March 2009 - Boost-users - lists.preview.boost.org

Statechart problem
by Iwan Sanders 25 Mar '09

25 Mar '09

LS, I've implemented a state machine (synchronous) with a couple of states and their events. Its purpose is to implement an USDT CAN stack. Because the lower level driver (made that too) passes the incoming CAN messages through a callback function I needed to derive one state in the state machine from: a) the expected boost state base b) my own interface which handles the callback for new messages (observer) The state machine is performing well with one exception, hence this email. The callback function is a member of a struct which is derived from a & b and it is called by the CAN driver. But then when I want to notify the state that the machine is currently in with a post_event this event seems to be discarded even though it should react on it (the machine state has transitions defined for this event and the current state is that state). I also tried using the transit call but that doesn't do anything either. It is just this one member-function that is the problem and before rewriting the state-machine to an asynchronous state machine I wanted to consult some other users. Regards, Iwan Sanders

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Re: [Boost-users] [asio] Disable nagle algorithm on Windows XP
by 张亚霏 25 Mar '09

25 Mar '09

try native WSA API "setsockopt" with the TCP_NODELAY option. if it still does not work, there may be something wrong with your windows xp. or debug the asio ------------------ best wishes to you 张亚霏 ------------------ Original ------------------ From: "Tobias J?hnel"<tjaehnel(a)gmail.com>; Date: Wed, Mar 25, 2009 10:58 PM To: "boost-users"<boost-users(a)lists.boost.org>; Subject: Re: [Boost-users] [asio] Disable nagle algorithm on Windows XP Hi Igor, thanks for your reply. I guess you mean setting non_blocking_io to false. Tried to enter those lines, but still have no change: boost::asio::socket_base::non_blocking_io command(false); socket.io_control(command); Tobias On Wed, Mar 25, 2009 at 3:07 PM, Igor R <boost.lists(a)gmail.com> wrote: >> I'm already using blocking sockets as suggest in above document. > > According to that document, you should not enocounter this problem > when using blocking sockets. Probably your socket is not blocking? > To make a socket blocking you should write something like this: > boost::asio::socket_base::non_blocking_io command(true); > socket.io_control(command); > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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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

after referring the source code, i hardly found difference between ip::tcp::socket::send & ip::tcp::socket::write_some, but about some arguments. "socket_ops::send" directly invokes system call:"sendmsg" to send message. ------------------ 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] Disable nagle algorithm on Windows XP
by Tobias Jähnel 25 Mar '09

25 Mar '09

Hi, I'm developing a TCP-Client using boost::asio and discovered that ACKs to responses from the server are sent with some delay (~200ms) and I get the data not before this ACK has been sent. When I disable nagle in registry as described by Microsoft it works fine. (See: http://support.microsoft.com/kb/823764) To avoid those registry hacks I want to find another way to get rid of this latency. I'm already using blocking sockets as suggest in above document. I also tried to set the no_delay option but this has no effect at all. boost::asio::ip::tcp::no_delay option(true); socket.set_option(option); == Code Snippets == I use the boost asio library as follows: // open connection (from synchronous TCP daytime client example) boost::asio::io_service io_service; tcp::resolver resolver(io_service); tcp::resolver::query query(ipaddress, port); tcp::resolver::iterator endpoint_iterator = resolver.resolve(query); tcp::resolver::iterator end; boost::system::error_code error = boost::asio::error::host_not_found; while (error && endpoint_iterator != end) { socket.close(); socket.connect(*endpoint_iterator++, error); } // send some data boost::asio::write(socket, boost::asio::buffer(package, size)); // reception is done inside a thread while(true) { // receive data size_t length = socket.read_some(boost::asio::buffer(resp), error); if (error == boost::asio::error::eof) { // Connection closed cleanly by peer. // ... do sth. } else if (error) { // Some error has happened // ... do sth. } // ... process received data and notify main thread to send the next piece of data } ======= Thank you for all suggestions. Tobias

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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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