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1 # EXTRACT VARIOUSLY DELIMITED TEXT SEQUENCES FROM STRINGS. 2 # FOR FULL DOCUMENTATION SEE Balanced.pod 3 4 use 5.005; 5 use strict; 6 7 package Text::Balanced; 8 9 use Exporter; 10 use SelfLoader; 11 use vars qw { $VERSION @ISA %EXPORT_TAGS }; 12 13 use version; $VERSION = qv('2.0.0'); 14 @ISA = qw ( Exporter ); 15 16 %EXPORT_TAGS = ( ALL => [ qw( 17 &extract_delimited 18 &extract_bracketed 19 &extract_quotelike 20 &extract_codeblock 21 &extract_variable 22 &extract_tagged 23 &extract_multiple 24 25 &gen_delimited_pat 26 &gen_extract_tagged 27 28 &delimited_pat 29 ) ] ); 30 31 Exporter::export_ok_tags('ALL'); 32 33 # PROTOTYPES 34 35 sub _match_bracketed($$$$$$); 36 sub _match_variable($$); 37 sub _match_codeblock($$$$$$$); 38 sub _match_quotelike($$$$); 39 40 # HANDLE RETURN VALUES IN VARIOUS CONTEXTS 41 42 sub _failmsg { 43 my ($message, $pos) = @_; 44 $@ = bless { error=>$message, pos=>$pos }, "Text::Balanced::ErrorMsg"; 45 } 46 47 sub _fail 48 { 49 my ($wantarray, $textref, $message, $pos) = @_; 50 _failmsg $message, $pos if $message; 51 return (undef,$$textref,undef) if $wantarray; 52 return undef; 53 } 54 55 sub _succeed 56 { 57 $@ = undef; 58 my ($wantarray,$textref) = splice @_, 0, 2; 59 my ($extrapos, $extralen) = @_>18 ? splice(@_, -2, 2) : (0,0); 60 my ($startlen, $oppos) = @_[5,6]; 61 my $remainderpos = $_[2]; 62 if ($wantarray) 63 { 64 my @res; 65 while (my ($from, $len) = splice @_, 0, 2) 66 { 67 push @res, substr($$textref,$from,$len); 68 } 69 if ($extralen) { # CORRECT FILLET 70 my $extra = substr($res[0], $extrapos-$oppos, $extralen, "\n"); 71 $res[1] = "$extra$res[1]"; 72 eval { substr($$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 76 } 77 else { 78 pos($$textref) = $remainderpos; # RESET \G 79 } 80 return @res; 81 } 82 else 83 { 84 my $match = substr($$textref,$_[0],$_[1]); 85 substr($match,$extrapos-$_[0]-$startlen,$extralen,"") if $extralen; 86 my $extra = $extralen 87 ? substr($$textref, $extrapos, $extralen)."\n" : ""; 88 eval {substr($$textref,$_[4],$_[1]+$_[5])=$extra} ; #CHOP OUT PREFIX & MATCH, IF POSSIBLE 89 pos($$textref) = $_[4]; # RESET \G 90 return $match; 91 } 92 } 93 94 # BUILD A PATTERN MATCHING A SIMPLE DELIMITED STRING 95 96 sub gen_delimited_pat($;$) # ($delimiters;$escapes) 97 { 98 my ($dels, $escs) = @_; 99 return "" unless $dels =~ /\S/; 100 $escs = '\\' unless $escs; 101 $escs .= substr($escs,-1) x (length($dels)-length($escs)); 102 my @pat = (); 103 my $i; 104 for ($i=0; $i<length $dels; $i++) 105 { 106 my $del = quotemeta substr($dels,$i,1); 107 my $esc = quotemeta substr($escs,$i,1); 108 if ($del eq $esc) 109 { 110 push @pat, "$del(?:[^$del]*(?:(?:$del$del)[^$del]*)*)$del"; 111 } 112 else 113 { 114 push @pat, "$del(?:[^$esc$del]*(?:$esc.[^$esc$del]*)*)$del"; 115 } 116 } 117 my $pat = join '|', @pat; 118 return "(?:$pat)"; 119 } 120 121 *delimited_pat = \&gen_delimited_pat; 122 123 124 # THE EXTRACTION FUNCTIONS 125 126 sub extract_delimited (;$$$$) 127 { 128 my $textref = defined $_[0] ? \$_[0] : \$_; 129 my $wantarray = wantarray; 130 my $del = defined $_[1] ? $_[1] : qq{\'\"\`}; 131 my $pre = defined $_[2] ? $_[2] : '\s*'; 132 my $esc = defined $_[3] ? $_[3] : qq{\\}; 133 my $pat = gen_delimited_pat($del, $esc); 134 my $startpos = pos $$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($$textref)-$endpos, # REMAINDER 143 $startpos, $prelen; # PREFIX 144 } 145 146 sub extract_bracketed (;$$$) 147 { 148 my $textref = defined $_[0] ? \$_[0] : \$_; 149 my $ldel = defined $_[1] ? $_[1] : '{([<'; 150 my $pre = defined $_[2] ? $_[2] : '\s*'; 151 my $wantarray = wantarray; 152 my $qdel = ""; 153 my $quotelike; 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; 159 my $rdel = $ldel; 160 unless ($rdel =~ tr/[({</])}>/) 161 { 162 return _fail $wantarray, $textref, 163 "Did not find a suitable bracket in delimiter: \"$_[1]\"", 164 0; 165 } 166 my $posbug = pos; 167 $ldel = join('|', map { quotemeta $_ } split('', $ldel)); 168 $rdel = join('|', map { quotemeta $_ } split('', $rdel)); 169 pos = $posbug; 170 171 my $startpos = pos $$textref || 0; 172 my @match = _match_bracketed($textref,$pre, $ldel, $qdel, $quotelike, $rdel); 173 174 return _fail ($wantarray, $textref) unless @match; 175 176 return _succeed ( $wantarray, $textref, 177 $match[2], $match[5]+2, # MATCH 178 @match[8,9], # REMAINDER 179 @match[0,1], # PREFIX 180 ); 181 } 182 183 sub _match_bracketed($$$$$$) # $textref, $pre, $ldel, $qdel, $quotelike, $rdel 184 { 185 my ($textref, $pre, $ldel, $qdel, $quotelike, $rdel) = @_; 186 my ($startpos, $ldelpos, $endpos) = (pos $$textref = pos $$textref||0); 187 unless ($$textref =~ m/\G$pre/gc) 188 { 189 _failmsg "Did not find prefix: /$pre/", $startpos; 190 return; 191 } 192 193 $ldelpos = pos $$textref; 194 195 unless ($$textref =~ m/\G($ldel)/gc) 196 { 197 _failmsg "Did not find opening bracket after prefix: \"$pre\"", 198 pos $$textref; 199 pos $$textref = $startpos; 200 return; 201 } 202 203 my @nesting = ( $1 ); 204 my $textlen = length $$textref; 205 while (pos $$textref < $textlen) 206 { 207 next if $$textref =~ m/\G\\./gcs; 208 209 if ($$textref =~ m/\G($ldel)/gc) 210 { 211 push @nesting, $1; 212 } 213 elsif ($$textref =~ m/\G($rdel)/gc) 214 { 215 my ($found, $brackettype) = ($1, $1); 216 if ($#nesting < 0) 217 { 218 _failmsg "Unmatched closing bracket: \"$found\"", 219 pos $$textref; 220 pos $$textref = $startpos; 221 return; 222 } 223 my $expected = pop(@nesting); 224 $expected =~ tr/({[</)}]>/; 225 if ($expected ne $brackettype) 226 { 227 _failmsg qq{Mismatched closing bracket: expected "$expected" but found "$found"}, 228 pos $$textref; 229 pos $$textref = $startpos; 230 return; 231 } 232 last if $#nesting < 0; 233 } 234 elsif ($qdel && $$textref =~ m/\G([$qdel])/gc) 235 { 236 $$textref =~ m/\G[^\\$1]*(?:\\.[^\\$1]*)*(\Q$1\E)/gsc and next; 237 _failmsg "Unmatched embedded quote ($1)", 238 pos $$textref; 239 pos $$textref = $startpos; 240 return; 241 } 242 elsif ($quotelike && _match_quotelike($textref,"",1,0)) 243 { 244 next; 245 } 246 247 else { $$textref =~ m/\G(?:[a-zA-Z0-9]+|.)/gcs } 248 } 249 if ($#nesting>=0) 250 { 251 _failmsg "Unmatched opening bracket(s): " 252 . join("..",@nesting)."..", 253 pos $$textref; 254 pos $$textref = $startpos; 255 return; 256 } 257 258 $endpos = pos $$textref; 259 260 return ( 261 $startpos, $ldelpos-$startpos, # PREFIX 262 $ldelpos, 1, # OPENING BRACKET 263 $ldelpos+1, $endpos-$ldelpos-2, # CONTENTS 264 $endpos-1, 1, # CLOSING BRACKET 265 $endpos, length($$textref)-$endpos, # REMAINDER 266 ); 267 } 268 269 sub _revbracket($) 270 { 271 my $brack = reverse $_[0]; 272 $brack =~ tr/[({</])}>/; 273 return $brack; 274 } 275 276 my $XMLNAME = q{[a-zA-Z_:][a-zA-Z0-9_:.-]*}; 277 278 sub extract_tagged (;$$$$$) # ($text, $opentag, $closetag, $pre, \%options) 279 { 280 my $textref = defined $_[0] ? \$_[0] : \$_; 281 my $ldel = $_[1]; 282 my $rdel = $_[2]; 283 my $pre = defined $_[3] ? $_[3] : '\s*'; 284 my %options = defined $_[4] ? %{$_[4]} : (); 285 my $omode = defined $options{fail} ? $options{fail} : ''; 286 my $bad = ref($options{reject}) eq 'ARRAY' ? join('|', @{$options{reject}}) 287 : defined($options{reject}) ? $options{reject} 288 : '' 289 ; 290 my $ignore = ref($options{ignore}) eq 'ARRAY' ? join('|', @{$options{ignore}}) 291 : defined($options{ignore}) ? $options{ignore} 292 : '' 293 ; 294 295 if (!defined $ldel) { $ldel = '<\w+(?:' . gen_delimited_pat(q{'"}) . '|[^>])*>'; } 296 $@ = undef; 297 298 my @match = _match_tagged($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore); 299 300 return _fail(wantarray, $textref) unless @match; 301 return _succeed wantarray, $textref, 302 $match[2], $match[3]+$match[5]+$match[7], # MATCH 303 @match[8..9,0..1,2..7]; # REM, PRE, BITS 304 } 305 306 sub _match_tagged # ($$$$$$$) 307 { 308 my ($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore) = @_; 309 my $rdelspec; 310 311 my ($startpos, $opentagpos, $textpos, $parapos, $closetagpos, $endpos) = ( pos($$textref) = pos($$textref)||0 ); 312 313 unless ($$textref =~ m/\G($pre)/gc) 314 { 315 _failmsg "Did not find prefix: /$pre/", pos $$textref; 316 goto failed; 317 } 318 319 $opentagpos = pos($$textref); 320 321 unless ($$textref =~ m/\G$ldel/gc) 322 { 323 _failmsg "Did not find opening tag: /$ldel/", pos $$textref; 324 goto failed; 325 } 326 327 $textpos = pos($$textref); 328 329 if (!defined $rdel) 330 { 331 $rdelspec = substr($$textref, $-[0], $+[0] - $-[0]); 332 unless ($rdelspec =~ s/\A([[(<{]+)($XMLNAME).*/ quotemeta "$1\/$2". _revbracket($1) /oes) 333 { 334 _failmsg "Unable to construct closing tag to match: $rdel", 335 pos $$textref; 336 goto failed; 337 } 338 } 339 else 340 { 341 $rdelspec = eval "qq{$rdel}" || do { 342 my $del; 343 for (qw,~ ! ^ & * ) _ + - = } ] : " ; ' > . ? / | ',) 344 { next if $rdel =~ /\Q$_/; $del = $_; last } 345 unless ($del) { 346 use Carp; 347 croak "Can't interpolate right delimiter $rdel" 348 } 349 eval "qq$del$rdel$del"; 350 }; 351 } 352 353 while (pos($$textref) < length($$textref)) 354 { 355 next if $$textref =~ m/\G\\./gc; 356 357 if ($$textref =~ m/\G(\n[ \t]*\n)/gc ) 358 { 359 $parapos = pos($$textref) - length($1) 360 unless defined $parapos; 361 } 362 elsif ($$textref =~ m/\G($rdelspec)/gc ) 363 { 364 $closetagpos = pos($$textref)-length($1); 365 goto matched; 366 } 367 elsif ($ignore && $$textref =~ m/\G(?:$ignore)/gc) 368 { 369 next; 370 } 371 elsif ($bad && $$textref =~ m/\G($bad)/gcs) 372 { 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; 376 goto failed; 377 } 378 elsif ($$textref =~ m/\G($ldel)/gc) 379 { 380 my $tag = $1; 381 pos($$textref) -= length($tag); # REWIND TO NESTED TAG 382 unless (_match_tagged(@_)) # MATCH NESTED TAG 383 { 384 goto short if $omode eq 'PARA' || $omode eq 'MAX'; 385 _failmsg "Found unbalanced nested tag: $tag", 386 pos $$textref; 387 goto failed; 388 } 389 } 390 else { $$textref =~ m/./gcs } 391 } 392 393 short: 394 $closetagpos = pos($$textref); 395 goto matched if $omode eq 'MAX'; 396 goto failed unless $omode eq 'PARA'; 397 398 if (defined $parapos) { pos($$textref) = $parapos } 399 else { $parapos = pos($$textref) } 400 401 return ( 402 $startpos, $opentagpos-$startpos, # PREFIX 403 $opentagpos, $textpos-$opentagpos, # OPENING TAG 404 $textpos, $parapos-$textpos, # TEXT 405 $parapos, 0, # NO CLOSING TAG 406 $parapos, length($$textref)-$parapos, # REMAINDER 407 ); 408 409 matched: 410 $endpos = pos($$textref); 411 return ( 412 $startpos, $opentagpos-$startpos, # PREFIX 413 $opentagpos, $textpos-$opentagpos, # OPENING TAG 414 $textpos, $closetagpos-$textpos, # TEXT 415 $closetagpos, $endpos-$closetagpos, # CLOSING TAG 416 $endpos, length($$textref)-$endpos, # REMAINDER 417 ); 418 419 failed: 420 _failmsg "Did not find closing tag", pos $$textref unless $@; 421 pos($$textref) = $startpos; 422 return; 423 } 424 425 sub extract_variable (;$$) 426 { 427 my $textref = defined $_[0] ? \$_[0] : \$_; 428 return ("","","") unless defined $$textref; 429 my $pre = defined $_[1] ? $_[1] : '\s*'; 430 431 my @match = _match_variable($textref,$pre); 432 433 return _fail wantarray, $textref unless @match; 434 435 return _succeed wantarray, $textref, 436 @match[2..3,4..5,0..1]; # MATCH, REMAINDER, PREFIX 437 } 438 439 sub _match_variable($$) 440 { 441 # $# 442 # $^ 443 # $$ 444 my ($textref, $pre) = @_; 445 my $startpos = pos($$textref) = pos($$textref)||0; 446 unless ($$textref =~ m/\G($pre)/gc) 447 { 448 _failmsg "Did not find prefix: /$pre/", pos $$textref; 449 return; 450 } 451 my $varpos = pos($$textref); 452 unless ($$textref =~ m{\G\$\s*(?!::)(\d+|[][&`'+*./|,";%=~:?!\@<>()-]|\^[a-z]?)}gci) 453 { 454 unless ($$textref =~ m/\G((\$#?|[*\@\%]|\\&)+)/gc) 455 { 456 _failmsg "Did not find leading dereferencer", pos $$textref; 457 pos $$textref = $startpos; 458 return; 459 } 460 my $deref = $1; 461 462 unless ($$textref =~ m/\G\s*(?:::|')?(?:[_a-z]\w*(?:::|'))*[_a-z]\w*/gci 463 or _match_codeblock($textref, "", '\{', '\}', '\{', '\}', 0) 464 or $deref eq '$#' or $deref eq '$$' ) 465 { 466 _failmsg "Bad identifier after dereferencer", pos $$textref; 467 pos $$textref = $startpos; 468 return; 469 } 470 } 471 472 while (1) 473 { 474 next if $$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 $$textref =~ m/\G\s*->\s*\w+(?![{([])/gc; 484 last; 485 } 486 487 my $endpos = pos($$textref); 488 return ($startpos, $varpos-$startpos, 489 $varpos, $endpos-$varpos, 490 $endpos, length($$textref)-$endpos 491 ); 492 } 493 494 sub extract_codeblock (;$$$$$) 495 { 496 my $textref = defined $_[0] ? \$_[0] : \$_; 497 my $wantarray = wantarray; 498 my $ldel_inner = defined $_[1] ? $_[1] : '{'; 499 my $pre = defined $_[2] ? $_[2] : '\s*'; 500 my $ldel_outer = defined $_[3] ? $_[3] : $ldel_inner; 501 my $rd = $_[4]; 502 my $rdel_inner = $ldel_inner; 503 my $rdel_outer = $ldel_outer; 504 my $posbug = pos; 505 for ($ldel_inner, $ldel_outer) { tr/[]()<>{}\0-\377/[[((<<{{/ds } 506 for ($rdel_inner, $rdel_outer) { tr/[]()<>{}\0-\377/]]))>>}}/ds } 507 for ($ldel_inner, $ldel_outer, $rdel_inner, $rdel_outer) 508 { 509 $_ = '('.join('|',map { quotemeta $_ } split('',$_)).')' 510 } 511 pos = $posbug; 512 513 my @match = _match_codeblock($textref, $pre, 514 $ldel_outer, $rdel_outer, 515 $ldel_inner, $rdel_inner, 516 $rd); 517 return _fail($wantarray, $textref) unless @match; 518 return _succeed($wantarray, $textref, 519 @match[2..3,4..5,0..1] # MATCH, REMAINDER, PREFIX 520 ); 521 522 } 523 524 sub _match_codeblock($$$$$$$) 525 { 526 my ($textref, $pre, $ldel_outer, $rdel_outer, $ldel_inner, $rdel_inner, $rd) = @_; 527 my $startpos = pos($$textref) = pos($$textref) || 0; 528 unless ($$textref =~ m/\G($pre)/gc) 529 { 530 _failmsg qq{Did not match prefix /$pre/ at"} . 531 substr($$textref,pos($$textref),20) . 532 q{..."}, 533 pos $$textref; 534 return; 535 } 536 my $codepos = pos($$textref); 537 unless ($$textref =~ m/\G($ldel_outer)/gc) # OUTERMOST DELIMITER 538 { 539 _failmsg qq{Did not find expected opening bracket at "} . 540 substr($$textref,pos($$textref),20) . 541 q{..."}, 542 pos $$textref; 543 pos $$textref = $startpos; 544 return; 545 } 546 my $closing = $1; 547 $closing =~ tr/([<{/)]>}/; 548 my $matched; 549 my $patvalid = 1; 550 while (pos($$textref) < length($$textref)) 551 { 552 $matched = ''; 553 if ($rd && $$textref =~ m#\G(\Q(?)\E|\Q(s?)\E|\Q(s)\E)#gc) 554 { 555 $patvalid = 0; 556 next; 557 } 558 559 if ($$textref =~ m/\G\s*#.*/gc) 560 { 561 next; 562 } 563 564 if ($$textref =~ m/\G\s*($rdel_outer)/gc) 565 { 566 unless ($matched = ($closing && $1 eq $closing) ) 567 { 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'}, 572 pos $$textref; 573 } 574 last; 575 } 576 577 if (_match_variable($textref,'\s*') || 578 _match_quotelike($textref,'\s*',$patvalid,$patvalid) ) 579 { 580 $patvalid = 0; 581 next; 582 } 583 584 585 # NEED TO COVER MANY MORE CASES HERE!!! 586 if ($$textref =~ m#\G\s*(?!$ldel_inner) 587 ( [-+*x/%^&|.]=? 588 | [!=]~ 589 | =(?!>) 590 | (\*\*|&&|\|\||<<|>>)=? 591 | split|grep|map|return 592 | [([] 593 )#gcx) 594 { 595 $patvalid = 1; 596 next; 597 } 598 599 if ( _match_codeblock($textref, '\s*', $ldel_inner, $rdel_inner, $ldel_inner, $rdel_inner, $rd) ) 600 { 601 $patvalid = 1; 602 next; 603 } 604 605 if ($$textref =~ m/\G\s*$ldel_outer/gc) 606 { 607 _failmsg q{Improperly nested codeblock at "} . 608 substr($$textref,pos($$textref),20) . 609 q{..."}, 610 pos $$textref; 611 last; 612 } 613 614 $patvalid = 0; 615 $$textref =~ m/\G\s*(\w+|[-=>]>|.|\Z)/gc; 616 } 617 continue { $@ = undef } 618 619 unless ($matched) 620 { 621 _failmsg 'No match found for opening bracket', pos $$textref 622 unless $@; 623 return; 624 } 625 626 my $endpos = pos($$textref); 627 return ( $startpos, $codepos-$startpos, 628 $codepos, $endpos-$codepos, 629 $endpos, length($$textref)-$endpos, 630 ); 631 } 632 633 634 my %mods = ( 635 'none' => '[cgimsox]*', 636 'm' => '[cgimsox]*', 637 's' => '[cegimsox]*', 638 'tr' => '[cds]*', 639 'y' => '[cds]*', 640 'qq' => '', 641 'qx' => '', 642 'qw' => '', 643 'qr' => '[imsx]*', 644 'q' => '', 645 ); 646 647 sub extract_quotelike (;$$) 648 { 649 my $textref = $_[0] ? \$_[0] : \$_; 650 my $wantarray = wantarray; 651 my $pre = defined $_[1] ? $_[1] : '\s*'; 652 653 my @match = _match_quotelike($textref,$pre,1,0); 654 return _fail($wantarray, $textref) unless @match; 655 return _succeed($wantarray, $textref, 656 $match[2], $match[18]-$match[2], # MATCH 657 @match[18,19], # REMAINDER 658 @match[0,1], # PREFIX 659 @match[2..17], # THE BITS 660 @match[20,21], # ANY FILLET? 661 ); 662 }; 663 664 sub _match_quotelike($$$$) # ($textref, $prepat, $allow_raw_match) 665 { 666 my ($textref, $pre, $rawmatch, $qmark) = @_; 667 668 my ($textlen,$startpos, 669 $oppos, 670 $preld1pos,$ld1pos,$str1pos,$rd1pos, 671 $preld2pos,$ld2pos,$str2pos,$rd2pos, 672 $modpos) = ( length($$textref), pos($$textref) = pos($$textref) || 0 ); 673 674 unless ($$textref =~ m/\G($pre)/gc) 675 { 676 _failmsg qq{Did not find prefix /$pre/ at "} . 677 substr($$textref, pos($$textref), 20) . 678 q{..."}, 679 pos $$textref; 680 return; 681 } 682 $oppos = pos($$textref); 683 684 my $initial = substr($$textref,$oppos,1); 685 686 if ($initial && $initial =~ m|^[\"\'\`]| 687 || $rawmatch && $initial =~ m|^/| 688 || $qmark && $initial =~ m|^\?|) 689 { 690 unless ($$textref =~ m/ \Q$initial\E [^\\$initial]* (\\.[^\\$initial]*)* \Q$initial\E /gcsx) 691 { 692 _failmsg qq{Did not find closing delimiter to match '$initial' at "} . 693 substr($$textref, $oppos, 20) . 694 q{..."}, 695 pos $$textref; 696 pos $$textref = $startpos; 697 return; 698 } 699 $modpos= pos($$textref); 700 $rd1pos = $modpos-1; 701 702 if ($initial eq '/' || $initial eq '?') 703 { 704 $$textref =~ m/\G$mods{none}/gc 705 } 706 707 my $endpos = pos($$textref); 708 return ( 709 $startpos, $oppos-$startpos, # PREFIX 710 $oppos, 0, # NO OPERATOR 711 $oppos, 1, # LEFT DEL 712 $oppos+1, $rd1pos-$oppos-1, # STR/PAT 713 $rd1pos, 1, # RIGHT DEL 714 $modpos, 0, # NO 2ND LDEL 715 $modpos, 0, # NO 2ND STR 716 $modpos, 0, # NO 2ND RDEL 717 $modpos, $endpos-$modpos, # MODIFIERS 718 $endpos, $textlen-$endpos, # REMAINDER 719 ); 720 } 721 722 unless ($$textref =~ m{\G(\b(?:m|s|qq|qx|qw|q|qr|tr|y)\b(?=\s*\S)|<<)}gc) 723 { 724 _failmsg q{No quotelike operator found after prefix at "} . 725 substr($$textref, pos($$textref), 20) . 726 q{..."}, 727 pos $$textref; 728 pos $$textref = $startpos; 729 return; 730 } 731 732 my $op = $1; 733 $preld1pos = pos($$textref); 734 if ($op eq '<<') { 735 $ld1pos = pos($$textref); 736 my $label; 737 if ($$textref =~ m{\G([A-Za-z_]\w*)}gc) { 738 $label = $1; 739 } 740 elsif ($$textref =~ m{ \G ' ([^'\\]* (?:\\.[^'\\]*)*) ' 741 | \G " ([^"\\]* (?:\\.[^"\\]*)*) " 742 | \G ` ([^`\\]* (?:\\.[^`\\]*)*) ` 743 }gcsx) { 744 $label = $+; 745 } 746 else { 747 $label = ""; 748 } 749 my $extrapos = pos($$textref); 750 $$textref =~ m{.*\n}gc; 751 $str1pos = pos($$textref)--; 752 unless ($$textref =~ m{.*?\n(?=\Q$label\E\n)}gc) { 753 _failmsg qq{Missing here doc terminator ('$label') after "} . 754 substr($$textref, $startpos, 20) . 755 q{..."}, 756 pos $$textref; 757 pos $$textref = $startpos; 758 return; 759 } 760 $rd1pos = pos($$textref); 761 $$textref =~ m{\Q$label\E\n}gc; 762 $ld2pos = pos($$textref); 763 return ( 764 $startpos, $oppos-$startpos, # PREFIX 765 $oppos, length($op), # OPERATOR 766 $ld1pos, $extrapos-$ld1pos, # LEFT DEL 767 $str1pos, $rd1pos-$str1pos, # STR/PAT 768 $rd1pos, $ld2pos-$rd1pos, # RIGHT DEL 769 $ld2pos, 0, # NO 2ND LDEL 770 $ld2pos, 0, # NO 2ND STR 771 $ld2pos, 0, # NO 2ND RDEL 772 $ld2pos, 0, # NO MODIFIERS 773 $ld2pos, $textlen-$ld2pos, # REMAINDER 774 $extrapos, $str1pos-$extrapos, # FILLETED BIT 775 ); 776 } 777 778 $$textref =~ m/\G\s*/gc; 779 $ld1pos = pos($$textref); 780 $str1pos = $ld1pos+1; 781 782 unless ($$textref =~ m/\G(\S)/gc) # SHOULD USE LOOKAHEAD 783 { 784 _failmsg "No block delimiter found after quotelike $op", 785 pos $$textref; 786 pos $$textref = $startpos; 787 return; 788 } 789 pos($$textref) = $ld1pos; # HAVE TO DO THIS BECAUSE LOOKAHEAD BROKEN 790 my ($ldel1, $rdel1) = ("\Q$1","\Q$1"); 791 if ($ldel1 =~ /[[(<{]/) 792 { 793 $rdel1 =~ tr/[({</])}>/; 794 defined(_match_bracketed($textref,"",$ldel1,"","",$rdel1)) 795 || do { pos $$textref = $startpos; return }; 796 $ld2pos = pos($$textref); 797 $rd1pos = $ld2pos-1; 798 } 799 else 800 { 801 $$textref =~ /\G$ldel1[^\\$ldel1]*(\\.[^\\$ldel1]*)*$ldel1/gcs 802 || do { pos $$textref = $startpos; return }; 803 $ld2pos = $rd1pos = pos($$textref)-1; 804 } 805 806 my $second_arg = $op =~ /s|tr|y/ ? 1 : 0; 807 if ($second_arg) 808 { 809 my ($ldel2, $rdel2); 810 if ($ldel1 =~ /[[(<{]/) 811 { 812 unless ($$textref =~ /\G\s*(\S)/gc) # SHOULD USE LOOKAHEAD 813 { 814 _failmsg "Missing second block for quotelike $op", 815 pos $$textref; 816 pos $$textref = $startpos; 817 return; 818 } 819 $ldel2 = $rdel2 = "\Q$1"; 820 $rdel2 =~ tr/[({</])}>/; 821 } 822 else 823 { 824 $ldel2 = $rdel2 = $ldel1; 825 } 826 $str2pos = $ld2pos+1; 827 828 if ($ldel2 =~ /[[(<{]/) 829 { 830 pos($$textref)--; # OVERCOME BROKEN LOOKAHEAD 831 defined(_match_bracketed($textref,"",$ldel2,"","",$rdel2)) 832 || do { pos $$textref = $startpos; return }; 833 } 834 else 835 { 836 $$textref =~ /[^\\$ldel2]*(\\.[^\\$ldel2]*)*$ldel2/gcs 837 || do { pos $$textref = $startpos; return }; 838 } 839 $rd2pos = pos($$textref)-1; 840 } 841 else 842 { 843 $ld2pos = $str2pos = $rd2pos = $rd1pos; 844 } 845 846 $modpos = pos $$textref; 847 848 $$textref =~ m/\G($mods{$op})/gc; 849 my $endpos = pos $$textref; 850 851 return ( 852 $startpos, $oppos-$startpos, # PREFIX 853 $oppos, length($op), # OPERATOR 854 $ld1pos, 1, # LEFT DEL 855 $str1pos, $rd1pos-$str1pos, # STR/PAT 856 $rd1pos, 1, # RIGHT DEL 857 $ld2pos, $second_arg, # 2ND LDEL (MAYBE) 858 $str2pos, $rd2pos-$str2pos, # 2ND STR (MAYBE) 859 $rd2pos, $second_arg, # 2ND RDEL (MAYBE) 860 $modpos, $endpos-$modpos, # MODIFIERS 861 $endpos, $textlen-$endpos, # REMAINDER 862 ); 863 } 864 865 my $def_func = 866 [ 867 sub { extract_variable($_[0], '') }, 868 sub { extract_quotelike($_[0],'') }, 869 sub { extract_codeblock($_[0],'{}','') }, 870 ]; 871 872 sub extract_multiple (;$$$$) # ($text, $functions_ref, $max_fields, $ignoreunknown) 873 { 874 my $textref = defined($_[0]) ? \$_[0] : \$_; 875 my $posbug = pos; 876 my ($lastpos, $firstpos); 877 my @fields = (); 878 879 #for ($$textref) 880 { 881 my @func = defined $_[1] ? @{$_[1]} : @{$def_func}; 882 my $max = defined $_[2] && $_[2]>0 ? $_[2] : 1_000_000_000; 883 my $igunk = $_[3]; 884 885 pos $$textref ||= 0; 886 887 unless (wantarray) 888 { 889 use Carp; 890 carp "extract_multiple reset maximal count to 1 in scalar context" 891 if $^W && defined($_[2]) && $max > 1; 892 $max = 1 893 } 894 895 my $unkpos; 896 my $func; 897 my $class; 898 899 my @class; 900 foreach $func ( @func ) 901 { 902 if (ref($func) eq 'HASH') 903 { 904 push @class, (keys %$func)[0]; 905 $func = (values %$func)[0]; 906 } 907 else 908 { 909 push @class, undef; 910 } 911 } 912 913 FIELD: while (pos($$textref) < length($$textref)) 914 { 915 my ($field, $rem); 916 my @bits; 917 foreach my $i ( 0..$#func ) 918 { 919 my $pref; 920 $func = $func[$i]; 921 $class = $class[$i]; 922 $lastpos = pos $$textref; 923 if (ref($func) eq 'CODE') 924 { ($field,$rem,$pref) = @bits = $func->($$textref) } 925 elsif (ref($func) eq 'Text::Balanced::Extractor') 926 { @bits = $field = $func->extract($$textref) } 927 elsif( $$textref =~ m/\G$func/gc ) 928 { @bits = $field = defined($1) 929 ? $1 930 : substr($$textref, $-[0], $+[0] - $-[0]) 931 } 932 $pref ||= ""; 933 if (defined($field) && length($field)) 934 { 935 if (!$igunk) { 936 $unkpos = $lastpos 937 if length($pref) && !defined($unkpos); 938 if (defined $unkpos) 939 { 940 push @fields, substr($$textref, $unkpos, $lastpos-$unkpos).$pref; 941 $firstpos = $unkpos unless defined $firstpos; 942 undef $unkpos; 943 last FIELD if @fields == $max; 944 } 945 } 946 push @fields, $class 947 ? bless (\$field, $class) 948 : $field; 949 $firstpos = $lastpos unless defined $firstpos; 950 $lastpos = pos $$textref; 951 last FIELD if @fields == $max; 952 next FIELD; 953 } 954 } 955 if ($$textref =~ /\G(.)/gcs) 956 { 957 $unkpos = pos($$textref)-1 958 unless $igunk || defined $unkpos; 959 } 960 } 961 962 if (defined $unkpos) 963 { 964 push @fields, substr($$textref, $unkpos); 965 $firstpos = $unkpos unless defined $firstpos; 966 $lastpos = length $$textref; 967 } 968 last; 969 } 970 971 pos $$textref = $lastpos; 972 return @fields if wantarray; 973 974 $firstpos ||= 0; 975 eval { substr($$textref,$firstpos,$lastpos-$firstpos)=""; 976 pos $$textref = $firstpos }; 977 return $fields[0]; 978 } 979 980 981 sub gen_extract_tagged # ($opentag, $closetag, $pre, \%options) 982 { 983 my $ldel = $_[0]; 984 my $rdel = $_[1]; 985 my $pre = defined $_[2] ? $_[2] : '\s*'; 986 my %options = defined $_[3] ? %{$_[3]} : (); 987 my $omode = defined $options{fail} ? $options{fail} : ''; 988 my $bad = ref($options{reject}) eq 'ARRAY' ? join('|', @{$options{reject}}) 989 : defined($options{reject}) ? $options{reject} 990 : '' 991 ; 992 my $ignore = ref($options{ignore}) eq 'ARRAY' ? join('|', @{$options{ignore}}) 993 : defined($options{ignore}) ? $options{ignore} 994 : '' 995 ; 996 997 if (!defined $ldel) { $ldel = '<\w+(?:' . gen_delimited_pat(q{'"}) . '|[^>])*>'; } 998 999 my $posbug = pos; 1000 for ($ldel, $pre, $bad, $ignore) { $_ = qr/$_/ if $_ } 1001 pos = $posbug; 1002 1003 my $closure = sub 1004 { 1005 my $textref = defined $_[0] ? \$_[0] : \$_; 1006 my @match = Text::Balanced::_match_tagged($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore); 1007 1008 return _fail(wantarray, $textref) unless @match; 1009 return _succeed wantarray, $textref, 1010 $match[2], $match[3]+$match[5]+$match[7], # MATCH 1011 @match[8..9,0..1,2..7]; # REM, PRE, BITS 1012 }; 1013 1014 bless $closure, 'Text::Balanced::Extractor'; 1015 } 1016 1017 package Text::Balanced::Extractor; 1018 1019 sub extract($$) # ($self, $text) 1020 { 1021 &{$_[0]}($_[1]); 1022 } 1023 1024 package Text::Balanced::ErrorMsg; 1025 1026 use overload '""' => sub { "$_[0]->{error}, detected at offset $_[0]->{pos}" }; 1027 1028 1; 1029 1030 __END__ 1031 1032 =head1 NAME 1033 1034 Text::Balanced - Extract delimited text sequences from strings. 1035 1036 1037 =head1 SYNOPSIS 1038 1039 use Text::Balanced qw ( 1040 extract_delimited 1041 extract_bracketed 1042 extract_quotelike 1043 extract_codeblock 1044 extract_variable 1045 extract_tagged 1046 extract_multiple 1047 1048 gen_delimited_pat 1049 gen_extract_tagged 1050 ); 1051 1052 # Extract the initial substring of $text that is delimited by 1053 # two (unescaped) instances of the first character in $delim. 1054 1055 ($extracted, $remainder) = extract_delimited($text,$delim); 1056 1057 1058 # Extract the initial substring of $text that is bracketed 1059 # with a delimiter(s) specified by $delim (where the string 1060 # in $delim contains one or more of '(){}[]<>'). 1061 1062 ($extracted, $remainder) = extract_bracketed($text,$delim); 1063 1064 1065 # Extract the initial substring of $text that is bounded by 1066 # an XML tag. 1067 1068 ($extracted, $remainder) = extract_tagged($text); 1069 1070 1071 # Extract the initial substring of $text that is bounded by 1072 # a C<BEGIN>...C<END> pair. Don't allow nested C<BEGIN> tags 1073 1074 ($extracted, $remainder) = 1075 extract_tagged($text,"BEGIN","END",undef,{bad=>["BEGIN"]}); 1076 1077 1078 # Extract the initial substring of $text that represents a 1079 # Perl "quote or quote-like operation" 1080 1081 ($extracted, $remainder) = extract_quotelike($text); 1082 1083 1084 # Extract the initial substring of $text that represents a block 1085 # of Perl code, bracketed by any of character(s) specified by $delim 1086 # (where the string $delim contains one or more of '(){}[]<>'). 1087 1088 ($extracted, $remainder) = extract_codeblock($text,$delim); 1089 1090 1091 # Extract the initial substrings of $text that would be extracted by 1092 # one or more sequential applications of the specified functions 1093 # or regular expressions 1094 1095 @extracted = extract_multiple($text, 1096 [ \&extract_bracketed, 1097 \&extract_quotelike, 1098 \&some_other_extractor_sub, 1099 qr/[xyz]*/, 1100 'literal', 1101 ]); 1102 1103 # Create a string representing an optimized pattern (a la Friedl) 1104 # that matches a substring delimited by any of the specified characters 1105 # (in this case: any type of quote or a slash) 1106 1107 $patstring = gen_delimited_pat(q{'"`/}); 1108 1109 1110 # Generate a reference to an anonymous sub that is just like extract_tagged 1111 # but pre-compiled and optimized for a specific pair of tags, and consequently 1112 # much faster (i.e. 3 times faster). It uses qr// for better performance on 1113 # repeated calls, so it only works under Perl 5.005 or later. 1114 1115 $extract_head = gen_extract_tagged('<HEAD>','</HEAD>'); 1116 1117 ($extracted, $remainder) = $extract_head->($text); 1118 1119 1120 =head1 DESCRIPTION 1121 1122 The various C<extract_...> subroutines may be used to 1123 extract a delimited substring, possibly after skipping a 1124 specified prefix string. By default, that prefix is 1125 optional whitespace (C</\s*/>), but you can change it to whatever 1126 you wish (see below). 1127 1128 The substring to be extracted must appear at the 1129 current C<pos> location of the string's variable 1130 (or at index zero, if no C<pos> position is defined). 1131 In other words, the C<extract_...> subroutines I<don't> 1132 extract the first occurrence of a substring anywhere 1133 in a string (like an unanchored regex would). Rather, 1134 they extract an occurrence of the substring appearing 1135 immediately at the current matching position in the 1136 string (like a C<\G>-anchored regex would). 1137 1138 1139 1140 =head2 General behaviour in list contexts 1141 1142 In a list context, all the subroutines return a list, the first three 1143 elements of which are always: 1144 1145 =over 4 1146 1147 =item [0] 1148 1149 The extracted string, including the specified delimiters. 1150 If the extraction fails C<undef> is returned. 1151 1152 =item [1] 1153 1154 The remainder of the input string (i.e. the characters after the 1155 extracted string). On failure, the entire string is returned. 1156 1157 =item [2] 1158 1159 The skipped prefix (i.e. the characters before the extracted string). 1160 On failure, C<undef> is returned. 1161 1162 =back 1163 1164 Note that in a list context, the contents of the original input text (the first 1165 argument) are not modified in any way. 1166 1167 However, if the input text was passed in a variable, that variable's 1168 C<pos> value is updated to point at the first character after the 1169 extracted text. That means that in a list context the various 1170 subroutines can be used much like regular expressions. For example: 1171 1172 while ( $next = (extract_quotelike($text))[0] ) 1173 { 1174 # process next quote-like (in $next) 1175 } 1176 1177 1178 =head2 General behaviour in scalar and void contexts 1179 1180 In a scalar context, the extracted string is returned, having first been 1181 removed from the input text. Thus, the following code also processes 1182 each quote-like operation, but actually removes them from $text: 1183 1184 while ( $next = extract_quotelike($text) ) 1185 { 1186 # process next quote-like (in $next) 1187 } 1188 1189 Note that if the input text is a read-only string (i.e. a literal), 1190 no attempt is made to remove the extracted text. 1191 1192 In a void context the behaviour of the extraction subroutines is 1193 exactly the same as in a scalar context, except (of course) that the 1194 extracted substring is not returned. 1195 1196 =head2 A note about prefixes 1197 1198 Prefix patterns are matched without any trailing modifiers (C</gimsox> etc.) 1199 This can bite you if you're expecting a prefix specification like 1200 '.*?(?=<H1>)' to skip everything up to the first <H1> tag. Such a prefix 1201 pattern will only succeed if the <H1> tag is on the current line, since 1202 . normally doesn't match newlines. 1203 1204 To overcome this limitation, you need to turn on /s matching within 1205 the prefix pattern, using the C<(?s)> directive: '(?s).*?(?=<H1>)' 1206 1207 1208 =head2 C<extract_delimited> 1209 1210 The C<extract_delimited> function formalizes the common idiom 1211 of extracting a single-character-delimited substring from the start of 1212 a string. For example, to extract a single-quote delimited string, the 1213 following code is typically used: 1214 1215 ($remainder = $text) =~ s/\A('(\\.|[^'])*')//s; 1216 $extracted = $1; 1217 1218 but with C<extract_delimited> it can be simplified to: 1219 1220 ($extracted,$remainder) = extract_delimited($text, "'"); 1221 1222 C<extract_delimited> takes up to four scalars (the input text, the 1223 delimiters, a prefix pattern to be skipped, and any escape characters) 1224 and extracts the initial substring of the text that 1225 is appropriately delimited. If the delimiter string has multiple 1226 characters, the first one encountered in the text is taken to delimit 1227 the substring. 1228 The third argument specifies a prefix pattern that is to be skipped 1229 (but must be present!) before the substring is extracted. 1230 The final argument specifies the escape character to be used for each 1231 delimiter. 1232 1233 All arguments are optional. If the escape characters are not specified, 1234 every delimiter is escaped with a backslash (C<\>). 1235 If the prefix is not specified, the 1236 pattern C<'\s*'> - optional whitespace - is used. If the delimiter set 1237 is also not specified, the set C</["'`]/> is used. If the text to be processed 1238 is not specified either, C<$_> is used. 1239 1240 In list context, C<extract_delimited> returns a array of three 1241 elements, the extracted substring (I<including the surrounding 1242 delimiters>), the remainder of the text, and the skipped prefix (if 1243 any). If a suitable delimited substring is not found, the first 1244 element of the array is the empty string, the second is the complete 1245 original text, and the prefix returned in the third element is an 1246 empty string. 1247 1248 In a scalar context, just the extracted substring is returned. In 1249 a void context, the extracted substring (and any prefix) are simply 1250 removed from the beginning of the first argument. 1251 1252 Examples: 1253 1254 # Remove a single-quoted substring from the very beginning of $text: 1255 1256 $substring = extract_delimited($text, "'", ''); 1257 1258 # Remove a single-quoted Pascalish substring (i.e. one in which 1259 # doubling the quote character escapes it) from the very 1260 # beginning of $text: 1261 1262 $substring = extract_delimited($text, "'", '', "'"); 1263 1264 # Extract a single- or double- quoted substring from the 1265 # beginning of $text, optionally after some whitespace 1266 # (note the list context to protect $text from modification): 1267 1268 ($substring) = extract_delimited $text, q{"'}; 1269 1270 1271 # Delete the substring delimited by the first '/' in $text: 1272 1273 $text = join '', (extract_delimited($text,'/','[^/]*')[2,1]; 1274 1275 Note that this last example is I<not> the same as deleting the first 1276 quote-like pattern. For instance, if C<$text> contained the string: 1277 1278 "if ('./cmd' =~ m/$UNIXCMD/s) { $cmd = $1; }" 1279 1280 then after the deletion it would contain: 1281 1282 "if ('.$UNIXCMD/s) { $cmd = $1; }" 1283 1284 not: 1285 1286 "if ('./cmd' =~ ms) { $cmd = $1; }" 1287 1288 1289 See L<"extract_quotelike"> for a (partial) solution to this problem. 1290 1291 1292 =head2 C<extract_bracketed> 1293 1294 Like C<"extract_delimited">, the C<extract_bracketed> function takes 1295 up to three optional scalar arguments: a string to extract from, a delimiter 1296 specifier, and a prefix pattern. As before, a missing prefix defaults to 1297 optional whitespace and a missing text defaults to C<$_>. However, a missing 1298 delimiter specifier defaults to C<'{}()[]E<lt>E<gt>'> (see below). 1299 1300 C<extract_bracketed> extracts a balanced-bracket-delimited 1301 substring (using any one (or more) of the user-specified delimiter 1302 brackets: '(..)', '{..}', '[..]', or '<..>'). Optionally it will also 1303 respect quoted unbalanced brackets (see below). 1304 1305 A "delimiter bracket" is a bracket in list of delimiters passed as 1306 C<extract_bracketed>'s second argument. Delimiter brackets are 1307 specified by giving either the left or right (or both!) versions 1308 of the required bracket(s). Note that the order in which 1309 two or more delimiter brackets are specified is not significant. 1310 1311 A "balanced-bracket-delimited substring" is a substring bounded by 1312 matched brackets, such that any other (left or right) delimiter 1313 bracket I<within> the substring is also matched by an opposite 1314 (right or left) delimiter bracket I<at the same level of nesting>. Any 1315 type of bracket not in the delimiter list is treated as an ordinary 1316 character. 1317 1318 In other words, each type of bracket specified as a delimiter must be 1319 balanced and correctly nested within the substring, and any other kind of 1320 ("non-delimiter") bracket in the substring is ignored. 1321 1322 For example, given the string: 1323 1324 $text = "{ an '[irregularly :-(] {} parenthesized >:-)' string }"; 1325 1326 then a call to C<extract_bracketed> in a list context: 1327 1328 @result = extract_bracketed( $text, '{}' ); 1329 1330 would return: 1331 1332 ( "{ an '[irregularly :-(] {} parenthesized >:-)' string }" , "" , "" ) 1333 1334 since both sets of C<'{..}'> brackets are properly nested and evenly balanced. 1335 (In a scalar context just the first element of the array would be returned. In 1336 a void context, C<$text> would be replaced by an empty string.) 1337 1338 Likewise the call in: 1339 1340 @result = extract_bracketed( $text, '{[' ); 1341 1342 would return the same result, since all sets of both types of specified 1343 delimiter brackets are correctly nested and balanced. 1344 1345 However, the call in: 1346 1347 @result = extract_bracketed( $text, '{([<' ); 1348 1349 would fail, returning: 1350 1351 ( undef , "{ an '[irregularly :-(] {} parenthesized >:-)' string }" ); 1352 1353 because the embedded pairs of C<'(..)'>s and C<'[..]'>s are "cross-nested" and 1354 the embedded C<'E<gt>'> is unbalanced. (In a scalar context, this call would 1355 return an empty string. In a void context, C<$text> would be unchanged.) 1356 1357 Note that the embedded single-quotes in the string don't help in this 1358 case, since they have not been specified as acceptable delimiters and are 1359 therefore treated as non-delimiter characters (and ignored). 1360 1361 However, if a particular species of quote character is included in the 1362 delimiter specification, then that type of quote will be correctly handled. 1363 for example, if C<$text> is: 1364 1365 $text = '<A HREF=">>>>">link</A>'; 1366 1367 then 1368 1369 @result = extract_bracketed( $text, '<">' ); 1370 1371 returns: 1372 1373 ( '<A HREF=">>>>">', 'link</A>', "" ) 1374 1375 as expected. Without the specification of C<"> as an embedded quoter: 1376 1377 @result = extract_bracketed( $text, '<>' ); 1378 1379 the result would be: 1380 1381 ( '<A HREF=">', '>>>">link</A>', "" ) 1382 1383 In addition to the quote delimiters C<'>, C<">, and C<`>, full Perl quote-like 1384 quoting (i.e. q{string}, qq{string}, etc) can be specified by including the 1385 letter 'q' as a delimiter. Hence: 1386 1387 @result = extract_bracketed( $text, '<q>' ); 1388 1389 would correctly match something like this: 1390 1391 $text = '<leftop: conj /and/ conj>'; 1392 1393 See also: C<"extract_quotelike"> and C<"extract_codeblock">. 1394 1395 1396 =head2 C<extract_variable> 1397 1398 C<extract_variable> extracts any valid Perl variable or 1399 variable-involved expression, including scalars, arrays, hashes, array 1400 accesses, hash look-ups, method calls through objects, subroutine calls 1401 through subroutine references, etc. 1402 1403 The subroutine takes up to two optional arguments: 1404 1405 =over 4 1406 1407 =item 1. 1408 1409 A string to be processed (C<$_> if the string is omitted or C<undef>) 1410 1411 =item 2. 1412 1413 A string specifying a pattern to be matched as a prefix (which is to be 1414 skipped). If omitted, optional whitespace is skipped. 1415 1416 =back 1417 1418 On success in a list context, an array of 3 elements is returned. The 1419 elements are: 1420 1421 =over 4 1422 1423 =item [0] 1424 1425 the extracted variable, or variablish expression 1426 1427 =item [1] 1428 1429 the remainder of the input text, 1430 1431 =item [2] 1432 1433 the prefix substring (if any), 1434 1435 =back 1436 1437 On failure, all of these values (except the remaining text) are C<undef>. 1438 1439 In a scalar context, C<extract_variable> returns just the complete 1440 substring that matched a variablish expression. C<undef> is returned on 1441 failure. In addition, the original input text has the returned substring 1442 (and any prefix) removed from it. 1443 1444 In a void context, the input text just has the matched substring (and 1445 any specified prefix) removed. 1446 1447 1448 =head2 C<extract_tagged> 1449 1450 C<extract_tagged> extracts and segments text between (balanced) 1451 specified tags. 1452 1453 The subroutine takes up to five optional arguments: 1454 1455 =over 4 1456 1457 =item 1. 1458 1459 A string to be processed (C<$_> if the string is omitted or C<undef>) 1460 1461 =item 2. 1462 1463 A string specifying a pattern to be matched as the opening tag. 1464 If the pattern string is omitted (or C<undef>) then a pattern 1465 that matches any standard XML tag is used. 1466 1467 =item 3. 1468 1469 A string specifying a pattern to be matched at the closing tag. 1470 If the pattern string is omitted (or C<undef>) then the closing 1471 tag is constructed by inserting a C</> after any leading bracket 1472 characters in the actual opening tag that was matched (I<not> the pattern 1473 that matched the tag). For example, if the opening tag pattern 1474 is specified as C<'{{\w+}}'> and actually matched the opening tag 1475 C<"{{DATA}}">, then the constructed closing tag would be C<"{{/DATA}}">. 1476 1477 =item 4. 1478 1479 A string specifying a pattern to be matched as a prefix (which is to be 1480 skipped). If omitted, optional whitespace is skipped. 1481 1482 =item 5. 1483 1484 A hash reference containing various parsing options (see below) 1485 1486 =back 1487 1488 The various options that can be specified are: 1489 1490 =over 4 1491 1492 =item C<reject =E<gt> $listref> 1493 1494 The list reference contains one or more strings specifying patterns 1495 that must I<not> appear within the tagged text. 1496 1497 For example, to extract 1498 an HTML link (which should not contain nested links) use: 1499 1500 extract_tagged($text, '<A>', '</A>', undef, {reject => ['<A>']} ); 1501 1502 =item C<ignore =E<gt> $listref> 1503 1504 The list reference contains one or more strings specifying patterns 1505 that are I<not> be be treated as nested tags within the tagged text 1506 (even if they would match the start tag pattern). 1507 1508 For example, to extract an arbitrary XML tag, but ignore "empty" elements: 1509 1510 extract_tagged($text, undef, undef, undef, {ignore => ['<[^>]*/>']} ); 1511 1512 (also see L<"gen_delimited_pat"> below). 1513 1514 1515 =item C<fail =E<gt> $str> 1516 1517 The C<fail> option indicates the action to be taken if a matching end 1518 tag is not encountered (i.e. before the end of the string or some 1519 C<reject> pattern matches). By default, a failure to match a closing 1520 tag causes C<extract_tagged> to immediately fail. 1521 1522 However, if the string value associated with <reject> is "MAX", then 1523 C<extract_tagged> returns the complete text up to the point of failure. 1524 If the string is "PARA", C<extract_tagged> returns only the first paragraph 1525 after the tag (up to the first line that is either empty or contains 1526 only whitespace characters). 1527 If the string is "", the the default behaviour (i.e. failure) is reinstated. 1528 1529 For example, suppose the start tag "/para" introduces a paragraph, which then 1530 continues until the next "/endpara" tag or until another "/para" tag is 1531 encountered: 1532 1533 $text = "/para line 1\n\nline 3\n/para line 4"; 1534 1535 extract_tagged($text, '/para', '/endpara', undef, 1536 {reject => '/para', fail => MAX ); 1537 1538 # EXTRACTED: "/para line 1\n\nline 3\n" 1539 1540 Suppose instead, that if no matching "/endpara" tag is found, the "/para" 1541 tag refers only to the immediately following paragraph: 1542 1543 $text = "/para line 1\n\nline 3\n/para line 4"; 1544 1545 extract_tagged($text, '/para', '/endpara', undef, 1546 {reject => '/para', fail => MAX ); 1547 1548 # EXTRACTED: "/para line 1\n" 1549 1550 Note that the specified C<fail> behaviour applies to nested tags as well. 1551 1552 =back 1553 1554 On success in a list context, an array of 6 elements is returned. The elements are: 1555 1556 =over 4 1557 1558 =item [0] 1559 1560 the extracted tagged substring (including the outermost tags), 1561 1562 =item [1] 1563 1564 the remainder of the input text, 1565 1566 =item [2] 1567 1568 the prefix substring (if any), 1569 1570 =item [3] 1571 1572 the opening tag 1573 1574 =item [4] 1575 1576 the text between the opening and closing tags 1577 1578 =item [5] 1579 1580 the closing tag (or "" if no closing tag was found) 1581 1582 =back 1583 1584 On failure, all of these values (except the remaining text) are C<undef>. 1585 1586 In a scalar context, C<extract_tagged> returns just the complete 1587 substring that matched a tagged text (including the start and end 1588 tags). C<undef> is returned on failure. In addition, the original input 1589 text has the returned substring (and any prefix) removed from it. 1590 1591 In a void context, the input text just has the matched substring (and 1592 any specified prefix) removed. 1593 1594 1595 =head2 C<gen_extract_tagged> 1596 1597 (Note: This subroutine is only available under Perl5.005) 1598 1599 C<gen_extract_tagged> generates a new anonymous subroutine which 1600 extracts text between (balanced) specified tags. In other words, 1601 it generates a function identical in function to C<extract_tagged>. 1602 1603 The difference between C<extract_tagged> and the anonymous 1604 subroutines generated by 1605 C<gen_extract_tagged>, is that those generated subroutines: 1606 1607 =over 4 1608 1609 =item * 1610 1611 do not have to reparse tag specification or parsing options every time 1612 they are called (whereas C<extract_tagged> has to effectively rebuild 1613 its tag parser on every call); 1614 1615 =item * 1616 1617 make use of the new qr// construct to pre-compile the regexes they use 1618 (whereas C<extract_tagged> uses standard string variable interpolation 1619 to create tag-matching patterns). 1620 1621 =back 1622 1623 The subroutine takes up to four optional arguments (the same set as 1624 C<extract_tagged> except for the string to be processed). It returns 1625 a reference to a subroutine which in turn takes a single argument (the text to 1626 be extracted from). 1627 1628 In other words, the implementation of C<extract_tagged> is exactly 1629 equivalent to: 1630 1631 sub extract_tagged 1632 { 1633 my $text = shift; 1634 $extractor = gen_extract_tagged(@_); 1635 return $extractor->($text); 1636 } 1637 1638 (although C<extract_tagged> is not currently implemented that way, in order 1639 to preserve pre-5.005 compatibility). 1640 1641 Using C<gen_extract_tagged> to create extraction functions for specific tags 1642 is a good idea if those functions are going to be called more than once, since 1643 their performance is typically twice as good as the more general-purpose 1644 C<extract_tagged>. 1645 1646 1647 =head2 C<extract_quotelike> 1648 1649 C<extract_quotelike> attempts to recognize, extract, and segment any 1650 one of the various Perl quotes and quotelike operators (see 1651 L<perlop(3)>) Nested backslashed delimiters, embedded balanced bracket 1652 delimiters (for the quotelike operators), and trailing modifiers are 1653 all caught. For example, in: 1654 1655 extract_quotelike 'q # an octothorpe: \# (not the end of the q!) #' 1656 1657 extract_quotelike ' "You said, \"Use sed\"." ' 1658 1659 extract_quotelike ' s{([A-Z]{1,8}\.[A-Z]{3})} /\L$1\E/; ' 1660 1661 extract_quotelike ' tr/\\\/\\\\/\\\//ds; ' 1662 1663 the full Perl quotelike operations are all extracted correctly. 1664 1665 Note too that, when using the /x modifier on a regex, any comment 1666 containing the current pattern delimiter will cause the regex to be 1667 immediately terminated. In other words: 1668 1669 'm / 1670 (?i) # CASE INSENSITIVE 1671 [a-z_] # LEADING ALPHABETIC/UNDERSCORE 1672 [a-z0-9]* # FOLLOWED BY ANY NUMBER OF ALPHANUMERICS 1673 /x' 1674 1675 will be extracted as if it were: 1676 1677 'm / 1678 (?i) # CASE INSENSITIVE 1679 [a-z_] # LEADING ALPHABETIC/' 1680 1681 This behaviour is identical to that of the actual compiler. 1682 1683 C<extract_quotelike> takes two arguments: the text to be processed and 1684 a prefix to be matched at the very beginning of the text. If no prefix 1685 is specified, optional whitespace is the default. If no text is given, 1686 C<$_> is used. 1687 1688 In a list context, an array of 11 elements is returned. The elements are: 1689 1690 =over 4 1691 1692 =item [0] 1693 1694 the extracted quotelike substring (including trailing modifiers), 1695 1696 =item [1] 1697 1698 the remainder of the input text, 1699 1700 =item [2] 1701 1702 the prefix substring (if any), 1703 1704 =item [3] 1705 1706 the name of the quotelike operator (if any), 1707 1708 =item [4] 1709 1710 the left delimiter of the first block of the operation, 1711 1712 =item [5] 1713 1714 the text of the first block of the operation 1715 (that is, the contents of 1716 a quote, the regex of a match or substitution or the target list of a 1717 translation), 1718 1719 =item [6] 1720 1721 the right delimiter of the first block of the operation, 1722 1723 =item [7] 1724 1725 the left delimiter of the second block of the operation 1726 (that is, if it is a C<s>, C<tr>, or C<y>), 1727 1728 =item [8] 1729 1730 the text of the second block of the operation 1731 (that is, the replacement of a substitution or the translation list 1732 of a translation), 1733 1734 =item [9] 1735 1736 the right delimiter of the second block of the operation (if any), 1737 1738 =item [10] 1739 1740 the trailing modifiers on the operation (if any). 1741 1742 =back 1743 1744 For each of the fields marked "(if any)" the default value on success is 1745 an empty string. 1746 On failure, all of these values (except the remaining text) are C<undef>. 1747 1748 1749 In a scalar context, C<extract_quotelike> returns just the complete substring 1750 that matched a quotelike operation (or C<undef> on failure). In a scalar or 1751 void context, the input text has the same substring (and any specified 1752 prefix) removed. 1753 1754 Examples: 1755 1756 # Remove the first quotelike literal that appears in text 1757 1758 $quotelike = extract_quotelike($text,'.*?'); 1759 1760 # Replace one or more leading whitespace-separated quotelike 1761 # literals in $_ with "<QLL>" 1762 1763 do { $_ = join '<QLL>', (extract_quotelike)[2,1] } until $@; 1764 1765 1766 # Isolate the search pattern in a quotelike operation from $text 1767 1768 ($op,$pat) = (extract_quotelike $text)[3,5]; 1769 if ($op =~ /[ms]/) 1770 { 1771 print "search pattern: $pat\n"; 1772 } 1773 else 1774 { 1775 print "$op is not a pattern matching operation\n"; 1776 } 1777 1778 1779 =head2 C<extract_quotelike> and "here documents" 1780 1781 C<extract_quotelike> can successfully extract "here documents" from an input 1782 string, but with an important caveat in list contexts. 1783 1784 Unlike other types of quote-like literals, a here document is rarely 1785 a contiguous substring. For example, a typical piece of code using 1786 here document might look like this: 1787 1788 <<'EOMSG' || die; 1789 This is the message. 1790 EOMSG 1791 exit; 1792 1793 Given this as an input string in a scalar context, C<extract_quotelike> 1794 would correctly return the string "<<'EOMSG'\nThis is the message.\nEOMSG", 1795 leaving the string " || die;\nexit;" in the original variable. In other words, 1796 the two separate pieces of the here document are successfully extracted and 1797 concatenated. 1798 1799 In a list context, C<extract_quotelike> would return the list 1800 1801 =over 4 1802 1803 =item [0] 1804 1805 "<<'EOMSG'\nThis is the message.\nEOMSG\n" (i.e. the full extracted here document, 1806 including fore and aft delimiters), 1807 1808 =item [1] 1809 1810 " || die;\nexit;" (i.e. the remainder of the input text, concatenated), 1811 1812 =item [2] 1813 1814 "" (i.e. the prefix substring -- trivial in this case), 1815 1816 =item [3] 1817 1818 "<<" (i.e. the "name" of the quotelike operator) 1819 1820 =item [4] 1821 1822 "'EOMSG'" (i.e. the left delimiter of the here document, including any quotes), 1823 1824 =item [5] 1825 1826 "This is the message.\n" (i.e. the text of the here document), 1827 1828 =item [6] 1829 1830 "EOMSG" (i.e. the right delimiter of the here document), 1831 1832 =item [7..10] 1833 1834 "" (a here document has no second left delimiter, second text, second right 1835 delimiter, or trailing modifiers). 1836 1837 =back 1838 1839 However, the matching position of the input variable would be set to 1840 "exit;" (i.e. I<after> the closing delimiter of the here document), 1841 which would cause the earlier " || die;\nexit;" to be skipped in any 1842 sequence of code fragment extractions. 1843 1844 To avoid this problem, when it encounters a here document whilst 1845 extracting from a modifiable string, C<extract_quotelike> silently 1846 rearranges the string to an equivalent piece of Perl: 1847 1848 <<'EOMSG' 1849 This is the message. 1850 EOMSG 1851 || die; 1852 exit; 1853 1854 in which the here document I<is> contiguous. It still leaves the 1855 matching position after the here document, but now the rest of the line 1856 on which the here document starts is not skipped. 1857 1858 To prevent <extract_quotelike> from mucking about with the input in this way 1859 (this is the only case where a list-context C<extract_quotelike> does so), 1860 you can pass the input variable as an interpolated literal: 1861 1862 $quotelike = extract_quotelike("$var"); 1863 1864 1865 =head2 C<extract_codeblock> 1866 1867 C<extract_codeblock> attempts to recognize and extract a balanced 1868 bracket delimited substring that may contain unbalanced brackets 1869 inside Perl quotes or quotelike operations. That is, C<extract_codeblock> 1870 is like a combination of C<"extract_bracketed"> and 1871 C<"extract_quotelike">. 1872 1873 C<extract_codeblock> takes the same initial three parameters as C<extract_bracketed>: 1874 a text to process, a set of delimiter brackets to look for, and a prefix to 1875 match first. It also takes an optional fourth parameter, which allows the 1876 outermost delimiter brackets to be specified separately (see below). 1877 1878 Omitting the first argument (input text) means process C<$_> instead. 1879 Omitting the second argument (delimiter brackets) indicates that only C<'{'> is to be used. 1880 Omitting the third argument (prefix argument) implies optional whitespace at the start. 1881 Omitting the fourth argument (outermost delimiter brackets) indicates that the 1882 value of the second argument is to be used for the outermost delimiters. 1883 1884 Once the prefix an dthe outermost opening delimiter bracket have been 1885 recognized, code blocks are extracted by stepping through the input text and 1886 trying the following alternatives in sequence: 1887 1888 =over 4 1889 1890 =item 1. 1891 1892 Try and match a closing delimiter bracket. If the bracket was the same 1893 species as the last opening bracket, return the substring to that 1894 point. If the bracket was mismatched, return an error. 1895 1896 =item 2. 1897 1898 Try to match a quote or quotelike operator. If found, call 1899 C<extract_quotelike> to eat it. If C<extract_quotelike> fails, return 1900 the error it returned. Otherwise go back to step 1. 1901 1902 =item 3. 1903 1904 Try to match an opening delimiter bracket. If found, call 1905 C<extract_codeblock> recursively to eat the embedded block. If the 1906 recursive call fails, return an error. Otherwise, go back to step 1. 1907 1908 =item 4. 1909 1910 Unconditionally match a bareword or any other single character, and 1911 then go back to step 1. 1912 1913 =back 1914 1915 1916 Examples: 1917 1918 # Find a while loop in the text 1919 1920 if ($text =~ s/.*?while\s*\{/{/) 1921 { 1922 $loop = "while " . extract_codeblock($text); 1923 } 1924 1925 # Remove the first round-bracketed list (which may include 1926 # round- or curly-bracketed code blocks or quotelike operators) 1927 1928 extract_codeblock $text, "(){}", '[^(]*'; 1929 1930 1931 The ability to specify a different outermost delimiter bracket is useful 1932 in some circumstances. For example, in the Parse::RecDescent module, 1933 parser actions which are to be performed only on a successful parse 1934 are specified using a C<E<lt>defer:...E<gt>> directive. For example: 1935 1936 sentence: subject verb object 1937 <defer: {$::theVerb = $item{verb}} > 1938 1939 Parse::RecDescent uses C<extract_codeblock($text, '{}E<lt>E<gt>')> to extract the code 1940 within the C<E<lt>defer:...E<gt>> directive, but there's a problem. 1941 1942 A deferred action like this: 1943 1944 <defer: {if ($count>10) {$count--}} > 1945 1946 will be incorrectly parsed as: 1947 1948 <defer: {if ($count> 1949 1950 because the "less than" operator is interpreted as a closing delimiter. 1951 1952 But, by extracting the directive using 1953 S<C<extract_codeblock($text, '{}', undef, 'E<lt>E<gt>')>> 1954 the '>' character is only treated as a delimited at the outermost 1955 level of the code block, so the directive is parsed correctly. 1956 1957 =head2 C<extract_multiple> 1958 1959 The C<extract_multiple> subroutine takes a string to be processed and a 1960 list of extractors (subroutines or regular expressions) to apply to that string. 1961 1962 In an array context C<extract_multiple> returns an array of substrings 1963 of the original string, as extracted by the specified extractors. 1964 In a scalar context, C<extract_multiple> returns the first 1965 substring successfully extracted from the original string. In both 1966 scalar and void contexts the original string has the first successfully 1967 extracted substring removed from it. In all contexts 1968 C<extract_multiple> starts at the current C<pos> of the string, and 1969 sets that C<pos> appropriately after it matches. 1970 1971 Hence, the aim of of a call to C<extract_multiple> in a list context 1972 is to split the processed string into as many non-overlapping fields as 1973 possible, by repeatedly applying each of the specified extractors 1974 to the remainder of the string. Thus C<extract_multiple> is 1975 a generalized form of Perl's C<split> subroutine. 1976 1977 The subroutine takes up to four optional arguments: 1978 1979 =over 4 1980 1981 =item 1. 1982 1983 A string to be processed (C<$_> if the string is omitted or C<undef>) 1984 1985 =item 2. 1986 1987 A reference to a list of subroutine references and/or qr// objects and/or 1988 literal strings and/or hash references, specifying the extractors 1989 to be used to split the string. If this argument is omitted (or 1990 C<undef>) the list: 1991 1992 [ 1993 sub { extract_variable($_[0], '') }, 1994 sub { extract_quotelike($_[0],'') }, 1995 sub { extract_codeblock($_[0],'{}','') }, 1996 ] 1997 1998 is used. 1999 2000 2001 =item 3. 2002 2003 An number specifying the maximum number of fields to return. If this 2004 argument is omitted (or C<undef>), split continues as long as possible. 2005 2006 If the third argument is I<N>, then extraction continues until I<N> fields 2007 have been successfully extracted, or until the string has been completely 2008 processed. 2009 2010 Note that in scalar and void contexts the value of this argument is 2011 automatically reset to 1 (under C<-w>, a warning is issued if the argument 2012 has to be reset). 2013 2014 =item 4. 2015 2016 A value indicating whether unmatched substrings (see below) within the 2017 text should be skipped or returned as fields. If the value is true, 2018 such substrings are skipped. Otherwise, they are returned. 2019 2020 =back 2021 2022 The extraction process works by applying each extractor in 2023 sequence to the text string. 2024 2025 If the extractor is a subroutine it is called in a list context and is 2026 expected to return a list of a single element, namely the extracted 2027 text. It may optionally also return two further arguments: a string 2028 representing the text left after extraction (like $' for a pattern 2029 match), and a string representing any prefix skipped before the 2030 extraction (like $` in a pattern match). Note that this is designed 2031 to facilitate the use of other Text::Balanced subroutines with 2032 C<extract_multiple>. Note too that the value returned by an extractor 2033 subroutine need not bear any relationship to the corresponding substring 2034 of the original text (see examples below). 2035 2036 If the extractor is a precompiled regular expression or a string, 2037 it is matched against the text in a scalar context with a leading 2038 '\G' and the gc modifiers enabled. The extracted value is either 2039 $1 if that variable is defined after the match, or else the 2040 complete match (i.e. $&). 2041 2042 If the extractor is a hash reference, it must contain exactly one element. 2043 The value of that element is one of the 2044 above extractor types (subroutine reference, regular expression, or string). 2045 The key of that element is the name of a class into which the successful 2046 return value of the extractor will be blessed. 2047 2048 If an extractor returns a defined value, that value is immediately 2049 treated as the next extracted field and pushed onto the list of fields. 2050 If the extractor was specified in a hash reference, the field is also 2051 blessed into the appropriate class, 2052 2053 If the extractor fails to match (in the case of a regex extractor), or returns an empty list or an undefined value (in the case of a subroutine extractor), it is 2054 assumed to have failed to extract. 2055 If none of the extractor subroutines succeeds, then one 2056 character is extracted from the start of the text and the extraction 2057 subroutines reapplied. Characters which are thus removed are accumulated and 2058 eventually become the next field (unless the fourth argument is true, in which 2059 case they are discarded). 2060 2061 For example, the following extracts substrings that are valid Perl variables: 2062 2063 @fields = extract_multiple($text, 2064 [ sub { extract_variable($_[0]) } ], 2065 undef, 1); 2066 2067 This example separates a text into fields which are quote delimited, 2068 curly bracketed, and anything else. The delimited and bracketed 2069 parts are also blessed to identify them (the "anything else" is unblessed): 2070 2071 @fields = extract_multiple($text, 2072 [ 2073 { Delim => sub { extract_delimited($_[0],q{'"}) } }, 2074 { Brack => sub { extract_bracketed($_[0],'{}') } }, 2075 ]); 2076 2077 This call extracts the next single substring that is a valid Perl quotelike 2078 operator (and removes it from $text): 2079 2080 $quotelike = extract_multiple($text, 2081 [ 2082 sub { extract_quotelike($_[0]) }, 2083 ], undef, 1); 2084 2085 Finally, here is yet another way to do comma-separated value parsing: 2086 2087 @fields = extract_multiple($csv_text, 2088 [ 2089 sub { extract_delimited($_[0],q{'"}) }, 2090 qr/([^,]+)(.*)/, 2091 ], 2092 undef,1); 2093 2094 The list in the second argument means: 2095 I<"Try and extract a ' or " delimited string, otherwise extract anything up to a comma...">. 2096 The undef third argument means: 2097 I<"...as many times as possible...">, 2098 and the true value in the fourth argument means 2099 I<"...discarding anything else that appears (i.e. the commas)">. 2100 2101 If you wanted the commas preserved as separate fields (i.e. like split 2102 does if your split pattern has capturing parentheses), you would 2103 just make the last parameter undefined (or remove it). 2104 2105 2106 =head2 C<gen_delimited_pat> 2107 2108 The C<gen_delimited_pat> subroutine takes a single (string) argument and 2109 > builds a Friedl-style optimized regex that matches a string delimited 2110 by any one of the characters in the single argument. For example: 2111 2112 gen_delimited_pat(q{'"}) 2113 2114 returns the regex: 2115 2116 (?:\"(?:\\\"|(?!\").)*\"|\'(?:\\\'|(?!\').)*\') 2117 2118 Note that the specified delimiters are automatically quotemeta'd. 2119 2120 A typical use of C<gen_delimited_pat> would be to build special purpose tags 2121 for C<extract_tagged>. For example, to properly ignore "empty" XML elements 2122 (which might contain quoted strings): 2123 2124 my $empty_tag = '<(' . gen_delimited_pat(q{'"}) . '|.)+/>'; 2125 2126 extract_tagged($text, undef, undef, undef, {ignore => [$empty_tag]} ); 2127 2128 2129 C<gen_delimited_pat> may also be called with an optional second argument, 2130 which specifies the "escape" character(s) to be used for each delimiter. 2131 For example to match a Pascal-style string (where ' is the delimiter 2132 and '' is a literal ' within the string): 2133 2134 gen_delimited_pat(q{'},q{'}); 2135 2136 Different escape characters can be specified for different delimiters. 2137 For example, to specify that '/' is the escape for single quotes 2138 and '%' is the escape for double quotes: 2139 2140 gen_delimited_pat(q{'"},q{/%}); 2141 2142 If more delimiters than escape chars are specified, the last escape char 2143 is used for the remaining delimiters. 2144 If no escape char is specified for a given specified delimiter, '\' is used. 2145 2146 =head2 C<delimited_pat> 2147 2148 Note that C<gen_delimited_pat> was previously called C<delimited_pat>. 2149 That name may still be used, but is now deprecated. 2150 2151 2152 =head1 DIAGNOSTICS 2153 2154 In a list context, all the functions return C<(undef,$original_text)> 2155 on failure. In a scalar context, failure is indicated by returning C<undef> 2156 (in this case the input text is not modified in any way). 2157 2158 In addition, on failure in I<any> context, the C<$@> variable is set. 2159 Accessing C<$@-E<gt>{error}> returns one of the error diagnostics listed 2160 below. 2161 Accessing C<$@-E<gt>{pos}> returns the offset into the original string at 2162 which the error was detected (although not necessarily where it occurred!) 2163 Printing C<$@> directly produces the error message, with the offset appended. 2164 On success, the C<$@> variable is guaranteed to be C<undef>. 2165 2166 The available diagnostics are: 2167 2168 =over 4 2169 2170 =item C<Did not find a suitable bracket: "%s"> 2171 2172 The delimiter provided to C<extract_bracketed> was not one of 2173 C<'()[]E<lt>E<gt>{}'>. 2174 2175 =item C<Did not find prefix: /%s/> 2176 2177 A non-optional prefix was specified but wasn't found at the start of the text. 2178 2179 =item C<Did not find opening bracket after prefix: "%s"> 2180 2181 C<extract_bracketed> or C<extract_codeblock> was expecting a 2182 particular kind of bracket at the start of the text, and didn't find it. 2183 2184 =item C<No quotelike operator found after prefix: "%s"> 2185 2186 C<extract_quotelike> didn't find one of the quotelike operators C<q>, 2187 C<qq>, C<qw>, C<qx>, C<s>, C<tr> or C<y> at the start of the substring 2188 it was extracting. 2189 2190 =item C<Unmatched closing bracket: "%c"> 2191 2192 C<extract_bracketed>, C<extract_quotelike> or C<extract_codeblock> encountered 2193 a closing bracket where none was expected. 2194 2195 =item C<Unmatched opening bracket(s): "%s"> 2196 2197 C<extract_bracketed>, C<extract_quotelike> or C<extract_codeblock> ran 2198 out of characters in the text before closing one or more levels of nested 2199 brackets. 2200 2201 =item C<Unmatched embedded quote (%s)> 2202 2203 C<extract_bracketed> attempted to match an embedded quoted substring, but 2204 failed to find a closing quote to match it. 2205 2206 =item C<Did not find closing delimiter to match '%s'> 2207 2208 C<extract_quotelike> was unable to find a closing delimiter to match the 2209 one that opened the quote-like operation. 2210 2211 =item C<Mismatched closing bracket: expected "%c" but found "%s"> 2212 2213 C<extract_bracketed>, C<extract_quotelike> or C<extract_codeblock> found 2214 a valid bracket delimiter, but it was the wrong species. This usually 2215 indicates a nesting error, but may indicate incorrect quoting or escaping. 2216 2217 =item C<No block delimiter found after quotelike "%s"> 2218 2219 C<extract_quotelike> or C<extract_codeblock> found one of the 2220 quotelike operators C<q>, C<qq>, C<qw>, C<qx>, C<s>, C<tr> or C<y> 2221 without a suitable block after it. 2222 2223 =item C<Did not find leading dereferencer> 2224 2225 C<extract_variable> was expecting one of '$', '@', or '%' at the start of 2226 a variable, but didn't find any of them. 2227 2228 =item C<Bad identifier after dereferencer> 2229 2230 C<extract_variable> found a '$', '@', or '%' indicating a variable, but that 2231 character was not followed by a legal Perl identifier. 2232 2233 =item C<Did not find expected opening bracket at %s> 2234 2235 C<extract_codeblock> failed to find any of the outermost opening brackets 2236 that were specified. 2237 2238 =item C<Improperly nested codeblock at %s> 2239 2240 A nested code block was found that started with a delimiter that was specified 2241 as being only to be used as an outermost bracket. 2242 2243 =item C<Missing second block for quotelike "%s"> 2244 2245 C<extract_codeblock> or C<extract_quotelike> found one of the 2246 quotelike operators C<s>, C<tr> or C<y> followed by only one block. 2247 2248 =item C<No match found for opening bracket> 2249 2250 C<extract_codeblock> failed to find a closing bracket to match the outermost 2251 opening bracket. 2252 2253 =item C<Did not find opening tag: /%s/> 2254 2255 C<extract_tagged> did not find a suitable opening tag (after any specified 2256 prefix was removed). 2257 2258 =item C<Unable to construct closing tag to match: /%s/> 2259 2260 C<extract_tagged> matched the specified opening tag and tried to 2261 modify the matched text to produce a matching closing tag (because 2262 none was specified). It failed to generate the closing tag, almost 2263 certainly because the opening tag did not start with a 2264 bracket of some kind. 2265 2266 =item C<Found invalid nested tag: %s> 2267 2268 C<extract_tagged> found a nested tag that appeared in the "reject" list 2269 (and the failure mode was not "MAX" or "PARA"). 2270 2271 =item C<Found unbalanced nested tag: %s> 2272 2273 C<extract_tagged> found a nested opening tag that was not matched by a 2274 corresponding nested closing tag (and the failure mode was not "MAX" or "PARA"). 2275 2276 =item C<Did not find closing tag> 2277 2278 C<extract_tagged> reached the end of the text without finding a closing tag 2279 to match the original opening tag (and the failure mode was not 2280 "MAX" or "PARA"). 2281 2282 2283 2284 2285 =back 2286 2287 2288 =head1 AUTHOR 2289 2290 Damian Conway (damian@conway.org) 2291 2292 2293 =head1 BUGS AND IRRITATIONS 2294 2295 There are undoubtedly serious bugs lurking somewhere in this code, if 2296 only because parts of it give the impression of understanding a great deal 2297 more about Perl than they really do. 2298 2299 Bug reports and other feedback are most welcome. 2300 2301 2302 =head1 COPYRIGHT 2303 2304 Copyright (c) 1997-2001, Damian Conway. All Rights Reserved. 2305 This module is free software. It may be used, redistributed 2306 and/or modified under the same terms as Perl itself.
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