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Re: [Boost-users] [corrected]How to delay the initialisation of a member in a C++ base class until the ctor of derived class is executed?
by Zhi Tan 25 Mar '09

25 Mar '09

> Date: Wed, 25 Mar 2009 20:13:02 +1100 > From: Alex MDC <alex.mdc(a)gmail.com> > > Since you're passing the size into the derived constructor, why don't you > just pass it through to the base constructor? > > class base > { > public: > base(size_t array_size):size(array_size) > { > p_array.reset(new unsigned char[size]); > } > private: > size_t size; > boost::shared_array<unsigned char> p_array; > }; > > class derived > { > public: > derived(size_t array_size):base(array_size) > { > } > }; > > > Will that work for you? Exactly. Thank you.

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Re: [Boost-users] Boost-users Digest, Vol 1945, Issue 2
by tom tan 25 Mar '09

25 Mar '09

From: Matthieu Brucher <matthieu.brucher(a)gmail.com> >Perhaps simply: > >class base >{ >public: > base(size_t size):size(size), p_array(new unsigned char[size]){} >private: > size_t size; > boost::shared_array<unsigned char> p_array; >}; > >And then: > >class derived:public base >{ >public: > derived(size_t array_size):base(array_size) > { > } >}; > >Do not declare size and p_array again, they will be different than the >ones in the base class... but in this case array_size is re-assigned after p_array was allocated, thus not reflecting the size of the allocated buffer; What I wished to achieve is: 1) the buffer is allocated inside the base class while 2) the size is designated inside the derived class. >From: Christopher Currie <christopher(a)currie.com> >Also, shared_ptr won't work for arrays, you'll want to used >"shared_array" instead. That's right, I was thinking of shared_array while I was typing, but ... >You might also think twice about this, and decide if having a shared >copy of the buffer is really what you want, or if you're just using >the smart pointer for memory management. If so, consider using >"scoped_array" and defining a copy constructor with the appropriate >semantics. >If you go this route, you may just as well stick with 'vector'. It's >less work, and probably far less overhead than you think. I need some dynamically allocated space that can later be casted to C pointers, so that it can be passed to a Win32 API function that accepts C pointers only. vectors are dynamic, but they don't cast to C arrays naturally. In fact, I am wrapping that API in C++. is there a better way?

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How to convert graphtraits<Graph>::in_edge to graphtraits<Graph>::edge
by Phani Deepak 25 Mar '09

25 Mar '09

hi, i have stored some bundled properties for an edge. * class EdgeProperties { public: int targetI;// Terminal No. interms of target node int sourceI;// Terminal No. interms of source node EdgeProperties(int s,int t):sourceI(s-1),targetI(t-1) { } };* my Graph is : *typedef boost::adjacency_list<boost::listS,boost::listS,boost::bidirectionalS, EdgeProperties *> Graph; Graph g; * Now iam iterating through in_edges of some vertex v; *graphtraits<Graph>::in_edge_iterator iedge_s,iedge_end; for(boost::tie(iedge_s,iedge_end) = boost::in_edges(v,g); iedge_s!=iedge_end; ++iedge_s){ EdgeProperties *ep = g[*iedge_s]; // <==== **Line 10** cout << ep->sourceI << endl; // <==== **This is giving segmentation fault;** } * I checked the *ep* pointer. it is coming out as null in line 10; is there any problem while using *in_edge_descriptor* as *edge_descriptor**( for g[edge_descriptor]* ) in *Line 10* ?? * *please help. - Phani. * *

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[corrected]How to delay the initialisation of a member in a C++ base class until the ctor of derived class is executed?
by tom tan 25 Mar '09

25 Mar '09

Here's the scenario: I want define a base class that allocate some buffer once for all derived classes, while the size of the buffer varies among different derived classes. I could achieve it in this way: class base { public: base():size(), p_array(0){} private: size_t size; boost::shared_array<unsigned char> p_array; }; in the derived class: class derived { public: derived(size_t array_size):size(array_size) { p_array.reset(new unsigned char[size]); } }; However, in order to simplify the design of the derived class, I really want to put this line: p_array.reset(new unsigned char[size]); to somewhere in the base class, thus writing it only once. In other words,I wished to achieve this: 1) the buffer is allocated inside the base class while 2) the size is designated inside the derived class. Is there any C++ design pattern could achieve it? Thanks

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Re: [Boost-users] [asio] ip::tcp::socket - differences between send &write_some
by 张亚霏 25 Mar '09

25 Mar '09

concerning ... ------------------ best wishes to you 张亚霏 ------------------ Original ------------------ From: "Lennyk"<lennyk430(a)gmail.com>; Date: Wed, Mar 25, 2009 04:59 PM To: "boost-users"<boost-users(a)lists.boost.org>; Subject: [Boost-users] [asio] ip::tcp::socket - differences between send &write_some Hi, What is the difference in implementation between the ip::tcp::socket::send & ip::tcp::socket::write_some on Linux sys sockets? What kind of system calls are used in both calls? Thanks! _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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[asio] ip::tcp::socket - differences between send & write_some
by Lennyk 25 Mar '09

25 Mar '09

Hi, What is the difference in implementation between the ip::tcp::socket::send & ip::tcp::socket::write_some on Linux sys sockets? What kind of system calls are used in both calls? Thanks!

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Is there a way to delay the initialisation of a member in a C++ base class until the ctor of the derived class is executed?
by tom tan 25 Mar '09

25 Mar '09

Here's the scenario: I want define a base class that allocate some buffer once for all derived classes, while the size of the buffer varies among different derived classes. I could achieve it in this way: class base { public: base():size(), p_array(0){} private: size_t size; boost::shared_ptr<unsigned char> p_array; }; in the derived class: class derived { public: derived(size_t array_size):size(array_size) { p_array.reset(new unsigned char[size]); } private: size_t size; boost::shared_ptr<unsigned char> p_array; }; However, in order to simplify the design of the derived class, I really want to put this line: p_array.reset(new unsigned char[size]); to somewhere in the base class, thus writing it only once. Is there any C++ design pattern could achieve it? Thanks

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linking agaisnt boost
by arun ramakrishnan 25 Mar '09

25 Mar '09

A nube question . I have been trying to understand the whole link process in VC++ . I use visual studio 8. I was trying to install the prebuild boost libs from boostpro and I tried to build my source against 1) , 2) and 3) . The three are. 1)Multithread, static runtime libboost_thread-vc80-mt-s-1_38.lib 2)Multithread libboost_thread-vc80-mt-1_38.lib 3)Multithread , DLL boost_thread-vc80-mt-1_38.dll boost_thread-vc80-mt-1_38.lib I expected there to be Multithreaded static lib and then a multithreaded dynamic shared dll . Just 2 of them , not 3 . Could someone explain the need for 3 and not just 2. OR point me to a article or something please . I have vaguely figured that 1) static boost and static CRT . 2) static boost and dynamic CRT. 3) dynamic boost and dynamic CRT. am i right ? I believe boost automatically picks up the right libs based on your project . So , when i tried to build a simple project using these libs . while using the /MT option for code generation , 1) was used as I expected it to. while using the /MD option for code generation , it linked to 2) . I am not able to build using 3) , in spite of a lot of probing into the VC8 configuration options . Also , what configuration would be needed to make my project use the boost dll i.e 3). thanks in advance .

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Re: [Boost-users] BoostCon 2009 Schedule Now Live
by Paul 25 Mar '09

25 Mar '09

I beg you to recorded the conference on video/audio for those who aren't able to make the trip ... 2009/3/25 David Abrahams <dave(a)boostpro.com> > The official schedule is now live at http://www.boostcon.com/program! A > few highlights of the "mouth-watering content" (in the words of one > enrollee) are: > > * A keynote address from Andrei Alexandrescu called "Iterators Must Go." > It's sure to be provocative! > > * Troy Straszheim's presentations on how high-energy physicists are > using Boost to process massive datasets as they go "Icefishing for > Neutrinos" and on Kamasu, his library for offloading computation to > your machine's GPU. > > * Two hands-on sessions where we'll start recoding parts of Boost for > C++0x, applying rvalue references, variadic templates, decltype, and > advanced SFINAE capabilities using the latest GCC. > > * "Practical C++ Test-Driven Development with Boost.Test and Bmock," by > Asher Sterkin > > * A session on compiler construction using Boost.Spirit v2, from Hartmut > Kaiser and Joel de Guzman > > The complete list of sessions covers a wide range of other Boost and > C++-related topics. It is available at > http://www.boostcon.com/program/sessions. Please have a look, and > please, sign up for the conference! Remember, registration for the > whole week is just $599 before April 1st. > > -- > Dave Abrahams > BoostPro Computing > http://www.boostpro.com > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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Looking for guidance on how best to use Boost ASIO in this scenario
by console shark 24 Mar '09

24 Mar '09

I have the following scenario: Up to 1000 client users. 1 Server (or multiple instances of a server). The server(s) read a set of 5-15 incoming data feeds that update as often as 10 to 50 times per second. Each feed is updating at a different interval, as information comes in (essentially random). The server processes the data as it arrives from these feeds and when it finds a useful piece of information, it sends a message to some subset of the 1000 clients. The clients are not all interested in the same thing. It could be that each client has a different interest, and it could be that many times per second each client will need to be notified of that interest. That should be the worst case scenario, as meaningful changes in information probably won't require updates to the client that often, even though the 5-15 feeds are constantly updating. So what is the best way to structure this design using ASIO? Should the 1000 clients actually be set up as servers, and the server really just contact them by connecting each time there is an update that interest them? Or should the 1000 clients all connect with a permanent connection, polling for updates? Thanks for any advice.

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