1 # EXTRACT VARIOUSLY DELIMITED TEXT SEQUENCES FROM STRINGS.
2 # FOR FULL DOCUMENTATION SEE Balanced.pod
7 package Text::Balanced;
11 use vars qw { $VERSION @ISA %EXPORT_TAGS };
13 use version; $VERSION = qv('1.99.1');
14 @ISA = qw ( Exporter );
16 %EXPORT_TAGS = ( ALL => [ qw(
31 Exporter::export_ok_tags('ALL');
35 sub _match_bracketed($$$$$$);
36 sub _match_variable($$);
37 sub _match_codeblock($$$$$$$);
38 sub _match_quotelike($$$$);
40 # HANDLE RETURN VALUES IN VARIOUS CONTEXTS
43 my ($message, $pos) = @_;
44 $@ = bless { error=>$message, pos=>$pos }, "Text::Balanced::ErrorMsg";
49 my ($wantarray, $textref, $message, $pos) = @_;
50 _failmsg $message, $pos if $message;
51 return (undef,$$textref,undef) if $wantarray;
58 my ($wantarray,$textref) = splice @_, 0, 2;
59 my ($extrapos, $extralen) = @_>18 ? splice(@_, -2, 2) : (0,0);
60 my ($startlen, $oppos) = @_[5,6];
61 my $remainderpos = $_[2];
65 while (my ($from, $len) = splice @_, 0, 2)
67 push @res, substr($$textref,$from,$len);
69 if ($extralen) { # CORRECT FILLET
70 my $extra = substr($res[0], $extrapos-$oppos, $extralen, "\n");
71 $res[1] = "$extra$res[1]";
72 eval { substr($$textref,$remainderpos,0) = $extra;
73 substr($$textref,$extrapos,$extralen,"\n")} ;
74 #REARRANGE HERE DOC AND FILLET IF POSSIBLE
75 pos($$textref) = $remainderpos-$extralen+1; # RESET \G
78 pos($$textref) = $remainderpos; # RESET \G
84 my $match = substr($$textref,$_[0],$_[1]);
85 substr($match,$extrapos-$_[0]-$startlen,$extralen,"") if $extralen;
87 ? substr($$textref, $extrapos, $extralen)."\n" : "";
88 eval {substr($$textref,$_[4],$_[1]+$_[5])=$extra} ; #CHOP OUT PREFIX & MATCH, IF POSSIBLE
89 pos($$textref) = $_[4]; # RESET \G
94 # BUILD A PATTERN MATCHING A SIMPLE DELIMITED STRING
96 sub gen_delimited_pat($;$) # ($delimiters;$escapes)
98 my ($dels, $escs) = @_;
99 return "" unless $dels =~ /\S/;
100 $escs = '\\' unless $escs;
101 $escs .= substr($escs,-1) x (length($dels)-length($escs));
104 for ($i=0; $i<length $dels; $i++)
106 my $del = quotemeta substr($dels,$i,1);
107 my $esc = quotemeta substr($escs,$i,1);
110 push @pat, "$del(?:[^$del]*(?:(?:$del$del)[^$del]*)*)$del";
114 push @pat, "$del(?:[^$esc$del]*(?:$esc.[^$esc$del]*)*)$del";
117 my $pat = join '|', @pat;
121 *delimited_pat = \&gen_delimited_pat;
124 # THE EXTRACTION FUNCTIONS
126 sub extract_delimited (;$$$$)
128 my $textref = defined $_[0] ? \$_[0] : \$_;
129 my $wantarray = wantarray;
130 my $del = defined $_[1] ? $_[1] : qq{\'\"\`};
131 my $pre = defined $_[2] ? $_[2] : '\s*';
132 my $esc = defined $_[3] ? $_[3] : qq{\\};
133 my $pat = gen_delimited_pat($del, $esc);
134 my $startpos = pos $$textref || 0;
135 return _fail($wantarray, $textref, "Not a delimited pattern", 0)
136 unless $$textref =~ m/\G($pre)($pat)/gc;
137 my $prelen = length($1);
138 my $matchpos = $startpos+$prelen;
139 my $endpos = pos $$textref;
140 return _succeed $wantarray, $textref,
141 $matchpos, $endpos-$matchpos, # MATCH
142 $endpos, length($$textref)-$endpos, # REMAINDER
143 $startpos, $prelen; # PREFIX
146 sub extract_bracketed (;$$$)
148 my $textref = defined $_[0] ? \$_[0] : \$_;
149 my $ldel = defined $_[1] ? $_[1] : '{([<';
150 my $pre = defined $_[2] ? $_[2] : '\s*';
151 my $wantarray = wantarray;
154 $ldel =~ s/'//g and $qdel .= q{'};
155 $ldel =~ s/"//g and $qdel .= q{"};
156 $ldel =~ s/`//g and $qdel .= q{`};
157 $ldel =~ s/q//g and $quotelike = 1;
158 $ldel =~ tr/[](){}<>\0-\377/[[(({{<</ds;
160 unless ($rdel =~ tr/[({</])}>/)
162 return _fail $wantarray, $textref,
163 "Did not find a suitable bracket in delimiter: \"$_[1]\"",
167 $ldel = join('|', map { quotemeta $_ } split('', $ldel));
168 $rdel = join('|', map { quotemeta $_ } split('', $rdel));
171 my $startpos = pos $$textref || 0;
172 my @match = _match_bracketed($textref,$pre, $ldel, $qdel, $quotelike, $rdel);
174 return _fail ($wantarray, $textref) unless @match;
176 return _succeed ( $wantarray, $textref,
177 $match[2], $match[5]+2, # MATCH
178 @match[8,9], # REMAINDER
179 @match[0,1], # PREFIX
183 sub _match_bracketed($$$$$$) # $textref, $pre, $ldel, $qdel, $quotelike, $rdel
185 my ($textref, $pre, $ldel, $qdel, $quotelike, $rdel) = @_;
186 my ($startpos, $ldelpos, $endpos) = (pos $$textref = pos $$textref||0);
187 unless ($$textref =~ m/\G$pre/gc)
189 _failmsg "Did not find prefix: /$pre/", $startpos;
193 $ldelpos = pos $$textref;
195 unless ($$textref =~ m/\G($ldel)/gc)
197 _failmsg "Did not find opening bracket after prefix: \"$pre\"",
199 pos $$textref = $startpos;
203 my @nesting = ( $1 );
204 my $textlen = length $$textref;
205 while (pos $$textref < $textlen)
207 next if $$textref =~ m/\G\\./gcs;
209 if ($$textref =~ m/\G($ldel)/gc)
213 elsif ($$textref =~ m/\G($rdel)/gc)
215 my ($found, $brackettype) = ($1, $1);
218 _failmsg "Unmatched closing bracket: \"$found\"",
220 pos $$textref = $startpos;
223 my $expected = pop(@nesting);
224 $expected =~ tr/({[</)}]>/;
225 if ($expected ne $brackettype)
227 _failmsg qq{Mismatched closing bracket: expected "$expected" but found "$found"},
229 pos $$textref = $startpos;
232 last if $#nesting < 0;
234 elsif ($qdel && $$textref =~ m/\G([$qdel])/gc)
236 $$textref =~ m/\G[^\\$1]*(?:\\.[^\\$1]*)*(\Q$1\E)/gsc and next;
237 _failmsg "Unmatched embedded quote ($1)",
239 pos $$textref = $startpos;
242 elsif ($quotelike && _match_quotelike($textref,"",1,0))
247 else { $$textref =~ m/\G(?:[a-zA-Z0-9]+|.)/gcs }
251 _failmsg "Unmatched opening bracket(s): "
252 . join("..",@nesting)."..",
254 pos $$textref = $startpos;
258 $endpos = pos $$textref;
261 $startpos, $ldelpos-$startpos, # PREFIX
262 $ldelpos, 1, # OPENING BRACKET
263 $ldelpos+1, $endpos-$ldelpos-2, # CONTENTS
264 $endpos-1, 1, # CLOSING BRACKET
265 $endpos, length($$textref)-$endpos, # REMAINDER
271 my $brack = reverse $_[0];
272 $brack =~ tr/[({</])}>/;
276 my $XMLNAME = q{[a-zA-Z_:][a-zA-Z0-9_:.-]*};
278 sub extract_tagged (;$$$$$) # ($text, $opentag, $closetag, $pre, \%options)
280 my $textref = defined $_[0] ? \$_[0] : \$_;
283 my $pre = defined $_[3] ? $_[3] : '\s*';
284 my %options = defined $_[4] ? %{$_[4]} : ();
285 my $omode = defined $options{fail} ? $options{fail} : '';
286 my $bad = ref($options{reject}) eq 'ARRAY' ? join('|', @{$options{reject}})
287 : defined($options{reject}) ? $options{reject}
290 my $ignore = ref($options{ignore}) eq 'ARRAY' ? join('|', @{$options{ignore}})
291 : defined($options{ignore}) ? $options{ignore}
295 if (!defined $ldel) { $ldel = '<\w+(?:' . gen_delimited_pat(q{'"}) . '|[^>])*>'; }
298 my @match = _match_tagged($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore);
300 return _fail(wantarray, $textref) unless @match;
301 return _succeed wantarray, $textref,
302 $match[2], $match[3]+$match[5]+$match[7], # MATCH
303 @match[8..9,0..1,2..7]; # REM, PRE, BITS
306 sub _match_tagged # ($$$$$$$)
308 my ($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore) = @_;
311 my ($startpos, $opentagpos, $textpos, $parapos, $closetagpos, $endpos) = ( pos($$textref) = pos($$textref)||0 );
313 unless ($$textref =~ m/\G($pre)/gc)
315 _failmsg "Did not find prefix: /$pre/", pos $$textref;
319 $opentagpos = pos($$textref);
321 unless ($$textref =~ m/\G$ldel/gc)
323 _failmsg "Did not find opening tag: /$ldel/", pos $$textref;
327 $textpos = pos($$textref);
331 $rdelspec = substr($$textref, $-[0], $+[0] - $-[0]);
332 unless ($rdelspec =~ s/\A([[(<{]+)($XMLNAME).*/ quotemeta "$1\/$2". _revbracket($1) /oes)
334 _failmsg "Unable to construct closing tag to match: $rdel",
341 $rdelspec = eval "qq{$rdel}" || do {
343 for (qw,~ ! ^ & * ) _ + - = } ] : " ; ' > . ? / | ',)
344 { next if $rdel =~ /\Q$_/; $del = $_; last }
347 croak "Can't interpolate right delimiter $rdel"
349 eval "qq$del$rdel$del";
353 while (pos($$textref) < length($$textref))
355 next if $$textref =~ m/\G\\./gc;
357 if ($$textref =~ m/\G(\n[ \t]*\n)/gc )
359 $parapos = pos($$textref) - length($1)
360 unless defined $parapos;
362 elsif ($$textref =~ m/\G($rdelspec)/gc )
364 $closetagpos = pos($$textref)-length($1);
367 elsif ($ignore && $$textref =~ m/\G(?:$ignore)/gc)
371 elsif ($bad && $$textref =~ m/\G($bad)/gcs)
373 pos($$textref) -= length($1); # CUT OFF WHATEVER CAUSED THE SHORTNESS
374 goto short if ($omode eq 'PARA' || $omode eq 'MAX');
375 _failmsg "Found invalid nested tag: $1", pos $$textref;
378 elsif ($$textref =~ m/\G($ldel)/gc)
381 pos($$textref) -= length($tag); # REWIND TO NESTED TAG
382 unless (_match_tagged(@_)) # MATCH NESTED TAG
384 goto short if $omode eq 'PARA' || $omode eq 'MAX';
385 _failmsg "Found unbalanced nested tag: $tag",
390 else { $$textref =~ m/./gcs }
394 $closetagpos = pos($$textref);
395 goto matched if $omode eq 'MAX';
396 goto failed unless $omode eq 'PARA';
398 if (defined $parapos) { pos($$textref) = $parapos }
399 else { $parapos = pos($$textref) }
402 $startpos, $opentagpos-$startpos, # PREFIX
403 $opentagpos, $textpos-$opentagpos, # OPENING TAG
404 $textpos, $parapos-$textpos, # TEXT
405 $parapos, 0, # NO CLOSING TAG
406 $parapos, length($$textref)-$parapos, # REMAINDER
410 $endpos = pos($$textref);
412 $startpos, $opentagpos-$startpos, # PREFIX
413 $opentagpos, $textpos-$opentagpos, # OPENING TAG
414 $textpos, $closetagpos-$textpos, # TEXT
415 $closetagpos, $endpos-$closetagpos, # CLOSING TAG
416 $endpos, length($$textref)-$endpos, # REMAINDER
420 _failmsg "Did not find closing tag", pos $$textref unless $@;
421 pos($$textref) = $startpos;
425 sub extract_variable (;$$)
427 my $textref = defined $_[0] ? \$_[0] : \$_;
428 return ("","","") unless defined $$textref;
429 my $pre = defined $_[1] ? $_[1] : '\s*';
431 my @match = _match_variable($textref,$pre);
433 return _fail wantarray, $textref unless @match;
435 return _succeed wantarray, $textref,
436 @match[2..3,4..5,0..1]; # MATCH, REMAINDER, PREFIX
439 sub _match_variable($$)
444 my ($textref, $pre) = @_;
445 my $startpos = pos($$textref) = pos($$textref)||0;
446 unless ($$textref =~ m/\G($pre)/gc)
448 _failmsg "Did not find prefix: /$pre/", pos $$textref;
451 my $varpos = pos($$textref);
452 unless ($$textref =~ m{\G\$\s*(?!::)(\d+|[][&`'+*./|,";%=~:?!\@<>()-]|\^[a-z]?)}gci)
454 unless ($$textref =~ m/\G((\$#?|[*\@\%]|\\&)+)/gc)
456 _failmsg "Did not find leading dereferencer", pos $$textref;
457 pos $$textref = $startpos;
462 unless ($$textref =~ m/\G\s*(?:::|')?(?:[_a-z]\w*(?:::|'))*[_a-z]\w*/gci
463 or _match_codeblock($textref, "", '\{', '\}', '\{', '\}', 0)
464 or $deref eq '$#' or $deref eq '$$' )
466 _failmsg "Bad identifier after dereferencer", pos $$textref;
467 pos $$textref = $startpos;
474 next if $$textref =~ m/\G\s*(?:->)?\s*[{]\w+[}]/gc;
475 next if _match_codeblock($textref,
476 qr/\s*->\s*(?:[_a-zA-Z]\w+\s*)?/,
477 qr/[({[]/, qr/[)}\]]/,
478 qr/[({[]/, qr/[)}\]]/, 0);
479 next if _match_codeblock($textref,
480 qr/\s*/, qr/[{[]/, qr/[}\]]/,
481 qr/[{[]/, qr/[}\]]/, 0);
482 next if _match_variable($textref,'\s*->\s*');
483 next if $$textref =~ m/\G\s*->\s*\w+(?![{([])/gc;
487 my $endpos = pos($$textref);
488 return ($startpos, $varpos-$startpos,
489 $varpos, $endpos-$varpos,
490 $endpos, length($$textref)-$endpos
494 sub extract_codeblock (;$$$$$)
496 my $textref = defined $_[0] ? \$_[0] : \$_;
497 my $wantarray = wantarray;
498 my $ldel_inner = defined $_[1] ? $_[1] : '{';
499 my $pre = defined $_[2] ? $_[2] : '\s*';
500 my $ldel_outer = defined $_[3] ? $_[3] : $ldel_inner;
502 my $rdel_inner = $ldel_inner;
503 my $rdel_outer = $ldel_outer;
505 for ($ldel_inner, $ldel_outer) { tr/[]()<>{}\0-\377/[[((<<{{/ds }
506 for ($rdel_inner, $rdel_outer) { tr/[]()<>{}\0-\377/]]))>>}}/ds }
507 for ($ldel_inner, $ldel_outer, $rdel_inner, $rdel_outer)
509 $_ = '('.join('|',map { quotemeta $_ } split('',$_)).')'
513 my @match = _match_codeblock($textref, $pre,
514 $ldel_outer, $rdel_outer,
515 $ldel_inner, $rdel_inner,
517 return _fail($wantarray, $textref) unless @match;
518 return _succeed($wantarray, $textref,
519 @match[2..3,4..5,0..1] # MATCH, REMAINDER, PREFIX
524 sub _match_codeblock($$$$$$$)
526 my ($textref, $pre, $ldel_outer, $rdel_outer, $ldel_inner, $rdel_inner, $rd) = @_;
527 my $startpos = pos($$textref) = pos($$textref) || 0;
528 unless ($$textref =~ m/\G($pre)/gc)
530 _failmsg qq{Did not match prefix /$pre/ at"} .
531 substr($$textref,pos($$textref),20) .
536 my $codepos = pos($$textref);
537 unless ($$textref =~ m/\G($ldel_outer)/gc) # OUTERMOST DELIMITER
539 _failmsg qq{Did not find expected opening bracket at "} .
540 substr($$textref,pos($$textref),20) .
543 pos $$textref = $startpos;
547 $closing =~ tr/([<{/)]>}/;
550 while (pos($$textref) < length($$textref))
553 if ($rd && $$textref =~ m#\G(\Q(?)\E|\Q(s?)\E|\Q(s)\E)#gc)
559 if ($$textref =~ m/\G\s*#.*/gc)
564 if ($$textref =~ m/\G\s*($rdel_outer)/gc)
566 unless ($matched = ($closing && $1 eq $closing) )
568 next if $1 eq '>'; # MIGHT BE A "LESS THAN"
569 _failmsg q{Mismatched closing bracket at "} .
570 substr($$textref,pos($$textref),20) .
571 qq{...". Expected '$closing'},
577 if (_match_variable($textref,'\s*') ||
578 _match_quotelike($textref,'\s*',$patvalid,$patvalid) )
585 # NEED TO COVER MANY MORE CASES HERE!!!
586 if ($$textref =~ m#\G\s*(?!$ldel_inner)
590 | (\*\*|&&|\|\||<<|>>)=?
591 | split|grep|map|return
599 if ( _match_codeblock($textref, '\s*', $ldel_inner, $rdel_inner, $ldel_inner, $rdel_inner, $rd) )
605 if ($$textref =~ m/\G\s*$ldel_outer/gc)
607 _failmsg q{Improperly nested codeblock at "} .
608 substr($$textref,pos($$textref),20) .
615 $$textref =~ m/\G\s*(\w+|[-=>]>|.|\Z)/gc;
617 continue { $@ = undef }
621 _failmsg 'No match found for opening bracket', pos $$textref
626 my $endpos = pos($$textref);
627 return ( $startpos, $codepos-$startpos,
628 $codepos, $endpos-$codepos,
629 $endpos, length($$textref)-$endpos,
635 'none' => '[cgimsox]*',
637 's' => '[cegimsox]*',
647 sub extract_quotelike (;$$)
649 my $textref = $_[0] ? \$_[0] : \$_;
650 my $wantarray = wantarray;
651 my $pre = defined $_[1] ? $_[1] : '\s*';
653 my @match = _match_quotelike($textref,$pre,1,0);
654 return _fail($wantarray, $textref) unless @match;
655 return _succeed($wantarray, $textref,
656 $match[2], $match[18]-$match[2], # MATCH
657 @match[18,19], # REMAINDER
658 @match[0,1], # PREFIX
659 @match[2..17], # THE BITS
660 @match[20,21], # ANY FILLET?
664 sub _match_quotelike($$$$) # ($textref, $prepat, $allow_raw_match)
666 my ($textref, $pre, $rawmatch, $qmark) = @_;
668 my ($textlen,$startpos,
670 $preld1pos,$ld1pos,$str1pos,$rd1pos,
671 $preld2pos,$ld2pos,$str2pos,$rd2pos,
672 $modpos) = ( length($$textref), pos($$textref) = pos($$textref) || 0 );
674 unless ($$textref =~ m/\G($pre)/gc)
676 _failmsg qq{Did not find prefix /$pre/ at "} .
677 substr($$textref, pos($$textref), 20) .
682 $oppos = pos($$textref);
684 my $initial = substr($$textref,$oppos,1);
686 if ($initial && $initial =~ m|^[\"\'\`]|
687 || $rawmatch && $initial =~ m|^/|
688 || $qmark && $initial =~ m|^\?|)
690 unless ($$textref =~ m/ \Q$initial\E [^\\$initial]* (\\.[^\\$initial]*)* \Q$initial\E /gcsx)
692 _failmsg qq{Did not find closing delimiter to match '$initial' at "} .
693 substr($$textref, $oppos, 20) .
696 pos $$textref = $startpos;
699 $modpos= pos($$textref);
702 if ($initial eq '/' || $initial eq '?')
704 $$textref =~ m/\G$mods{none}/gc
707 my $endpos = pos($$textref);
709 $startpos, $oppos-$startpos, # PREFIX
710 $oppos, 0, # NO OPERATOR
711 $oppos, 1, # LEFT DEL
712 $oppos+1, $rd1pos-$oppos-1, # STR/PAT
713 $rd1pos, 1, # RIGHT DEL
714 $modpos, 0, # NO 2ND LDEL
715 $modpos, 0, # NO 2ND STR
716 $modpos, 0, # NO 2ND RDEL
717 $modpos, $endpos-$modpos, # MODIFIERS
718 $endpos, $textlen-$endpos, # REMAINDER
723 m{\G(\b(?:m|s|qq|qx|qw|q|qr|tr|y)\b(?=\s*\S)|<<(?=\s*["'A-Za-z_]))}gc)
725 _failmsg q{No quotelike operator found after prefix at "} .
726 substr($$textref, pos($$textref), 20) .
729 pos $$textref = $startpos;
734 $preld1pos = pos($$textref);
736 $ld1pos = pos($$textref);
738 if ($$textref =~ m{\G([A-Za-z_]\w*)}gc) {
741 elsif ($$textref =~ m{ \G ' ([^'\\]* (?:\\.[^'\\]*)*) '
742 | \G " ([^"\\]* (?:\\.[^"\\]*)*) "
743 | \G ` ([^`\\]* (?:\\.[^`\\]*)*) `
750 my $extrapos = pos($$textref);
751 $$textref =~ m{.*\n}gc;
752 $str1pos = pos($$textref)--;
753 unless ($$textref =~ m{.*?\n(?=\Q$label\E\n)}gc) {
754 _failmsg qq{Missing here doc terminator ('$label') after "} .
755 substr($$textref, $startpos, 20) .
758 pos $$textref = $startpos;
761 $rd1pos = pos($$textref);
762 $$textref =~ m{\Q$label\E\n}gc;
763 $ld2pos = pos($$textref);
765 $startpos, $oppos-$startpos, # PREFIX
766 $oppos, length($op), # OPERATOR
767 $ld1pos, $extrapos-$ld1pos, # LEFT DEL
768 $str1pos, $rd1pos-$str1pos, # STR/PAT
769 $rd1pos, $ld2pos-$rd1pos, # RIGHT DEL
770 $ld2pos, 0, # NO 2ND LDEL
771 $ld2pos, 0, # NO 2ND STR
772 $ld2pos, 0, # NO 2ND RDEL
773 $ld2pos, 0, # NO MODIFIERS
774 $ld2pos, $textlen-$ld2pos, # REMAINDER
775 $extrapos, $str1pos-$extrapos, # FILLETED BIT
779 $$textref =~ m/\G\s*/gc;
780 $ld1pos = pos($$textref);
781 $str1pos = $ld1pos+1;
783 unless ($$textref =~ m/\G(\S)/gc) # SHOULD USE LOOKAHEAD
785 _failmsg "No block delimiter found after quotelike $op",
787 pos $$textref = $startpos;
790 pos($$textref) = $ld1pos; # HAVE TO DO THIS BECAUSE LOOKAHEAD BROKEN
791 my ($ldel1, $rdel1) = ("\Q$1","\Q$1");
792 if ($ldel1 =~ /[[(<{]/)
794 $rdel1 =~ tr/[({</])}>/;
795 defined(_match_bracketed($textref,"",$ldel1,"","",$rdel1))
796 || do { pos $$textref = $startpos; return };
800 $$textref =~ /$ldel1[^\\$ldel1]*(\\.[^\\$ldel1]*)*$ldel1/gcs
801 || do { pos $$textref = $startpos; return };
803 $ld2pos = $rd1pos = pos($$textref)-1;
805 my $second_arg = $op =~ /s|tr|y/ ? 1 : 0;
809 if ($ldel1 =~ /[[(<{]/)
811 unless ($$textref =~ /\G\s*(\S)/gc) # SHOULD USE LOOKAHEAD
813 _failmsg "Missing second block for quotelike $op",
815 pos $$textref = $startpos;
818 $ldel2 = $rdel2 = "\Q$1";
819 $rdel2 =~ tr/[({</])}>/;
823 $ldel2 = $rdel2 = $ldel1;
825 $str2pos = $ld2pos+1;
827 if ($ldel2 =~ /[[(<{]/)
829 pos($$textref)--; # OVERCOME BROKEN LOOKAHEAD
830 defined(_match_bracketed($textref,"",$ldel2,"","",$rdel2))
831 || do { pos $$textref = $startpos; return };
835 $$textref =~ /[^\\$ldel2]*(\\.[^\\$ldel2]*)*$ldel2/gcs
836 || do { pos $$textref = $startpos; return };
838 $rd2pos = pos($$textref)-1;
842 $ld2pos = $str2pos = $rd2pos = $rd1pos;
845 $modpos = pos $$textref;
847 $$textref =~ m/\G($mods{$op})/gc;
848 my $endpos = pos $$textref;
851 $startpos, $oppos-$startpos, # PREFIX
852 $oppos, length($op), # OPERATOR
853 $ld1pos, 1, # LEFT DEL
854 $str1pos, $rd1pos-$str1pos, # STR/PAT
855 $rd1pos, 1, # RIGHT DEL
856 $ld2pos, $second_arg, # 2ND LDEL (MAYBE)
857 $str2pos, $rd2pos-$str2pos, # 2ND STR (MAYBE)
858 $rd2pos, $second_arg, # 2ND RDEL (MAYBE)
859 $modpos, $endpos-$modpos, # MODIFIERS
860 $endpos, $textlen-$endpos, # REMAINDER
866 sub { extract_variable($_[0], '') },
867 sub { extract_quotelike($_[0],'') },
868 sub { extract_codeblock($_[0],'{}','') },
871 sub extract_multiple (;$$$$) # ($text, $functions_ref, $max_fields, $ignoreunknown)
873 my $textref = defined($_[0]) ? \$_[0] : \$_;
875 my ($lastpos, $firstpos);
880 my @func = defined $_[1] ? @{$_[1]} : @{$def_func};
881 my $max = defined $_[2] && $_[2]>0 ? $_[2] : 1_000_000_000;
889 carp "extract_multiple reset maximal count to 1 in scalar context"
890 if $^W && defined($_[2]) && $max > 1;
899 foreach $func ( @func )
901 if (ref($func) eq 'HASH')
903 push @class, (keys %$func)[0];
904 $func = (values %$func)[0];
912 FIELD: while (pos($$textref) < length($$textref))
916 foreach my $i ( 0..$#func )
921 $lastpos = pos $$textref;
922 if (ref($func) eq 'CODE')
923 { ($field,$rem,$pref) = @bits = $func->($$textref) }
924 elsif (ref($func) eq 'Text::Balanced::Extractor')
925 { @bits = $field = $func->extract($$textref) }
926 elsif( $$textref =~ m/\G$func/gc )
927 { @bits = $field = defined($1)
929 : substr($$textref, $-[0], $+[0] - $-[0])
932 if (defined($field) && length($field))
936 if length($pref) && !defined($unkpos);
939 push @fields, substr($$textref, $unkpos, $lastpos-$unkpos).$pref;
940 $firstpos = $unkpos unless defined $firstpos;
942 last FIELD if @fields == $max;
946 ? bless (\$field, $class)
948 $firstpos = $lastpos unless defined $firstpos;
949 $lastpos = pos $$textref;
950 last FIELD if @fields == $max;
954 if ($$textref =~ /\G(.)/gcs)
956 $unkpos = pos($$textref)-1
957 unless $igunk || defined $unkpos;
963 push @fields, substr($$textref, $unkpos);
964 $firstpos = $unkpos unless defined $firstpos;
965 $lastpos = length $$textref;
970 pos $$textref = $lastpos;
971 return @fields if wantarray;
974 eval { substr($$textref,$firstpos,$lastpos-$firstpos)="";
975 pos $$textref = $firstpos };
980 sub gen_extract_tagged # ($opentag, $closetag, $pre, \%options)
984 my $pre = defined $_[2] ? $_[2] : '\s*';
985 my %options = defined $_[3] ? %{$_[3]} : ();
986 my $omode = defined $options{fail} ? $options{fail} : '';
987 my $bad = ref($options{reject}) eq 'ARRAY' ? join('|', @{$options{reject}})
988 : defined($options{reject}) ? $options{reject}
991 my $ignore = ref($options{ignore}) eq 'ARRAY' ? join('|', @{$options{ignore}})
992 : defined($options{ignore}) ? $options{ignore}
996 if (!defined $ldel) { $ldel = '<\w+(?:' . gen_delimited_pat(q{'"}) . '|[^>])*>'; }
999 for ($ldel, $pre, $bad, $ignore) { $_ = qr/$_/ if $_ }
1004 my $textref = defined $_[0] ? \$_[0] : \$_;
1005 my @match = Text::Balanced::_match_tagged($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore);
1007 return _fail(wantarray, $textref) unless @match;
1008 return _succeed wantarray, $textref,
1009 $match[2], $match[3]+$match[5]+$match[7], # MATCH
1010 @match[8..9,0..1,2..7]; # REM, PRE, BITS
1013 bless $closure, 'Text::Balanced::Extractor';
1016 package Text::Balanced::Extractor;
1018 sub extract($$) # ($self, $text)
1023 package Text::Balanced::ErrorMsg;
1025 use overload '""' => sub { "$_[0]->{error}, detected at offset $_[0]->{pos}" };
1033 Text::Balanced - Extract delimited text sequences from strings.
1038 use Text::Balanced qw (
1051 # Extract the initial substring of $text that is delimited by
1052 # two (unescaped) instances of the first character in $delim.
1054 ($extracted, $remainder) = extract_delimited($text,$delim);
1057 # Extract the initial substring of $text that is bracketed
1058 # with a delimiter(s) specified by $delim (where the string
1059 # in $delim contains one or more of '(){}[]<>').
1061 ($extracted, $remainder) = extract_bracketed($text,$delim);
1064 # Extract the initial substring of $text that is bounded by
1067 ($extracted, $remainder) = extract_tagged($text);
1070 # Extract the initial substring of $text that is bounded by
1071 # a C<BEGIN>...C<END> pair. Don't allow nested C<BEGIN> tags
1073 ($extracted, $remainder) =
1074 extract_tagged($text,"BEGIN","END",undef,{bad=>["BEGIN"]});
1077 # Extract the initial substring of $text that represents a
1078 # Perl "quote or quote-like operation"
1080 ($extracted, $remainder) = extract_quotelike($text);
1083 # Extract the initial substring of $text that represents a block
1084 # of Perl code, bracketed by any of character(s) specified by $delim
1085 # (where the string $delim contains one or more of '(){}[]<>').
1087 ($extracted, $remainder) = extract_codeblock($text,$delim);
1090 # Extract the initial substrings of $text that would be extracted by
1091 # one or more sequential applications of the specified functions
1092 # or regular expressions
1094 @extracted = extract_multiple($text,
1095 [ \&extract_bracketed,
1096 \&extract_quotelike,
1097 \&some_other_extractor_sub,
1102 # Create a string representing an optimized pattern (a la Friedl)
1103 # that matches a substring delimited by any of the specified characters
1104 # (in this case: any type of quote or a slash)
1106 $patstring = gen_delimited_pat(q{'"`/});
1109 # Generate a reference to an anonymous sub that is just like extract_tagged
1110 # but pre-compiled and optimized for a specific pair of tags, and consequently
1111 # much faster (i.e. 3 times faster). It uses qr// for better performance on
1112 # repeated calls, so it only works under Perl 5.005 or later.
1114 $extract_head = gen_extract_tagged('<HEAD>','</HEAD>');
1116 ($extracted, $remainder) = $extract_head->($text);
1121 The various C<extract_...> subroutines may be used to
1122 extract a delimited substring, possibly after skipping a
1123 specified prefix string. By default, that prefix is
1124 optional whitespace (C</\s*/>), but you can change it to whatever
1125 you wish (see below).
1127 The substring to be extracted must appear at the
1128 current C<pos> location of the string's variable
1129 (or at index zero, if no C<pos> position is defined).
1130 In other words, the C<extract_...> subroutines I<don't>
1131 extract the first occurance of a substring anywhere
1132 in a string (like an unanchored regex would). Rather,
1133 they extract an occurance of the substring appearing
1134 immediately at the current matching position in the
1135 string (like a C<\G>-anchored regex would).
1139 =head2 General behaviour in list contexts
1141 In a list context, all the subroutines return a list, the first three
1142 elements of which are always:
1148 The extracted string, including the specified delimiters.
1149 If the extraction fails C<undef> is returned.
1153 The remainder of the input string (i.e. the characters after the
1154 extracted string). On failure, the entire string is returned.
1158 The skipped prefix (i.e. the characters before the extracted string).
1159 On failure, C<undef> is returned.
1163 Note that in a list context, the contents of the original input text (the first
1164 argument) are not modified in any way.
1166 However, if the input text was passed in a variable, that variable's
1167 C<pos> value is updated to point at the first character after the
1168 extracted text. That means that in a list context the various
1169 subroutines can be used much like regular expressions. For example:
1171 while ( $next = (extract_quotelike($text))[0] )
1173 # process next quote-like (in $next)
1177 =head2 General behaviour in scalar and void contexts
1179 In a scalar context, the extracted string is returned, having first been
1180 removed from the input text. Thus, the following code also processes
1181 each quote-like operation, but actually removes them from $text:
1183 while ( $next = extract_quotelike($text) )
1185 # process next quote-like (in $next)
1188 Note that if the input text is a read-only string (i.e. a literal),
1189 no attempt is made to remove the extracted text.
1191 In a void context the behaviour of the extraction subroutines is
1192 exactly the same as in a scalar context, except (of course) that the
1193 extracted substring is not returned.
1195 =head2 A note about prefixes
1197 Prefix patterns are matched without any trailing modifiers (C</gimsox> etc.)
1198 This can bite you if you're expecting a prefix specification like
1199 '.*?(?=<H1>)' to skip everything up to the first <H1> tag. Such a prefix
1200 pattern will only succeed if the <H1> tag is on the current line, since
1201 . normally doesn't match newlines.
1203 To overcome this limitation, you need to turn on /s matching within
1204 the prefix pattern, using the C<(?s)> directive: '(?s).*?(?=<H1>)'
1207 =head2 C<extract_delimited>
1209 The C<extract_delimited> function formalizes the common idiom
1210 of extracting a single-character-delimited substring from the start of
1211 a string. For example, to extract a single-quote delimited string, the
1212 following code is typically used:
1214 ($remainder = $text) =~ s/\A('(\\.|[^'])*')//s;
1217 but with C<extract_delimited> it can be simplified to:
1219 ($extracted,$remainder) = extract_delimited($text, "'");
1221 C<extract_delimited> takes up to four scalars (the input text, the
1222 delimiters, a prefix pattern to be skipped, and any escape characters)
1223 and extracts the initial substring of the text that
1224 is appropriately delimited. If the delimiter string has multiple
1225 characters, the first one encountered in the text is taken to delimit
1227 The third argument specifies a prefix pattern that is to be skipped
1228 (but must be present!) before the substring is extracted.
1229 The final argument specifies the escape character to be used for each
1232 All arguments are optional. If the escape characters are not specified,
1233 every delimiter is escaped with a backslash (C<\>).
1234 If the prefix is not specified, the
1235 pattern C<'\s*'> - optional whitespace - is used. If the delimiter set
1236 is also not specified, the set C</["'`]/> is used. If the text to be processed
1237 is not specified either, C<$_> is used.
1239 In list context, C<extract_delimited> returns a array of three
1240 elements, the extracted substring (I<including the surrounding
1241 delimiters>), the remainder of the text, and the skipped prefix (if
1242 any). If a suitable delimited substring is not found, the first
1243 element of the array is the empty string, the second is the complete
1244 original text, and the prefix returned in the third element is an
1247 In a scalar context, just the extracted substring is returned. In
1248 a void context, the extracted substring (and any prefix) are simply
1249 removed from the beginning of the first argument.
1253 # Remove a single-quoted substring from the very beginning of $text:
1255 $substring = extract_delimited($text, "'", '');
1257 # Remove a single-quoted Pascalish substring (i.e. one in which
1258 # doubling the quote character escapes it) from the very
1259 # beginning of $text:
1261 $substring = extract_delimited($text, "'", '', "'");
1263 # Extract a single- or double- quoted substring from the
1264 # beginning of $text, optionally after some whitespace
1265 # (note the list context to protect $text from modification):
1267 ($substring) = extract_delimited $text, q{"'};
1270 # Delete the substring delimited by the first '/' in $text:
1272 $text = join '', (extract_delimited($text,'/','[^/]*')[2,1];
1274 Note that this last example is I<not> the same as deleting the first
1275 quote-like pattern. For instance, if C<$text> contained the string:
1277 "if ('./cmd' =~ m/$UNIXCMD/s) { $cmd = $1; }"
1279 then after the deletion it would contain:
1281 "if ('.$UNIXCMD/s) { $cmd = $1; }"
1285 "if ('./cmd' =~ ms) { $cmd = $1; }"
1288 See L<"extract_quotelike"> for a (partial) solution to this problem.
1291 =head2 C<extract_bracketed>
1293 Like C<"extract_delimited">, the C<extract_bracketed> function takes
1294 up to three optional scalar arguments: a string to extract from, a delimiter
1295 specifier, and a prefix pattern. As before, a missing prefix defaults to
1296 optional whitespace and a missing text defaults to C<$_>. However, a missing
1297 delimiter specifier defaults to C<'{}()[]E<lt>E<gt>'> (see below).
1299 C<extract_bracketed> extracts a balanced-bracket-delimited
1300 substring (using any one (or more) of the user-specified delimiter
1301 brackets: '(..)', '{..}', '[..]', or '<..>'). Optionally it will also
1302 respect quoted unbalanced brackets (see below).
1304 A "delimiter bracket" is a bracket in list of delimiters passed as
1305 C<extract_bracketed>'s second argument. Delimiter brackets are
1306 specified by giving either the left or right (or both!) versions
1307 of the required bracket(s). Note that the order in which
1308 two or more delimiter brackets are specified is not significant.
1310 A "balanced-bracket-delimited substring" is a substring bounded by
1311 matched brackets, such that any other (left or right) delimiter
1312 bracket I<within> the substring is also matched by an opposite
1313 (right or left) delimiter bracket I<at the same level of nesting>. Any
1314 type of bracket not in the delimiter list is treated as an ordinary
1317 In other words, each type of bracket specified as a delimiter must be
1318 balanced and correctly nested within the substring, and any other kind of
1319 ("non-delimiter") bracket in the substring is ignored.
1321 For example, given the string:
1323 $text = "{ an '[irregularly :-(] {} parenthesized >:-)' string }";
1325 then a call to C<extract_bracketed> in a list context:
1327 @result = extract_bracketed( $text, '{}' );
1331 ( "{ an '[irregularly :-(] {} parenthesized >:-)' string }" , "" , "" )
1333 since both sets of C<'{..}'> brackets are properly nested and evenly balanced.
1334 (In a scalar context just the first element of the array would be returned. In
1335 a void context, C<$text> would be replaced by an empty string.)
1337 Likewise the call in:
1339 @result = extract_bracketed( $text, '{[' );
1341 would return the same result, since all sets of both types of specified
1342 delimiter brackets are correctly nested and balanced.
1344 However, the call in:
1346 @result = extract_bracketed( $text, '{([<' );
1348 would fail, returning:
1350 ( undef , "{ an '[irregularly :-(] {} parenthesized >:-)' string }" );
1352 because the embedded pairs of C<'(..)'>s and C<'[..]'>s are "cross-nested" and
1353 the embedded C<'E<gt>'> is unbalanced. (In a scalar context, this call would
1354 return an empty string. In a void context, C<$text> would be unchanged.)
1356 Note that the embedded single-quotes in the string don't help in this
1357 case, since they have not been specified as acceptable delimiters and are
1358 therefore treated as non-delimiter characters (and ignored).
1360 However, if a particular species of quote character is included in the
1361 delimiter specification, then that type of quote will be correctly handled.
1362 for example, if C<$text> is:
1364 $text = '<A HREF=">>>>">link</A>';
1368 @result = extract_bracketed( $text, '<">' );
1372 ( '<A HREF=">>>>">', 'link</A>', "" )
1374 as expected. Without the specification of C<"> as an embedded quoter:
1376 @result = extract_bracketed( $text, '<>' );
1378 the result would be:
1380 ( '<A HREF=">', '>>>">link</A>', "" )
1382 In addition to the quote delimiters C<'>, C<">, and C<`>, full Perl quote-like
1383 quoting (i.e. q{string}, qq{string}, etc) can be specified by including the
1384 letter 'q' as a delimiter. Hence:
1386 @result = extract_bracketed( $text, '<q>' );
1388 would correctly match something like this:
1390 $text = '<leftop: conj /and/ conj>';
1392 See also: C<"extract_quotelike"> and C<"extract_codeblock">.
1395 =head2 C<extract_variable>
1397 C<extract_variable> extracts any valid Perl variable or
1398 variable-involved expression, including scalars, arrays, hashes, array
1399 accesses, hash look-ups, method calls through objects, subroutine calles
1400 through subroutine references, etc.
1402 The subroutine takes up to two optional arguments:
1408 A string to be processed (C<$_> if the string is omitted or C<undef>)
1412 A string specifying a pattern to be matched as a prefix (which is to be
1413 skipped). If omitted, optional whitespace is skipped.
1417 On success in a list context, an array of 3 elements is returned. The
1424 the extracted variable, or variablish expression
1428 the remainder of the input text,
1432 the prefix substring (if any),
1436 On failure, all of these values (except the remaining text) are C<undef>.
1438 In a scalar context, C<extract_variable> returns just the complete
1439 substring that matched a variablish expression. C<undef> is returned on
1440 failure. In addition, the original input text has the returned substring
1441 (and any prefix) removed from it.
1443 In a void context, the input text just has the matched substring (and
1444 any specified prefix) removed.
1447 =head2 C<extract_tagged>
1449 C<extract_tagged> extracts and segments text between (balanced)
1452 The subroutine takes up to five optional arguments:
1458 A string to be processed (C<$_> if the string is omitted or C<undef>)
1462 A string specifying a pattern to be matched as the opening tag.
1463 If the pattern string is omitted (or C<undef>) then a pattern
1464 that matches any standard XML tag is used.
1468 A string specifying a pattern to be matched at the closing tag.
1469 If the pattern string is omitted (or C<undef>) then the closing
1470 tag is constructed by inserting a C</> after any leading bracket
1471 characters in the actual opening tag that was matched (I<not> the pattern
1472 that matched the tag). For example, if the opening tag pattern
1473 is specified as C<'{{\w+}}'> and actually matched the opening tag
1474 C<"{{DATA}}">, then the constructed closing tag would be C<"{{/DATA}}">.
1478 A string specifying a pattern to be matched as a prefix (which is to be
1479 skipped). If omitted, optional whitespace is skipped.
1483 A hash reference containing various parsing options (see below)
1487 The various options that can be specified are:
1491 =item C<reject =E<gt> $listref>
1493 The list reference contains one or more strings specifying patterns
1494 that must I<not> appear within the tagged text.
1496 For example, to extract
1497 an HTML link (which should not contain nested links) use:
1499 extract_tagged($text, '<A>', '</A>', undef, {reject => ['<A>']} );
1501 =item C<ignore =E<gt> $listref>
1503 The list reference contains one or more strings specifying patterns
1504 that are I<not> be be treated as nested tags within the tagged text
1505 (even if they would match the start tag pattern).
1507 For example, to extract an arbitrary XML tag, but ignore "empty" elements:
1509 extract_tagged($text, undef, undef, undef, {ignore => ['<[^>]*/>']} );
1511 (also see L<"gen_delimited_pat"> below).
1514 =item C<fail =E<gt> $str>
1516 The C<fail> option indicates the action to be taken if a matching end
1517 tag is not encountered (i.e. before the end of the string or some
1518 C<reject> pattern matches). By default, a failure to match a closing
1519 tag causes C<extract_tagged> to immediately fail.
1521 However, if the string value associated with <reject> is "MAX", then
1522 C<extract_tagged> returns the complete text up to the point of failure.
1523 If the string is "PARA", C<extract_tagged> returns only the first paragraph
1524 after the tag (up to the first line that is either empty or contains
1525 only whitespace characters).
1526 If the string is "", the the default behaviour (i.e. failure) is reinstated.
1528 For example, suppose the start tag "/para" introduces a paragraph, which then
1529 continues until the next "/endpara" tag or until another "/para" tag is
1532 $text = "/para line 1\n\nline 3\n/para line 4";
1534 extract_tagged($text, '/para', '/endpara', undef,
1535 {reject => '/para', fail => MAX );
1537 # EXTRACTED: "/para line 1\n\nline 3\n"
1539 Suppose instead, that if no matching "/endpara" tag is found, the "/para"
1540 tag refers only to the immediately following paragraph:
1542 $text = "/para line 1\n\nline 3\n/para line 4";
1544 extract_tagged($text, '/para', '/endpara', undef,
1545 {reject => '/para', fail => MAX );
1547 # EXTRACTED: "/para line 1\n"
1549 Note that the specified C<fail> behaviour applies to nested tags as well.
1553 On success in a list context, an array of 6 elements is returned. The elements are:
1559 the extracted tagged substring (including the outermost tags),
1563 the remainder of the input text,
1567 the prefix substring (if any),
1575 the text between the opening and closing tags
1579 the closing tag (or "" if no closing tag was found)
1583 On failure, all of these values (except the remaining text) are C<undef>.
1585 In a scalar context, C<extract_tagged> returns just the complete
1586 substring that matched a tagged text (including the start and end
1587 tags). C<undef> is returned on failure. In addition, the original input
1588 text has the returned substring (and any prefix) removed from it.
1590 In a void context, the input text just has the matched substring (and
1591 any specified prefix) removed.
1594 =head2 C<gen_extract_tagged>
1596 (Note: This subroutine is only available under Perl5.005)
1598 C<gen_extract_tagged> generates a new anonymous subroutine which
1599 extracts text between (balanced) specified tags. In other words,
1600 it generates a function identical in function to C<extract_tagged>.
1602 The difference between C<extract_tagged> and the anonymous
1603 subroutines generated by
1604 C<gen_extract_tagged>, is that those generated subroutines:
1610 do not have to reparse tag specification or parsing options every time
1611 they are called (whereas C<extract_tagged> has to effectively rebuild
1612 its tag parser on every call);
1616 make use of the new qr// construct to pre-compile the regexes they use
1617 (whereas C<extract_tagged> uses standard string variable interpolation
1618 to create tag-matching patterns).
1622 The subroutine takes up to four optional arguments (the same set as
1623 C<extract_tagged> except for the string to be processed). It returns
1624 a reference to a subroutine which in turn takes a single argument (the text to
1627 In other words, the implementation of C<extract_tagged> is exactly
1633 $extractor = gen_extract_tagged(@_);
1634 return $extractor->($text);
1637 (although C<extract_tagged> is not currently implemented that way, in order
1638 to preserve pre-5.005 compatibility).
1640 Using C<gen_extract_tagged> to create extraction functions for specific tags
1641 is a good idea if those functions are going to be called more than once, since
1642 their performance is typically twice as good as the more general-purpose
1646 =head2 C<extract_quotelike>
1648 C<extract_quotelike> attempts to recognize, extract, and segment any
1649 one of the various Perl quotes and quotelike operators (see
1650 L<perlop(3)>) Nested backslashed delimiters, embedded balanced bracket
1651 delimiters (for the quotelike operators), and trailing modifiers are
1652 all caught. For example, in:
1654 extract_quotelike 'q # an octothorpe: \# (not the end of the q!) #'
1656 extract_quotelike ' "You said, \"Use sed\"." '
1658 extract_quotelike ' s{([A-Z]{1,8}\.[A-Z]{3})} /\L$1\E/; '
1660 extract_quotelike ' tr/\\\/\\\\/\\\//ds; '
1662 the full Perl quotelike operations are all extracted correctly.
1664 Note too that, when using the /x modifier on a regex, any comment
1665 containing the current pattern delimiter will cause the regex to be
1666 immediately terminated. In other words:
1669 (?i) # CASE INSENSITIVE
1670 [a-z_] # LEADING ALPHABETIC/UNDERSCORE
1671 [a-z0-9]* # FOLLOWED BY ANY NUMBER OF ALPHANUMERICS
1674 will be extracted as if it were:
1677 (?i) # CASE INSENSITIVE
1678 [a-z_] # LEADING ALPHABETIC/'
1680 This behaviour is identical to that of the actual compiler.
1682 C<extract_quotelike> takes two arguments: the text to be processed and
1683 a prefix to be matched at the very beginning of the text. If no prefix
1684 is specified, optional whitespace is the default. If no text is given,
1687 In a list context, an array of 11 elements is returned. The elements are:
1693 the extracted quotelike substring (including trailing modifiers),
1697 the remainder of the input text,
1701 the prefix substring (if any),
1705 the name of the quotelike operator (if any),
1709 the left delimiter of the first block of the operation,
1713 the text of the first block of the operation
1714 (that is, the contents of
1715 a quote, the regex of a match or substitution or the target list of a
1720 the right delimiter of the first block of the operation,
1724 the left delimiter of the second block of the operation
1725 (that is, if it is a C<s>, C<tr>, or C<y>),
1729 the text of the second block of the operation
1730 (that is, the replacement of a substitution or the translation list
1735 the right delimiter of the second block of the operation (if any),
1739 the trailing modifiers on the operation (if any).
1743 For each of the fields marked "(if any)" the default value on success is
1745 On failure, all of these values (except the remaining text) are C<undef>.
1748 In a scalar context, C<extract_quotelike> returns just the complete substring
1749 that matched a quotelike operation (or C<undef> on failure). In a scalar or
1750 void context, the input text has the same substring (and any specified
1755 # Remove the first quotelike literal that appears in text
1757 $quotelike = extract_quotelike($text,'.*?');
1759 # Replace one or more leading whitespace-separated quotelike
1760 # literals in $_ with "<QLL>"
1762 do { $_ = join '<QLL>', (extract_quotelike)[2,1] } until $@;
1765 # Isolate the search pattern in a quotelike operation from $text
1767 ($op,$pat) = (extract_quotelike $text)[3,5];
1770 print "search pattern: $pat\n";
1774 print "$op is not a pattern matching operation\n";
1778 =head2 C<extract_quotelike> and "here documents"
1780 C<extract_quotelike> can successfully extract "here documents" from an input
1781 string, but with an important caveat in list contexts.
1783 Unlike other types of quote-like literals, a here document is rarely
1784 a contiguous substring. For example, a typical piece of code using
1785 here document might look like this:
1788 This is the message.
1792 Given this as an input string in a scalar context, C<extract_quotelike>
1793 would correctly return the string "<<'EOMSG'\nThis is the message.\nEOMSG",
1794 leaving the string " || die;\nexit;" in the original variable. In other words,
1795 the two separate pieces of the here document are successfully extracted and
1798 In a list context, C<extract_quotelike> would return the list
1804 "<<'EOMSG'\nThis is the message.\nEOMSG\n" (i.e. the full extracted here document,
1805 including fore and aft delimiters),
1809 " || die;\nexit;" (i.e. the remainder of the input text, concatenated),
1813 "" (i.e. the prefix substring -- trivial in this case),
1817 "<<" (i.e. the "name" of the quotelike operator)
1821 "'EOMSG'" (i.e. the left delimiter of the here document, including any quotes),
1825 "This is the message.\n" (i.e. the text of the here document),
1829 "EOMSG" (i.e. the right delimiter of the here document),
1833 "" (a here document has no second left delimiter, second text, second right
1834 delimiter, or trailing modifiers).
1838 However, the matching position of the input variable would be set to
1839 "exit;" (i.e. I<after> the closing delimiter of the here document),
1840 which would cause the earlier " || die;\nexit;" to be skipped in any
1841 sequence of code fragment extractions.
1843 To avoid this problem, when it encounters a here document whilst
1844 extracting from a modifiable string, C<extract_quotelike> silently
1845 rearranges the string to an equivalent piece of Perl:
1848 This is the message.
1853 in which the here document I<is> contiguous. It still leaves the
1854 matching position after the here document, but now the rest of the line
1855 on which the here document starts is not skipped.
1857 To prevent <extract_quotelike> from mucking about with the input in this way
1858 (this is the only case where a list-context C<extract_quotelike> does so),
1859 you can pass the input variable as an interpolated literal:
1861 $quotelike = extract_quotelike("$var");
1864 =head2 C<extract_codeblock>
1866 C<extract_codeblock> attempts to recognize and extract a balanced
1867 bracket delimited substring that may contain unbalanced brackets
1868 inside Perl quotes or quotelike operations. That is, C<extract_codeblock>
1869 is like a combination of C<"extract_bracketed"> and
1870 C<"extract_quotelike">.
1872 C<extract_codeblock> takes the same initial three parameters as C<extract_bracketed>:
1873 a text to process, a set of delimiter brackets to look for, and a prefix to
1874 match first. It also takes an optional fourth parameter, which allows the
1875 outermost delimiter brackets to be specified separately (see below).
1877 Omitting the first argument (input text) means process C<$_> instead.
1878 Omitting the second argument (delimiter brackets) indicates that only C<'{'> is to be used.
1879 Omitting the third argument (prefix argument) implies optional whitespace at the start.
1880 Omitting the fourth argument (outermost delimiter brackets) indicates that the
1881 value of the second argument is to be used for the outermost delimiters.
1883 Once the prefix an dthe outermost opening delimiter bracket have been
1884 recognized, code blocks are extracted by stepping through the input text and
1885 trying the following alternatives in sequence:
1891 Try and match a closing delimiter bracket. If the bracket was the same
1892 species as the last opening bracket, return the substring to that
1893 point. If the bracket was mismatched, return an error.
1897 Try to match a quote or quotelike operator. If found, call
1898 C<extract_quotelike> to eat it. If C<extract_quotelike> fails, return
1899 the error it returned. Otherwise go back to step 1.
1903 Try to match an opening delimiter bracket. If found, call
1904 C<extract_codeblock> recursively to eat the embedded block. If the
1905 recursive call fails, return an error. Otherwise, go back to step 1.
1909 Unconditionally match a bareword or any other single character, and
1910 then go back to step 1.
1917 # Find a while loop in the text
1919 if ($text =~ s/.*?while\s*\{/{/)
1921 $loop = "while " . extract_codeblock($text);
1924 # Remove the first round-bracketed list (which may include
1925 # round- or curly-bracketed code blocks or quotelike operators)
1927 extract_codeblock $text, "(){}", '[^(]*';
1930 The ability to specify a different outermost delimiter bracket is useful
1931 in some circumstances. For example, in the Parse::RecDescent module,
1932 parser actions which are to be performed only on a successful parse
1933 are specified using a C<E<lt>defer:...E<gt>> directive. For example:
1935 sentence: subject verb object
1936 <defer: {$::theVerb = $item{verb}} >
1938 Parse::RecDescent uses C<extract_codeblock($text, '{}E<lt>E<gt>')> to extract the code
1939 within the C<E<lt>defer:...E<gt>> directive, but there's a problem.
1941 A deferred action like this:
1943 <defer: {if ($count>10) {$count--}} >
1945 will be incorrectly parsed as:
1947 <defer: {if ($count>
1949 because the "less than" operator is interpreted as a closing delimiter.
1951 But, by extracting the directive using
1952 S<C<extract_codeblock($text, '{}', undef, 'E<lt>E<gt>')>>
1953 the '>' character is only treated as a delimited at the outermost
1954 level of the code block, so the directive is parsed correctly.
1956 =head2 C<extract_multiple>
1958 The C<extract_multiple> subroutine takes a string to be processed and a
1959 list of extractors (subroutines or regular expressions) to apply to that string.
1961 In an array context C<extract_multiple> returns an array of substrings
1962 of the original string, as extracted by the specified extractors.
1963 In a scalar context, C<extract_multiple> returns the first
1964 substring successfully extracted from the original string. In both
1965 scalar and void contexts the original string has the first successfully
1966 extracted substring removed from it. In all contexts
1967 C<extract_multiple> starts at the current C<pos> of the string, and
1968 sets that C<pos> appropriately after it matches.
1970 Hence, the aim of of a call to C<extract_multiple> in a list context
1971 is to split the processed string into as many non-overlapping fields as
1972 possible, by repeatedly applying each of the specified extractors
1973 to the remainder of the string. Thus C<extract_multiple> is
1974 a generalized form of Perl's C<split> subroutine.
1976 The subroutine takes up to four optional arguments:
1982 A string to be processed (C<$_> if the string is omitted or C<undef>)
1986 A reference to a list of subroutine references and/or qr// objects and/or
1987 literal strings and/or hash references, specifying the extractors
1988 to be used to split the string. If this argument is omitted (or
1992 sub { extract_variable($_[0], '') },
1993 sub { extract_quotelike($_[0],'') },
1994 sub { extract_codeblock($_[0],'{}','') },
2002 An number specifying the maximum number of fields to return. If this
2003 argument is omitted (or C<undef>), split continues as long as possible.
2005 If the third argument is I<N>, then extraction continues until I<N> fields
2006 have been successfully extracted, or until the string has been completely
2009 Note that in scalar and void contexts the value of this argument is
2010 automatically reset to 1 (under C<-w>, a warning is issued if the argument
2015 A value indicating whether unmatched substrings (see below) within the
2016 text should be skipped or returned as fields. If the value is true,
2017 such substrings are skipped. Otherwise, they are returned.
2021 The extraction process works by applying each extractor in
2022 sequence to the text string.
2024 If the extractor is a subroutine it is called in a list context and is
2025 expected to return a list of a single element, namely the extracted
2026 text. It may optionally also return two further arguments: a string
2027 representing the text left after extraction (like $' for a pattern
2028 match), and a string representing any prefix skipped before the
2029 extraction (like $` in a pattern match). Note that this is designed
2030 to facilitate the use of other Text::Balanced subroutines with
2031 C<extract_multiple>. Note too that the value returned by an extractor
2032 subroutine need not bear any relationship to the corresponding substring
2033 of the original text (see examples below).
2035 If the extractor is a precompiled regular expression or a string,
2036 it is matched against the text in a scalar context with a leading
2037 '\G' and the gc modifiers enabled. The extracted value is either
2038 $1 if that variable is defined after the match, or else the
2039 complete match (i.e. $&).
2041 If the extractor is a hash reference, it must contain exactly one element.
2042 The value of that element is one of the
2043 above extractor types (subroutine reference, regular expression, or string).
2044 The key of that element is the name of a class into which the successful
2045 return value of the extractor will be blessed.
2047 If an extractor returns a defined value, that value is immediately
2048 treated as the next extracted field and pushed onto the list of fields.
2049 If the extractor was specified in a hash reference, the field is also
2050 blessed into the appropriate class,
2052 If the extractor fails to match (in the case of a regex extractor), or returns an empty list or an undefined value (in the case of a subroutine extractor), it is
2053 assumed to have failed to extract.
2054 If none of the extractor subroutines succeeds, then one
2055 character is extracted from the start of the text and the extraction
2056 subroutines reapplied. Characters which are thus removed are accumulated and
2057 eventually become the next field (unless the fourth argument is true, in which
2058 case they are disgarded).
2060 For example, the following extracts substrings that are valid Perl variables:
2062 @fields = extract_multiple($text,
2063 [ sub { extract_variable($_[0]) } ],
2066 This example separates a text into fields which are quote delimited,
2067 curly bracketed, and anything else. The delimited and bracketed
2068 parts are also blessed to identify them (the "anything else" is unblessed):
2070 @fields = extract_multiple($text,
2072 { Delim => sub { extract_delimited($_[0],q{'"}) } },
2073 { Brack => sub { extract_bracketed($_[0],'{}') } },
2076 This call extracts the next single substring that is a valid Perl quotelike
2077 operator (and removes it from $text):
2079 $quotelike = extract_multiple($text,
2081 sub { extract_quotelike($_[0]) },
2084 Finally, here is yet another way to do comma-separated value parsing:
2086 @fields = extract_multiple($csv_text,
2088 sub { extract_delimited($_[0],q{'"}) },
2093 The list in the second argument means:
2094 I<"Try and extract a ' or " delimited string, otherwise extract anything up to a comma...">.
2095 The undef third argument means:
2096 I<"...as many times as possible...">,
2097 and the true value in the fourth argument means
2098 I<"...discarding anything else that appears (i.e. the commas)">.
2100 If you wanted the commas preserved as separate fields (i.e. like split
2101 does if your split pattern has capturing parentheses), you would
2102 just make the last parameter undefined (or remove it).
2105 =head2 C<gen_delimited_pat>
2107 The C<gen_delimited_pat> subroutine takes a single (string) argument and
2108 > builds a Friedl-style optimized regex that matches a string delimited
2109 by any one of the characters in the single argument. For example:
2111 gen_delimited_pat(q{'"})
2115 (?:\"(?:\\\"|(?!\").)*\"|\'(?:\\\'|(?!\').)*\')
2117 Note that the specified delimiters are automatically quotemeta'd.
2119 A typical use of C<gen_delimited_pat> would be to build special purpose tags
2120 for C<extract_tagged>. For example, to properly ignore "empty" XML elements
2121 (which might contain quoted strings):
2123 my $empty_tag = '<(' . gen_delimited_pat(q{'"}) . '|.)+/>';
2125 extract_tagged($text, undef, undef, undef, {ignore => [$empty_tag]} );
2128 C<gen_delimited_pat> may also be called with an optional second argument,
2129 which specifies the "escape" character(s) to be used for each delimiter.
2130 For example to match a Pascal-style string (where ' is the delimiter
2131 and '' is a literal ' within the string):
2133 gen_delimited_pat(q{'},q{'});
2135 Different escape characters can be specified for different delimiters.
2136 For example, to specify that '/' is the escape for single quotes
2137 and '%' is the escape for double quotes:
2139 gen_delimited_pat(q{'"},q{/%});
2141 If more delimiters than escape chars are specified, the last escape char
2142 is used for the remaining delimiters.
2143 If no escape char is specified for a given specified delimiter, '\' is used.
2145 =head2 C<delimited_pat>
2147 Note that C<gen_delimited_pat> was previously called C<delimited_pat>.
2148 That name may still be used, but is now deprecated.
2153 In a list context, all the functions return C<(undef,$original_text)>
2154 on failure. In a scalar context, failure is indicated by returning C<undef>
2155 (in this case the input text is not modified in any way).
2157 In addition, on failure in I<any> context, the C<$@> variable is set.
2158 Accessing C<$@-E<gt>{error}> returns one of the error diagnostics listed
2160 Accessing C<$@-E<gt>{pos}> returns the offset into the original string at
2161 which the error was detected (although not necessarily where it occurred!)
2162 Printing C<$@> directly produces the error message, with the offset appended.
2163 On success, the C<$@> variable is guaranteed to be C<undef>.
2165 The available diagnostics are:
2169 =item C<Did not find a suitable bracket: "%s">
2171 The delimiter provided to C<extract_bracketed> was not one of
2172 C<'()[]E<lt>E<gt>{}'>.
2174 =item C<Did not find prefix: /%s/>
2176 A non-optional prefix was specified but wasn't found at the start of the text.
2178 =item C<Did not find opening bracket after prefix: "%s">
2180 C<extract_bracketed> or C<extract_codeblock> was expecting a
2181 particular kind of bracket at the start of the text, and didn't find it.
2183 =item C<No quotelike operator found after prefix: "%s">
2185 C<extract_quotelike> didn't find one of the quotelike operators C<q>,
2186 C<qq>, C<qw>, C<qx>, C<s>, C<tr> or C<y> at the start of the substring
2189 =item C<Unmatched closing bracket: "%c">
2191 C<extract_bracketed>, C<extract_quotelike> or C<extract_codeblock> encountered
2192 a closing bracket where none was expected.
2194 =item C<Unmatched opening bracket(s): "%s">
2196 C<extract_bracketed>, C<extract_quotelike> or C<extract_codeblock> ran
2197 out of characters in the text before closing one or more levels of nested
2200 =item C<Unmatched embedded quote (%s)>
2202 C<extract_bracketed> attempted to match an embedded quoted substring, but
2203 failed to find a closing quote to match it.
2205 =item C<Did not find closing delimiter to match '%s'>
2207 C<extract_quotelike> was unable to find a closing delimiter to match the
2208 one that opened the quote-like operation.
2210 =item C<Mismatched closing bracket: expected "%c" but found "%s">
2212 C<extract_bracketed>, C<extract_quotelike> or C<extract_codeblock> found
2213 a valid bracket delimiter, but it was the wrong species. This usually
2214 indicates a nesting error, but may indicate incorrect quoting or escaping.
2216 =item C<No block delimiter found after quotelike "%s">
2218 C<extract_quotelike> or C<extract_codeblock> found one of the
2219 quotelike operators C<q>, C<qq>, C<qw>, C<qx>, C<s>, C<tr> or C<y>
2220 without a suitable block after it.
2222 =item C<Did not find leading dereferencer>
2224 C<extract_variable> was expecting one of '$', '@', or '%' at the start of
2225 a variable, but didn't find any of them.
2227 =item C<Bad identifier after dereferencer>
2229 C<extract_variable> found a '$', '@', or '%' indicating a variable, but that
2230 character was not followed by a legal Perl identifier.
2232 =item C<Did not find expected opening bracket at %s>
2234 C<extract_codeblock> failed to find any of the outermost opening brackets
2235 that were specified.
2237 =item C<Improperly nested codeblock at %s>
2239 A nested code block was found that started with a delimiter that was specified
2240 as being only to be used as an outermost bracket.
2242 =item C<Missing second block for quotelike "%s">
2244 C<extract_codeblock> or C<extract_quotelike> found one of the
2245 quotelike operators C<s>, C<tr> or C<y> followed by only one block.
2247 =item C<No match found for opening bracket>
2249 C<extract_codeblock> failed to find a closing bracket to match the outermost
2252 =item C<Did not find opening tag: /%s/>
2254 C<extract_tagged> did not find a suitable opening tag (after any specified
2255 prefix was removed).
2257 =item C<Unable to construct closing tag to match: /%s/>
2259 C<extract_tagged> matched the specified opening tag and tried to
2260 modify the matched text to produce a matching closing tag (because
2261 none was specified). It failed to generate the closing tag, almost
2262 certainly because the opening tag did not start with a
2263 bracket of some kind.
2265 =item C<Found invalid nested tag: %s>
2267 C<extract_tagged> found a nested tag that appeared in the "reject" list
2268 (and the failure mode was not "MAX" or "PARA").
2270 =item C<Found unbalanced nested tag: %s>
2272 C<extract_tagged> found a nested opening tag that was not matched by a
2273 corresponding nested closing tag (and the failure mode was not "MAX" or "PARA").
2275 =item C<Did not find closing tag>
2277 C<extract_tagged> reached the end of the text without finding a closing tag
2278 to match the original opening tag (and the failure mode was not
2289 Damian Conway (damian@conway.org)
2292 =head1 BUGS AND IRRITATIONS
2294 There are undoubtedly serious bugs lurking somewhere in this code, if
2295 only because parts of it give the impression of understanding a great deal
2296 more about Perl than they really do.
2298 Bug reports and other feedback are most welcome.
2303 Copyright (c) 1997-2001, Damian Conway. All Rights Reserved.
2304 This module is free software. It may be used, redistributed
2305 and/or modified under the same terms as Perl itself.