition_.notify_one(); } I tried it with and without the lock (in the 2nd snippet) but the 2nd snippet code is never getting called and just seems to vanish when wait is specified. When wait isn't specified, it all works. (Non-wait is just the same thing without any of the locks/conditions.) Any thoughts on where to look to proceed or what documents to read ? Thanks, and apologies for the inexperience. New to boost..

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Search and replace in text files with Boost.Xpressive
by Júlio Hoffimann 04 Apr '11

04 Apr '11

What is the better approach with Boost to catch a file with some wildcard-prefixed variables and replace them by numerical values? Example: $ cat file.tmpl ============ var1 = $something ... ... $coord1 $coord2 ... $coordN ... ... ============ $ cat file.dat ============ var1 = 2.35323 ... ... 1.4 3.5 124 910 ... ... ============ The Boost libraries i know for regular expressions are Boost.Regex and Boost.Xpressive. I like the second, because it's header only, has static and dynamic regular expressions and uses it's own namespace. In other words, it incorporates the features of Boost.Regex in a more elegant way. As far as i know, Boost.Xpressive treats only std::string and C-like strings. What i need to do for work with text files? Put them inside a std::string? About the performance, the files has approximately 10^3 lines, the search and replace will be an issue? Regards, Júlio.

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Using boost::shared_ptr with std::set
by przemyslaw.sliwa＠uk.bnpparibas.com 04 Apr '11

04 Apr '11

Hello, I have to use a set of shared pointers to objects. The struct I have to use looks like struct eventIntLim { enum eType { eStart = 0, eEnd }; eType type; double varianceBump; eventIntLim(eType t, double v) : type(t), varianceBump(v) {} bool operator < (const eventIntLim &rhs) const { return fabs(varianceBump) < fabs(rhs.varianceBump); } }; and the definition of the set is typedef boost::shared_ptr<eventIntLim> eventIntLimPtr; typedef std::set<eventIntLimPtr, lessThan> eventIntLimPtrSet; typedef std::map<size_t, eventIntLimPtrSet> eventIntLimMap; In order to sort the objects in the set I have to use the functor struct lessThan : public std::binary_function<boost::shared_ptr<eventIntLim>, boost::shared_ptr<eventIntLim>, bool> { bool operator ()(const boost::shared_ptr<eventIntLim> &lhs, const boost::shared_ptr<eventIntLim> &rhs) const { return (*lhs) < (*rhs); } }; This is quite long and I believe boost can shorten it a lot. I have tried it with boost::lamba and boost::bind but could not make it working. Basically I would like to eliminate the need of writing the definition of struct lessThan. Could someone help me with that? Cheers ___________________________________________________________ This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and delete this e-mail. Any unauthorised copying, disclosure or distribution of the material in this e-mail is prohibited. Please refer to http://www.bnpparibas.co.uk/en/information/legal_information.asp?Code=ECAS-… for additional disclosures.

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[MPL] initialization of member that might be non-copyable
by Noah Roberts 04 Apr '11

04 Apr '11

I'm working on something similar to the construct devised in the MPL book Section 9.5 (class composition). Some objects in the composed type might require initialization. I've solved this problem. However, in solving that problem I've now required that any type going into the composition must be copyable. However, since the original composition code doesn't make this requirement I've been trying to find a way to retain the ability to contain types that are non-copyable. Here's some code: template < typename Field > struct field_value { typedef Field field; typedef typename Field::type ftype; ftype value; field_value(ftype const& t) : value(t) {} field_value() : value() {} }; template < typename Field, typename ParamFields, typename Enable = void > struct initializer { template < typename Params > static typename Field::type apply(Params &) { return Field::type(); } }; template < typename Field, typename ParamFields > struct initializer<Field,ParamFields, typename boost::enable_if< boost::mpl::contains<typename Params::fields, typename FieldValue::field> >::type > { template < typename Params > static typename Field::type apply(Params & params) { return get<Field>(params); } }; template < typename FieldValue, typename Params > FieldValue init_field(Params & pars) { return initializer<typename FieldValue::field, typename Params::fields >::apply(pars); } template < typename FieldValue, typename More > struct record_base : FieldValue, More { template < typename Params > record_base(Params & pars) : FieldValue(init_field<FieldValue>(pars)) , More(pars) {} record_base() : FieldValue(), More() {} }; struct empty_record_base { template < typename Ignored > empty_record_base(Ignored&){} empty_record_base() {} }; template < typename MplSequence > struct build_record { typedef boost::mpl::placeholders::_1 _1; typedef boost::mpl::placeholders::_2 _2; typedef typename boost::mpl::fold < MplSequence , empty_record_base , record_base< field_value<_2>, _1 > >::type type; // type should be record_base< field_value<field0> // , record_base< field_value<field1> // , ... record_base<field_value<fieldN>, empty_record_base> // > ... // > }; It's at this point: template < typename Params > record_base(Params & pars) : FieldValue(init_field<FieldValue>(pars)) , More(pars) {} That I need to apply something, I know not what, to correctly initialize the field with either a parameter argument or nothing. I can't think of any construct that would make that possible but I don't necessarily know everything. Is there some way that this can be accomplished?

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