view release on metacpan or  search on metacpan

ext/Opcode/Opcode.pm  view on Meta::CPAN

package Opcode 1.69;

use strict;

use Carp;
use Exporter 'import';
use XSLoader;

sub opset (;@);
sub opset_to_hex ($);
sub opdump (;$);
use subs our @EXPORT_OK = qw(
	opset ops_to_opset
	opset_to_ops opset_to_hex invert_opset
	empty_opset full_opset
	opdesc opcodes opmask define_optag
	opmask_add verify_opset opdump
);

XSLoader::load();

_init_optags();

sub ops_to_opset { opset @_ }	# alias for old name

sub opset_to_hex ($) {
    return "(invalid opset)" unless verify_opset($_[0]);
    unpack("h*",$_[0]);
}

sub opdump (;$) {
	my $pat = shift;
    # handy utility: perl -MOpcode=opdump -e 'opdump File'
    foreach(opset_to_ops(full_opset)) {
        my $op = sprintf "  %12s  %s\n", $_, opdesc($_);
		next if defined $pat and $op !~ m/$pat/i;
		print $op;
    }
}



sub _init_optags {
    my(%all, %seen);
    @all{opset_to_ops(full_opset)} = (); # keys only

    local($_);
    local($/) = "\n=cut"; # skip to optags definition section
    <DATA>;
    $/ = "\n=";		# now read in 'pod section' chunks
    while(<DATA>) {
	next unless m/^item\s+(:\w+)/;
	my $tag = $1;

	# Split into lines, keep only indented lines
	my @lines = grep { m/^\s/    } split(/\n/);
	foreach (@lines) { s/(?:\t|--).*//  } # delete comments
	my @ops   = map  { split ' ' } @lines; # get op words

	foreach(@ops) {
	    warn "$tag - $_ already tagged in $seen{$_}\n" if $seen{$_};
	    $seen{$_} = $tag;
	    delete $all{$_};
	}
	# opset will croak on invalid names
	define_optag($tag, opset(@ops));
    }
    close(DATA);
    warn "Untagged opnames: ".join(' ',keys %all)."\n" if %all;
}


1;

__DATA__

=head1 NAME

Opcode - Disable named opcodes when compiling perl code

=head1 SYNOPSIS

  use Opcode;


=head1 DESCRIPTION

Perl code is always compiled into an internal format before execution.

Evaluating perl code (e.g. via "eval" or "do 'file'") causes
the code to be compiled into an internal format and then,
provided there was no error in the compilation, executed.
The internal format is based on many distinct I<opcodes>.

By default no opmask is in effect and any code can be compiled.

The Opcode module allow you to define an I<operator mask> to be in
effect when perl I<next> compiles any code.  Attempting to compile code
which contains a masked opcode will cause the compilation to fail
with an error. The code will not be executed.

=head1 NOTE

The Opcode module is not usually used directly. See the ops pragma and
Safe modules for more typical uses.

=head1 WARNING

The Opcode module does not implement an effective sandbox for
evaluating untrusted code with the perl interpreter.

Bugs in the perl interpreter that could be abused to bypass
Opcode restrictions are not treated as vulnerabilities. See
L<perlsecpolicy> for additional information.

The authors make B<no warranty>, implied or otherwise, about the
suitability of this software for safety or security purposes.

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.

Your mileage will vary. If in any doubt B<do not use it>.


=head1 Operator Names and Operator Lists

The canonical list of operator names is the contents of the array
PL_op_name defined and initialised in file F<opcode.h> of the Perl
source distribution (and installed into the perl library).

Each operator has both a terse name (its opname) and a more verbose or
recognisable descriptive name. The opdesc function can be used to
return a list of descriptions for a list of operators.

Many of the functions and methods listed below take a list of
operators as parameters. Most operator lists can be made up of several
types of element. Each element can be one of

=over 8

=item an operator name (opname)

Operator names are typically small lowercase words like enterloop,
leaveloop, last, next, redo etc. Sometimes they are rather cryptic
like gv2cv, i_ncmp and ftsvtx.

=item an operator tag name (optag)

Operator tags can be used to refer to groups (or sets) of operators.
Tag names always begin with a colon. The Opcode module defines several
optags and the user can define others using the define_optag function.

=item a negated opname or optag

An opname or optag can be prefixed with an exclamation mark, e.g., !mkdir.
Negating an opname or optag means remove the corresponding ops from the
accumulated set of ops at that point.

=item an operator set (opset)

An I<opset> as a binary string of approximately 44 bytes which holds a
set or zero or more operators.

The opset and opset_to_ops functions can be used to convert from
a list of operators to an opset and I<vice versa>.

Wherever a list of operators can be given you can use one or more opsets.
See also Manipulating Opsets below.

=back


=head1 Opcode Functions

The Opcode package contains functions for manipulating operator names
tags and sets. All are available for export by the package.

=over 8

=item opcodes

In a scalar context opcodes returns the number of opcodes in this
version of perl (around 350 for perl-5.7.0).

In a list context it returns a list of all the operator names.
(Not yet implemented, use @names = opset_to_ops(full_opset).)

=item opset (OP, ...)

Returns an opset containing the listed operators.

=item opset_to_ops (OPSET)

Returns a list of operator names corresponding to those operators in
the set.

=item opset_to_hex (OPSET)

Returns a string representation of an opset. Can be handy for debugging.

=item full_opset

Returns an opset which includes all operators.

=item empty_opset

Returns an opset which contains no operators.

=item invert_opset (OPSET)

Returns an opset which is the inverse set of the one supplied.

=item verify_opset (OPSET, ...)

Returns true if the supplied opset looks like a valid opset (is the
right length etc) otherwise it returns false. If an optional second
parameter is true then verify_opset will croak on an invalid opset
instead of returning false.

Most of the other Opcode functions call verify_opset automatically
and will croak if given an invalid opset.

=item define_optag (OPTAG, OPSET)

Define OPTAG as a symbolic name for OPSET. Optag names always start
with a colon C<:>.

The optag name used must not be defined already (define_optag will
croak if it is already defined). Optag names are global to the perl
process and optag definitions cannot be altered or deleted once
defined.

It is strongly recommended that applications using Opcode should use a
leading capital letter on their tag names since lowercase names are
reserved for use by the Opcode module. If using Opcode within a module
you should prefix your tags names with the name of your module to
ensure uniqueness and thus avoid clashes with other modules.

=item opmask_add (OPSET)

Adds the supplied opset to the current opmask. Note that there is
currently I<no> mechanism for unmasking ops once they have been masked.
This is intentional.

=item opmask

Returns an opset corresponding to the current opmask.

=item opdesc (OP, ...)

This takes a list of operator names and returns the corresponding list
of operator descriptions.

=item opdump (PAT)

Dumps to STDOUT a two column list of op names and op descriptions.
If an optional pattern is given then only lines which match the
(case insensitive) pattern will be output.

It's designed to be used as a handy command line utility:

	perl -MOpcode=opdump -e opdump
	perl -MOpcode=opdump -e 'opdump Eval'

=back

=head1 Manipulating Opsets

Opsets may be manipulated using the perl bit vector operators & (and), | (or),
^ (xor) and ~ (negate/invert).

However you should never rely on the numerical position of any opcode
within the opset. In other words both sides of a bit vector operator
should be opsets returned from Opcode functions.

Also, since the number of opcodes in your current version of perl might
not be an exact multiple of eight, there may be unused bits in the last
byte of an upset. This should not cause any problems (Opcode functions
ignore those extra bits) but it does mean that using the ~ operator
will typically not produce the same 'physical' opset 'string' as the
invert_opset function.


=head1 TO DO (maybe)

    $bool = opset_eq($opset1, $opset2)	true if opsets are logically
					equivalent
    $yes = opset_can($opset, @ops)	true if $opset has all @ops set

    @diff = opset_diff($opset1, $opset2) => ('foo', '!bar', ...)

=cut

# the =cut above is used by _init_optags() to get here quickly

=head1 Predefined Opcode Tags

=over 5

=item :base_core

    null stub scalar pushmark wantarray const defined undef

    rv2sv sassign padsv_store

    rv2av aassign aelem aelemfast aelemfast_lex aslice kvaslice
    av2arylen aelemfastlex_store

    rv2hv helem hslice kvhslice each values keys exists delete
    aeach akeys avalues multideref argelem argdefelem argcheck

    preinc i_preinc predec i_predec postinc i_postinc
    postdec i_postdec int hex oct abs pow multiply i_multiply
    divide i_divide modulo i_modulo add i_add subtract i_subtract

    left_shift right_shift bit_and bit_xor bit_or nbit_and
    nbit_xor nbit_or sbit_and sbit_xor sbit_or negate i_negate not
    complement ncomplement scomplement

    lt i_lt gt i_gt le i_le ge i_ge eq i_eq ne i_ne ncmp i_ncmp
    slt sgt sle sge seq sne scmp
    isa

    substr substr_left vec stringify study pos length index
    rindex ord chr

    ucfirst lcfirst uc lc fc quotemeta trans transr chop schop
    chomp schomp

    match split qr

    list lslice splice push pop shift unshift reverse

    cond_expr flip flop andassign orassign dorassign and or dor xor
    helemexistsor

    warn die lineseq nextstate scope enter leave

    rv2cv anoncode prototype coreargs avhvswitch anonconst
    emptyavhv

    entersub leavesub leavesublv return method method_named
    method_super method_redir method_redir_super
     -- XXX loops via recursion?

    cmpchain_and cmpchain_dup

    is_bool
    is_weak weaken unweaken