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[asio] are defer/dispatch/post identical?
by Frédéric 18 Sep '18

18 Sep '18

Hi, Is there a difference between defer, dispatch and post free functions? They look very similar, there files look the same apart from the fact that they call defer, dispatch and post of the executor. The doc in executor seems to be the same. Thanks, F

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Cannot cast from std::string to seastar::sstring.
by José Guilherme Vanz 17 Sep '18

17 Sep '18

Hi guys, I'm investigating a [bug](https://github.com/scylladb/scylla/issues/2905) in the Seastar/lexical_cast and I got stuck. Let me introduce what's going on and the further investigation that I did. The Seastar framework uses the boost program options to parse the command line arguments. But when the user try to pass a command line argument of seastar::sstring (Seastar string type) with a white space, the lib tells us that is invalid value. Turns out the boost program options call lexical_cast to cast from std::string to seastar::sstring. This cast is failing. The lexical_cast uses a stream to extract the value from the source, but the operator>> stops in the white space. Making the second validation in the same [line](https://github.com/boostorg/lexical_cast/blob/boost-1.66.0/include/bo… false. Note, there is a [call](https://github.com/boostorg/lexical_cast/blob/boost-1.66.0/include/bo… to unsetf to ensure that the white space will be skipped: stream.unsetf(std::ios::skipws);. What's am I trying to do is figure out where the problems live? Is there a bug in boost or is a sstring implemantion problem? Am I missing something? Thanks!

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Re: [Boost-users] Looking for a mechanism (boost::asio
by Bjorn Reese 15 Sep '18

15 Sep '18

On 09/14/18 23:21, Tim Burgess via Boost-users wrote: > I need my main code to pause until I receive a response from the > hardware. I don’t want to use a timer, as this would be potentially Sounds like you need a promise/future.

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Re: [Boost-users] Looking for a mechanism (boost::asio
by tim＠raisedbar.net 15 Sep '18

15 Sep '18

OK, I’ve just read the preamble for the ASIO library (Chapter 32) and it seems that this library, whilst extremely useful, does exactly the opposite of what I’m trying to achieve, as it allows main code execution to continue whilst waiting for a response from an external device. I need my main code to pause until I receive a response from the hardware. I don’t want to use a timer, as this would be potentially unreliable - I can never know how long a pause would be required and there would be the danger of having the code hanging around wasting time if the timer value is too generous. Best wishes. Tim Burgess From: Boost-users <boost-users-bounces(a)lists.boost.org> On Behalf Of Tim Burgess via Boost-users Sent: 14 September 2018 20:49 To: boost-users(a)lists.boost.org Cc: tim(a)raisedbar.net Subject: Re: [Boost-users] Looking for a mechanism Thanks – I’ll go and do some reading. Just to add more information: the hardware is a MIDI device, with the sent messages being groups of 6 individual short MIDI messages, so a total of 18 7-bit bytes per transmitted query. The response messages are groups of 4 MIDI short messages. There is something like 200 parameters to be queried – the MIDI connection is either via traditional DIN cables with a transfer rate of 31kbps, or over USB. Over the USB connection the manufacturer estimates that I should be able to get a full set of responses back in around 100ms. I’m using the rtMIDI library to do the heavy lifting in terms of handling the MIDI I/O devices and handling themessage formatting. Best wishes. Tim Burgess From: Boost-users <boost-users-bounces(a)lists.boost.org <mailto:boost-users-bounces@lists.boost.org> > On Behalf Of Keith Bennett via Boost-users Sent: 14 September 2018 18:54 To: boost-users(a)lists.boost.org <mailto:boost-users@lists.boost.org> Cc: Keith Bennett <kanezor(a)gmail.com <mailto:kanezor@gmail.com> > Subject: Re: [Boost-users] Looking for a mechanism Without more information it'd be hard to say. Are you familiar with Boost ASIO? It's a common method of handling asynchronous communication, though how much it can be used in your situation may depend on the particular hardware interface. The typical situation for a single-threaded process is to set up an executor context, maybe set up signal handlers, then make an asynchronous call using ASIO's objects. When making the asynchronous calls, you provide a callback function object. Your callback function object may then make another request during its processing. ASIO handles the under-the-hood abstraction (and generally simplifies it for most situations). But it's up to you to ensure that your call sequence is safe: for example ASIO will not prevent you from making multiple simultaneous writes to the same file descriptor despite it being unsafe in many situations. My understanding is that your callback is placed onto a function queue rather than called directly (contrast to POSIX signals where the OS interrupts whatever function is running right now). That can hurt your response performance if you're doing long-running tasks so it's worth considering. On Fri, Sep 14, 2018 at 12:03 PM Tim Burgess via Boost-users <boost-users(a)lists.boost.org <mailto:boost-users@lists.boost.org> > wrote: Hi, I’m trying to find a method of solving the problem detailed below using Boost (or an alternative: 1 – I have to send a series of messages to a hardware device to query its internal parameter values at application load-time. This I can do; 2 – I have a callback that receives responses from the hardware, though I get some replies go missing due to saturation; 3 * The hardware manufacturer tells me that I should send 1 query then wait for the response before sending the next query. I could use Sleep, but this depends on a specific wait time and I’m not sure if it suspends all processing, including my callback, so this doesn’t look satisfactory. What I’m looking for is a “wait until response” kind of thing, but I haven’t found such a thing so far, though I have found several wait routines for handling multiple threads. I’d appreciate any guidance as to what to look for, as my searches are obviously not asking the right questions. Best wishes. Tim Burgess Raised Bar Ltd. E: tim(a)raisedbar.net <mailto:tim@raisedbar.net> M: +44 (0)7989 486976 _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org <mailto:Boost-users@lists.boost.org> https://lists.boost.org/mailman/listinfo.cgi/boost-users -- Keith Bennett

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Looking for a mechanism
by tim＠raisedbar.net 14 Sep '18

14 Sep '18

Hi, I'm trying to find a method of solving the problem detailed below using Boost (or an alternative: 1 - I have to send a series of messages to a hardware device to query its internal parameter values at application load-time. This I can do; 2 - I have a callback that receives responses from the hardware, though I get some replies go missing due to saturation; 3 * The hardware manufacturer tells me that I should send 1 query then wait for the response before sending the next query. I could use Sleep, but this depends on a specific wait time and I'm not sure if it suspends all processing, including my callback, so this doesn't look satisfactory. What I'm looking for is a "wait until response" kind of thing, but I haven't found such a thing so far, though I have found several wait routines for handling multiple threads. I'd appreciate any guidance as to what to look for, as my searches are obviously not asking the right questions. Best wishes. Tim Burgess Raised Bar Ltd. E: <mailto:tim@raisedbar.net> tim(a)raisedbar.net M: +44 (0)7989 486976

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[Beast] Downloading multiple urls in parallel
by Sean Farrow 13 Sep '18

13 Sep '18

Hi, Are there functions within beast to allow me to start downloading multiple url's in parallel and then handle each returned result with a different continuation function? Any help appreciated. Kind regards Sean.

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[ASIO] Reestablish TCP connection after EOF
by csizmadiatamas 12 Sep '18

12 Sep '18

I would like to make a c++ TCP client using boost::asio based on this article: https://www.gamedev.net/blogs/entry/2249317-a-guide-to-getting-started-with… I have an existing server which behaviour is similar to a router configuration. You can connect to it and as soon as you have a command promt you can send a command to the server. It executes it and sends back the result and a command promt. Then you can send the next command... There is no problem with this part. My code is able to establish the connection, send and recive data until my client gets EOF. It means the server broke the connection. I would like my client to be able to reestablish the connection and this part is not working. Very much would appreciate your help. *Here is my header:* #pragma once #include <boost/asio.hpp> #include <boost/thread.hpp> #include <boost/asio/io_context_strand.hpp> class Hive; class Connection; class Connection : public boost::enable_shared_from_this< Connection > { friend class Hive; private: static const int m_reconnect_interval = 15000; boost::shared_ptr< Hive > m_hive; boost::asio::ip::tcp::socket m_socket; boost::asio::io_service::strand m_io_strand; boost::asio::deadline_timer m_keepalive_timer; boost::asio::deadline_timer m_reconnect_timer; boost::posix_time::ptime m_last_time; std::vector< uint8_t > m_recv_buffer; std::list< int32_t > m_pending_recvs; std::list< std::vector< uint8_t > > m_pending_sends; int32_t m_receive_buffer_size; int32_t m_keepalive_timer_interval; protected: Connection( boost::shared_ptr< Hive > hive ); virtual ~Connection(); private: Connection( const Connection & rhs ); Connection & operator =( const Connection & rhs ); void StartSend(); void StartRecv( int32_t total_bytes ); void StartKeepAliveTimer(); void StartReconnectTimer(); void StartError(const boost::system::error_code &error, std::string caller); void DispatchSend( std::vector< uint8_t > buffer ); void DispatchRecv( int32_t total_bytes ); void DispatchTimer( const boost::system::error_code & error ); void ReconnectTimer( const boost::system::error_code & error ); void HandleConnect( const boost::system::error_code & error ); void HandleSend( const boost::system::error_code & error, std::list< std::vector< uint8_t > >::iterator itr ); void HandleRecv( const boost::system::error_code & error, int32_t actual_bytes ); void HandleKeepAliveTimer(const boost::system::error_code &error); void HandleReconnectTimer( const boost::system::error_code & error ); void Reconnect(); private: // Called when the connection has successfully connected to the local host. virtual void OnAccept( const std::string & host, uint16_t port ) = 0; // Called when the connection has successfully connected to the remote host. virtual void OnConnect( const std::string & host, uint16_t port ) = 0; // Called when data has been sent by the connection. virtual void OnSend( const std::vector< uint8_t > & buffer ) = 0; // Called when data has been received by the connection. virtual void OnRecv( std::vector< uint8_t > & buffer ) = 0; // Called on each timer event. virtual void OnTimer( const boost::posix_time::time_duration & delta ) = 0; // Called when an error is encountered. virtual void OnError(const std::string error) = 0; public: // Starts an a/synchronous connect. void Connect(const std::string &host, const std::string &port); // Posts data to be sent to the connection. void Send(std::string message); // Posts a recv for the connection to process. If total_bytes is 0, then // as many bytes as possible up to GetReceiveBufferSize() will be // waited for. If Recv is not 0, then the connection will wait for exactly // total_bytes before invoking OnRecv. void Recv( int32_t total_bytes = 0 ); // Posts an asynchronous disconnect event for the object to process. void Disconnect(); }; class Hive : public boost::enable_shared_from_this< Hive > { private: boost::asio::io_service m_io_service; boost::shared_ptr< boost::asio::io_service::work > m_work_ptr; private: Hive( const Hive & rhs ); Hive & operator =( const Hive & rhs ); public: Hive(); virtual ~Hive(); // Returns the io_service of this object. boost::asio::io_service & GetService(); // Polls the networking subsystem once from the current thread and returns. void Poll(); // Runs the networking system on the current thread. This function blocks // until the networking system is stopped, so do not call on a single // threaded application with no other means of being able to call Stop // unless you code in such logic. void Run(); // Stops the networking system. All work is finished and no more // networking interactions will be possible afterwards until Reset is called. void Stop(); // Restarts the networking system after Stop as been called. A new work // object is created ad the shutdown flag is cleared. void Reset(); }; *and here is my cpp:* #include "network.h" #include <boost/interprocess/detail/atomic.hpp> #include <boost/interprocess/detail/config_begin.hpp> #include <boost/interprocess/detail/workaround.hpp> #include <boost/cstdint.hpp> #include <iostream> Hive::Hive() : m_work_ptr( new boost::asio::io_service::work( m_io_service ) ) { } Hive::~Hive() { } boost::asio::io_service & Hive::GetService() { return m_io_service; } void Hive::Poll() { m_io_service.poll(); } void Hive::Run() { m_io_service.run(); } void Hive::Stop() { m_work_ptr.reset(); m_io_service.run(); m_io_service.stop(); } void Hive::Reset() { m_io_service.reset(); m_work_ptr.reset( new boost::asio::io_service::work( m_io_service ) ); } Connection::Connection( boost::shared_ptr< Hive > hive ) : m_hive( hive ), m_socket( hive->GetService() ), m_io_strand( hive->GetService() ), m_keepalive_timer( hive->GetService() ), m_reconnect_timer(hive->GetService()), m_receive_buffer_size( 4096 ), m_keepalive_timer_interval( 2000 ) { } Connection::~Connection() { } void Connection::StartSend() { if( !m_pending_sends.empty() ) boost::asio::async_write( m_socket, boost::asio::buffer( m_pending_sends.front() ), boost::asio::bind_executor(m_io_strand, boost::bind( &Connection::HandleSend, shared_from_this(), boost::asio::placeholders::error, m_pending_sends.begin() ) ) ); } void Connection::StartRecv( int32_t total_bytes ) { if( total_bytes > 0 ) { m_recv_buffer.resize( total_bytes ); boost::asio::async_read( m_socket, boost::asio::buffer( m_recv_buffer ), boost::asio::bind_executor(m_io_strand, boost::bind( &Connection::HandleRecv, shared_from_this(), _1, _2 ) ) ); } else { m_recv_buffer.resize( m_receive_buffer_size ); m_socket.async_read_some( boost::asio::buffer( m_recv_buffer ), boost::asio::bind_executor(m_io_strand, boost::bind( &Connection::HandleRecv, shared_from_this(), _1, _2 ) ) ); } } void Connection::StartKeepAliveTimer() { std::cout << "[" << __FUNCTION__ << "] " << std::endl; m_last_time = boost::posix_time::microsec_clock::local_time(); m_keepalive_timer.expires_from_now( boost::posix_time::milliseconds( m_keepalive_timer_interval ) ); m_keepalive_timer.async_wait( boost::asio::bind_executor(m_io_strand, boost::bind( &Connection::DispatchTimer, shared_from_this(), _1 ) ) ); } void Connection::StartReconnectTimer() { std::cout << "[" << __FUNCTION__ << "] " << std::endl; m_last_time = boost::posix_time::microsec_clock::local_time(); m_reconnect_timer.expires_from_now( boost::posix_time::milliseconds( m_reconnect_interval ) ); m_reconnect_timer.async_wait( boost::asio::bind_executor(m_io_strand, boost::bind( &Connection::ReconnectTimer, shared_from_this(), _1 ) ) ); } void Connection::StartError(const boost::system::error_code &error, std::string caller) { OnError(caller + " " + error.message() + "(" + error.category().name() + ":" + std::to_string(error.value()) + ")"); boost::system::error_code ec; m_socket.shutdown(boost::asio::ip::tcp::socket::shutdown_both, ec); m_socket.close(ec); m_keepalive_timer.cancel(ec); if (error == boost::asio::error::misc_errors::eof || error == boost::system::errc::timed_out) StartReconnectTimer(); } void Connection::HandleConnect( const boost::system::error_code & error ) { if( error ) StartError(error, __FUNCTION__); else { if( m_socket.is_open() ) { OnConnect( m_socket.remote_endpoint().address().to_string(), m_socket.remote_endpoint().port() ); m_reconnect_timer.cancel(); StartKeepAliveTimer(); } else StartError(error, __FUNCTION__); } } void Connection::HandleSend( const boost::system::error_code & error, std::list< std::vector< uint8_t > >::iterator itr ) { if( error ) StartError(error, __FUNCTION__); else { OnSend( *itr ); m_pending_sends.erase( itr ); StartSend(); } } void Connection::HandleRecv( const boost::system::error_code & error, int32_t actual_bytes ) { if( error ) StartError(error, __FUNCTION__); else { m_recv_buffer.resize( actual_bytes ); OnRecv( m_recv_buffer ); m_pending_recvs.pop_front(); if( !m_pending_recvs.empty() ) StartRecv( m_pending_recvs.front() ); } } void Connection::HandleKeepAliveTimer(const boost::system::error_code &error) { if( error ) StartError(error, __FUNCTION__); else { OnTimer( boost::posix_time::microsec_clock::local_time() - m_last_time ); StartKeepAliveTimer(); } } void Connection::HandleReconnectTimer( const boost::system::error_code & error ) { std::cout << "[" << __FUNCTION__ << "] Calling reconnect... " << std::endl; Reconnect(); } void Connection::DispatchSend( std::vector< uint8_t > buffer ) { bool should_start_send = m_pending_sends.empty(); m_pending_sends.push_back( buffer ); if( should_start_send ) StartSend(); } void Connection::DispatchRecv( int32_t total_bytes ) { bool should_start_receive = m_pending_recvs.empty(); m_pending_recvs.push_back( total_bytes ); if( should_start_receive ) StartRecv( total_bytes ); } void Connection::DispatchTimer( const boost::system::error_code & error ) { boost::asio::post(m_io_strand, boost::bind(&Connection::HandleKeepAliveTimer, shared_from_this(), error ) ); } void Connection::ReconnectTimer( const boost::system::error_code & error ) { boost::asio::post(m_io_strand, boost::bind( &Connection::HandleReconnectTimer, shared_from_this(), error ) ); } void Connection::Connect(const std::string &host, const std::string &port) { std::cout << "[" << __FUNCTION__ << "] connecting to "<< host << ":" << port << std::endl; boost::system::error_code ec; boost::asio::ip::tcp::resolver resolver( m_hive->GetService() ); boost::asio::ip::tcp::resolver::query query( host, port ); boost::asio::ip::tcp::resolver::iterator iterator = resolver.resolve( query ); m_socket.async_connect( *iterator, boost::asio::bind_executor(m_io_strand, boost::bind( &Connection::HandleConnect, shared_from_this(), _1 ) ) ); } void Connection::Reconnect() { m_hive->Reset(); Connect("10.40.60.72", "23"); } void Connection::Disconnect() { boost::asio::post(m_io_strand, boost::bind(&Connection::HandleKeepAliveTimer, shared_from_this(), boost::asio::error::connection_reset ) ); } void Connection::Recv( int32_t total_bytes ) { boost::asio::post(m_io_strand, boost::bind( &Connection::DispatchRecv, shared_from_this(), total_bytes ) ); } void Connection::Send(std::string message) { std::vector< uint8_t > request; std::copy( message.begin(), message.end(), std::back_inserter( request ) ); boost::asio::post(m_io_strand, boost::bind( &Connection::DispatchSend, shared_from_this(), request ) ); } -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Users-f2553780.html

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Memory header not found
by Sudhanshu Dubey 11 Sep '18

11 Sep '18

Hey guys, I am new here and wanted some help from you guys. I was trying to upgrade and compile the FElt software, a software for finite element analysis. The source code is here : https://github.com/AkMecha/felt Now, the problem is that during compilation, one of the source file is including some header file from the boost library. The chain of including goes on and reaches the memory.hpp file which is present in /usr/include/boost/config/no_tr1/ directory. This memory.hpp is in turn including the memory header file from the standard C++ library, but it can't find that memory header file. And this is strange because I personally went and checked that the memory header is there in the standard location, as you can see below : sudhanshu@sudhanshu-Inspiron-15-3567:/usr/include/c++/7.3.0$ ls algorithm cerrno complex cstdio decimal initializer_list map queue stdlib.h typeindex any cfenv complex.h cstdlib deque iomanip math.h random streambuf typeinfo array cfloat condition_variable cstring exception ios memory ratio string type_traits atomic chrono csetjmp ctgmath experimental iosfwd mutex regex string_view unordered_map backward cinttypes csignal ctime ext iostream new scoped_allocator system_error unordered_set bits ciso646 cstdalign cuchar fenv.h istream numeric set tgmath.h utility bitset climits cstdarg cwchar forward_list iterator optional shared_mutex thread valarray cassert clocale cstdbool cwctype fstream limits ostream sstream tr1 variant ccomplex cmath cstddef cxxabi.h functional list parallel stack tr2 vector cctype codecvt cstdint debug future locale profile stdexcept tuple The error message shown during the compilation is : [ 51%] Building C object src/Burluap/CMakeFiles/burluap.dir/apply.c.o In file included from /usr/include/boost/smart_ptr/shared_ptr.hpp:23:0, from /usr/include/boost/shared_ptr.hpp:17, from /home/sudhanshu/Pictures/felt/include/matrix.h:23, from /home/sudhanshu/Pictures/felt/src/Burluap/descriptor.h:35, from /home/sudhanshu/Pictures/felt/src/Burluap/trap.h:31, from /home/sudhanshu/Pictures/felt/src/Burluap/apply.c:29: /usr/include/boost/config/no_tr1/memory.hpp:21:12: fatal error: memory: No such file or directory # include <memory> ^~~~~~~~ compilation terminated. src/Burluap/CMakeFiles/burluap.dir/build.make:62: recipe for target 'src/Burluap/CMakeFiles/burluap.dir/apply.c.o' failed make[2]: *** [src/Burluap/CMakeFiles/burluap.dir/apply.c.o] Error 1 CMakeFiles/Makefile2:504: recipe for target 'src/Burluap/CMakeFiles/burluap.dir/all' failed make[1]: *** [src/Burluap/CMakeFiles/burluap.dir/all] Error 2 Makefile:129: recipe for target 'all' failed make: *** [all] Error 2 So can I get some help as to what should I do to make the memory.hpp find the memory header file? -- Sudhanshu Dubey https://hacksd.wordpress.com https://github.com/Sudhanshu-Dubey14

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ASIO?
by tim＠raisedbar.net 05 Sep '18

05 Sep '18

Hi, I'm looking for a mechanism allowing me to enumerate serial (Com) ports on Windows/Mac. I also need to be able to retrieve the name of a given serial device. I've had a quick look at boost::asio, but it isn't clear to me if it can do what I want. I'd be grateful for any advice, including alternatives if boost and/or ASIO aren't up to the job. Best wishes. Tim Burgess Raised Bar Ltd. E: <mailto:tim@raisedbar.net> tim(a)raisedbar.net M: +44 (0)7989 486976

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mcgregor_common_subgraphs usage/complexity/performance/runtime
by Julian Wolf 01 Sep '18

01 Sep '18

Hello everyone, I'm new to Boost and today I tried to use the mcgregor_common_subgraphs functions but can't find an explanation why the function shows such bad performance when I use it. According to the documentation [1] the algorithm runs in O(V1 * V2) for the entire space with V being the number of vertices in the two graphs. So not great, but I'd expect that to run in reasonable time for graphs with less than 100 vertices. But in my case it doesn't, therefore any help appreciated whether I have some error or misconception on my side or whether this is expected performance. What I'm trying to achieve: I want to check whether two graphs have a common subgraph of size x. x depends on the size of smaller graph, I'm using a factor y for this with 0 < y < 1. With smaller values for x (e.g. x = 0.7 * V1) the example returns very fast, which makes sense since a smaller part of the search space needs to be explored. If I increase the factor to 0.8 * V1 or even run through the whole search space the program does not terminate within 10 minutes (where I canceled) I'll attach a working example as well as two graphs (44 and 46 vertices) showing the behaviour described. # gcc CommonSubgraph.cpp -o common_subgraph_example -lboost_graph -lstdc++ # time ./common_subgraph_example 0.7 graph1.dot graph2.dot Factor 0.7 Size: 30 real 0m0.043s # time ./common_subgraph_example 0.8 graph1.dot graph2.dot Factor 0.8 ^C real 10m39.741s My system runs openSUSE Tumbleweed with Boost 1.67 > rpm -q --whatprovides /usr/include/boost/graph/mcgregor_common_subgraphs.hpp libboost_headers1_67_0-devel-1.67.0-2.3.x86_64 Thank you! Julian [1] https://www.boost.org/doc/libs/1_68_0/libs/graph/doc/ mcgregor_common_subgraphs.html

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