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#include <iostream>
#include <boost/asio.hpp>
#include <boost/thread.hpp>
#include <boost/bind.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
class printer
{
public:
printer(boost::asio::io_service& io)
: strand_(io),
timer1_(io, boost::posix_time::seconds(1)),
timer2_(io, boost::posix_time::seconds(1)),
count_(0)
{
timer1_.async_wait(strand_.wrap(boost::bind(&printer::print1, this)));
timer2_.async_wait(strand_.wrap(boost::bind(&printer::print2, this)));
}
~printer()
{
std::cout << "Final count is " << count_ << "\n";
}
void print1()
{
if (count_ < 10)
{
std::cout << "Timer 1: " << count_ << "\n";
++count_;
timer1_.expires_at(timer1_.expires_at() + boost::posix_time::seconds(1));
timer1_.async_wait(strand_.wrap(boost::bind(&printer::print1, this)));
}
}
void print2()
{
if (count_ < 10)
{
std::cout << "Timer 2: " << count_ << "\n";
++count_;
timer2_.expires_at(timer2_.expires_at() + boost::posix_time::seconds(1));
timer2_.async_wait(strand_.wrap(boost::bind(&printer::print2, this)));
}
}
private:
boost::asio::strand strand_;
boost::asio::deadline_timer timer1_;
boost::asio::deadline_timer timer2_;
int count_;
};
int main()
{
boost::asio::io_service io;
printer p(io);
boost::thread t(boost::bind(&boost::asio::io_service::run, &io));
io.run();
t.join();
return 0;
}
上面是boost::asio的范例(http://www.boost.org/doc/libs/1_ ... /tuttimer5/src.html)。
演示用strand来同步线程。
我搞不懂的是,有两个线程调用io.run,一个是主线程,一个是分线程(t).
是不是一个会调用printer::print1(), 另一个调用printer::print2()? 那么谁调用print1,谁用print2? 在哪里说明的。
还是两个线程都调用两个printer1/2?
看起来象后者,那么,为了演示的目的,是不是只要一个print1()就可以了?
如果是这样,那么当去掉print2及strand后, 输出的结果就不会同步,可是,我怎么得不到这个结果。 到底我是错哪里了? |