io_serviceでコールを実行せずにboost :: asio :: async_readを使用してタイムアウトを実装します。

Question

入力ソース（この場合はstdin）からタイムアウトを読み取ろうとしています。これに適合しなければならない既存のアプリケーションの設計上、私のio_serviceでrunを呼び出すことはできません。ここで

は、これまでの私の試みです：私の第一印象で

#include <boost/asio.hpp> 
#include <boost/bind.hpp> 
#include <boost/optional.hpp> 

void set_result(boost::optional<boost::system::error_code> * a, boost::system::error_code b) { 
    if(b == 0) 
     a->reset(b); 
} 

void receive(boost::asio::io_service & io, boost::asio::posix::stream_descriptor & stream, boost::asio::streambuf & result){ 
    boost::optional<boost::system::error_code> timer_result; 
    boost::optional<boost::system::error_code> read_result; 

    boost::asio::deadline_timer timer(io); 
    timer.expires_from_now(boost::posix_time::milliseconds(5000)); 
    timer.async_wait(boost::bind(&set_result, &timer_result, _1)); 

    boost::asio::async_read(
      stream, 
      result, 
      boost::asio::transfer_at_least(1), 
      boost::bind(&set_result, &read_result, _1)); 
    boost::system::error_code ec; 

    while(1) { 
     io.reset(); 
     io.poll_one(ec); 

     if (read_result) { 
      timer.cancel(); 
      return; 

     } else if (timer_result) 
      throw std::runtime_error("timeout"); 
    } 
} 

void receive(boost::asio::io_service & io, boost::asio::posix::stream_descriptor & stream, size_t size, boost::asio::streambuf & result){ 
    while(result.size() < size) 
     receive(io, stream, result); 
} 

int main(int argc, const char *argv[]) 
{ 
    boost::asio::io_service io; 
    boost::asio::posix::stream_descriptor in(io, ::dup(STDIN_FILENO)); 

    for(int i = 0; i < 5; i++){ 
     std::cout << i << " Type in 4 chareters and press enter" << std::endl << std::endl; 
     std::cout << "in> "; 
     std::cout.flush(); 
     try { 
      boost::asio::streambuf buf; 
      receive(io, in, 5, buf); 
      std::cout << "out> "; 
      std::copy(boost::asio::buffer_cast<const char *>(buf.data()), boost::asio::buffer_cast<const char *>(buf.data()) + buf.size(), std::ostream_iterator<char>(std::cout)); 

     } catch (const std::exception & e) { 
      std::cout << e.what() << std::endl; 
     } 
    } 

    return 0; 
} 

、私はそれが働いていたと思ったが、テストアプリで周りの多くを再生した後、私はいくつかのセグメンテーションフォールトを得ました。

最初のクエリがタイムアウトするのを待ってから次の5文字を​​入力すると、何か問題が発生することがわかりました。ここで

はvalgrindの言うことです：

==17216== Memcheck, a memory error detector 
==17216== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al. 
==17216== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info 
==17216== Command: ./ccTalkScan 
==17216== 
0 Type in 4 chareters and press enter 

asdf 
0 system:0 
1 Type in 4 chareters and press enter 

0 system:125 
0 system:0 
==17216== Invalid read of size 8 
==17216== at 0x546EB4A: ??? (setcontext.S:60) 
==17216== by 0x425245: receive(boost::asio::io_service&, boost::asio::posix::basic_stream_descriptor<boost::asio::posix::stream_descriptor_service>&, unsigned long, boost::asio::basic_streambuf<std::allocator<char> >&) (ccTalkScan.cxx:321) 
==17216== by 0x42535E: main (ccTalkScan.cxx:333) 
==17216== Address 0x7feffdfa8 is not stack'd, malloc'd or (recently) free'd 
==17216== 
==17216== Invalid read of size 8 
==17216== at 0x546EB52: ??? (setcontext.S:63) 
==17216== by 0x425245: receive(boost::asio::io_service&, boost::asio::posix::basic_stream_descriptor<boost::asio::posix::stream_descriptor_service>&, unsigned long, boost::asio::basic_streambuf<std::allocator<char> >&) (ccTalkScan.cxx:321) 
==17216== by 0x42535E: main (ccTalkScan.cxx:333) 
==17216== Address 0x7feffdf98 is not stack'd, malloc'd or (recently) free'd 
==17216== 
==17216== Invalid read of size 8 
==17216== at 0x546EB59: ??? (setcontext.S:64) 
==17216== by 0x425245: receive(boost::asio::io_service&, boost::asio::posix::basic_stream_descriptor<boost::asio::posix::stream_descriptor_service>&, unsigned long, boost::asio::basic_streambuf<std::allocator<char> >&) (ccTalkScan.cxx:321) 
==17216== by 0x42535E: main (ccTalkScan.cxx:333) 
==17216== Address 0x7feffdf68 is not stack'd, malloc'd or (recently) free'd 
==17216== 
==17216== Invalid read of size 8 
==17216== at 0x546EB4A: ??? (setcontext.S:60) 
==17216== by 0x5E4BD2C: (below main) (in /lib64/libc-2.12.2.so) 
==17216== Address 0x7feffe018 is not stack'd, malloc'd or (recently) free'd 
==17216== 
==17216== Invalid read of size 8 
==17216== at 0x546EB52: ??? (setcontext.S:63) 
==17216== by 0x5E4BD2C: (below main) (in /lib64/libc-2.12.2.so) 
==17216== Address 0x7feffe008 is not stack'd, malloc'd or (recently) free'd 
==17216== 
==17216== Invalid read of size 8 
==17216== at 0x546EB59: ??? (setcontext.S:64) 
==17216== by 0x5E4BD2C: (below main) (in /lib64/libc-2.12.2.so) 
==17216== Address 0x7feffdfd8 is not stack'd, malloc'd or (recently) free'd 
==17216== 
timeout 
2 Type in 4 chareters and press enter 

0 system:0 
timeout 
3 Type in 4 chareters and press enter 

asdf 
==17216== Syscall param readv(vector[...]) points to unaddressable byte(s) 
==17216== at 0x5EF7A81: readv (in /lib64/libc-2.12.2.so) 
==17216== by 0x42A77A: boost::asio::detail::descriptor_ops::non_blocking_read(int, iovec*, unsigned long, boost::system::error_code&, unsigned long&) (descriptor_ops.ipp:153) 
==17216== by 0x4355D1: boost::asio::detail::descriptor_read_op_base<boost::asio::mutable_buffers_1>::do_perform(boost::asio::detail::reactor_op*) (descriptor_read_op.hpp:55) 
==17216== by 0x4275DA: boost::asio::detail::reactor_op::perform() (reactor_op.hpp:40) 
==17216== by 0x4288F9: boost::asio::detail::epoll_reactor::run(bool, boost::asio::detail::op_queue<boost::asio::detail::task_io_service_operation>&) (epoll_reactor.ipp:286) 
==17216== by 0x429577: boost::asio::detail::task_io_service::do_one(boost::asio::detail::scoped_lock<boost::asio::detail::posix_mutex>&, boost::asio::detail::task_io_service::idle_thread_info*) (task_io_service.ipp:264) 
==17216== by 0x429165: boost::asio::detail::task_io_service::poll_one(boost::system::error_code&) (task_io_service.ipp:188) 
==17216== by 0x4299B8: boost::asio::io_service::poll_one(boost::system::error_code&) (io_service.ipp:103) 
==17216== by 0x424FDF: receive(boost::asio::io_service&, boost::asio::posix::basic_stream_descriptor<boost::asio::posix::stream_descriptor_service>&, boost::asio::basic_streambuf<std::allocator<char> >&) (ccTalkScan.cxx:308) 
==17216== by 0x425245: receive(boost::asio::io_service&, boost::asio::posix::basic_stream_descriptor<boost::asio::posix::stream_descriptor_service>&, unsigned long, boost::asio::basic_streambuf<std::allocator<char> >&) (ccTalkScan.cxx:321) 
==17216== by 0x42535E: main (ccTalkScan.cxx:333) 
==17216== Address 0x65ba920 is 0 bytes inside a block of size 512 free'd 
==17216== at 0x4C25C4F: operator delete(void*) (vg_replace_malloc.c:387) 
==17216== by 0x432317: __gnu_cxx::new_allocator<char>::deallocate(char*, unsigned long) (new_allocator.h:95) 
==17216== by 0x430D67: std::_Vector_base<char, std::allocator<char> >::_M_deallocate(char*, unsigned long) (stl_vector.h:146) 
==17216== by 0x42F4A0: std::_Vector_base<char, std::allocator<char> >::~_Vector_base() (stl_vector.h:132) 
==17216== by 0x42CF5E: std::vector<char, std::allocator<char> >::~vector() (stl_vector.h:313) 
==17216== by 0x42AEB5: boost::asio::basic_streambuf<std::allocator<char> >::~basic_streambuf() (basic_streambuf.hpp:114) 
==17216== by 0x425374: main (ccTalkScan.cxx:333) 
==17216== 
0 system:0 
4 Type in 4 chareters and press enter 

0 system:125 
0 system:0 
timeout 
==17216== 
==17216== HEAP SUMMARY: 
==17216==  in use at exit: 168 bytes in 3 blocks 
==17216== total heap usage: 63 allocs, 60 frees, 22,070 bytes allocated 

私はそれを修正するために別のものを試してみましたが、私はここの事か2を誤解しているかもしれないと思います。だから、いくつかの助けがいいだろう、そして一例が最も高く評価されるだろう;）

Answer 1

上記の実装の問題は、タイムアウトするasync_readsが決してキャンセルされないということです。これを行う方法は次のとおりです。

while(1) { 
     io.reset(); 
     io.poll_one(ec); 

     if (read_result) { 
      timer.cancel(); // cancel the timeout operation as it has not completed yet 
      return; 

     } else if (timer_result) { 
      stream.cancel(); // cancel the read operation as it has not completed yet 
      throw std::runtime_error("timeout"); 
     } 
    }