attributes.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.

.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  \*(C+ will
.\" give a nicer C++.  Capital omega is used to do unbreakable dashes and
.\" therefore won't be available.  \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\"
.\" If the F register is turned on, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.ie \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.el \{\
.    de IX
..
.\}
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "attributes 3"
.TH attributes 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"
attributes \- get/set subroutine or variable attributes
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\&  sub foo : method ;
\&  my ($x,@y,%z) : Bent = 1;
\&  my $s = sub : method { ... };
\&
\&  use attributes ();    # optional, to get subroutine declarations
\&  my @attrlist = attributes::get(\e&foo);
\&
\&  use attributes \*(Aqget\*(Aq; # import the attributes::get subroutine
\&  my @attrlist = get \e&foo;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Subroutine declarations and definitions may optionally have attribute lists
associated with them.  (Variable \f(CW\*(C`my\*(C'\fR declarations also may, but see the
warning below.)  Perl handles these declarations by passing some information
about the call site and the thing being declared along with the attribute
list to this module.  In particular, the first example above is equivalent to
the following:
.PP
.Vb 1
\&    use attributes _\|_PACKAGE_\|_, \e&foo, \*(Aqmethod\*(Aq;
.Ve
.PP
The second example in the synopsis does something equivalent to this:
.PP
.Vb 6
\&    use attributes ();
\&    my ($x,@y,%z);
\&    attributes::\->import(_\|_PACKAGE_\|_, \e$x, \*(AqBent\*(Aq);
\&    attributes::\->import(_\|_PACKAGE_\|_, \e@y, \*(AqBent\*(Aq);
\&    attributes::\->import(_\|_PACKAGE_\|_, \e%z, \*(AqBent\*(Aq);
\&    ($x,@y,%z) = 1;
.Ve
.PP
Yes, that's a lot of expansion.
.PP
\&\fB\s-1WARNING\s0\fR: attribute declarations for variables are still evolving.
The semantics and interfaces of such declarations could change in
future versions.  They are present for purposes of experimentation
with what the semantics ought to be.  Do not rely on the current
implementation of this feature.
.PP
There are only a few attributes currently handled by Perl itself (or
directly by this module, depending on how you look at it.)  However,
package-specific attributes are allowed by an extension mechanism.
(See \*(L"Package-specific Attribute Handling\*(R" below.)
.PP
The setting of subroutine attributes happens at compile time.
Variable attributes in \f(CW\*(C`our\*(C'\fR declarations are also applied at compile time.
However, \f(CW\*(C`my\*(C'\fR variables get their attributes applied at run-time.
This means that you have to \fIreach\fR the run-time component of the \f(CW\*(C`my\*(C'\fR
before those attributes will get applied.  For example:
.PP
.Vb 1
\&    my $x : Bent = 42 if 0;
.Ve
.PP
will neither assign 42 to \f(CW$x\fR \fInor\fR will it apply the \f(CW\*(C`Bent\*(C'\fR attribute
to the variable.
.PP
An attempt to set an unrecognized attribute is a fatal error.  (The
error is trappable, but it still stops the compilation within that
\&\f(CW\*(C`eval\*(C'\fR.)  Setting an attribute with a name that's all lowercase
letters that's not a built-in attribute (such as \*(L"foo\*(R") will result in
a warning with \fB\-w\fR or \f(CW\*(C`use warnings \*(Aqreserved\*(Aq\*(C'\fR.
.Sh "Built-in Attributes"
.IX Subsection "Built-in Attributes"
The following are the built-in attributes for subroutines:
.IP "locked" 4
.IX Item "locked"
\&\fB5.005 threads only!  The use of the \*(L"locked\*(R" attribute currently
only makes sense if you are using the deprecated \*(L"Perl 5.005 threads\*(R"
implementation of threads.\fR
.Sp
Setting this attribute is only meaningful when the subroutine or
method is to be called by multiple threads.  When set on a method
subroutine (i.e., one marked with the \fBmethod\fR attribute below),
Perl ensures that any invocation of it implicitly locks its first
argument before execution.  When set on a non-method subroutine,
Perl ensures that a lock is taken on the subroutine itself before
execution.  The semantics of the lock are exactly those of one