| Current File : //usr/lib64/perl5/vendor_perl/Net/DNS/Text.pm |
package Net::DNS::Text;
#
# $Id: Text.pm 1070 2012-12-09 21:18:09Z willem $
#
use vars qw($VERSION);
$VERSION = (qw$LastChangedRevision: 1070 $)[1];
=head1 NAME
Net::DNS::Text - Domain Name System text representation
=head1 SYNOPSIS
use Net::DNS::Text;
$object = new Net::DNS::Text('example');
$string = $object->string;
$object = decode Net::DNS::Text( \$data, $offset );
( $object, $next ) = decode Net::DNS::Text( \$data, $offset );
$data = $object->encode;
$text = $object->value;
=head1 DESCRIPTION
The C<Net::DNS::Text> module implements a class of text objects
with associated class and instance methods.
Each text object instance has a fixed identity throughout its
lifetime.
=cut
use strict;
use integer;
use Carp;
use constant ASCII => eval {
require Encode;
Encode::find_encoding('ASCII'); # return encoding object
} || 0;
use constant UTF8 => eval {
die if Encode::decode_utf8( chr(91) ) ne '['; # not UTF-EBCDIC [see UTR#16 3.6]
Encode::find_encoding('UTF8'); # return encoding object
} || 0;
=head1 METHODS
=head2 new
$object = new Net::DNS::Text('example');
Creates a text object which encapsulates a single character
string component of a resource record.
Arbitrary single-byte characters can be represented by \ followed
by exactly three decimal digits. Such characters are devoid of
any special meaning.
A character preceded by \ represents itself, without any special
interpretation.
=cut
my %unescape; ## precalculated numeric escape table
sub new {
my $self = bless [], shift;
croak 'argument undefined' unless defined $_[0];
local $_ = &_encode_utf8;
s/^([\042\047])(.*)\1$/$2/; # strip paired quotes
s/\134\134/\134\066\066\066/g; # disguise escaped escape
s/\134([\060-\062][\060-\071]{2})/$unescape{$1}/eg; # numeric escape
s/\134\066\066\066/\134\134/g; # reveal escaped escape
s/\134(.)/$1/g; # character escape
while ( length $_ > 255 ) {
my $chunk = substr( $_, 0, 255 ); # carve into chunks
substr( $chunk, -length($1) ) = '' if $chunk =~ /.([\300-\377][\200-\277]+)$/;
push @$self, $chunk;
substr( $_, 0, length $chunk ) = '';
}
push @$self, $_;
return $self;
}
=head2 decode
$object = decode Net::DNS::Text( \$buffer, $offset );
( $object, $next ) = decode Net::DNS::Text( \$buffer, $offset );
Creates a text object which represents the decoded data at the
indicated offset within the data buffer.
The argument list consists of a reference to a scalar containing
the wire-format data and offset of the text data.
The returned offset value indicates the start of the next item in
the data buffer.
=cut
sub decode {
my $class = shift;
my $buffer = shift; # reference to data buffer
my $offset = shift || 0; # offset within buffer
my $size = unpack "\@$offset C", $$buffer;
my $next = ++$offset + $size;
croak 'corrupt wire-format data' if $next > length $$buffer;
my $self = bless [ unpack( "\@$offset a$size", $$buffer ) ], $class;
return wantarray ? ( $self, $next ) : $self;
}
=head2 encode
$data = $object->encode;
Returns the wire-format encoded representation of the text object
suitable for inclusion in a DNS packet buffer.
=cut
sub encode {
my $self = shift;
join '', map { pack 'C a*', length $_, $_ } @$self;
}
=head2 value
$value = $text->value;
Character string representation of the text object.
=cut
my %escape; # precalculated ASCII/UTF-8 escape table
sub value {
my $self = shift;
_decode_utf8( join '', @$self );
}
=head2 string
$string = $text->string;
Conditionally quoted zone file representation of the text object.
=cut
my $QQ = _decode_utf8( pack 'C', 34 );
sub string {
my $self = shift;
my @utf8 = map { s/([^\040\060-\132\141-\172])/$escape{$1}/eg; $_ } @$self;
my $string = _decode_utf8( join '', @utf8 );
# Note: Script-specific rules determine which Unicode characters match \s
return $string unless $string =~ /^$|\s|["\$'();@]/; # unquoted contiguous
join '', $QQ, $string, $QQ; # quoted string
}
########################################
use vars qw($AUTOLOAD);
sub AUTOLOAD { ## Default method
no strict;
@_ = ("method $AUTOLOAD undefined");
goto &{'Carp::confess'};
}
sub DESTROY { } ## Avoid tickling AUTOLOAD (in cleanup)
sub _decode_utf8 {
return UTF8->decode(shift) if UTF8;
return ASCII->decode(shift) if ASCII && not UTF8;
unless (ASCII) {
my $s = shift;
# partial transliteration for non-ASCII character encodings
$s =~ tr
[\055\040-\054\056-\176\000-\377]
[- !"#$%&'()*+,./0-9:;<=>?@A-Z\[\\\]^_`a-z{|}~?];
return $s; # native 8-bit code
}
}
sub _encode_utf8 {
return UTF8->encode(shift) if UTF8;
return ASCII->encode(shift) if ASCII && not UTF8;
unless (ASCII) {
my $s = shift;
# partial transliteration for non-ASCII character encodings
$s =~ tr
[- !"#$%&'()*+,./0-9:;<=>?@A-Z\[\\\]^_`a-z{|}~\000-\377]
[\055\040-\054\056-\176\077];
return $s; # ASCII
}
}
%escape = eval { ## precalculated ASCII/UTF-8 escape table
my %table;
my @C0 = ( 0 .. 31 ); # control characters
my @NA = UTF8 ? ( 192, 193, 245 .. 255 ) : ( 128 .. 255 );
foreach ( 0 .. 255 ) { # transparent
$table{pack( 'C', $_ )} = pack 'C', $_;
}
foreach ( 34, 92 ) { # escape character
$table{pack( 'C', $_ )} = pack 'C*', 92, $_;
}
foreach ( @C0, 127, @NA ) { # \ddd
$table{pack( 'C', $_ )} = _encode_utf8 sprintf( '\\%03u', $_ );
}
return %table;
};
%unescape = eval { ## precalculated numeric escape table
my %table;
foreach ( 0 .. 255 ) {
$table{_encode_utf8 sprintf( '%03u', $_ )} = pack 'C', $_;
}
$table{_encode_utf8('092')} = pack 'Ca*', 92, _encode_utf8 '666';
return %table;
};
1;
__END__
########################################
=head1 BUGS
Coding strategy is intended to avoid creating unnecessary argument
lists and stack frames. This improves efficiency at the expense of
code readability.
Platform specific character coding features are conditionally
compiled into the code.
=head1 COPYRIGHT
Copyright (c)2009-2011 Dick Franks.
All rights reserved.
This program is free software; you may redistribute it and/or
modify it under the same terms as Perl itself.
=head1 SEE ALSO
L<perl>, L<Net::DNS>, RFC1035, RFC3629,
Unicode Technical Report #16
=cut