boost::asio学习 - multithreaded programs
今天在测试boost::asio Tutorial中的 Timer.5 - Synchronising handlers in multithreaded programs 程序时，发现数据处理始终是在主线程中执行的，为了验证“If you find yourself running into these limitations, an alternative approach is to have a pool of threads calling io_service::run()”遂对timer.cpp进行了一些修改：
1.取消使用boost::asio::strand::wrap()来封装回调函数；
2.在printer::print1()中强制线程sleep(1)来检测多线程的并发处理；
完整代码如下：
timer.cpp
1
#include
<
iostream
>
2
#include
<
boost
/
asio.hpp
>
3
#include
<
boost
/
thread.hpp
>
4
#include
<
boost
/
bind.hpp
>
5
#include
<
boost
/
date_time
/
posix_time
/
posix_time.hpp
>
6
7
class
printer
8
{
9
public
:
10
printer(boost::asio::io_service
&
io)
11
: strand_(io),
12
timer1_(io, boost::posix_time::seconds(
1
)),
13
timer2_(io, boost::posix_time::seconds(
1
)),
14
count_(
0
)
15
{
16
timer1_.async_wait(boost::bind(
&
printer::print1,
this
));
17
timer2_.async_wait(boost::bind(
&
printer::print2,
this
));
18
}
19
20
~
printer()
21
{
22
std::cout
<<
"
Final count is
"
<<
count_
<<
"
\n
"
;
23
}
24
25
void
print1()
26
{
27
std::cout
<<
boost::this_thread::get_id()
<<
"
\n
"
;
28
29
if
(count_
<
10
)
30
{
31
std::cout
<<
"
Timer 1:
"
<<
count_
<<
"
\n
"
;
32
++
count_;
33
34
timer1_.expires_at(timer1_.expires_at()
+
boost::posix_time::seconds(
1
));
35
timer1_.async_wait(boost::bind(
&
printer::print1,
this
));
36
}
37
sleep(
1
);
38
}
39
40
void
print2()
41
{
42
std::cout
<<
boost::this_thread::get_id()
<<
"
\n
"
;
43
44
if
(count_
<
10
)
45
{
46
std::cout
<<
"
Timer 2:
"
<<
count_
<<
"
\n
"
;
47
++
count_;
48
49
timer2_.expires_at(timer2_.expires_at()
+
boost::posix_time::seconds(
1
));
50
timer2_.async_wait(boost::bind(
&
printer::print2,
this
));
51
}
52
}
53
54
private
:
55
boost::asio::strand strand_;
56
boost::asio::deadline_timer timer1_;
57
boost::asio::deadline_timer timer2_;
58
int
count_;
59
};
60
61
int
main()
62
{
63
std::cout
<<
boost::this_thread::get_id()
<<
"
\n
"
;
64
65
boost::asio::io_service io;
66
printer p(io);
67
boost::thread t(boost::bind(
&
boost::asio::io_service::run,
&
io));
68
io.run();
69
t.join();
70
71
return
0
;
72
}
程序运行输出：
0x850e050
0x850e050
Timer 1: 0
0x850e810
Timer 2: 1
0x850e810
Timer 1: 2
0x850e050
Timer 2: 3
0x850e050
Timer 1: 4
0x850e810
Timer 2: 5
0x850e810
Timer 1: 6
0x850e050
Timer 2: 7
0x850e050
Timer 1: 8
0x850e810
Timer 2: 9
0x850e810
0x850e050
从输出结果可以看出：当多个线程运行同一个io_service::run()时，它们将并发执行该io_service上的待处理的handlers！