March 2012 - Boost-users - lists.boost.org

My homemade object pool
by 饭桶 31 Mar '12

31 Mar '12

Hi all Here is my objectpool implemention which inspired by boost pool. Which have following features. Features: 1.Allocate an object from pre-allocate memory, when free an object just put it back to pool. 2.Call object's contructor at pool memory allocating or get object from pool, or do nothing. 3.Call object's deconstructor when "delete" object if constructor's been calling at "new" object 3.Call object's deconstructor when destroy objectpool if constructor's been calling at memory allocating 4.Can pass an function object to be invoke when "new" object, this can be used as a constructor if object's constructor don't be invokded when "new" object 5.Thread safe can be enable/disable by tempalte parameter 6.Callback can be raw pointer is T is not inherit from enable_shared_from this can be shared_ptr vers vice. There are several tasks need to do, like the allnodesset can be generated at callring of foreach. Delegate memory allocating to allocator, etc.. The whole project and unit test can be found at https://maxsrecyclebin.svn.sourceforge.net/svnroot/maxsrecyclebin/objectpoo… Is there any comments? Thanks ////////////////////////////////////////////////////////////////////////////////////// #include <istream> #include <list> #include <boost/shared_ptr.hpp> #include <boost/bind.hpp> #include <set> #include <algorithm> #include <boost/type_traits.hpp> #include <boost/enable_shared_from_this.hpp> #include <boost/thread/pthread/mutex.hpp> namespace maxutility { enum InitialType {None,ObjInitial,PoolAllocate}; template <typename T> class DummyCallableObj { public: void operator ()(boost::shared_ptr<T> &ptr) { //do nothing } }; template<bool isthreadsafe> class obthreadlock; template<> class obthreadlock<true> { public: void lock(){obmutex.lock();} bool try_lock(){return obmutex.try_lock();} void unlock(){obmutex.unlock();} private: boost::mutex obmutex; }; template<> class obthreadlock<false> { public: void lock(){}; bool try_lock(){return true;}; void unlock(){}; }; template <typename T,bool isthreadsafe=false,typename InitalFunction=DummyCallableObj<T> > class ObjectPool { #define LOCAL_LOCK boost::lock_guard<obthreadlock<isthreadsafe> > lg(obthreadlock_); protected: /** * @brief Declaration for furture usage **/ typedef T Node; typedef std::list<char *> FRAGMENTTYPE; typedef std::list<Node *> NODELIST; public: ObjectPool(InitialType initialtype=ObjInitial,size_t initialsize=512,size_t maxsize=0) { busyCount=0; this->poolsize=0; this->initialtype=initialtype; this->maxsize=maxsize; extend(initialsize); } ObjectPool(InitalFunction initalFunction=DummyCallableObj<T>(), InitialType initialtype=PoolAllocate, size_t initialsize=512, size_t maxsize=0) //:ObjectPool(initialtype,initialsize,maxsize) //Delegating constructors, c++11 only { busyCount=0; this->poolsize=0; this->initialtype=initialtype; this->maxsize=maxsize; this->initalFunction=initalFunction; extend(initialsize); } ~ObjectPool() { if(0!=busyCount) throw new std::exception(); if(PoolAllocate==initialtype) for(Node *p:allnodes) p->~Node(); for(char *pFragment:fragments) delete pFragment; } virtual boost::shared_ptr<T> create() { LOCAL_LOCK; boost::shared_ptr<T> ptr(static_cast<T*>(getFreeNode()),boost::bind(&ObjectPool<T,isthreadsafe,InitalFunction>::free,this,_1)); initalFunction(ptr); return ptr; } bool empty() { return !busyCount; } size_t size() { return busyCount; } size_t capacity() { return poolsize; } template <typename FUNCTION> void foreach(FUNCTION f) { LOCAL_LOCK; NODELIST freenodes=this->freenodes; //make a local copy freenodes.sort(); NODELIST busynodes(allnodes.size()); typename NODELIST::iterator busynodesend=std::set_difference( allnodes.begin(),allnodes.end(),freenodes.begin(),freenodes.end(),busynodes.begin() ); for(typename NODELIST::iterator iter=busynodes.begin(); iter!=busynodesend; iter++) { invokeFunction<FUNCTION,Node, boost::is_base_of<boost::enable_shared_from_this<Node>,Node >::value >()(f,*iter); } } protected: template<typename _Function,typename N,bool isuseshareptr> class invokeFunction; template<typename _Function,typename N> class invokeFunction<_Function,N,false> { public: void operator ()(_Function __f,N *p) { __f(p); } }; template<typename _Function,typename N> class invokeFunction<_Function,N,true> { public: void operator ()(_Function __f,N *p) { boost::shared_ptr<N> ptr=p->shared_from_this(); __f(ptr); } }; protected: void free(T *p) { LOCAL_LOCK; if(!p) return; destroyObj(static_cast<Node*>(p),ObjInitial); //removeBusyNode(static_cast<Node*>(p)); freenodes.push_back(static_cast<Node*>(p)); busyCount--; } Node *getFreeNode() { Node *ptr=nullptr; if(freenodes.empty()) //no new free node if(!extend()) //try to extend return ptr; //false ptr=freenodes.front(); //now it must contain free node freenodes.pop_front(); constructObj(ptr,ObjInitial); busyCount++; return ptr; } bool extend(size_t size=0) { if((0!=maxsize&&poolsize>=maxsize&&poolsize!=0) ) return false; //we reach the maximum size //poolsize=0 first allocation //size=0 extend twice size of current size //poolsize=size=0 we got a problem size_t extSize=((0==poolsize)?size:2*poolsize); char *pFragment=new char[extSize*sizeof(Node)]; if(!pFragment) return false; fragments.push_back(pFragment); poolsize+=extSize; for(Node *p=(Node*)pFragment; extSize--; p++) { constructObj(p,PoolAllocate); freenodes.push_back(p); allnodes.push_back(p); } allnodes.sort(); return true; } void constructObj(Node *p,InitialType phase) { if(phase==initialtype) ::new(p)Node; } void destroyObj(Node *p,InitialType phase) { if(phase==initialtype) p->~Node(); } size_t poolsize; InitialType initialtype; size_t maxsize; FRAGMENTTYPE fragments; NODELIST freenodes; NODELIST allnodes; size_t busyCount; InitalFunction initalFunction; obthreadlock<isthreadsafe> obthreadlock_; }; };

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Unit concept
by Mario Charest 31 Mar '12

31 Mar '12

Everyone, I sent a message a couple of weeks ago but got no reply. I'm trying again. I've been reading and experimenting with Boost::Units. I have a hard time understanding how one deals with the same unit in different scale. Say I want to use thou, inch, feet, all interchangeably. My problem is I`m not sure which strategy to use. Pointers would be welcome.

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Can I use std::queue as ASIO io object for asynchronise operation?
by liubl 31 Mar '12

31 Mar '12

Hi, I want to implement a message queue between multiple thread, with multiple thread post message to the queue and one single thread process the message. I don't want the single processing thread to be blocked by the os when there is no message to be processed. I don't know if I can use ASIO lib to help me implement it. In my thought, the single processing thread read the queue asynchronisely and be invoked if there is one message ready on the queue, just like there is data ready on the socket. Is it doable? And is its performance better than the blocking method using conditional_variable? Regards, -Bruce

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[Concepts & EnableIf] Is void special?
by Robert Jones 31 Mar '12

31 Mar '12

Hi Peeps Can anyone cast any light on this... I want to write function which accepts a single pass range of X's, so something like this struct X { }; template <typename T> BOOST_CONCEPT_REQUIRES( (( boost::SinglePassRangeConcept<T> )), ( typename boost::enable_if<boost::is_same<typename boost::range_value<T>::type, X>, void>::type )) my_function( const T & range ); Is that a reasonable construction, or is there a better way to say it? Next, it doesn't seem to work. It does seem to work if the type to which enable_if resolves is anything except void, but not for void. Why is this? TIA - Rob.

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Python error
by Kraus Philipp 30 Mar '12

30 Mar '12

Hello, I build Boost with Python 3.2 and get this error: Building Boost.Build engine with toolset gcc... tools/build/v2/engine/bin.linuxx86_64/b2 Detecting Python version... 3.2 Detecting Python root... File "<string>", line 1 import sys; print sys.prefix ^ SyntaxError: invalid syntax Unicode/ICU support for Boost.Regex?... not found. Generating Boost.Build configuration in project-config.jam... I don't need the ICU support and it seems all libraries are build correctly Phil

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shared_ptr and circular dependency
by Christopher Pisz 30 Mar '12

30 Mar '12

What are one's options when the code one is working on contains a circular dependency and one is trying to update it to use a shared_ptr vs a raw pointer? I don't think I can easily get rid of the preexisting circular dependency. The original author has created an inheritance where the base needs the derived. We all know this is wrong, but it would take quite a bit to analyze how it is used and be removed. Am I out of luck? Fictitious Example (best minimal example including the problems the preexisting code has): // File MasterClient.h #include "BaseClient.h" #include <set> class MasterClient : BaseClient { public: // Constructor adds this to the collection of clients // It is later included in the processing of all clients MasterClient(); // SNIP private: typedef std::set<Base *> Clients; Clients clients_; // Thread function that iterates over all clients // including this instance and makes calls on them void Process(); }; // file BaseClient.h class MasterClient; class BaseClient { public: // Constructor BaseClient(MasterClient * master); // SNIP interface private: MasterClient * master_; // I really need this to be a shared_ptr // Thread function that makes calls to the MasterClient virtual void Process(); }; ---------------------------- I gave it my best shot and have 2 errors that I can't figure out: C2664: BaseClient::BaseClient(boost::shared_ptr<T>) cannot convert parameter 1 from boost::shared_ptr<T> to boost::shared_ptr<T> C2385: ambiguous access of 'shared_from_this' I have to use enable shared from this to be passing around the shared_ptr from myself, no? I am also worried about using this in the intializer list, is it a problem? I believe both classes cannot inherit from it. I am not sure how to change it up. any suggestions? We are using VC2008, so I cannot use the standard shared_ptr yet, but I believe the boost version is the same... My attempt: /* * BaseClient.h */ #ifndef BASECLIENT_H #define BASECLIENT_H #include <boost/shared_ptr.hpp> #include <boost/enable_shared_from_this.hpp> //------------------------------- class MasterClient; //------------------------------- class BaseClient : public boost::enable_shared_from_this<BaseClient> { public: typedef boost::shared_ptr<BaseClient> SharedPtr; // Enforces that every instance must be a shared_ptr for shared_from_this requirement static BaseClient::SharedPtr Create(boost::shared_ptr<MasterClient> master); protected: BaseClient(boost::shared_ptr<MasterClient> master); virtual ~BaseClient(); boost::shared_ptr<MasterClient> master_; }; #endif /* * BaseClient.cpp */ #include "BaseClient.h" #include "MasterClient.h" //------------------------------- BaseClient::SharedPtr BaseClient::Create(boost::shared_ptr<MasterClient> master) { return BaseClient::SharedPtr(new BaseClient(master)); } //------------------------------- BaseClient::BaseClient(boost::shared_ptr<MasterClient> master) : master_(master) { master->InsertClient(shared_from_this()); } //------------------------------- BaseClient::~BaseClient() { } /* * MasterClient.h */ #ifndef MASTERCLIENT_H #define MASTERCLIENT_H #include "BaseClient.h" #include <boost/shared_ptr.hpp> #include <boost/enable_shared_from_this.hpp> #include <set> //------------------------------- class MasterClient : public BaseClient , public boost::enable_shared_from_this<MasterClient> { public: typedef boost::shared_ptr<MasterClient> SharedPtr; // Enforces that every instance must be a shared_ptr for shared_from_this requirement static MasterClient::SharedPtr Create(); protected: typedef std::set<BaseClient::SharedPtr> Clients; Clients clients_; MasterClient(); ~MasterClient(); }; #endif /* * MasterClient.cpp */ #include "MasterClient.h" //------------------------------- MasterClient::SharedPtr MasterClient::Create() { return MasterClient::SharedPtr(new MasterClient()); } //------------------------------- MasterClient::MasterClient() : BaseClient(MasterClient::shared_from_this()) { } //------------------------------- MasterClient::~MasterClient() { }

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Crash in boost::thread::sleep(xt) (boost 1.42 on Windows 32 bit)
by Arno 30 Mar '12

30 Mar '12

Hi all, we recognize in our tests, that one of our threads seem to crash in boost:thread::sleep(xt). Is there a known issue with the sleep() function under MS Visual Studio 2008, with boost 1.42? It was tested on Windows 7 and Windows XP 32 Bit OS. Our thread crashes also in the debugger, when all exceptions are on, without any notice. But only this one thread goes away, the debugger stop at a breakpoint, which was set at a place, where it was recognized that this thread no longer runs. The error occure, in a multithreaded environment, with at least around 30 active threads. The sleep is outsite any critical section (no mutex and/or no semaphore is active). Any hints are welcome. regards Arno

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[boost.locale] Question about boundary rules
by alex_perry 29 Mar '12

29 Mar '12

Have just been exploring boost.locale which I hadn't used before. However I'm not quite understanding some of the behaviour for boundary rules when segmenting text. Fortunately I can see this behaviour happening in the example code so its probably my misunderstanding and easily corrected. If I compile http://www.boost.org/doc/libs/1_49_0/libs/locale/doc/html/boundary_8cpp-exa… and run it I get :- [...skipped to avoid long quote ] Part [Linux2.6] has number(s) Part [ ] has no word characters Part [and] has letter(s) Part [ ] has no word characters Part [Windows7] has number(s) letter(s) Part [ ] has no word characters [...] However I don't understand why "Linux2.6" is detected as having number(s) but no letters whilst "Windows7" is detected as having both. It doesn't appear to be the decimal point "Linux26" has the same behaviour (whilst "Linux2" is detected as having both). I haven't debugged this just glanced at the code (which seems to be setting these flags based on all the icu ruleBasedBreakIterator getRuleStatusVec()). Thought I would just ask whether I'm misunderstanding something fundemental here before trying to understand what is going on here and where (if there is one) the problem is TIA Alex Perry ps Just in case this is a known platform / version issue I was running this on :- Windows7 MSVC 10 boost 1.49 icu 4.9.1 -- View this message in context: http://boost.2283326.n4.nabble.com/boost-locale-Question-about-boundary-rul… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost 1.46.1 vs. boost 1.49.0 ?
by JIA Pei 28 Mar '12

28 Mar '12

Hi, all: My code is as simple as: > path tempp(dir_path, native ); It used to work for boost 1.42. And now, it's working fine with boost 1.49.0 ... However, current Ubuntu 11.10 affords boost 1.46.1. Whenever I tried to compile my code with boost 1.46.1, I got the following errors: invalid conversion from ‘bool (*)(const string&) {aka bool (*)(const > std::basic_string<char>&)}’ to ‘boost::enable_if_c<true, void>::type* {aka > void*}’ [-fpermissive] In addition, I notice there are some other errors at the same time, which seems to have something to do with filesystem3 ? Invalid arguments ' > Candidates are: > bool is_directory(boost::filesystem3::file_status) > bool is_directory(const boost::filesystem3::path &) > bool is_directory(const boost::filesystem3::path &, > boost::system::error_code &) > ' However, why my code is able to compile with boost 1.49.0 then? Cheers Pei -- Pei JIA Email: jp4work(a)gmail.com cell: +1 604-362-5816 Welcome to Vision Open http://www.visionopen.com

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Boost interprocess message_queue thread-safe?
by Rajalakshmi Iyer 28 Mar '12

28 Mar '12

Hello, I am trying to use the Boost Inter-process message queue and wanted to know the application needs to take care of synchronization. The documentation lists 'Message queues' under the 'Synchronization' section and mentions: 'A message queue is similar to a list of messages. Threads can put messages in the queue and they can also remove messages from the queue' So is the message queue thread-safe? My use case is several multi-threaded processes on a single host writing to the message queue and another multi-threaded process on the same host reading from the message queue. Thanks! -- Twitter: @Blismobile <http://twitter.com/#!/blismobile> BlisMobile Media 32 Percy Street, London W1T 2DE www.blismobile.com [image: BlisMobile] <http://www.blismobile.com/>[image: Follow on Twitter]<http://twitter.com/#!/blismobile>[image: Blis Website] <http://www.blismobile.com/> This communication is from BlisMobile Media, which is a trading name of Breeze Tech (UK) Ltd, a company registered in England and Wales with registered number 06455773. Its registered office is 32 Percy Street, London W1T 2DE, United Kingdom. This communication contains information that is confidential and may also be privileged. It is for the exclusive use of the intended recipient(s). If you are not the intended recipient(s), please (1) notify info(a)blismobile.com by forwarding this email and delete all copies from your system and (2) note that disclosure, distribution, copying or use of this communication is strictly prohibited. Email communications cannot be guaranteed to be secure or free from error or viruses. All emails sent to or from a Blismobile email account are securely archived and stored by an external supplier. This email does not constitute a contractual agreement; such agreements are in specified contractual or Insertion Order (IO) form only and exclusively contain all the terms to which Breeze Tech )UK) Ltd will be bound. To the extent permitted by law, Breeze Tech (UK) Ltd does not accept any liability for use of or reliance on the contents of this email by any person save by the intended recipient(s) to the extent agreed in a contract or Insertion Order. Opinions, conclusions and other information in this email which have not been delivered by way of the business of Breeze Tech (UK) Ltd are neither given nor endorsed by it.

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