Index: /branches/release-40/extlib/Text/Balanced.pm =================================================================== --- /branches/release-40/extlib/Text/Balanced.pm (revision 2566) +++ /branches/release-40/extlib/Text/Balanced.pm (revision 2566) @@ -0,0 +1,2306 @@ +# EXTRACT VARIOUSLY DELIMITED TEXT SEQUENCES FROM STRINGS. +# FOR FULL DOCUMENTATION SEE Balanced.pod + +use 5.005; +use strict; + +package Text::Balanced; + +use Exporter; +use SelfLoader; +use vars qw { $VERSION @ISA %EXPORT_TAGS }; + +use version; $VERSION = qv('2.0.0'); +@ISA = qw ( Exporter ); + +%EXPORT_TAGS = ( ALL => [ qw( + &extract_delimited + &extract_bracketed + &extract_quotelike + &extract_codeblock + &extract_variable + &extract_tagged + &extract_multiple + + &gen_delimited_pat + &gen_extract_tagged + + &delimited_pat + ) ] ); + +Exporter::export_ok_tags('ALL'); + +# PROTOTYPES + +sub _match_bracketed($$$$$$); +sub _match_variable($$); +sub _match_codeblock($$$$$$$); +sub _match_quotelike($$$$); + +# HANDLE RETURN VALUES IN VARIOUS CONTEXTS + +sub _failmsg { + my ($message, $pos) = @_; + $@ = bless { error=>$message, pos=>$pos }, "Text::Balanced::ErrorMsg"; +} + +sub _fail +{ + my ($wantarray, $textref, $message, $pos) = @_; + _failmsg $message, $pos if $message; + return (undef,$$textref,undef) if $wantarray; + return undef; +} + +sub _succeed +{ + $@ = undef; + my ($wantarray,$textref) = splice @_, 0, 2; + my ($extrapos, $extralen) = @_>18 ? splice(@_, -2, 2) : (0,0); + my ($startlen, $oppos) = @_[5,6]; + my $remainderpos = $_[2]; + if ($wantarray) + { + my @res; + while (my ($from, $len) = splice @_, 0, 2) + { + push @res, substr($$textref,$from,$len); + } + if ($extralen) { # CORRECT FILLET + my $extra = substr($res[0], $extrapos-$oppos, $extralen, "\n"); + $res[1] = "$extra$res[1]"; + eval { substr($$textref,$remainderpos,0) = $extra; + substr($$textref,$extrapos,$extralen,"\n")} ; + #REARRANGE HERE DOC AND FILLET IF POSSIBLE + pos($$textref) = $remainderpos-$extralen+1; # RESET \G + } + else { + pos($$textref) = $remainderpos; # RESET \G + } + return @res; + } + else + { + my $match = substr($$textref,$_[0],$_[1]); + substr($match,$extrapos-$_[0]-$startlen,$extralen,"") if $extralen; + my $extra = $extralen + ? substr($$textref, $extrapos, $extralen)."\n" : ""; + eval {substr($$textref,$_[4],$_[1]+$_[5])=$extra} ; #CHOP OUT PREFIX & MATCH, IF POSSIBLE + pos($$textref) = $_[4]; # RESET \G + return $match; + } +} + +# BUILD A PATTERN MATCHING A SIMPLE DELIMITED STRING + +sub gen_delimited_pat($;$) # ($delimiters;$escapes) +{ + my ($dels, $escs) = @_; + return "" unless $dels =~ /\S/; + $escs = '\\' unless $escs; + $escs .= substr($escs,-1) x (length($dels)-length($escs)); + my @pat = (); + my $i; + for ($i=0; $i\0-\377/[[(({{</) + { + return _fail $wantarray, $textref, + "Did not find a suitable bracket in delimiter: \"$_[1]\"", + 0; + } + my $posbug = pos; + $ldel = join('|', map { quotemeta $_ } split('', $ldel)); + $rdel = join('|', map { quotemeta $_ } split('', $rdel)); + pos = $posbug; + + my $startpos = pos $$textref || 0; + my @match = _match_bracketed($textref,$pre, $ldel, $qdel, $quotelike, $rdel); + + return _fail ($wantarray, $textref) unless @match; + + return _succeed ( $wantarray, $textref, + $match[2], $match[5]+2, # MATCH + @match[8,9], # REMAINDER + @match[0,1], # PREFIX + ); +} + +sub _match_bracketed($$$$$$) # $textref, $pre, $ldel, $qdel, $quotelike, $rdel +{ + my ($textref, $pre, $ldel, $qdel, $quotelike, $rdel) = @_; + my ($startpos, $ldelpos, $endpos) = (pos $$textref = pos $$textref||0); + unless ($$textref =~ m/\G$pre/gc) + { + _failmsg "Did not find prefix: /$pre/", $startpos; + return; + } + + $ldelpos = pos $$textref; + + unless ($$textref =~ m/\G($ldel)/gc) + { + _failmsg "Did not find opening bracket after prefix: \"$pre\"", + pos $$textref; + pos $$textref = $startpos; + return; + } + + my @nesting = ( $1 ); + my $textlen = length $$textref; + while (pos $$textref < $textlen) + { + next if $$textref =~ m/\G\\./gcs; + + if ($$textref =~ m/\G($ldel)/gc) + { + push @nesting, $1; + } + elsif ($$textref =~ m/\G($rdel)/gc) + { + my ($found, $brackettype) = ($1, $1); + if ($#nesting < 0) + { + _failmsg "Unmatched closing bracket: \"$found\"", + pos $$textref; + pos $$textref = $startpos; + return; + } + my $expected = pop(@nesting); + $expected =~ tr/({[/; + if ($expected ne $brackettype) + { + _failmsg qq{Mismatched closing bracket: expected "$expected" but found "$found"}, + pos $$textref; + pos $$textref = $startpos; + return; + } + last if $#nesting < 0; + } + elsif ($qdel && $$textref =~ m/\G([$qdel])/gc) + { + $$textref =~ m/\G[^\\$1]*(?:\\.[^\\$1]*)*(\Q$1\E)/gsc and next; + _failmsg "Unmatched embedded quote ($1)", + pos $$textref; + pos $$textref = $startpos; + return; + } + elsif ($quotelike && _match_quotelike($textref,"",1,0)) + { + next; + } + + else { $$textref =~ m/\G(?:[a-zA-Z0-9]+|.)/gcs } + } + if ($#nesting>=0) + { + _failmsg "Unmatched opening bracket(s): " + . join("..",@nesting)."..", + pos $$textref; + pos $$textref = $startpos; + return; + } + + $endpos = pos $$textref; + + return ( + $startpos, $ldelpos-$startpos, # PREFIX + $ldelpos, 1, # OPENING BRACKET + $ldelpos+1, $endpos-$ldelpos-2, # CONTENTS + $endpos-1, 1, # CLOSING BRACKET + $endpos, length($$textref)-$endpos, # REMAINDER + ); +} + +sub _revbracket($) +{ + my $brack = reverse $_[0]; + $brack =~ tr/[({/; + return $brack; +} + +my $XMLNAME = q{[a-zA-Z_:][a-zA-Z0-9_:.-]*}; + +sub extract_tagged (;$$$$$) # ($text, $opentag, $closetag, $pre, \%options) +{ + my $textref = defined $_[0] ? \$_[0] : \$_; + my $ldel = $_[1]; + my $rdel = $_[2]; + my $pre = defined $_[3] ? $_[3] : '\s*'; + my %options = defined $_[4] ? %{$_[4]} : (); + my $omode = defined $options{fail} ? $options{fail} : ''; + my $bad = ref($options{reject}) eq 'ARRAY' ? join('|', @{$options{reject}}) + : defined($options{reject}) ? $options{reject} + : '' + ; + my $ignore = ref($options{ignore}) eq 'ARRAY' ? join('|', @{$options{ignore}}) + : defined($options{ignore}) ? $options{ignore} + : '' + ; + + if (!defined $ldel) { $ldel = '<\w+(?:' . gen_delimited_pat(q{'"}) . '|[^>])*>'; } + $@ = undef; + + my @match = _match_tagged($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore); + + return _fail(wantarray, $textref) unless @match; + return _succeed wantarray, $textref, + $match[2], $match[3]+$match[5]+$match[7], # MATCH + @match[8..9,0..1,2..7]; # REM, PRE, BITS +} + +sub _match_tagged # ($$$$$$$) +{ + my ($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore) = @_; + my $rdelspec; + + my ($startpos, $opentagpos, $textpos, $parapos, $closetagpos, $endpos) = ( pos($$textref) = pos($$textref)||0 ); + + unless ($$textref =~ m/\G($pre)/gc) + { + _failmsg "Did not find prefix: /$pre/", pos $$textref; + goto failed; + } + + $opentagpos = pos($$textref); + + unless ($$textref =~ m/\G$ldel/gc) + { + _failmsg "Did not find opening tag: /$ldel/", pos $$textref; + goto failed; + } + + $textpos = pos($$textref); + + if (!defined $rdel) + { + $rdelspec = substr($$textref, $-[0], $+[0] - $-[0]); + unless ($rdelspec =~ s/\A([[(<{]+)($XMLNAME).*/ quotemeta "$1\/$2". _revbracket($1) /oes) + { + _failmsg "Unable to construct closing tag to match: $rdel", + pos $$textref; + goto failed; + } + } + else + { + $rdelspec = eval "qq{$rdel}" || do { + my $del; + for (qw,~ ! ^ & * ) _ + - = } ] : " ; ' > . ? / | ',) + { next if $rdel =~ /\Q$_/; $del = $_; last } + unless ($del) { + use Carp; + croak "Can't interpolate right delimiter $rdel" + } + eval "qq$del$rdel$del"; + }; + } + + while (pos($$textref) < length($$textref)) + { + next if $$textref =~ m/\G\\./gc; + + if ($$textref =~ m/\G(\n[ \t]*\n)/gc ) + { + $parapos = pos($$textref) - length($1) + unless defined $parapos; + } + elsif ($$textref =~ m/\G($rdelspec)/gc ) + { + $closetagpos = pos($$textref)-length($1); + goto matched; + } + elsif ($ignore && $$textref =~ m/\G(?:$ignore)/gc) + { + next; + } + elsif ($bad && $$textref =~ m/\G($bad)/gcs) + { + pos($$textref) -= length($1); # CUT OFF WHATEVER CAUSED THE SHORTNESS + goto short if ($omode eq 'PARA' || $omode eq 'MAX'); + _failmsg "Found invalid nested tag: $1", pos $$textref; + goto failed; + } + elsif ($$textref =~ m/\G($ldel)/gc) + { + my $tag = $1; + pos($$textref) -= length($tag); # REWIND TO NESTED TAG + unless (_match_tagged(@_)) # MATCH NESTED TAG + { + goto short if $omode eq 'PARA' || $omode eq 'MAX'; + _failmsg "Found unbalanced nested tag: $tag", + pos $$textref; + goto failed; + } + } + else { $$textref =~ m/./gcs } + } + +short: + $closetagpos = pos($$textref); + goto matched if $omode eq 'MAX'; + goto failed unless $omode eq 'PARA'; + + if (defined $parapos) { pos($$textref) = $parapos } + else { $parapos = pos($$textref) } + + return ( + $startpos, $opentagpos-$startpos, # PREFIX + $opentagpos, $textpos-$opentagpos, # OPENING TAG + $textpos, $parapos-$textpos, # TEXT + $parapos, 0, # NO CLOSING TAG + $parapos, length($$textref)-$parapos, # REMAINDER + ); + +matched: + $endpos = pos($$textref); + return ( + $startpos, $opentagpos-$startpos, # PREFIX + $opentagpos, $textpos-$opentagpos, # OPENING TAG + $textpos, $closetagpos-$textpos, # TEXT + $closetagpos, $endpos-$closetagpos, # CLOSING TAG + $endpos, length($$textref)-$endpos, # REMAINDER + ); + +failed: + _failmsg "Did not find closing tag", pos $$textref unless $@; + pos($$textref) = $startpos; + return; +} + +sub extract_variable (;$$) +{ + my $textref = defined $_[0] ? \$_[0] : \$_; + return ("","","") unless defined $$textref; + my $pre = defined $_[1] ? $_[1] : '\s*'; + + my @match = _match_variable($textref,$pre); + + return _fail wantarray, $textref unless @match; + + return _succeed wantarray, $textref, + @match[2..3,4..5,0..1]; # MATCH, REMAINDER, PREFIX +} + +sub _match_variable($$) +{ +# $# +# $^ +# $$ + my ($textref, $pre) = @_; + my $startpos = pos($$textref) = pos($$textref)||0; + unless ($$textref =~ m/\G($pre)/gc) + { + _failmsg "Did not find prefix: /$pre/", pos $$textref; + return; + } + my $varpos = pos($$textref); + unless ($$textref =~ m{\G\$\s*(?!::)(\d+|[][&`'+*./|,";%=~:?!\@<>()-]|\^[a-z]?)}gci) + { + unless ($$textref =~ m/\G((\$#?|[*\@\%]|\\&)+)/gc) + { + _failmsg "Did not find leading dereferencer", pos $$textref; + pos $$textref = $startpos; + return; + } + my $deref = $1; + + unless ($$textref =~ m/\G\s*(?:::|')?(?:[_a-z]\w*(?:::|'))*[_a-z]\w*/gci + or _match_codeblock($textref, "", '\{', '\}', '\{', '\}', 0) + or $deref eq '$#' or $deref eq '$$' ) + { + _failmsg "Bad identifier after dereferencer", pos $$textref; + pos $$textref = $startpos; + return; + } + } + + while (1) + { + next if $$textref =~ m/\G\s*(?:->)?\s*[{]\w+[}]/gc; + next if _match_codeblock($textref, + qr/\s*->\s*(?:[_a-zA-Z]\w+\s*)?/, + qr/[({[]/, qr/[)}\]]/, + qr/[({[]/, qr/[)}\]]/, 0); + next if _match_codeblock($textref, + qr/\s*/, qr/[{[]/, qr/[}\]]/, + qr/[{[]/, qr/[}\]]/, 0); + next if _match_variable($textref,'\s*->\s*'); + next if $$textref =~ m/\G\s*->\s*\w+(?![{([])/gc; + last; + } + + my $endpos = pos($$textref); + return ($startpos, $varpos-$startpos, + $varpos, $endpos-$varpos, + $endpos, length($$textref)-$endpos + ); +} + +sub extract_codeblock (;$$$$$) +{ + my $textref = defined $_[0] ? \$_[0] : \$_; + my $wantarray = wantarray; + my $ldel_inner = defined $_[1] ? $_[1] : '{'; + my $pre = defined $_[2] ? $_[2] : '\s*'; + my $ldel_outer = defined $_[3] ? $_[3] : $ldel_inner; + my $rd = $_[4]; + my $rdel_inner = $ldel_inner; + my $rdel_outer = $ldel_outer; + my $posbug = pos; + for ($ldel_inner, $ldel_outer) { tr/[]()<>{}\0-\377/[[((<<{{/ds } + for ($rdel_inner, $rdel_outer) { tr/[]()<>{}\0-\377/]]))>>}}/ds } + for ($ldel_inner, $ldel_outer, $rdel_inner, $rdel_outer) + { + $_ = '('.join('|',map { quotemeta $_ } split('',$_)).')' + } + pos = $posbug; + + my @match = _match_codeblock($textref, $pre, + $ldel_outer, $rdel_outer, + $ldel_inner, $rdel_inner, + $rd); + return _fail($wantarray, $textref) unless @match; + return _succeed($wantarray, $textref, + @match[2..3,4..5,0..1] # MATCH, REMAINDER, PREFIX + ); + +} + +sub _match_codeblock($$$$$$$) +{ + my ($textref, $pre, $ldel_outer, $rdel_outer, $ldel_inner, $rdel_inner, $rd) = @_; + my $startpos = pos($$textref) = pos($$textref) || 0; + unless ($$textref =~ m/\G($pre)/gc) + { + _failmsg qq{Did not match prefix /$pre/ at"} . + substr($$textref,pos($$textref),20) . + q{..."}, + pos $$textref; + return; + } + my $codepos = pos($$textref); + unless ($$textref =~ m/\G($ldel_outer)/gc) # OUTERMOST DELIMITER + { + _failmsg qq{Did not find expected opening bracket at "} . + substr($$textref,pos($$textref),20) . + q{..."}, + pos $$textref; + pos $$textref = $startpos; + return; + } + my $closing = $1; + $closing =~ tr/([<{/)]>}/; + my $matched; + my $patvalid = 1; + while (pos($$textref) < length($$textref)) + { + $matched = ''; + if ($rd && $$textref =~ m#\G(\Q(?)\E|\Q(s?)\E|\Q(s)\E)#gc) + { + $patvalid = 0; + next; + } + + if ($$textref =~ m/\G\s*#.*/gc) + { + next; + } + + if ($$textref =~ m/\G\s*($rdel_outer)/gc) + { + unless ($matched = ($closing && $1 eq $closing) ) + { + next if $1 eq '>'; # MIGHT BE A "LESS THAN" + _failmsg q{Mismatched closing bracket at "} . + substr($$textref,pos($$textref),20) . + qq{...". Expected '$closing'}, + pos $$textref; + } + last; + } + + if (_match_variable($textref,'\s*') || + _match_quotelike($textref,'\s*',$patvalid,$patvalid) ) + { + $patvalid = 0; + next; + } + + + # NEED TO COVER MANY MORE CASES HERE!!! + if ($$textref =~ m#\G\s*(?!$ldel_inner) + ( [-+*x/%^&|.]=? + | [!=]~ + | =(?!>) + | (\*\*|&&|\|\||<<|>>)=? + | split|grep|map|return + | [([] + )#gcx) + { + $patvalid = 1; + next; + } + + if ( _match_codeblock($textref, '\s*', $ldel_inner, $rdel_inner, $ldel_inner, $rdel_inner, $rd) ) + { + $patvalid = 1; + next; + } + + if ($$textref =~ m/\G\s*$ldel_outer/gc) + { + _failmsg q{Improperly nested codeblock at "} . + substr($$textref,pos($$textref),20) . + q{..."}, + pos $$textref; + last; + } + + $patvalid = 0; + $$textref =~ m/\G\s*(\w+|[-=>]>|.|\Z)/gc; + } + continue { $@ = undef } + + unless ($matched) + { + _failmsg 'No match found for opening bracket', pos $$textref + unless $@; + return; + } + + my $endpos = pos($$textref); + return ( $startpos, $codepos-$startpos, + $codepos, $endpos-$codepos, + $endpos, length($$textref)-$endpos, + ); +} + + +my %mods = ( + 'none' => '[cgimsox]*', + 'm' => '[cgimsox]*', + 's' => '[cegimsox]*', + 'tr' => '[cds]*', + 'y' => '[cds]*', + 'qq' => '', + 'qx' => '', + 'qw' => '', + 'qr' => '[imsx]*', + 'q' => '', + ); + +sub extract_quotelike (;$$) +{ + my $textref = $_[0] ? \$_[0] : \$_; + my $wantarray = wantarray; + my $pre = defined $_[1] ? $_[1] : '\s*'; + + my @match = _match_quotelike($textref,$pre,1,0); + return _fail($wantarray, $textref) unless @match; + return _succeed($wantarray, $textref, + $match[2], $match[18]-$match[2], # MATCH + @match[18,19], # REMAINDER + @match[0,1], # PREFIX + @match[2..17], # THE BITS + @match[20,21], # ANY FILLET? + ); +}; + +sub _match_quotelike($$$$) # ($textref, $prepat, $allow_raw_match) +{ + my ($textref, $pre, $rawmatch, $qmark) = @_; + + my ($textlen,$startpos, + $oppos, + $preld1pos,$ld1pos,$str1pos,$rd1pos, + $preld2pos,$ld2pos,$str2pos,$rd2pos, + $modpos) = ( length($$textref), pos($$textref) = pos($$textref) || 0 ); + + unless ($$textref =~ m/\G($pre)/gc) + { + _failmsg qq{Did not find prefix /$pre/ at "} . + substr($$textref, pos($$textref), 20) . + q{..."}, + pos $$textref; + return; + } + $oppos = pos($$textref); + + my $initial = substr($$textref,$oppos,1); + + if ($initial && $initial =~ m|^[\"\'\`]| + || $rawmatch && $initial =~ m|^/| + || $qmark && $initial =~ m|^\?|) + { + unless ($$textref =~ m/ \Q$initial\E [^\\$initial]* (\\.[^\\$initial]*)* \Q$initial\E /gcsx) + { + _failmsg qq{Did not find closing delimiter to match '$initial' at "} . + substr($$textref, $oppos, 20) . + q{..."}, + pos $$textref; + pos $$textref = $startpos; + return; + } + $modpos= pos($$textref); + $rd1pos = $modpos-1; + + if ($initial eq '/' || $initial eq '?') + { + $$textref =~ m/\G$mods{none}/gc + } + + my $endpos = pos($$textref); + return ( + $startpos, $oppos-$startpos, # PREFIX + $oppos, 0, # NO OPERATOR + $oppos, 1, # LEFT DEL + $oppos+1, $rd1pos-$oppos-1, # STR/PAT + $rd1pos, 1, # RIGHT DEL + $modpos, 0, # NO 2ND LDEL + $modpos, 0, # NO 2ND STR + $modpos, 0, # NO 2ND RDEL + $modpos, $endpos-$modpos, # MODIFIERS + $endpos, $textlen-$endpos, # REMAINDER + ); + } + + unless ($$textref =~ m{\G(\b(?:m|s|qq|qx|qw|q|qr|tr|y)\b(?=\s*\S)|<<)}gc) + { + _failmsg q{No quotelike operator found after prefix at "} . + substr($$textref, pos($$textref), 20) . + q{..."}, + pos $$textref; + pos $$textref = $startpos; + return; + } + + my $op = $1; + $preld1pos = pos($$textref); + if ($op eq '<<') { + $ld1pos = pos($$textref); + my $label; + if ($$textref =~ m{\G([A-Za-z_]\w*)}gc) { + $label = $1; + } + elsif ($$textref =~ m{ \G ' ([^'\\]* (?:\\.[^'\\]*)*) ' + | \G " ([^"\\]* (?:\\.[^"\\]*)*) " + | \G ` ([^`\\]* (?:\\.[^`\\]*)*) ` + }gcsx) { + $label = $+; + } + else { + $label = ""; + } + my $extrapos = pos($$textref); + $$textref =~ m{.*\n}gc; + $str1pos = pos($$textref)--; + unless ($$textref =~ m{.*?\n(?=\Q$label\E\n)}gc) { + _failmsg qq{Missing here doc terminator ('$label') after "} . + substr($$textref, $startpos, 20) . + q{..."}, + pos $$textref; + pos $$textref = $startpos; + return; + } + $rd1pos = pos($$textref); + $$textref =~ m{\Q$label\E\n}gc; + $ld2pos = pos($$textref); + return ( + $startpos, $oppos-$startpos, # PREFIX + $oppos, length($op), # OPERATOR + $ld1pos, $extrapos-$ld1pos, # LEFT DEL + $str1pos, $rd1pos-$str1pos, # STR/PAT + $rd1pos, $ld2pos-$rd1pos, # RIGHT DEL + $ld2pos, 0, # NO 2ND LDEL + $ld2pos, 0, # NO 2ND STR + $ld2pos, 0, # NO 2ND RDEL + $ld2pos, 0, # NO MODIFIERS + $ld2pos, $textlen-$ld2pos, # REMAINDER + $extrapos, $str1pos-$extrapos, # FILLETED BIT + ); + } + + $$textref =~ m/\G\s*/gc; + $ld1pos = pos($$textref); + $str1pos = $ld1pos+1; + + unless ($$textref =~ m/\G(\S)/gc) # SHOULD USE LOOKAHEAD + { + _failmsg "No block delimiter found after quotelike $op", + pos $$textref; + pos $$textref = $startpos; + return; + } + pos($$textref) = $ld1pos; # HAVE TO DO THIS BECAUSE LOOKAHEAD BROKEN + my ($ldel1, $rdel1) = ("\Q$1","\Q$1"); + if ($ldel1 =~ /[[(<{]/) + { + $rdel1 =~ tr/[({/; + defined(_match_bracketed($textref,"",$ldel1,"","",$rdel1)) + || do { pos $$textref = $startpos; return }; + $ld2pos = pos($$textref); + $rd1pos = $ld2pos-1; + } + else + { + $$textref =~ /\G$ldel1[^\\$ldel1]*(\\.[^\\$ldel1]*)*$ldel1/gcs + || do { pos $$textref = $startpos; return }; + $ld2pos = $rd1pos = pos($$textref)-1; + } + + my $second_arg = $op =~ /s|tr|y/ ? 1 : 0; + if ($second_arg) + { + my ($ldel2, $rdel2); + if ($ldel1 =~ /[[(<{]/) + { + unless ($$textref =~ /\G\s*(\S)/gc) # SHOULD USE LOOKAHEAD + { + _failmsg "Missing second block for quotelike $op", + pos $$textref; + pos $$textref = $startpos; + return; + } + $ldel2 = $rdel2 = "\Q$1"; + $rdel2 =~ tr/[({/; + } + else + { + $ldel2 = $rdel2 = $ldel1; + } + $str2pos = $ld2pos+1; + + if ($ldel2 =~ /[[(<{]/) + { + pos($$textref)--; # OVERCOME BROKEN LOOKAHEAD + defined(_match_bracketed($textref,"",$ldel2,"","",$rdel2)) + || do { pos $$textref = $startpos; return }; + } + else + { + $$textref =~ /[^\\$ldel2]*(\\.[^\\$ldel2]*)*$ldel2/gcs + || do { pos $$textref = $startpos; return }; + } + $rd2pos = pos($$textref)-1; + } + else + { + $ld2pos = $str2pos = $rd2pos = $rd1pos; + } + + $modpos = pos $$textref; + + $$textref =~ m/\G($mods{$op})/gc; + my $endpos = pos $$textref; + + return ( + $startpos, $oppos-$startpos, # PREFIX + $oppos, length($op), # OPERATOR + $ld1pos, 1, # LEFT DEL + $str1pos, $rd1pos-$str1pos, # STR/PAT + $rd1pos, 1, # RIGHT DEL + $ld2pos, $second_arg, # 2ND LDEL (MAYBE) + $str2pos, $rd2pos-$str2pos, # 2ND STR (MAYBE) + $rd2pos, $second_arg, # 2ND RDEL (MAYBE) + $modpos, $endpos-$modpos, # MODIFIERS + $endpos, $textlen-$endpos, # REMAINDER + ); +} + +my $def_func = +[ + sub { extract_variable($_[0], '') }, + sub { extract_quotelike($_[0],'') }, + sub { extract_codeblock($_[0],'{}','') }, +]; + +sub extract_multiple (;$$$$) # ($text, $functions_ref, $max_fields, $ignoreunknown) +{ + my $textref = defined($_[0]) ? \$_[0] : \$_; + my $posbug = pos; + my ($lastpos, $firstpos); + my @fields = (); + + #for ($$textref) + { + my @func = defined $_[1] ? @{$_[1]} : @{$def_func}; + my $max = defined $_[2] && $_[2]>0 ? $_[2] : 1_000_000_000; + my $igunk = $_[3]; + + pos $$textref ||= 0; + + unless (wantarray) + { + use Carp; + carp "extract_multiple reset maximal count to 1 in scalar context" + if $^W && defined($_[2]) && $max > 1; + $max = 1 + } + + my $unkpos; + my $func; + my $class; + + my @class; + foreach $func ( @func ) + { + if (ref($func) eq 'HASH') + { + push @class, (keys %$func)[0]; + $func = (values %$func)[0]; + } + else + { + push @class, undef; + } + } + + FIELD: while (pos($$textref) < length($$textref)) + { + my ($field, $rem); + my @bits; + foreach my $i ( 0..$#func ) + { + my $pref; + $func = $func[$i]; + $class = $class[$i]; + $lastpos = pos $$textref; + if (ref($func) eq 'CODE') + { ($field,$rem,$pref) = @bits = $func->($$textref) } + elsif (ref($func) eq 'Text::Balanced::Extractor') + { @bits = $field = $func->extract($$textref) } + elsif( $$textref =~ m/\G$func/gc ) + { @bits = $field = defined($1) + ? $1 + : substr($$textref, $-[0], $+[0] - $-[0]) + } + $pref ||= ""; + if (defined($field) && length($field)) + { + if (!$igunk) { + $unkpos = $lastpos + if length($pref) && !defined($unkpos); + if (defined $unkpos) + { + push @fields, substr($$textref, $unkpos, $lastpos-$unkpos).$pref; + $firstpos = $unkpos unless defined $firstpos; + undef $unkpos; + last FIELD if @fields == $max; + } + } + push @fields, $class + ? bless (\$field, $class) + : $field; + $firstpos = $lastpos unless defined $firstpos; + $lastpos = pos $$textref; + last FIELD if @fields == $max; + next FIELD; + } + } + if ($$textref =~ /\G(.)/gcs) + { + $unkpos = pos($$textref)-1 + unless $igunk || defined $unkpos; + } + } + + if (defined $unkpos) + { + push @fields, substr($$textref, $unkpos); + $firstpos = $unkpos unless defined $firstpos; + $lastpos = length $$textref; + } + last; + } + + pos $$textref = $lastpos; + return @fields if wantarray; + + $firstpos ||= 0; + eval { substr($$textref,$firstpos,$lastpos-$firstpos)=""; + pos $$textref = $firstpos }; + return $fields[0]; +} + + +sub gen_extract_tagged # ($opentag, $closetag, $pre, \%options) +{ + my $ldel = $_[0]; + my $rdel = $_[1]; + my $pre = defined $_[2] ? $_[2] : '\s*'; + my %options = defined $_[3] ? %{$_[3]} : (); + my $omode = defined $options{fail} ? $options{fail} : ''; + my $bad = ref($options{reject}) eq 'ARRAY' ? join('|', @{$options{reject}}) + : defined($options{reject}) ? $options{reject} + : '' + ; + my $ignore = ref($options{ignore}) eq 'ARRAY' ? join('|', @{$options{ignore}}) + : defined($options{ignore}) ? $options{ignore} + : '' + ; + + if (!defined $ldel) { $ldel = '<\w+(?:' . gen_delimited_pat(q{'"}) . '|[^>])*>'; } + + my $posbug = pos; + for ($ldel, $pre, $bad, $ignore) { $_ = qr/$_/ if $_ } + pos = $posbug; + + my $closure = sub + { + my $textref = defined $_[0] ? \$_[0] : \$_; + my @match = Text::Balanced::_match_tagged($textref, $pre, $ldel, $rdel, $omode, $bad, $ignore); + + return _fail(wantarray, $textref) unless @match; + return _succeed wantarray, $textref, + $match[2], $match[3]+$match[5]+$match[7], # MATCH + @match[8..9,0..1,2..7]; # REM, PRE, BITS + }; + + bless $closure, 'Text::Balanced::Extractor'; +} + +package Text::Balanced::Extractor; + +sub extract($$) # ($self, $text) +{ + &{$_[0]}($_[1]); +} + +package Text::Balanced::ErrorMsg; + +use overload '""' => sub { "$_[0]->{error}, detected at offset $_[0]->{pos}" }; + +1; + +__END__ + +=head1 NAME + +Text::Balanced - Extract delimited text sequences from strings. + + +=head1 SYNOPSIS + + use Text::Balanced qw ( + extract_delimited + extract_bracketed + extract_quotelike + extract_codeblock + extract_variable + extract_tagged + extract_multiple + + gen_delimited_pat + gen_extract_tagged + ); + + # Extract the initial substring of $text that is delimited by + # two (unescaped) instances of the first character in $delim. + + ($extracted, $remainder) = extract_delimited($text,$delim); + + + # Extract the initial substring of $text that is bracketed + # with a delimiter(s) specified by $delim (where the string + # in $delim contains one or more of '(){}[]<>'). + + ($extracted, $remainder) = extract_bracketed($text,$delim); + + + # Extract the initial substring of $text that is bounded by + # an XML tag. + + ($extracted, $remainder) = extract_tagged($text); + + + # Extract the initial substring of $text that is bounded by + # a C...C pair. Don't allow nested C tags + + ($extracted, $remainder) = + extract_tagged($text,"BEGIN","END",undef,{bad=>["BEGIN"]}); + + + # Extract the initial substring of $text that represents a + # Perl "quote or quote-like operation" + + ($extracted, $remainder) = extract_quotelike($text); + + + # Extract the initial substring of $text that represents a block + # of Perl code, bracketed by any of character(s) specified by $delim + # (where the string $delim contains one or more of '(){}[]<>'). + + ($extracted, $remainder) = extract_codeblock($text,$delim); + + + # Extract the initial substrings of $text that would be extracted by + # one or more sequential applications of the specified functions + # or regular expressions + + @extracted = extract_multiple($text, + [ \&extract_bracketed, + \&extract_quotelike, + \&some_other_extractor_sub, + qr/[xyz]*/, + 'literal', + ]); + +# Create a string representing an optimized pattern (a la Friedl) +# that matches a substring delimited by any of the specified characters +# (in this case: any type of quote or a slash) + + $patstring = gen_delimited_pat(q{'"`/}); + + +# Generate a reference to an anonymous sub that is just like extract_tagged +# but pre-compiled and optimized for a specific pair of tags, and consequently +# much faster (i.e. 3 times faster). It uses qr// for better performance on +# repeated calls, so it only works under Perl 5.005 or later. + + $extract_head = gen_extract_tagged('',''); + + ($extracted, $remainder) = $extract_head->($text); + + +=head1 DESCRIPTION + +The various C subroutines may be used to +extract a delimited substring, possibly after skipping a +specified prefix string. By default, that prefix is +optional whitespace (C), but you can change it to whatever +you wish (see below). + +The substring to be extracted must appear at the +current C location of the string's variable +(or at index zero, if no C position is defined). +In other words, the C subroutines I +extract the first occurrence of a substring anywhere +in a string (like an unanchored regex would). Rather, +they extract an occurrence of the substring appearing +immediately at the current matching position in the +string (like a C<\G>-anchored regex would). + + + +=head2 General behaviour in list contexts + +In a list context, all the subroutines return a list, the first three +elements of which are always: + +=over 4 + +=item [0] + +The extracted string, including the specified delimiters. +If the extraction fails C is returned. + +=item [1] + +The remainder of the input string (i.e. the characters after the +extracted string). On failure, the entire string is returned. + +=item [2] + +The skipped prefix (i.e. the characters before the extracted string). +On failure, C is returned. + +=back + +Note that in a list context, the contents of the original input text (the first +argument) are not modified in any way. + +However, if the input text was passed in a variable, that variable's +C value is updated to point at the first character after the +extracted text. That means that in a list context the various +subroutines can be used much like regular expressions. For example: + + while ( $next = (extract_quotelike($text))[0] ) + { + # process next quote-like (in $next) + } + + +=head2 General behaviour in scalar and void contexts + +In a scalar context, the extracted string is returned, having first been +removed from the input text. Thus, the following code also processes +each quote-like operation, but actually removes them from $text: + + while ( $next = extract_quotelike($text) ) + { + # process next quote-like (in $next) + } + +Note that if the input text is a read-only string (i.e. a literal), +no attempt is made to remove the extracted text. + +In a void context the behaviour of the extraction subroutines is +exactly the same as in a scalar context, except (of course) that the +extracted substring is not returned. + +=head2 A note about prefixes + +Prefix patterns are matched without any trailing modifiers (C etc.) +This can bite you if you're expecting a prefix specification like +'.*?(?=

)' to skip everything up to the first

tag. Such a prefix +pattern will only succeed if the

tag is on the current line, since +. normally doesn't match newlines. + +To overcome this limitation, you need to turn on /s matching within +the prefix pattern, using the C<(?s)> directive: '(?s).*?(?=

)' + + +=head2 C + +The C function formalizes the common idiom +of extracting a single-character-delimited substring from the start of +a string. For example, to extract a single-quote delimited string, the +following code is typically used: + + ($remainder = $text) =~ s/\A('(\\.|[^'])*')//s; + $extracted = $1; + +but with C it can be simplified to: + + ($extracted,$remainder) = extract_delimited($text, "'"); + +C takes up to four scalars (the input text, the +delimiters, a prefix pattern to be skipped, and any escape characters) +and extracts the initial substring of the text that +is appropriately delimited. If the delimiter string has multiple +characters, the first one encountered in the text is taken to delimit +the substring. +The third argument specifies a prefix pattern that is to be skipped +(but must be present!) before the substring is extracted. +The final argument specifies the escape character to be used for each +delimiter. + +All arguments are optional. If the escape characters are not specified, +every delimiter is escaped with a backslash (C<\>). +If the prefix is not specified, the +pattern C<'\s*'> - optional whitespace - is used. If the delimiter set +is also not specified, the set C is used. If the text to be processed +is not specified either, C<$_> is used. + +In list context, C returns a array of three +elements, the extracted substring (I), the remainder of the text, and the skipped prefix (if +any). If a suitable delimited substring is not found, the first +element of the array is the empty string, the second is the complete +original text, and the prefix returned in the third element is an +empty string. + +In a scalar context, just the extracted substring is returned. In +a void context, the extracted substring (and any prefix) are simply +removed from the beginning of the first argument. + +Examples: + + # Remove a single-quoted substring from the very beginning of $text: + + $substring = extract_delimited($text, "'", ''); + + # Remove a single-quoted Pascalish substring (i.e. one in which + # doubling the quote character escapes it) from the very + # beginning of $text: + + $substring = extract_delimited($text, "'", '', "'"); + + # Extract a single- or double- quoted substring from the + # beginning of $text, optionally after some whitespace + # (note the list context to protect $text from modification): + + ($substring) = extract_delimited $text, q{"'}; + + + # Delete the substring delimited by the first '/' in $text: + + $text = join '', (extract_delimited($text,'/','[^/]*')[2,1]; + +Note that this last example is I the same as deleting the first +quote-like pattern. For instance, if C<$text> contained the string: + + "if ('./cmd' =~ m/$UNIXCMD/s) { $cmd = $1; }" + +then after the deletion it would contain: + + "if ('.$UNIXCMD/s) { $cmd = $1; }" + +not: + + "if ('./cmd' =~ ms) { $cmd = $1; }" + + +See L<"extract_quotelike"> for a (partial) solution to this problem. + + +=head2 C + +Like C<"extract_delimited">, the C function takes +up to three optional scalar arguments: a string to extract from, a delimiter +specifier, and a prefix pattern. As before, a missing prefix defaults to +optional whitespace and a missing text defaults to C<$_>. However, a missing +delimiter specifier defaults to C<'{}()[]EE'> (see below). + +C extracts a balanced-bracket-delimited +substring (using any one (or more) of the user-specified delimiter +brackets: '(..)', '{..}', '[..]', or '<..>'). Optionally it will also +respect quoted unbalanced brackets (see below). + +A "delimiter bracket" is a bracket in list of delimiters passed as +C's second argument. Delimiter brackets are +specified by giving either the left or right (or both!) versions +of the required bracket(s). Note that the order in which +two or more delimiter brackets are specified is not significant. + +A "balanced-bracket-delimited substring" is a substring bounded by +matched brackets, such that any other (left or right) delimiter +bracket I the substring is also matched by an opposite +(right or left) delimiter bracket I. Any +type of bracket not in the delimiter list is treated as an ordinary +character. + +In other words, each type of bracket specified as a delimiter must be +balanced and correctly nested within the substring, and any other kind of +("non-delimiter") bracket in the substring is ignored. + +For example, given the string: + + $text = "{ an '[irregularly :-(] {} parenthesized >:-)' string }"; + +then a call to C in a list context: + + @result = extract_bracketed( $text, '{}' ); + +would return: + + ( "{ an '[irregularly :-(] {} parenthesized >:-)' string }" , "" , "" ) + +since both sets of C<'{..}'> brackets are properly nested and evenly balanced. +(In a scalar context just the first element of the array would be returned. In +a void context, C<$text> would be replaced by an empty string.) + +Likewise the call in: + + @result = extract_bracketed( $text, '{[' ); + +would return the same result, since all sets of both types of specified +delimiter brackets are correctly nested and balanced. + +However, the call in: + + @result = extract_bracketed( $text, '{([<' ); + +would fail, returning: + + ( undef , "{ an '[irregularly :-(] {} parenthesized >:-)' string }" ); + +because the embedded pairs of C<'(..)'>s and C<'[..]'>s are "cross-nested" and +the embedded C<'E'> is unbalanced. (In a scalar context, this call would +return an empty string. In a void context, C<$text> would be unchanged.) + +Note that the embedded single-quotes in the string don't help in this +case, since they have not been specified as acceptable delimiters and are +therefore treated as non-delimiter characters (and ignored). + +However, if a particular species of quote character is included in the +delimiter specification, then that type of quote will be correctly handled. +for example, if C<$text> is: + + $text = 'link'; + +then + + @result = extract_bracketed( $text, '<">' ); + +returns: + + ( '', 'link', "" ) + +as expected. Without the specification of C<"> as an embedded quoter: + + @result = extract_bracketed( $text, '<>' ); + +the result would be: + + ( 'link', "" ) + +In addition to the quote delimiters C<'>, C<">, and C<`>, full Perl quote-like +quoting (i.e. q{string}, qq{string}, etc) can be specified by including the +letter 'q' as a delimiter. Hence: + + @result = extract_bracketed( $text, '' ); + +would correctly match something like this: + + $text = ''; + +See also: C<"extract_quotelike"> and C<"extract_codeblock">. + + +=head2 C + +C extracts any valid Perl variable or +variable-involved expression, including scalars, arrays, hashes, array +accesses, hash look-ups, method calls through objects, subroutine calls +through subroutine references, etc. + +The subroutine takes up to two optional arguments: + +=over 4 + +=item 1. + +A string to be processed (C<$_> if the string is omitted or C) + +=item 2. + +A string specifying a pattern to be matched as a prefix (which is to be +skipped). If omitted, optional whitespace is skipped. + +=back + +On success in a list context, an array of 3 elements is returned. The +elements are: + +=over 4 + +=item [0] + +the extracted variable, or variablish expression + +=item [1] + +the remainder of the input text, + +=item [2] + +the prefix substring (if any), + +=back + +On failure, all of these values (except the remaining text) are C. + +In a scalar context, C returns just the complete +substring that matched a variablish expression. C is returned on +failure. In addition, the original input text has the returned substring +(and any prefix) removed from it. + +In a void context, the input text just has the matched substring (and +any specified prefix) removed. + + +=head2 C + +C extracts and segments text between (balanced) +specified tags. + +The subroutine takes up to five optional arguments: + +=over 4 + +=item 1. + +A string to be processed (C<$_> if the string is omitted or C) + +=item 2. + +A string specifying a pattern to be matched as the opening tag. +If the pattern string is omitted (or C) then a pattern +that matches any standard XML tag is used. + +=item 3. + +A string specifying a pattern to be matched at the closing tag. +If the pattern string is omitted (or C) then the closing +tag is constructed by inserting a C after any leading bracket +characters in the actual opening tag that was matched (I the pattern +that matched the tag). For example, if the opening tag pattern +is specified as C<'{{\w+}}'> and actually matched the opening tag +C<"{{DATA}}">, then the constructed closing tag would be C<"{{/DATA}}">. + +=item 4. + +A string specifying a pattern to be matched as a prefix (which is to be +skipped). If omitted, optional whitespace is skipped. + +=item 5. + +A hash reference containing various parsing options (see below) + +=back + +The various options that can be specified are: + +=over 4 + +=item C $listref> + +The list reference contains one or more strings specifying patterns +that must I appear within the tagged text. + +For example, to extract +an HTML link (which should not contain nested links) use: + + extract_tagged($text, '', '', undef, {reject => ['']} ); + +=item C $listref> + +The list reference contains one or more strings specifying patterns +that are I be be treated as nested tags within the tagged text +(even if they would match the start tag pattern). + +For example, to extract an arbitrary XML tag, but ignore "empty" elements: + + extract_tagged($text, undef, undef, undef, {ignore => ['<[^>]*/>']} ); + +(also see L<"gen_delimited_pat"> below). + + +=item C $str> + +The C option indicates the action to be taken if a matching end +tag is not encountered (i.e. before the end of the string or some +C pattern matches). By default, a failure to match a closing +tag causes C to immediately fail. + +However, if the string value associated with is "MAX", then +C returns the complete text up to the point of failure. +If the string is "PARA", C returns only the first paragraph +after the tag (up to the first line that is either empty or contains +only whitespace characters). +If the string is "", the the default behaviour (i.e. failure) is reinstated. + +For example, suppose the start tag "/para" introduces a paragraph, which then +continues until the next "/endpara" tag or until another "/para" tag is +encountered: + + $text = "/para line 1\n\nline 3\n/para line 4"; + + extract_tagged($text, '/para', '/endpara', undef, + {reject => '/para', fail => MAX ); + + # EXTRACTED: "/para line 1\n\nline 3\n" + +Suppose instead, that if no matching "/endpara" tag is found, the "/para" +tag refers only to the immediately following paragraph: + + $text = "/para line 1\n\nline 3\n/para line 4"; + + extract_tagged($text, '/para', '/endpara', undef, + {reject => '/para', fail => MAX ); + + # EXTRACTED: "/para line 1\n" + +Note that the specified C behaviour applies to nested tags as well. + +=back + +On success in a list context, an array of 6 elements is returned. The elements are: + +=over 4 + +=item [0] + +the extracted tagged substring (including the outermost tags), + +=item [1] + +the remainder of the input text, + +=item [2] + +the prefix substring (if any), + +=item [3] + +the opening tag + +=item [4] + +the text between the opening and closing tags + +=item [5] + +the closing tag (or "" if no closing tag was found) + +=back + +On failure, all of these values (except the remaining text) are C. + +In a scalar context, C returns just the complete +substring that matched a tagged text (including the start and end +tags). C is returned on failure. In addition, the original input +text has the returned substring (and any prefix) removed from it. + +In a void context, the input text just has the matched substring (and +any specified prefix) removed. + + +=head2 C + +(Note: This subroutine is only available under Perl5.005) + +C generates a new anonymous subroutine which +extracts text between (balanced) specified tags. In other words, +it generates a function identical in function to C. + +The difference between C and the anonymous +subroutines generated by +C, is that those generated subroutines: + +=over 4 + +=item * + +do not have to reparse tag specification or parsing options every time +they are called (whereas C has to effectively rebuild +its tag parser on every call); + +=item * + +make use of the new qr// construct to pre-compile the regexes they use +(whereas C uses standard string variable interpolation +to create tag-matching patterns). + +=back + +The subroutine takes up to four optional arguments (the same set as +C except for the string to be processed). It returns +a reference to a subroutine which in turn takes a single argument (the text to +be extracted from). + +In other words, the implementation of C is exactly +equivalent to: + + sub extract_tagged + { + my $text = shift; + $extractor = gen_extract_tagged(@_); + return $extractor->($text); + } + +(although C is not currently implemented that way, in order +to preserve pre-5.005 compatibility). + +Using C to create extraction functions for specific tags +is a good idea if those functions are going to be called more than once, since +their performance is typically twice as good as the more general-purpose +C. + + +=head2 C + +C attempts to recognize, extract, and segment any +one of the various Perl quotes and quotelike operators (see +L) Nested backslashed delimiters, embedded balanced bracket +delimiters (for the quotelike operators), and trailing modifiers are +all caught. For example, in: + + extract_quotelike 'q # an octothorpe: \# (not the end of the q!) #' + + extract_quotelike ' "You said, \"Use sed\"." ' + + extract_quotelike ' s{([A-Z]{1,8}\.[A-Z]{3})} /\L$1\E/; ' + + extract_quotelike ' tr/\\\/\\\\/\\\//ds; ' + +the full Perl quotelike operations are all extracted correctly. + +Note too that, when using the /x modifier on a regex, any comment +containing the current pattern delimiter will cause the regex to be +immediately terminated. In other words: + + 'm / + (?i) # CASE INSENSITIVE + [a-z_] # LEADING ALPHABETIC/UNDERSCORE + [a-z0-9]* # FOLLOWED BY ANY NUMBER OF ALPHANUMERICS + /x' + +will be extracted as if it were: + + 'm / + (?i) # CASE INSENSITIVE + [a-z_] # LEADING ALPHABETIC/' + +This behaviour is identical to that of the actual compiler. + +C takes two arguments: the text to be processed and +a prefix to be matched at the very beginning of the text. If no prefix +is specified, optional whitespace is the default. If no text is given, +C<$_> is used. + +In a list context, an array of 11 elements is returned. The elements are: + +=over 4 + +=item [0] + +the extracted quotelike substring (including trailing modifiers), + +=item [1] + +the remainder of the input text, + +=item [2] + +the prefix substring (if any), + +=item [3] + +the name of the quotelike operator (if any), + +=item [4] + +the left delimiter of the first block of the operation, + +=item [5] + +the text of the first block of the operation +(that is, the contents of +a quote, the regex of a match or substitution or the target list of a +translation), + +=item [6] + +the right delimiter of the first block of the operation, + +=item [7] + +the left delimiter of the second block of the operation +(that is, if it is a C, C, or C), + +=item [8] + +the text of the second block of the operation +(that is, the replacement of a substitution or the translation list +of a translation), + +=item [9] + +the right delimiter of the second block of the operation (if any), + +=item [10] + +the trailing modifiers on the operation (if any). + +=back + +For each of the fields marked "(if any)" the default value on success is +an empty string. +On failure, all of these values (except the remaining text) are C. + + +In a scalar context, C returns just the complete substring +that matched a quotelike operation (or C on failure). In a scalar or +void context, the input text has the same substring (and any specified +prefix) removed. + +Examples: + + # Remove the first quotelike literal that appears in text + + $quotelike = extract_quotelike($text,'.*?'); + + # Replace one or more leading whitespace-separated quotelike + # literals in $_ with "" + + do { $_ = join '', (extract_quotelike)[2,1] } until $@; + + + # Isolate the search pattern in a quotelike operation from $text + + ($op,$pat) = (extract_quotelike $text)[3,5]; + if ($op =~ /[ms]/) + { + print "search pattern: $pat\n"; + } + else + { + print "$op is not a pattern matching operation\n"; + } + + +=head2 C and "here documents" + +C can successfully extract "here documents" from an input +string, but with an important caveat in list contexts. + +Unlike other types of quote-like literals, a here document is rarely +a contiguous substring. For example, a typical piece of code using +here document might look like this: + + <<'EOMSG' || die; + This is the message. + EOMSG + exit; + +Given this as an input string in a scalar context, C +would correctly return the string "<<'EOMSG'\nThis is the message.\nEOMSG", +leaving the string " || die;\nexit;" in the original variable. In other words, +the two separate pieces of the here document are successfully extracted and +concatenated. + +In a list context, C would return the list + +=over 4 + +=item [0] + +"<<'EOMSG'\nThis is the message.\nEOMSG\n" (i.e. the full extracted here document, +including fore and aft delimiters), + +=item [1] + +" || die;\nexit;" (i.e. the remainder of the input text, concatenated), + +=item [2] + +"" (i.e. the prefix substring -- trivial in this case), + +=item [3] + +"<<" (i.e. the "name" of the quotelike operator) + +=item [4] + +"'EOMSG'" (i.e. the left delimiter of the here document, including any quotes), + +=item [5] + +"This is the message.\n" (i.e. the text of the here document), + +=item [6] + +"EOMSG" (i.e. the right delimiter of the here document), + +=item [7..10] + +"" (a here document has no second left delimiter, second text, second right +delimiter, or trailing modifiers). + +=back + +However, the matching position of the input variable would be set to +"exit;" (i.e. I the closing delimiter of the here document), +which would cause the earlier " || die;\nexit;" to be skipped in any +sequence of code fragment extractions. + +To avoid this problem, when it encounters a here document whilst +extracting from a modifiable string, C silently +rearranges the string to an equivalent piece of Perl: + + <<'EOMSG' + This is the message. + EOMSG + || die; + exit; + +in which the here document I contiguous. It still leaves the +matching position after the here document, but now the rest of the line +on which the here document starts is not skipped. + +To prevent from mucking about with the input in this way +(this is the only case where a list-context C does so), +you can pass the input variable as an interpolated literal: + + $quotelike = extract_quotelike("$var"); + + +=head2 C + +C attempts to recognize and extract a balanced +bracket delimited substring that may contain unbalanced brackets +inside Perl quotes or quotelike operations. That is, C +is like a combination of C<"extract_bracketed"> and +C<"extract_quotelike">. + +C takes the same initial three parameters as C: +a text to process, a set of delimiter brackets to look for, and a prefix to +match first. It also takes an optional fourth parameter, which allows the +outermost delimiter brackets to be specified separately (see below). + +Omitting the first argument (input text) means process C<$_> instead. +Omitting the second argument (delimiter brackets) indicates that only C<'{'> is to be used. +Omitting the third argument (prefix argument) implies optional whitespace at the start. +Omitting the fourth argument (outermost delimiter brackets) indicates that the +value of the second argument is to be used for the outermost delimiters. + +Once the prefix an dthe outermost opening delimiter bracket have been +recognized, code blocks are extracted by stepping through the input text and +trying the following alternatives in sequence: + +=over 4 + +=item 1. + +Try and match a closing delimiter bracket. If the bracket was the same +species as the last opening bracket, return the substring to that +point. If the bracket was mismatched, return an error. + +=item 2. + +Try to match a quote or quotelike operator. If found, call +C to eat it. If C fails, return +the error it returned. Otherwise go back to step 1. + +=item 3. + +Try to match an opening delimiter bracket. If found, call +C recursively to eat the embedded block. If the +recursive call fails, return an error. Otherwise, go back to step 1. + +=item 4. + +Unconditionally match a bareword or any other single character, and +then go back to step 1. + +=back + + +Examples: + + # Find a while loop in the text + + if ($text =~ s/.*?while\s*\{/{/) + { + $loop = "while " . extract_codeblock($text); + } + + # Remove the first round-bracketed list (which may include + # round- or curly-bracketed code blocks or quotelike operators) + + extract_codeblock $text, "(){}", '[^(]*'; + + +The ability to specify a different outermost delimiter bracket is useful +in some circumstances. For example, in the Parse::RecDescent module, +parser actions which are to be performed only on a successful parse +are specified using a Cdefer:...E> directive. For example: + + sentence: subject verb object + + +Parse::RecDescent uses CE')> to extract the code +within the Cdefer:...E> directive, but there's a problem. + +A deferred action like this: + + 10) {$count--}} > + +will be incorrectly parsed as: + + + +because the "less than" operator is interpreted as a closing delimiter. + +But, by extracting the directive using +SE')>> +the '>' character is only treated as a delimited at the outermost +level of the code block, so the directive is parsed correctly. + +=head2 C + +The C subroutine takes a string to be processed and a +list of extractors (subroutines or regular expressions) to apply to that string. + +In an array context C returns an array of substrings +of the original string, as extracted by the specified extractors. +In a scalar context, C returns the first +substring successfully extracted from the original string. In both +scalar and void contexts the original string has the first successfully +extracted substring removed from it. In all contexts +C starts at the current C of the string, and +sets that C appropriately after it matches. + +Hence, the aim of of a call to C in a list context +is to split the processed string into as many non-overlapping fields as +possible, by repeatedly applying each of the specified extractors +to the remainder of the string. Thus C is +a generalized form of Perl's C subroutine. + +The subroutine takes up to four optional arguments: + +=over 4 + +=item 1. + +A string to be processed (C<$_> if the string is omitted or C) + +=item 2. + +A reference to a list of subroutine references and/or qr// objects and/or +literal strings and/or hash references, specifying the extractors +to be used to split the string. If this argument is omitted (or +C) the list: + + [ + sub { extract_variable($_[0], '') }, + sub { extract_quotelike($_[0],'') }, + sub { extract_codeblock($_[0],'{}','') }, + ] + +is used. + + +=item 3. + +An number specifying the maximum number of fields to return. If this +argument is omitted (or C), split continues as long as possible. + +If the third argument is I, then extraction continues until I fields +have been successfully extracted, or until the string has been completely +processed. + +Note that in scalar and void contexts the value of this argument is +automatically reset to 1 (under C<-w>, a warning is issued if the argument +has to be reset). + +=item 4. + +A value indicating whether unmatched substrings (see below) within the +text should be skipped or returned as fields. If the value is true, +such substrings are skipped. Otherwise, they are returned. + +=back + +The extraction process works by applying each extractor in +sequence to the text string. + +If the extractor is a subroutine it is called in a list context and is +expected to return a list of a single element, namely the extracted +text. It may optionally also return two further arguments: a string +representing the text left after extraction (like $' for a pattern +match), and a string representing any prefix skipped before the +extraction (like $` in a pattern match). Note that this is designed +to facilitate the use of other Text::Balanced subroutines with +C. Note too that the value returned by an extractor +subroutine need not bear any relationship to the corresponding substring +of the original text (see examples below). + +If the extractor is a precompiled regular expression or a string, +it is matched against the text in a scalar context with a leading +'\G' and the gc modifiers enabled. The extracted value is either +$1 if that variable is defined after the match, or else the +complete match (i.e. $&). + +If the extractor is a hash reference, it must contain exactly one element. +The value of that element is one of the +above extractor types (subroutine reference, regular expression, or string). +The key of that element is the name of a class into which the successful +return value of the extractor will be blessed. + +If an extractor returns a defined value, that value is immediately +treated as the next extracted field and pushed onto the list of fields. +If the extractor was specified in a hash reference, the field is also +blessed into the appropriate class, + +If the extractor fails to match (in the case of a regex extractor), or returns an empty list or an undefined value (in the case of a subroutine extractor), it is +assumed to have failed to extract. +If none of the extractor subroutines succeeds, then one +character is extracted from the start of the text and the extraction +subroutines reapplied. Characters which are thus removed are accumulated and +eventually become the next field (unless the fourth argument is true, in which +case they are discarded). + +For example, the following extracts substrings that are valid Perl variables: + + @fields = extract_multiple($text, + [ sub { extract_variable($_[0]) } ], + undef, 1); + +This example separates a text into fields which are quote delimited, +curly bracketed, and anything else. The delimited and bracketed +parts are also blessed to identify them (the "anything else" is unblessed): + + @fields = extract_multiple($text, + [ + { Delim => sub { extract_delimited($_[0],q{'"}) } }, + { Brack => sub { extract_bracketed($_[0],'{}') } }, + ]); + +This call extracts the next single substring that is a valid Perl quotelike +operator (and removes it from $text): + + $quotelike = extract_multiple($text, + [ + sub { extract_quotelike($_[0]) }, + ], undef, 1); + +Finally, here is yet another way to do comma-separated value parsing: + + @fields = extract_multiple($csv_text, + [ + sub { extract_delimited($_[0],q{'"}) }, + qr/([^,]+)(.*)/, + ], + undef,1); + +The list in the second argument means: +I<"Try and extract a ' or " delimited string, otherwise extract anything up to a comma...">. +The undef third argument means: +I<"...as many times as possible...">, +and the true value in the fourth argument means +I<"...discarding anything else that appears (i.e. the commas)">. + +If you wanted the commas preserved as separate fields (i.e. like split +does if your split pattern has capturing parentheses), you would +just make the last parameter undefined (or remove it). + + +=head2 C + +The C subroutine takes a single (string) argument and + > builds a Friedl-style optimized regex that matches a string delimited +by any one of the characters in the single argument. For example: + + gen_delimited_pat(q{'"}) + +returns the regex: + + (?:\"(?:\\\"|(?!\").)*\"|\'(?:\\\'|(?!\').)*\') + +Note that the specified delimiters are automatically quotemeta'd. + +A typical use of C would be to build special purpose tags +for C. For example, to properly ignore "empty" XML elements +(which might contain quoted strings): + + my $empty_tag = '<(' . gen_delimited_pat(q{'"}) . '|.)+/>'; + + extract_tagged($text, undef, undef, undef, {ignore => [$empty_tag]} ); + + +C may also be called with an optional second argument, +which specifies the "escape" character(s) to be used for each delimiter. +For example to match a Pascal-style string (where ' is the delimiter +and '' is a literal ' within the string): + + gen_delimited_pat(q{'},q{'}); + +Different escape characters can be specified for different delimiters. +For example, to specify that '/' is the escape for single quotes +and '%' is the escape for double quotes: + + gen_delimited_pat(q{'"},q{/%}); + +If more delimiters than escape chars are specified, the last escape char +is used for the remaining delimiters. +If no escape char is specified for a given specified delimiter, '\' is used. + +=head2 C + +Note that C was previously called C. +That name may still be used, but is now deprecated. + + +=head1 DIAGNOSTICS + +In a list context, all the functions return C<(undef,$original_text)> +on failure. In a scalar context, failure is indicated by returning C +(in this case the input text is not modified in any way). + +In addition, on failure in I context, the C<$@> variable is set. +Accessing C<$@-E{error}> returns one of the error diagnostics listed +below. +Accessing C<$@-E{pos}> returns the offset into the original string at +which the error was detected (although not necessarily where it occurred!) +Printing C<$@> directly produces the error message, with the offset appended. +On success, the C<$@> variable is guaranteed to be C. + +The available diagnostics are: + +=over 4 + +=item C + +The delimiter provided to C was not one of +C<'()[]EE{}'>. + +=item C + +A non-optional prefix was specified but wasn't found at the start of the text. + +=item C + +C or C was expecting a +particular kind of bracket at the start of the text, and didn't find it. + +=item C + +C didn't find one of the quotelike operators C, +C, C, C, C, C or C at the start of the substring +it was extracting. + +=item C + +C, C or C encountered +a closing bracket where none was expected. + +=item C + +C, C or C ran +out of characters in the text before closing one or more levels of nested +brackets. + +=item C + +C attempted to match an embedded quoted substring, but +failed to find a closing quote to match it. + +=item C + +C was unable to find a closing delimiter to match the +one that opened the quote-like operation. + +=item C + +C, C or C found +a valid bracket delimiter, but it was the wrong species. This usually +indicates a nesting error, but may indicate incorrect quoting or escaping. + +=item C + +C or C found one of the +quotelike operators C, C, C, C, C, C or C +without a suitable block after it. + +=item C + +C was expecting one of '$', '@', or '%' at the start of +a variable, but didn't find any of them. + +=item C + +C found a '$', '@', or '%' indicating a variable, but that +character was not followed by a legal Perl identifier. + +=item C + +C failed to find any of the outermost opening brackets +that were specified. + +=item C + +A nested code block was found that started with a delimiter that was specified +as being only to be used as an outermost bracket. + +=item C + +C or C found one of the +quotelike operators C, C or C followed by only one block. + +=item C + +C failed to find a closing bracket to match the outermost +opening bracket. + +=item C + +C did not find a suitable opening tag (after any specified +prefix was removed). + +=item C + +C matched the specified opening tag and tried to +modify the matched text to produce a matching closing tag (because +none was specified). It failed to generate the closing tag, almost +certainly because the opening tag did not start with a +bracket of some kind. + +=item C + +C found a nested tag that appeared in the "reject" list +(and the failure mode was not "MAX" or "PARA"). + +=item C + +C found a nested opening tag that was not matched by a +corresponding nested closing tag (and the failure mode was not "MAX" or "PARA"). + +=item C + +C reached the end of the text without finding a closing tag +to match the original opening tag (and the failure mode was not +"MAX" or "PARA"). + + + + +=back + + +=head1 AUTHOR + +Damian Conway (damian@conway.org) + + +=head1 BUGS AND IRRITATIONS + +There are undoubtedly serious bugs lurking somewhere in this code, if +only because parts of it give the impression of understanding a great deal +more about Perl than they really do. + +Bug reports and other feedback are most welcome. + + +=head1 COPYRIGHT + + Copyright (c) 1997-2001, Damian Conway. All Rights Reserved. + This module is free software. It may be used, redistributed + and/or modified under the same terms as Perl itself.