opcode.pm

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package Opcode;

use 5.006_001;

use strict;

our($VERSION, @ISA, @EXPORT_OK);

$VERSION = "1.11";

use Carp;
use Exporter ();
use XSLoader ();

BEGIN {
    @ISA = qw(Exporter);
    @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
    );
}

sub opset (;@);
sub opset_to_hex ($);
sub opdump (;$);
use subs @EXPORT_OK;

XSLoader::load 'Opcode', $VERSION;

_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/--.*//  } # 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 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 eqiv

    $yes = opset_can($opset, @ops)	true if $opset has all @ops set

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