safe.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 "Safe 3"
.TH Safe 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.
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.SH "NAME"
Safe \- Compile and execute code in restricted compartments
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Safe;
\&
\&  $compartment = new Safe;
\&
\&  $compartment\->permit(qw(time sort :browse));
\&
\&  $result = $compartment\->reval($unsafe_code);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The Safe extension module allows the creation of compartments
in which perl code can be evaluated. Each compartment has
.IP "a new namespace" 8
.IX Item "a new namespace"
The \*(L"root\*(R" of the namespace (i.e. \*(L"main::\*(R") is changed to a
different package and code evaluated in the compartment cannot
refer to variables outside this namespace, even with run-time
glob lookups and other tricks.
.Sp
Code which is compiled outside the compartment can choose to place
variables into (or \fIshare\fR variables with) the compartment's namespace
and only that data will be visible to code evaluated in the
compartment.
.Sp
By default, the only variables shared with compartments are the
\&\*(L"underscore\*(R" variables \f(CW$_\fR and \f(CW@_\fR (and, technically, the less frequently
used \f(CW%_\fR, the _ filehandle and so on). This is because otherwise perl
operators which default to \f(CW$_\fR will not work and neither will the
assignment of arguments to \f(CW@_\fR on subroutine entry.
.IP "an operator mask" 8
.IX Item "an operator mask"
Each compartment has an associated \*(L"operator mask\*(R". Recall that
perl code is compiled into an internal format before execution.
Evaluating perl code (e.g. via \*(L"eval\*(R" or \*(L"do 'file'\*(R") causes
the code to be compiled into an internal format and then,
provided there was no error in the compilation, executed.
Code evaluated in a compartment compiles subject to the
compartment's operator mask. Attempting to evaluate code in a
compartment which contains a masked operator will cause the
compilation to fail with an error. The code will not be executed.
.Sp
The default operator mask for a newly created compartment is
the ':default' optag.
.Sp
It is important that you read the Opcode module documentation
for more information, especially for detailed definitions of opnames,
optags and opsets.
.Sp
Since it is only at the compilation stage that the operator mask
applies, controlled access to potentially unsafe operations can
be achieved by having a handle to a wrapper subroutine (written
outside the compartment) placed into the compartment. For example,
.Sp
.Vb 5
\&    $cpt = new Safe;
\&    sub wrapper {
\&        # vet arguments and perform potentially unsafe operations
\&    }
\&    $cpt\->share(\*(Aq&wrapper\*(Aq);
.Ve
.SH "WARNING"
.IX Header "WARNING"
The authors make \fBno warranty\fR, implied or otherwise, about the
suitability of this software for safety or security purposes.
.PP
The authors shall not in any case be liable for special, incidental,
consequential, indirect or other similar damages arising from the use
of this software.
.PP