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ASIO sockets and stream buffers
by Jeff Diewald 05 Feb '09

05 Feb '09

I'm having trouble with trying to connect my TCP sockets up to a stream buffer, and need some help. I've already opened my sending socket, or accepted a connection to get a new receiving socket, and I want to send messages back and forth. What I'd like to write is something like: void sendMessage(boost::asio::ip::tcp::socket* s) { ?? some stream type ?? str(s); str << ... write stuff ... << flush(); str >> ... read stuff ...; } I can't seem to find the right stream type that takes my existing socket. Does such a creature exist in the ASIO library? Help! Thanks in advance, Jeff Diewald JEOL USA

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Re: [Boost-users] boost and std collisons in c++0x
by Daniel Lidström 05 Feb '09

05 Feb '09

Hello, here is how I have solved this problem where I work: Create a header for each class that you want to use, that exists in both boost and std::tr1. For example, here's our local shared_ptr.h: #if !defined(SHARED_PTR_H__20080527T1436) #define SHARED_PTR_H__20080527T1436 #if defined(_MSC_VER) && _MSC_VER>=1500 && defined(_HAS_TR1) // Visual Studio 2008 TR1 version #include <memory> namespace GFLUtils = std::tr1; #else // Boost version #include <boost/shared_ptr.hpp> #include <boost/enable_shared_from_this.hpp> namespace GFLUtils = boost; #endif #endif If you also have to rely on VC6 (as we do) then you can't selectively import parts from a namespace (using boost::shared_ptr doesn't work). But if you only use more modern compiler, you can do this: #if !defined(SHARED_PTR_H__20080527T1436) #define SHARED_PTR_H__20080527T1436 #if defined(_MSC_VER) && _MSC_VER>=1500 && defined(_HAS_TR1) // Visual Studio 2008 TR1 version #include <memory> namespace GFLUtils { using std::tr1::shared_ptr; using std::tr1::enable_shared_from_this; } #else // Boost version #include <boost/shared_ptr.hpp> #include <boost/enable_shared_from_this.hpp> namespace GFLUtils { using boost::shared_ptr; using boost::enable_shared_from_this; } #endif #endif Hope this helps! Regards, Daniel Lidström Stockholm, Sweden _____ From: Ein Held [mailto:held_ein@yahoo.de] Sent: Wednesday, February 04, 2009 1:23 PM To: boost-users(a)lists.boost.org Subject: [Boost-users] boost and std collisons in c++0x Hello I would like to know more about boost's general attitude towards c++0x and the collisions of boost with std. As of now, we move both, ::boost- and ::std-namesspace in the global namespace via using xxx. This is exactly what we want - boost and the stl are both such fundamental libraries that using an explicit namespace specifier everytime we want to use content of these namespaces is not accaptable. This would just blow the code and make it unreadable. Once we move up to c++0x, we will not be able to keep this way of coding up. ::std::tr1 is merged into ::std and so the former tr1 classes will collide with the boost ones if explicit namespace identifiers are missing. I would like to stress the fact that code, perfectly fine to the boost documentation, will fail to compiler most likely. #include <iostream> //This one might include <array> using namespace std; #include <boost/array.hpp> using namespace boost; array<int,1> blub; //fail Is there anything planned to prevent this happen? Thank you

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[Accumulator] Build error in using BOOST::accumulator on WXP VC8
by dhruva 05 Feb '09

05 Feb '09

Hello, I am using BOOST::accumulator from 1.37. I get the following warning in the build on WXP using VC8 (MSVC 2005). I am exploring to find out where the problem could be, posting to find is someone has experienced this problem. Since our build treats warnings as errors, I am stuck. ...include\boost/fusion/container/vector/detail/deref_impl.hpp(46) : warning C4003: not enough actual parameters for macro 'index' -dhruva -- Contents reflect my personal views only! Add more friends to your messenger and enjoy! Go to http://messenger.yahoo.com/invite/

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[Python] Expose c++ instances to python
by Germán Diago 05 Feb '09

05 Feb '09

Hello. I'm trying to embed python to an application. I did that with success and I'm using boost.python to make some bindings to my API. What I would like, is that the interpreter has access to my objects at runtime, namely, I don't want to create objects from python code but to use the c++ objects, created in my c++ application, from python (and I have wrappers for those in boost.python). I don't know how to achieve this. I just know how to wrap classes, but I have no idea how to expose instances. Any idea how to achieve this? I googled and found nothing clear. Thanks in advance.

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[serialization] Sending user data to serialize()?
by Robert Dailey 04 Feb '09

04 Feb '09

Hi, I have a complex case I'm trying to work with. I may be doing this completely wrong so if there is a better design for this I'm always open for that. However for now I'm going to assume my particular problem can be solved. There exists two classes: A and B. Class A is defined as such: class A { public: template< typename Archive > void load( Archive& archive, unsigned int ) { archive & m_listOfB; } private: std::vector<int> m_listOfInt; boost::ptr_vector<B> m_listOfB; }; And class B is defined roughly as: class B { public: template< typename Archive > void load( Archive& archive, unsigned int ) { // Code isn't important here } }; Here's the problem: For each B that is deserialized by A::load(), I need to pass in a reference to m_listOfInt. So, essentially the load() function in B would look something like this: void load( Archive& archive, unsigned int, std::vector<int>& listOfInt ) { } I was hoping boost.bind could be used somewhere, but I just don't see how. One way to solve the problem is to call B::load() explicitly with the extra parameter, but I don't think that's an appropriate solution. Any ideas on how to solve this? Or perhaps I'm trying to solve the wrong problem.

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[boost.asio] repeating a timer
by Sean Farrow 04 Feb '09

04 Feb '09

Hi: I've just been looking at the boost asio timers, I was wondering whetherthere is a repeat timer, so that my call back will be executed everytime the timer completes. This needs to execute more than once. Any help apreciated. Sean.

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Finding the n smallest items in a list
by Ruediger Berlich 04 Feb '09

04 Feb '09

Hi there, I'm searching for a method to find the n smallest numbers in a list of m >> n numbers. The n numbers need to be sorted. m will usually be in the range of 100-1000, n will be 5 or less. So far I'm simply sorting the entire vector, which I assume is not very efficient, as the other m-n items in the container can remain unsorted. Is there a function in Boost that can help me in this situation ? Best Regards, Ruediger

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[date_time] posix_time::time_duration::operator<< fails for hours>23
by Soren Dreijer 04 Feb '09

04 Feb '09

I'm creating a posix_time::time_duration object based on the minutes() helper function. If I specify a large value, such as 2000, I get a time_duration of 33:20:00. Take a look at the following piece of code, though: time_duration td = minutes(2000); cout << to_simple_string(td); // OK cout << td; // Fails with an assertion in VS2008 The latter call fails with the following assertion in strftime.c on line 658: _VALIDATE_RETURN( ( ( timeptr->tm_hour >=0 ) && ( timeptr->tm_hour <= 23 ) ), EINVAL, FALSE) Apparently, operator<< expands to _expandtime(), which doesn't allow values for the hour to be greater than 23. Is this intended behavior, or should I just always use to_simple_string() rather than the convenient operator<< ?

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[asio] how to handle sync_accept error to avoid server hang on?
by tomasz jankowski 04 Feb '09

04 Feb '09

hello, actualy I'm testing my server. I'm making new connections faster than server is able to handle it. because of it server quickly is getting from system errno 24 (Too many open files). because of chaining async operation in asio design async_accept handler like below lead to server hang on. void AnldServer::handle_accept(const boost::system::error_code& e) { if (!e) { new_connection_->start(); new_connection_.reset(new AnldConnection(io_service_, request_handler_)); acceptor_.async_accept(new_connection_->socket(), boost::bind(&AnldServer::handle_accept, this, boost::asio::placeholders::error)); }else{ NDSLOG_NOTICE_S() << "Accept error: " << e << "\n"; } } Since we are not starting a new accept operation the io_service will run out of work to do and the server will hang on (if it was daemonised) or exit(if not). ofcourse server in production environment couldn't behaves like this. server must can handle such situation. my question is: how to fix it? just start async_accept without creating new_connection in case of error? like this for example? void AnldServer::handle_accept(const boost::system::error_code& e) { if (!e) { new_connection_->start(); new_connection_.reset(new AnldConnection(io_service_, request_handler_)); acceptor_.async_accept(new_connection_->socket(), boost::bind(&AnldServer::handle_accept, this, boost::asio::placeholders::error)); }else{ NDSLOG_NOTICE_S() << "Accept error: " << e << "\n"; acceptor_.async_accept(new_connection_->socket(), boost::bind(&AnldServer::handle_accept, this, boost::asio::placeholders::error)); } } I have just tested above code - it seems to work fine. but maybe someone have beter solution> or maybe it is good idea to add sleep(5) before async_accept in case of error? thanks, tom ---------------------------------------------------- Twoja rodzina na bliscy.pl Zobacz: http://klik.wp.pl/?adr=http%3A%2F%2Fcorto.www.wp.pl%2Fas%2Fbliscy.html&sid=…

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What does sys_err = 3 mean? or where can I find out?
by Andrew Bond 04 Feb '09

04 Feb '09

I am using Boost filesystem and I am getting an error (sys_err = 3). Where can I find a human-readable explanation of this error? Are there text explanations that can be included in my app to better inform the end user what the erro means? Any help will be much appreciated. Andrew Bond

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