Question

当我尝试获取（未设置！）时使用的当前到期时间 boost expires_from_now（）似乎实际上取消了计时器，但它实际上按预期运行，但最终没有调用处理程序。

或换句话说，当使用expires_from_now（）访问deadline_timer时它会立即调用处理程序，而不会在处理程序到期时调用它。

请考虑以下代码和相应的输出：

#include <boost/asio.hpp> 
#include <boost/thread.hpp> 
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/date_time/posix_time/posix_time_io.hpp>
#include <iostream> 

using namespace boost::posix_time;
using namespace std;

void handler1(const boost::system::error_code &ec) 
{ 
    if (ec == boost::asio::error::operation_aborted)
    {
        std::cout << microsec_clock::local_time() << " Handler1: Timer 1 was cancelled or retriggered." << std::endl; 
    }
    else
    {
        std::cout << microsec_clock::local_time() << " Handler1: expired." << std::endl; 
    }
} 

boost::asio::io_service io_service1; 

class Mytimer {
public:
    Mytimer();
    void startTimer();
    void runTimerThread();
    bool isRunning();
private:
    bool m_isRunning;
    boost::asio::deadline_timer* m_pTimer;
    boost::thread* m_pThread;
};

Mytimer::Mytimer()
  : m_pTimer(NULL),
    m_pThread(NULL)
{
    m_pTimer = new boost::asio::deadline_timer(io_service1); 
    m_pTimer->async_wait(handler1); 
}

void Mytimer::runTimerThread()
{
    io_service1.run();
}

void Mytimer::startTimer()
{
    m_pThread = new boost::thread(&Mytimer::runTimerThread, this);
    m_pTimer->expires_from_now(boost::posix_time::seconds(10));
}

bool Mytimer::isRunning()
{

    time_duration td = m_pTimer->expires_from_now();
    if (td.total_seconds() > 0)
    {
        return true;
    }
    return false;
}

int main() 
{ 
    time_facet *facet = new time_facet("%Y%m%d %H:%M:%S%f");
    std::cout.imbue(std::locale(std::cout.getloc(), facet));

    cout << microsec_clock::local_time() << " before timer construction" << endl;
    Mytimer timer;
    cout << microsec_clock::local_time() << " before startTimer()" << endl;
    timer.startTimer();
    cout << microsec_clock::local_time() << " IsRunning: " << timer.isRunning() << endl;
    for (int i = 0; i <= 20; i++)
    {
        sleep(1);
        cout << microsec_clock::local_time() << " IsRunning: " << timer.isRunning() << endl;
    }
}

20120412 22：41：45689235定时器施工前
  20120412 22：41：45689514在startTimer（）之前   20120412 22：41：45689619 IsRunning：1
  20120412 22：41：45689693处理程序1：计时器1被取消或重新触发   20120412 22：41：46689792 IsRunning：1
  20120412 22：41：47689994 IsRunning：1
  20120412 22：41：48690179 IsRunning：1
  20120412 22：41：49690375 IsRunning：1
  20120412 22：41：50690530 IsRunning：1
  20120412 22：41：51690712 IsRunning：1
  20120412 22：41：52690884 IsRunning：1
  20120412 22：41：53691069 IsRunning：1
  20120412 22：41：54691236 IsRunning：0
  20120412 22：41：55691428 IsRunning：0
  20120412 22：41：56691614 IsRunning：0
  20120412 22：41：57691810 IsRunning：0
  20120412 22：41：58692001 IsRunning：0
  20120412 22：41：59692193 IsRunning：0
  20120412 22：42：00692364 IsRunning：0
  20120412 22：42：01692542 IsRunning：0
  20120412 22：42：02692706 IsRunning：0
  20120412 22：42：03692886 IsRunning：0
  20120412 22：42：04693071 IsRunning：0
  20120412 22：42：05693267 IsRunning：0
  20120412 22：42：06693465 IsRunning：0

Answer 1

当我尝试使用boost获取（未设置！）当前到期时间 expires_from_now（）似乎实际上取消了计时器，但它实际上按预期运行，但最终没有调用处理程序。

这个假设是不正确的。当您创建deadline_timer

时

m_pTimer = new boost::asio::deadline_timer(io_service1);
m_pTimer->async_wait(handler1);

你告诉它立即过期。然后，当您开始io_service

时

m_pThread = new boost::thread(&Mytimer::runTimerThread, this);

您随后调用

m_pTimer->expires_from_now(boost::posix_time::seconds(10));

作为文档describes clearly，这将取消任何未完成的处理程序，重点是我的

此功能设定到期时间。 任何待处理的异步等待操作将被取消。每个已取消操作的处理程序将调用boost::asio::error::operation_aborted错误代码。

要解决此问题，请按以下步骤更改Mytimer::startTimer()方法

--- timer4.cc.orig  2012-04-13 11:18:47.000000000 -0500
+++ timer4.cc   2012-04-13 11:16:54.000000000 -0500
@@ -1,4 +1,3 @@
-
 #include <boost/asio.hpp> 
 #include <boost/thread.hpp> 
 #include <boost/date_time/posix_time/posix_time.hpp>
@@ -39,7 +38,6 @@
     m_pThread(NULL)
 {
     m_pTimer = new boost::asio::deadline_timer(io_service1); 
-    m_pTimer->async_wait(handler1); 
 }

 void Mytimer::runTimerThread()
@@ -49,8 +47,9 @@

 void Mytimer::startTimer()
 {
-    m_pThread = new boost::thread(&Mytimer::runTimerThread, this);
     m_pTimer->expires_from_now(boost::posix_time::seconds(10));
+    m_pTimer->async_wait(handler1); 
+    m_pThread = new boost::thread(&Mytimer::runTimerThread, this);
 }

 bool Mytimer::isRunning()

导致预期的行为

mbp:stackoverflow samm$ ./a.out
20120413 11:17:22922529 before timer construction
20120413 11:17:22923155 before startTimer()
20120413 11:17:22923530 IsRunning: 1
20120413 11:17:23924702 IsRunning: 1
20120413 11:17:24925971 IsRunning: 1
20120413 11:17:25927320 IsRunning: 1
20120413 11:17:26928715 IsRunning: 1
20120413 11:17:27929969 IsRunning: 1
20120413 11:17:28930601 IsRunning: 1
20120413 11:17:29931843 IsRunning: 1
20120413 11:17:30933098 IsRunning: 1
20120413 11:17:31934366 IsRunning: 0
20120413 11:17:32923594 Handler1: expired.
20120413 11:17:32934692 IsRunning: 0
20120413 11:17:33935922 IsRunning: 0
20120413 11:17:34936638 IsRunning: 0
20120413 11:17:35937905 IsRunning: 0
20120413 11:17:36939133 IsRunning: 0
20120413 11:17:37940407 IsRunning: 0
20120413 11:17:38941043 IsRunning: 0
20120413 11:17:39942319 IsRunning: 0
20120413 11:17:40942662 IsRunning: 0
20120413 11:17:41943989 IsRunning: 0
20120413 11:17:42945284 IsRunning: 0
20120413 11:17:43946555 IsRunning: 0
mbp:stackoverflow samm$

Answer 2

以下代码现在具有正确的deadline_timer初始化，并有一个私人布尔标志，允许确定，如果计时器当前正在运行。它还有一个成员本地处理程序。

class Mytimer {
public:
    Mytimer();
    void startTimer(int timeDelaySecs);
    void cancelTimer();
    void runTimerThread();
    bool isRunning();
    void timerHandler(const boost::system::error_code& ec); 
private:
    bool m_isRunning;
    boost::asio::deadline_timer* m_pTimer;
    boost::thread* m_pThread;
};

Mytimer::Mytimer()
    : m_pTimer(NULL),
      m_pThread(NULL)
{
    m_pTimer = new boost::asio::deadline_timer(io_service1); 
}

void Mytimer::runTimerThread()
{
    io_service1.run();
}

void Mytimer::startTimer(int timeDelaySecs)
{
    m_pTimer->expires_from_now(boost::posix_time::seconds(timeDelaySecs));
    m_pTimer->async_wait(boost::bind(&Mytimer::timerHandler, this, _1)); 
    m_pThread = new boost::thread(&Mytimer::runTimerThread, this);
    m_isRunning = true;
}

bool Mytimer::isRunning()
{
    return m_isRunning;
}

void Mytimer::timerHandler(const boost::system::error_code& ec) 
{ 
    if (ec == boost::asio::error::operation_aborted)
    {
        std::cout << microsec_clock::local_time() << " Handler1: Timer 1 was cancelled or retriggered." << std::endl; 
    }
    else
    {
        std::cout << microsec_clock::local_time() << " Handler1: expired." << std::endl; 
    }
    m_isRunning = false;
}

为什么boost asio函数expires_from_now（）取消deadline_timer？

2 个答案: