threads::shared.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::shared 3"
.TH threads::shared 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::shared \- Perl extension for sharing data structures between threads
.SH "VERSION"
.IX Header "VERSION"
This document describes threads::shared version 1.14
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&  use threads;
\&  use threads::shared;
\&
\&  my $var :shared;
\&  $var = $scalar_value;
\&  $var = $shared_ref_value;
\&  $var = share($simple_unshared_ref_value);
\&
\&  my ($scalar, @array, %hash);
\&  share($scalar);
\&  share(@array);
\&  share(%hash);
\&  my $bar = &share([]);
\&  $hash{bar} = &share({});
\&
\&  { lock(%hash); ...  }
\&
\&  cond_wait($scalar);
\&  cond_timedwait($scalar, time() + 30);
\&  cond_broadcast(@array);
\&  cond_signal(%hash);
\&
\&  my $lockvar :shared;
\&  # condition var != lock var
\&  cond_wait($var, $lockvar);
\&  cond_timedwait($var, time()+30, $lockvar);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
By default, variables are private to each thread, and each newly created
thread gets a private copy of each existing variable.  This module allows you
to share variables across different threads (and pseudo-forks on Win32).  It is
used together with the threads module.
.SH "EXPORT"
.IX Header "EXPORT"
\&\f(CW\*(C`share\*(C'\fR, \f(CW\*(C`cond_wait\*(C'\fR, \f(CW\*(C`cond_timedwait\*(C'\fR, \f(CW\*(C`cond_signal\*(C'\fR, \f(CW\*(C`cond_broadcast\*(C'\fR,
\&\f(CW\*(C`is_shared\*(C'\fR
.PP
Note that if this module is imported when threads has not yet been loaded,
then these functions all become no-ops.  This makes it possible to write
modules that will work in both threaded and non-threaded environments.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.IP "share \s-1VARIABLE\s0" 4
.IX Item "share VARIABLE"
\&\f(CW\*(C`share\*(C'\fR takes a value and marks it as shared. You can share a scalar, array,
hash, scalar ref, array ref, or hash ref.  \f(CW\*(C`share\*(C'\fR will return the shared
rvalue, but always as a reference.
.Sp
A variable can also be marked as shared at compile time by using the
\&\f(CW\*(C`:shared\*(C'\fR attribute: \f(CW\*(C`my $var :shared;\*(C'\fR.
.Sp
Due to problems with Perl's prototyping, if you want to share a newly created
reference, you need to use the \f(CW\*(C`&share([])\*(C'\fR and \f(CW\*(C`&share({})\*(C'\fR syntax.
.Sp
The only values that can be assigned to a shared scalar are other scalar
values, or shared refs:
.Sp
.Vb 4
\&  my $var :shared;
\&  $var = 1;              # ok
\&  $var = [];             # error
\&  $var = &share([]);     # ok
.Ve
.Sp
\&\f(CW\*(C`share\*(C'\fR will traverse up references exactly \fIone\fR level.  \f(CW\*(C`share(\e$a)\*(C'\fR is
equivalent to \f(CW\*(C`share($a)\*(C'\fR, while \f(CW\*(C`share(\e\e$a)\*(C'\fR is not.  This means that you
must create nested shared data structures by first creating individual shared
leaf nodes, and then adding them to a shared hash or array.
.Sp
.Vb 4
\&  my %hash :shared;
\&  $hash{\*(Aqmeaning\*(Aq} = &share([]);
\&  $hash{\*(Aqmeaning\*(Aq}[0] = &share({});
\&  $hash{\*(Aqmeaning\*(Aq}[0]{\*(Aqlife\*(Aq} = 42;
.Ve
.IP "is_shared \s-1VARIABLE\s0" 4
.IX Item "is_shared VARIABLE"
\&\f(CW\*(C`is_shared\*(C'\fR checks if the specified variable is shared or not.  If shared,
returns the variable's internal \s-1ID\s0 (similar to
\&\fIrefaddr()\fR).  Otherwise, returns \f(CW\*(C`undef\*(C'\fR.
.Sp
.Vb 5
\&  if (is_shared($var)) {
\&      print("\e$var is shared\en");
\&  } else {