这几天看了下perl的事件编程框架AnyEvent,重点参考了一下几篇文章：
http://search.cpan.org/~mlehmann/AnyEvent-7.05/lib/AnyEvent.pm
http://search.cpan.org/~mlehmann/AnyEvent-7.05/lib/AnyEvent/Intro.pod
https://www.jb51.net/article/55278.htm
1、什么是事件编程？
举个简单的例子，你浏览网页的时候，你点击一个图片，蹭的弹出一个东西，你不点，那就在那里，等待一个人来点它。如果你写过js，其实就是，你注册了很多的时间比如click，dbclick，keybord，submit等，那么浏览器就起到帮我们去监听这些事件的发生（Loop）。当有对应的事件发生的时候，我们也一般也设置了callback，比如onclick，onsubmit等，去响应这些事件，这基本就是事件编程的一个缩影了。
2、perl AnyEvent中的watcher
在AnyEvent中有5中watcher，分别是IO，timer，signal, child, idle.
2.1 io watcher
#!/usr/bin/perl
use AnyEvent;
my $cv = AnyEvent->condvar;
#open my $file , '<' , 'test.txt' or die "$!" ;
open F , '<' , 'test.txt' or die "$!" ;
my $io_watcher = AnyEvent->io (
fh => *F,
poll => 'r',
cb => sub {
chomp (my $input = sysread F ,my $buf ,1024); # read a line
warn "read: $buf\n" if $input >0 ; # output what has been read
#$cv->send if /quit/ ; # quit program if /quit/i
},
);
$cv->recv; # wait until user enters /quit/i
timer watcher
AnyEvent 的timer的一部分其实像javascript的setInterval :
#!/usr/bin/perl
use 5.016;
use AnyEvent ;
my $cv = AnyEvent->condvar ;
my $w = AnyEvent->timer(
after => 0 , #多少秒之后触发事件
interval => 2 , #多少秒触发事件
cb => sub {
say AnyEvent->time ," ",AnyEvent->now ;
}
);
$cv->recv;
signal watcher
前面我们在的文章中写到了perl中对于信号的处理 《perl信号处理简单学习》，这里主要是AnyEvent中对于这些事件的处理。
#!/usr/bin/perl
use 5.016;
use AnyEvent ;
#say for keys %SIG; 看一下又多少信号
my $cv = AnyEvent->condvar ;
my $w = AnyEvent->signal(
signal => 'INT',
cb => sub {
say AnyEvent->time ," ",AnyEvent->now ;
exit 1 ;
}
);
$cv->recv;
child watcher
#!/usr/bin/perl
use AnyEvent;
my $done = AnyEvent->condvar;
my $pid = fork or exit 5;
my $w = AnyEvent->child (
pid => $pid,
cb => sub {
my ($pid, $status) = @_;
warn "pid $pid exited with status $status";
$done->send;
},
);
# do something else, then wait for process exit
$done->recv;
idle watcher
就是如果main loop在空闲的时候做些什么呢？
#!/usr/bin/perl
use AnyEvent;
my @lines; # read data
my $idle_w;
$cv = AnyEvent->condvar;
my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
push @lines, scalar <STDIN>;
# start an idle watcher, if not already done
$idle_w ||= AnyEvent->idle (cb => sub {
# handle only one line, when there are lines left
if (my $line = shift @lines) {
print "handled when idle: $line";
} else {
# otherwise disable the idle watcher again
undef $idle_w;
}
});
});
$cv->recv;
