threads.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "threads 3"
.TH threads 3 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
threads \- Perl interpreter\-based threads
.SH "VERSION"
.IX Header "VERSION"
This document describes threads version 1.67
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\&    use threads (\*(Aqyield\*(Aq,
\&                 \*(Aqstack_size\*(Aq => 64*4096,
\&                 \*(Aqexit\*(Aq => \*(Aqthreads_only\*(Aq,
\&                 \*(Aqstringify\*(Aq);
\&
\&    sub start_thread {
\&        my @args = @_;
\&        print(\*(AqThread started: \*(Aq, join(\*(Aq \*(Aq, @args), "\en");
\&    }
\&    my $thr = threads\->create(\*(Aqstart_thread\*(Aq, \*(Aqargument\*(Aq);
\&    $thr\->join();
\&
\&    threads\->create(sub { print("I am a thread\en"); })\->join();
\&
\&    my $thr2 = async { foreach (@files) { ... } };
\&    $thr2\->join();
\&    if (my $err = $thr2\->error()) {
\&        warn("Thread error: $err\en");
\&    }
\&
\&    # Invoke thread in list context (implicit) so it can return a list
\&    my ($thr) = threads\->create(sub { return (qw/a b c/); });
\&    # or specify list context explicitly
\&    my $thr = threads\->create({\*(Aqcontext\*(Aq => \*(Aqlist\*(Aq},
\&                              sub { return (qw/a b c/); });
\&    my @results = $thr\->join();
\&
\&    $thr\->detach();
\&
\&    # Get a thread\*(Aqs object
\&    $thr = threads\->self();
\&    $thr = threads\->object($tid);
\&
\&    # Get a thread\*(Aqs ID
\&    $tid = threads\->tid();
\&    $tid = $thr\->tid();
\&    $tid = "$thr";
\&
\&    # Give other threads a chance to run
\&    threads\->yield();
\&    yield();
\&
\&    # Lists of non\-detached threads
\&    my @threads = threads\->list();
\&    my $thread_count = threads\->list();
\&
\&    my @running = threads\->list(threads::running);
\&    my @joinable = threads\->list(threads::joinable);
\&
\&    # Test thread objects
\&    if ($thr1 == $thr2) {
\&        ...
\&    }
\&
\&    # Manage thread stack size
\&    $stack_size = threads\->get_stack_size();
\&    $old_size = threads\->set_stack_size(32*4096);
\&
\&    # Create a thread with a specific context and stack size
\&    my $thr = threads\->create({ \*(Aqcontext\*(Aq    => \*(Aqlist\*(Aq,
\&                                \*(Aqstack_size\*(Aq => 32*4096,
\&                                \*(Aqexit\*(Aq       => \*(Aqthread_only\*(Aq },
\&                              \e&foo);
\&
\&    # Get thread\*(Aqs context
\&    my $wantarray = $thr\->wantarray();
\&
\&    # Check thread\*(Aqs state
\&    if ($thr\->is_running()) {
\&        sleep(1);
\&    }
\&    if ($thr\->is_joinable()) {
\&        $thr\->join();
\&    }
\&
\&    # Send a signal to a thread
\&    $thr\->kill(\*(AqSIGUSR1\*(Aq);
\&
\&    # Exit a thread
\&    threads\->exit();
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Perl 5.6 introduced something called interpreter threads.  Interpreter threads
are different from \fI5005threads\fR (the thread model of Perl 5.005) by creating
a new Perl interpreter per thread, and not sharing any data or state between
threads by default.
.PP
Prior to Perl 5.8, this has only been available to people embedding Perl, and
for emulating \fIfork()\fR on Windows.
.PP
The \fIthreads\fR \s-1API\s0 is loosely based on the old Thread.pm \s-1API\s0. It is very
important to note that variables are not shared between threads, all variables
are by default thread local.  To use shared variables one must also use
threads::shared:
.PP
.Vb 2
\&    use threads;
\&    use threads::shared;
.Ve
.PP
It is also important to note that you must enable threads by doing \f(CW\*(C`use
threads\*(C'\fR as early as possible in the script itself, and that it is not
possible to enable threading inside an \f(CW\*(C`eval ""\*(C'\fR, \f(CW\*(C`do\*(C'\fR, \f(CW\*(C`require\*(C'\fR, or
\&\f(CW\*(C`use\*(C'\fR.  In particular, if you are intending to share variables with
threads::shared, you must \f(CW\*(C`use threads\*(C'\fR before you \f(CW\*(C`use threads::shared\*(C'\fR.
(\f(CW\*(C`threads\*(C'\fR will emit a warning if you do it the other way around.)
.ie n .IP "$thr = threads\->create(\s-1FUNCTION\s0, \s-1ARGS\s0)" 4
.el .IP "\f(CW$thr\fR = threads\->create(\s-1FUNCTION\s0, \s-1ARGS\s0)" 4
.IX Item "$thr = threads->create(FUNCTION, ARGS)"
This will create a new thread that will begin execution with the specified
entry point function, and give it the \fI\s-1ARGS\s0\fR list as parameters.  It will
return the corresponding threads object, or \f(CW\*(C`undef\*(C'\fR if thread creation failed.
.Sp
\&\fI\s-1FUNCTION\s0\fR may either be the name of a function, an anonymous subroutine, or
a code ref.
.Sp
.Vb 5
\&    my $thr = threads\->create(\*(Aqfunc_name\*(Aq, ...);
\&        # or
\&    my $thr = threads\->create(sub { ... }, ...);
\&        # or
\&    my $thr = threads\->create(\e&func, ...);
.Ve
.Sp
The \f(CW\*(C`\->new()\*(C'\fR method is an alias for \f(CW\*(C`\->create()\*(C'\fR.
.ie n .IP "$thr\fR\->\fIjoin()" 4
.el .IP "\f(CW$thr\fR\->\fIjoin()\fR" 4
.IX Item "$thr->join()"
This will wait for the corresponding thread to complete its execution.  When
the thread finishes, \f(CW\*(C`\->join()\*(C'\fR will return the return value(s) of the
entry point function.
.Sp
The context (void, scalar or list) for the return value(s) for \f(CW\*(C`\->join()\*(C'\fR
is determined at the time of thread creation.
.Sp
.Vb 10
\&    # Create thread in list context (implicit)
\&    my ($thr1) = threads\->create(sub {
\&                                    my @results = qw(a b c);
\&                                    return (@results);
\&                                 });
\&    #   or (explicit)
\&    my $thr1 = threads\->create({\*(Aqcontext\*(Aq => \*(Aqlist\*(Aq},
\&                               sub {
\&                                    my @results = qw(a b c);
\&                                    return (@results);
\&                               });
\&    # Retrieve list results from thread
\&    my @res1 = $thr1\->join();
\&
\&    # Create thread in scalar context (implicit)
\&    my $thr2 = threads\->create(sub {
\&                                    my $result = 42;
\&                                    return ($result);
\&                                 });
\&    # Retrieve scalar result from thread
\&    my $res2 = $thr2\->join();
\&
\&    # Create a thread in void context (explicit)
\&    my $thr3 = threads\->create({\*(Aqvoid\*(Aq => 1},
\&                               sub { print("Hello, world\en"); });
\&    # Join the thread in void context (i.e., no return value)
\&    $thr3\->join();
.Ve
.Sp
See \*(L"\s-1THREAD\s0 \s-1CONTEXT\s0\*(R" for more details.
.Sp
If the program exits without all threads having either been joined or
detached, then a warning will be issued.
.Sp
Calling \f(CW\*(C`\->join()\*(C'\fR or \f(CW\*(C`\->detach()\*(C'\fR on an already joined thread will
cause an error to be thrown.
.ie n .IP "$thr\fR\->\fIdetach()" 4
.el .IP "\f(CW$thr\fR\->\fIdetach()\fR" 4
.IX Item "$thr->detach()"
Makes the thread unjoinable, and causes any eventual return value to be
discarded.  When the program exits, any detached threads that are still
running are silently terminated.
.Sp
If the program exits without all threads having either been joined or
detached, then a warning will be issued.
.Sp
Calling \f(CW\*(C`\->join()\*(C'\fR or \f(CW\*(C`\->detach()\*(C'\fR on an already detached thread
will cause an error to be thrown.
.IP "threads\->\fIdetach()\fR" 4