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+ ##
+ ## String::Divert - Diversion String Object
+ ## Copyright (c) 2003 Ralf S. Engelschall <rse@engelschall.com>
+ ##
+ ## This file is part of String::Divert, a Perl module for
+ ## dealing with strings containing nested diversions.
+ ##
+ ## This program is free software; you can redistribute it and/or
+ ## modify it under the terms of the GNU General Public License
+ ## as published by the Free Software Foundation; either version
+ ## 2.0 of the License, or (at your option) any later version.
+ ##
+ ## This program is distributed in the hope that it will be useful,
+ ## but WITHOUT ANY WARRANTY; without even the implied warranty of
+ ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ ## General Public License for more details.
+ ##
+ ## You should have received a copy of the GNU General Public License
+ ## along with this file; if not, write to the Free Software Foundation,
+ ## Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ ##
+ ## Divert.pm: Module Implementation
+ ##
+
+ use 5.005;
+ use strict;
+ use warnings;
+
+ # _________________________________________________________________________
+ #
+ # STANDARD OBJECT ORIENTED API
+ # _________________________________________________________________________
+ #
+
+ package String::Divert;
+
+ require Exporter;
+
+ our @ISA = qw(Exporter);
+ our @EXPORT_OK = qw(new destroy DESTROY
+ name overwrite
+ assign append string bool
+ fold unfold folding folder
+ divert undivert diversion
+ overload);
+ our $VERSION = '0.90';
+
+ # object construction
+ sub new ($;$) {
+ my ($proto, $name) = @_;
+
+ my $class = ref($proto) || $proto;
+ my $self = {};
+ bless ($self, $class);
+
+ $self->{name} = (defined($name) ? $name : '');
+ $self->{overwrite} = 'none';
+ $self->{chunks} = [ '' ];
+ $self->{diversion} = [];
+ $self->{foldermk} = '{#%s#}';
+ $self->{folderre} = '\{#([a-zA-Z_][a-zA-Z0-9_]*)#\}';
+
+ return $self;
+ }
+
+ # object destruction (explicit)
+ sub destroy ($) {
+ $_[0]->overload(0);
+ bless $_[0], 'UNIVERSAL';
+ undef $_[0];
+ return;
+ }
+
+ # object destruction (implicit)
+ sub DESTROY ($) {
+ return;
+ }
+
+ # operation: set/get name of object
+ sub name ($;$) {
+ my ($self, $name) = @_;
+ return $self->{diversion}->[-1]->name($name)
+ if (@{$self->{diversion}} > 0);
+ my $old_name = $self->{name};
+ if (defined($name)) {
+ $self->{name} = $name;
+ }
+ return $old_name;
+ }
+
+ # operation: set/get overwrite mode
+ sub overwrite ($;$) {
+ my ($self, $mode) = @_;
+ return $self->{diversion}->[-1]->overwrite($mode)
+ if (@{$self->{diversion}} > 0);
+ my $old_mode = $self->{overwrite};
+ if (defined($mode)) {
+ die "invalid mode argument"
+ if ($mode !~ m/^(none|once|always)$/);
+ $self->{overwrite} = $mode;
+ }
+ return $old_mode;
+ }
+
+ # internal: split string into chunks
+ sub _chunking ($) {
+ my ($self, $string) = @_;
+ my @chunks = ();
+ my $folderre = $self->{folderre};
+ while ($string =~ m/${folderre}()/s) {
+ my ($prolog, $id) = ($`, $1);
+ push(@chunks, $prolog) if ($prolog ne '');
+ die "empty folding object name"
+ if ($id eq '');
+ my $object = $self->folding($id);
+ $object = $self->new($id) if (not defined($object));
+ die "cannot reuse or create folding sub object \"$id\""
+ if (not defined($object));
+ push(@chunks, $object);
+ $string = $';
+ }
+ push(@chunks, $string) if ($string ne '');
+ return @chunks;
+ }
+
+ # operation: assign a string
+ sub assign ($$) {
+ my ($self, $string) = @_;
+ return $self->{diversion}->[-1]->assign($string)
+ if (@{$self->{diversion}} > 0);
+ die "cannot assign undefined string"
+ if (not defined($string));
+ die "cannot assign reference ".ref($string)." as string"
+ if (ref($string));
+ $self->{chunks} = [];
+ foreach my $chunk ($self->_chunking($string)) {
+ push(@{$self->{chunks}}, $chunk);
+ }
+ return $self;
+ }
+
+ # operation: append a string
+ sub append ($$) {
+ my ($self, $string) = @_;
+ return $self->{diversion}->[-1]->append($string)
+ if (@{$self->{diversion}} > 0);
+ die "cannot assign undefined string"
+ if (not defined($string));
+ die "cannot assign reference as string"
+ if (ref($string));
+ if ( $self->{overwrite} eq 'once'
+ or $self->{overwrite} eq 'always') {
+ $self->{chunks} = [];
+ foreach my $chunk ($self->_chunking($string)) {
+ push(@{$self->{chunks}}, $chunk);
+ }
+ $self->{overwrite} = 'none'
+ if ($self->{overwrite} eq 'once');
+ }
+ else {
+ foreach my $chunk ($self->_chunking($string)) {
+ if (ref($chunk)) {
+ push(@{$self->{chunks}}, $chunk);
+ }
+ else {
+ if (ref($self->{chunks}->[-1])) {
+ push(@{$self->{chunks}}, $chunk);
+ }
+ else {
+ $self->{chunks}->[-1] .= $chunk;
+ }
+ }
+ }
+ }
+ return $self;
+ }
+
+ # operation: unfold (and return) string contents temporarily
+ sub string ($) {
+ my ($self) = @_;
+ my $string = '';
+ return $self->{diversion}->[-1]->string()
+ if (@{$self->{diversion}} > 0);
+ foreach my $chunk (@{$self->{chunks}}) {
+ if (ref($chunk)) {
+ my $prefix = '';
+ if ($string =~ m|([^\n]*)(\r?\n)*$|s) {
+ $prefix = $1;
+ $prefix =~ s|[^ \t]| |sg;
+ }
+ my $block = $chunk->string(); # recursion!
+ $block =~ s|\n(?=.)|\n$prefix|sg if ($prefix ne '');
+ $string .= $block;
+ }
+ else {
+ $string .= $chunk;
+ }
+ }
+ return $string;
+ }
+
+ # operation: unfold string contents temporarily until already true or finally false
+ sub bool ($) {
+ my ($self) = @_;
+ my $string = '';
+ return $self->{diversion}->[-1]->bool()
+ if (@{$self->{diversion}} > 0);
+ foreach my $chunk (@{$self->{chunks}}) {
+ if (ref($chunk)) {
+ $string .= $chunk->string(); # recursion!
+ }
+ else {
+ $string .= $chunk;
+ }
+ return 1 if ($string);
+ }
+ return 0;
+ }
+
+ # operation: append folding sub-object
+ sub fold ($$) {
+ my ($self, $id) = @_;
+ return $self->{diversion}->[-1]->fold($id)
+ if (@{$self->{diversion}} > 0);
+ die "undefined folding object identifier"
+ if (not defined($id));
+ if (ref($id)) {
+ die "folding object not of class String::Divert"
+ if ( UNIVERSAL::isa($id, "String::Divert")
+ or UNIVERSAL::isa($id, "String::Divert::__OVERLOAD__"));
+ push(@{$self->{chunks}}, $id);
+ return $id;
+ }
+ else {
+ my $object = $self->folding($id);
+ $object = $self->new($id) if (not defined($object));
+ die "unable to create new folding object"
+ if (not defined($object));
+ push(@{$self->{chunks}}, $object);
+ return $object;
+ }
+ }
+
+ # operation: unfold string contents permanently
+ sub unfold ($) {
+ my ($self) = @_;
+ return $self->{diversion}->[-1]->unfold()
+ if (@{$self->{diversion}} > 0);
+ my $string = $self->string();
+ $self->{chunks} = [ $string ];
+ return $string;
+ }
+
+ # internal: compare whether two objects are the same
+ sub _isobjeq ($$) {
+ my ($obj1, $obj2) = @_;
+ my $ov1 = $obj1->overload();
+ my $ov2 = $obj2->overload();
+ $obj1->overload(0);
+ $obj2->overload(0);
+ my $rv = ($obj1 == $obj2);
+ $obj1->overload($ov1);
+ $obj2->overload($ov2);
+ return $rv;
+ }
+
+ # operation: lookup particular or all folding sub-object(s)
+ sub folding ($;$) {
+ my ($self, $id) = @_;
+ return $self->{diversion}->[-1]->folding($id)
+ if (@{$self->{diversion}} > 0);
+ if (defined($id)) {
+ my $folding = undef;
+ foreach my $chunk (@{$self->{chunks}}) {
+ if (ref($chunk)) {
+ if ( (ref($id) and &String::Divert::_isobjeq($chunk, $id))
+ or (not ref($id) and $chunk->name() eq $id) ) {
+ $folding = $chunk;
+ last;
+ }
+ $folding = $chunk->folding($id);
+ last if (defined($folding));
+ }
+ }
+ return $folding;
+ }
+ else {
+ my @foldings = ();
+ foreach my $chunk (@{$self->{chunks}}) {
+ if (ref($chunk)) {
+ foreach my $subchunk ($chunk->folding()) {
+ push(@foldings, $subchunk);
+ }
+ push(@foldings, $chunk);
+ }
+ }
+ return @foldings;
+ }
+ }
+
+ # operation: configure or generate textually represented folding object
+ sub folder ($$;$) {
+ my ($self, $a, $b) = @_;
+ if (defined($b)) {
+ # configure folder
+ my $test = sprintf($a, "foo");
+ my $id = ($test =~ m|${b}()|s);
+ die "folder construction format and matching regular expression do not correspond"
+ if ($id ne "foo");
+ $self->{foldermk} = $a;
+ $self->{folderre} = $b;
+ return;
+ }
+ else {
+ # create folder
+ my $folder = sprintf($self->{foldermk}, $a);
+ return $folder;
+ }
+ }
+
+ # operation: push diversion of operations to sub-object
+ sub divert ($$) {
+ my ($self, $id) = @_;
+ my $object = $self->folding($id);
+ die "folding sub-object \"$id\" not found"
+ if (not defined($object));
+ push(@{$self->{diversion}}, $object);
+ return $self;
+ }
+
+ # operation: pop diversion of operations to sub-object
+ sub undivert ($;$) {
+ my ($self, $num) = @_;
+ $num = 1 if (not defined($num));
+ $num = @{$self->{diversion}} if ($num == 0);
+ die "less number (".scalar(@{$self->{diversion}}).") of diversions active than requested ($num) to undivert"
+ if ($num > @{$self->{diversion}});
+ while ($num-- > 0) {
+ pop(@{$self->{diversion}});
+ }
+ return $self;
+ }
+
+ # operation: lookup last or all diversion(s)
+ sub diversion ($) {
+ my ($self) = @_;
+ if (not wantarray) {
+ # return last diversion only
+ return $self->{diversion}->[-1];
+ }
+ else {
+ # return all diversions (in reverse order of activation)
+ return reverse(@{$self->{diversion}});
+ }
+ }
+
+ # _________________________________________________________________________
+ #
+ # API SWITCHING
+ # _________________________________________________________________________
+ #
+
+ # object overloading toogle method
+ sub overload ($;$) {
+ # NOTICE: This function is special in that it exploits the fact
+ # that Perl's @_ contains just ALIASES for the arguments of
+ # the function and hence the function can adjust them. This
+ # allows us to tie() the variable of our object ($_[0]) into the
+ # overloading sub class or back to our main class. Just tie()ing
+ # a copy of $_[0] (usually named $self in the other methods)
+ # would be useless, because the Perl TIE mechanism is attached to
+ # _variables_ and not to the objects itself. Hence this function
+ # does no "my ($self, $mode) = @_;" and instead uses @_ directly
+ # throughout its body.
+ my $old_mode = (ref($_[0]) eq "String::Divert" ? 0 : 1);
+ if (defined($_[1])) {
+ if ($_[1]) {
+ # bless and tie into overloaded subclass
+ my $self = $_[0];
+ bless $_[0], "String::Divert::__OVERLOAD__";
+ #tie $_[0], "String::Divert::__OVERLOAD__", $self;
+ # according to "BUGS" section in "perldoc overload":
+ # "Relation between overloading and tie()ing is broken.
+ # Overloading is triggered or not basing on the previous
+ # class of tie()d value. This happens because the presence
+ # of overloading is checked too early, before any tie()d
+ # access is attempted. If the FETCH()ed class of the
+ # tie()d value does not change, a simple workaround is to
+ # access the value immediately after tie()ing, so that
+ # after this call the previous class coincides with the
+ # current one."... So, do this now!
+ #my $dummy = ref($_[0]);
+ }
+ else {
+ # untie and rebless into master class
+ #untie $_[0];
+ bless $_[0], "String::Divert";
+ }
+ }
+ return $old_mode;
+ }
+
+ # _________________________________________________________________________
+ #
+ # OPERATOR OVERLOADING API
+ # _________________________________________________________________________
+ #
+
+ package String::Divert::__OVERLOAD__;
+
+ our @ISA = qw(Exporter String::Divert);
+ our @EXPORT_OK = qw();
+
+ # define operator overloading
+ use overload (
+ '""' => \&op_string,
+ 'bool' => \&op_bool,
+ '0+' => \&op_numeric,
+ '.' => \&op_concat,
+ '.=' => \&op_append,
+ '*=' => \&op_fold,
+ '<>' => \&op_unfold,
+ '>>' => \&op_divert,
+ '<<' => \&op_undivert,
+ #'${}' => \&op_deref_string,
+ #'%{}' => \&op_deref_hash,
+ #'=' => \&op_copyconst,
+ #'nomethod' => \&op_unknown,
+ 'fallback' => 0
+ );
+
+ #sub TIESCALAR ($$) {
+ # my ($class, $self) = @_;
+ # bless $self, $class;
+ # return $self;
+ #}
+
+ #sub UNTIE ($) {
+ # my ($self) = @_;
+ # return;
+ #}
+
+ #sub FETCH ($) {
+ # my ($self) = @_;
+ # return $self;
+ #}
+
+ #sub STORE ($$) {
+ # my ($self, $other) = @_;
+ # return $self if (ref($other));
+ # $self->assign($other);
+ # my $dummy = ref($self);
+ # return $self;
+ #}
+
+ #sub op_copyconst {
+ # my ($self, $other, $reverse) = @_;
+ # # intentionally do not copy at all
+ # return $self;
+ #}
+
+ #sub op_deref_string ($$$) {
+ # my $self = shift;
+ # return $self;
+ #}
+
+ #sub op_deref_hash ($$$) {
+ # my $self = shift;
+ # return $self;
+ #}
+
+ sub op_string ($$$) {
+ my ($self, $other, $rev) = @_;
+ return $self->string();
+ }
+
+ sub op_bool ($$$) {
+ my ($self, $other, $reverse) = @_;
+ return $self->bool();
+ }
+
+ sub op_numeric ($$$) {
+ my ($self, $other, $reverse) = @_;
+ return $self->string();
+ }
+
+ sub op_concat ($$$) {
+ my ($self, $other, $reverse) = @_;
+ return ($reverse ? $other . $self->string() : $self->string() . $other);
+ }
+
+ sub op_append ($$$) {
+ my ($self, $other, $reverse) = @_;
+ $self->append($other);
+ return $self;
+ }
+
+ sub op_fold ($$$) {
+ my ($self, $other, $reverse) = @_;
+ $self->fold($other);
+ return $self;
+ }
+
+ sub op_unfold ($$$) {
+ my ($self, $other, $reverse) = @_;
+ $self->unfold;
+ return $self;
+ }
+
+ #sub op_folding ($$$) {
+ # my ($self, $other, $reverse) = @_;
+ # $self->folding($other);
+ # return $self;
+ #}
+
+ sub op_divert ($$$) {
+ my ($self, $other, $reverse) = @_;
+ $self->divert($other);
+ return $self;
+ }
+
+ sub op_undivert ($$$) {
+ my ($self, $other, $reverse) = @_;
+ $self->undivert($other);
+ return $self;
+ }
+
+ #sub op_diversion ($$$) {
+ # my ($self, $other, $reverse) = @_;
+ # $self->diversion();
+ # return $self;
+ #}
+
+ #sub op_unknown ($$$$) {
+ # my ($self, $other, $rev, $op) = @_;
+ # print "<op_unknown>: op=$op\n";
+ # return $self;
+ #}
+
+ 1;
+
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