May 2011 - Boost-users - lists.boost.org

[boost::thread] using futures
by Kazz 09 May '11

09 May '11

Hi All. I am trying to use Futures, but not getting the expected result. The code below works some times, and other times it throws exception "terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::promise_already_satisfied> >' what(): Promise already satisfied" Any help will be appreciated. Thanks Kazz. //-------------------------------------------// boost::promise<int> pt; // holds final calculated result void worker1() { // do any processing using algorithm A srand ( time ( NULL) ); int delay = rand() % 5 + 1; boost::this_thread::sleep( boost::posix_time::seconds(delay)); // result calculate pt.set_value(1); } void worker2() { // do any processing using algorithm B srand ( time ( NULL) ); int delay = rand() % 5 + 1; boost::this_thread::sleep( boost::posix_time::seconds(delay)); // result calculated pt.set_value(2); } int main() { boost::shared_future<int> ans(pt.get_future()); boost::thread th1(worker1); boost::thread th2(worker2); ans.wait(); std::cout<<ans.get()<<std::endl; std::cout<<"exiting"<<std::endl; return 0; }

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String serialization
by Robert Bielik 09 May '11

09 May '11

I'd like to (XML) serialize a non-STL string, and I'd like it to serialize in the same manner as STL string (i.e. just the plain string as CDATA). I can do it like: <myString> <s>The string...</s> </myString> but I'd like: <myString>The string...</myString> the serialization implementation of std::string is a menace to decipher... TIA /Rob

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[asio] IPv6 interface index
by Dylan Klomparens 09 May '11

09 May '11

Hello, I am trying to use Boost for some IPv6 and multicast network communication. I need to construct an IPv6 multicast socket that uses a specific network interface index. I was able to find the correct multicast option to set the network interface index in boost/asio/ip/detail/socket_option.hpp: explicit multicast_request(const boost::asio::ip::address_v6& multicast_address, unsigned long network_interface = 0) The problem is, I don't know how to find the correct value for the "network_interface" parameter. Is there a way to get the network_interface value using a local IPv6 address that I can provide? I looked in the documentation and examples, but couldn't find anything. -- Dylan

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[msm] EUML in a header file
by Nate Knight 09 May '11

09 May '11

Christophe, One problem I've run into with the EUML frontend is the the _EVENT, _ACTION and _STATE macros define non-static instance variables. So, if I define a state machine in a header file which then gets included in multiple source files (e.g. I have two classes which use the same state machine) I get linker errors about duplicate instances. For states, I can work around this issue by doing, for example, BOOST_MSM_EUML_DECLARE_STATE((),MyStateType) static MyStateType MyState; and then using MyState in the transition table. Events and Actions don't seem to have the corresponding _DECLARE_ macros, so this workaround isn't really feasible at this point in time. Any thoughts? Thanks Nate

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Usage of boost serialization binary_object
by Robert Bielik 09 May '11

09 May '11

Hi all, I'm wondering how to load a binary object from an archive ? I've managed to use binary_object to save it nicely, but I can't find any references on how to load it again :( TIA /Rob

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Re: [Boost-users] [msm] EUML and State construction
by Christophe Henry 09 May '11

09 May '11

>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> With gcc 4.5 and Boost 1.46.1, I get: >> >> simpletest.cpp: In function 'int main()': >> simpletest.cpp:30:75: error: no match for 'operator<<' in >> 'boost::msm::back::states_ << test_state_with_constructor(1)' > > Ok, I see what it is, I did not solve correctly my conflict between > proto and serialization. > I just committed a fix into the trunk (revision 71719), but it's not > working, I simply run into my next proto problem :( > > I'll continue working on this tomorrow. I fixed the second problem too (revision 71746) in the trunk. It should now work correctly. Thanks, Christophe

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Re: [Boost-users] ASIO sockets - 2nd write fails
by bill comment 09 May '11

09 May '11

> > 'new_connection_' always points to an invalid socket because after a > connection is established you always replace it with a new one. > yes. i was suspecting this but didn't fully understand. thanks for confirming. my solution was to change my architecture to that of the ChatServer sample where a reference to my Connection object (parallel to their participant/session) is handed to a new Client object (parallel to their room) so that it will live for the duration of the client app's connection and my server can write several responses. thanks for the responses.

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[forEach] Working with custom operator []
by Avishay Ben Shabtai 09 May '11

09 May '11

Hi i have a container class that defines 2 overloaded [] operators: T& operator[](const chat *); T& operator[](unsigned int); when i am using BOOST_FOREACH(T val,container) i get compilation errors but working directly with iterators is working ok, any idea?

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ASIO sockets - 2nd write fails
by bill comment 09 May '11

09 May '11

I am having a problem writing a TCP socket message using boost:asio async_* I am new to using boost asio sockets. reading what I could find (this list, samples, other forums) I have added boost::asio socket use to my application. What works is: accept, receive, parse and reply to a message. After my client sends a message and receives a response it remains connected and starts an async receive. Several seconds later my server tries to send another message to the client (by calling server::write()). the code runs ok up to connection::handle_writeMessage() where error is: 2719 “The file handle supplied is not valid”. I thought I read (links below) that using strand::wrap() to queue the async_* calls and io_service::post() to post the initial function call would allow a thread that didn’t call io_service::run() to initiate the sending or a message. http://stackoverflow.com/questions/4078484/using-boost-sockets-do-i-need-on… http://stackoverflow.com/questions/4090567/better-understanding-boosts-chat… http://groups.google.com/group/boost-list/browse_thread/thread/124a643a06d6… did I interpret this incorrectly? Did I code it wrong? Thank you for your time and advice. to develop my code I started with the http3 and chat server samples. Changes include: - server::threads is a class member - server::run() returns without waiting for threads to stop so I start other threads in my program - added server::stop() to stop threads. - server::write() is called from another thread. - connection::do_writeMessage() and connection::handle_writeMessage() are from the chat server sample. A summary of my server code is below. its long, but should be familiar from the samples. Server.hpp std::vector<boost::shared_ptr<boost::thread> > threads; server::server : thread_pool_size_(2), // 1 thread for wait, read, reply. 1 for unsolicited writes. acceptor_(io_service_), new_connection_(new connection(io_service_, request_handler_)), request_handler_() { async_accept(new_connection_->socket(), boost::bind(&server::handle_accept, this, boost::asio::placeholders::error)); } void server::run() { // 1 thread for wait, read, reply. 1 for unsolicited writes. // Create a pool of threads to run all of the io_services. //std::vector<boost::shared_ptr<boost::thread> > threads; for (std::size_t i = 0; i < thread_pool_size_; ++i) { boost::shared_ptr<boost::thread> thread(new boost::thread( boost::bind(&boost::asio::io_service::run, &io_service_))); threads.push_back(thread); } } void server::stop() { io_service_.stop(); // Wait for all threads in the pool to exit. for (std::size_t i = 0; i < threads.size(); ++i) { threads[i]->join(); } } server::handle_accept (const boost::system::error_code& e) { if (!e) { // read, parse and reply new_connection_->start(); new_connection_.reset(new connection(io_service_, request_handler_)); // ready to accept another connection cout << "waiting for new accept ..." << endl; acceptor_.async_accept(new_connection_->socket(), boost::bind(&server::handle_accept, this, boost::asio::placeholders::error)); } } // public // called from another thread in my program to send an unsolicited message to my connected client void server::write(const string& msg) { io_service_.post(boost::bind(&connection::do_writeMessage, new_connection_, msg)); } - - - - - - - - - - connection::connection(boost::asio::io_service& io_service, request_handler& handler) : strand_(io_service), socket_(io_service), request_handler_(handler) { _running = true; } void connection::start() { buffer_.fill (0); socket_.async_read_some(boost::asio::buffer(buffer_), strand_.wrap( boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred) ) ); } void connection::handle_read(const boost::system::error_code& e, std::size_t bytes_transferred) { if (!e) { // parse what we have so far. request_parser_.parse() is my code and it works correctly. // when successful result==true, request boost::tribool result; request_.reset(); boost::tie(result, boost::tuples::ignore) = request_parser_.parse( request_, buffer_.data(), buffer_.data() + bytes_transferred); if (result) { // we read an entire message // this is my code to process the message and put fill in the reply_ buffer. request_handler_.handle_request(request_, reply_); // send the reply boost::asio::async_write(socket_, reply_.to_buffers(), strand_.wrap( boost::bind(&connection::handle_writeResponse, shared_from_this(), boost::asio::placeholders::error) ) ); } else if (!result) { // there was an error reading the message boost::asio::async_write(socket_, reply_.to_buffers(), strand_.wrap( boost::bind(&connection::handle_writeResponse, shared_from_this(), boost::asio::placeholders::error) ) ); } else { // read some ok. need to read some more. socket_.async_read_some(boost::asio::buffer(buffer_), strand_.wrap( boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred) ) ); } } else { cout << "connection::handle_read: error: " << e.value() << " " << e.message() << endl; } // If an error occurs then no new asynchronous operations are started. This // means that all shared_ptr references to the connection object will // disappear and the object will be destroyed automatically after this // handler returns. The connection class's destructor closes the socket. } void connection::handle_writeResponse(const boost::system::error_code& e) { if (!e) { // test. This message is received by my client. do_writeMessage ("hello world"); // ready to read more start(); } else { cout << "connection::handle_writeMessage: error sending to client: " << e.value() << " " << e.message() << endl; } // No new asynchronous operations are started. This means that all shared_ptr // references to the connection object will disappear and the object will be // destroyed automatically after this handler returns. The connection class's // destructor closes the socket. } - - - - - - - - - - // call to this function is posed to io_service from server::write // public void connection::do_writeMessage(string msg) { bool write_in_progress = !_messagesToWrite.empty(); _messagesToWrite.push_back(msg); // if there are any in the queue, handle_writeMessage is already sending them. if (write_in_progress) { cout << "connection::do_writeMessage: write in progress." << endl; } else { // start the async write. boost::asio::async_write(socket_, boost::asio::buffer(_messagesToWrite.front().data(), _messagesToWrite.front().length()), strand_.wrap( boost::bind(&connection::handle_writeMessage, shared_from_this()/*this*/, boost::asio::placeholders::error) ) ); } } // async write is done. if no error and more messages to write, write them, too. void connection::handle_writeMessage(const boost::system::error_code& error) { if (!error) { cout << "connection::handle_writeMessage: message written ok." << endl; // remove the message we just wrote _messagesToWrite.pop_front(); // any more? if (!_messagesToWrite.empty()) { // write the next one and call this function when that'd done. boost::asio::async_write(socket_, boost::asio::buffer(_messagesToWrite.front().data(), _messagesToWrite.front().length()), strand_.wrap( boost::bind(&connection::handle_writeMessage, shared_from_this()/*this*/, boost::asio::placeholders::error) ) ); } else { cout << "connection::handle_writeMessage: no more messages" << endl; } } else { cout << "connection::handle_writeMessage: error: " << error.value() << " " << error.message() << endl; } // let this async chain end. } - - - - - - - - - - main() { pTCPServer = new http::server3::server (argv[TCPPortNumber]); if (pTCPServer) { pTCPServer->run(); } // start thread that will initiate 2nd message … … … }

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boost::function adding a lot of binary overhead
by Littlefield, Tyler 09 May '11

09 May '11

Hello all: I'm using boost::function in a few places so that I can use boost::bind to pass member pointers on objects, static member functions or just normal functions, but I'm noticing that I get a ton of extra overhead when compiling after I use boost::function in a new place. Is there a fix for this? I really like boost and some of it's features, but it's making my binaries huge. -- Take care, Ty my website: http://tds-solutions.net my blog: http://tds-solutions.net/blog skype: st8amnd127 “Programmers are in a race with the Universe to create bigger and better idiot-proof programs, while the Universe is trying to create bigger and better idiots. So far the Universe is winning.” “If Java had true garbage collection, most programs would delete themselves upon execution.”

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