This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
handle bracket stack better in recdescent parsing
[perl5.git] / ext / re / re.pm
CommitLineData
b3eb6a9b
GS
1package re;
2
99cc5cc6 3# pragma for controlling the regexp engine
de8c5301
YO
4use strict;
5use warnings;
6
da4061d3 7our $VERSION = "0.13";
de8c5301 8our @ISA = qw(Exporter);
ec781434 9our @EXPORT_OK = ('regmust',
192c1e27
JH
10 qw(is_regexp regexp_pattern
11 regname regnames regnames_count));
de8c5301
YO
12our %EXPORT_OK = map { $_ => 1 } @EXPORT_OK;
13
de8c5301
YO
14my %bitmask = (
15 taint => 0x00100000, # HINT_RE_TAINT
16 eval => 0x00200000, # HINT_RE_EVAL
17);
18
de8c5301
YO
19sub setcolor {
20 eval { # Ignore errors
21 require Term::Cap;
22
23 my $terminal = Tgetent Term::Cap ({OSPEED => 9600}); # Avoid warning.
24 my $props = $ENV{PERL_RE_TC} || 'md,me,so,se,us,ue';
25 my @props = split /,/, $props;
26 my $colors = join "\t", map {$terminal->Tputs($_,1)} @props;
27
28 $colors =~ s/\0//g;
29 $ENV{PERL_RE_COLORS} = $colors;
30 };
31 if ($@) {
32 $ENV{PERL_RE_COLORS} ||= qq'\t\t> <\t> <\t\t';
33 }
34
35}
36
37my %flags = (
38 COMPILE => 0x0000FF,
39 PARSE => 0x000001,
40 OPTIMISE => 0x000002,
41 TRIEC => 0x000004,
42 DUMP => 0x000008,
f7819f85 43 FLAGS => 0x000010,
de8c5301
YO
44
45 EXECUTE => 0x00FF00,
46 INTUIT => 0x000100,
47 MATCH => 0x000200,
48 TRIEE => 0x000400,
49
50 EXTRA => 0xFF0000,
51 TRIEM => 0x010000,
52 OFFSETS => 0x020000,
53 OFFSETSDBG => 0x040000,
54 STATE => 0x080000,
55 OPTIMISEM => 0x100000,
56 STACK => 0x280000,
e7707071 57 BUFFERS => 0x400000,
2c296965 58 GPOS => 0x800000,
de8c5301 59);
e7707071 60$flags{ALL} = -1 & ~($flags{OFFSETS}|$flags{OFFSETSDBG}|$flags{BUFFERS});
de8c5301 61$flags{All} = $flags{all} = $flags{DUMP} | $flags{EXECUTE};
2c296965 62$flags{Extra} = $flags{EXECUTE} | $flags{COMPILE} | $flags{GPOS};
de8c5301
YO
63$flags{More} = $flags{MORE} = $flags{All} | $flags{TRIEC} | $flags{TRIEM} | $flags{STATE};
64$flags{State} = $flags{DUMP} | $flags{EXECUTE} | $flags{STATE};
65$flags{TRIE} = $flags{DUMP} | $flags{EXECUTE} | $flags{TRIEC};
66
ec781434
NC
67if (defined &DynaLoader::boot_DynaLoader) {
68 require XSLoader;
da4061d3 69 XSLoader::load();
de8c5301 70}
ec781434
NC
71# else we're miniperl
72# We need to work for miniperl, because the XS toolchain uses Text::Wrap, which
73# uses re 'taint'.
de8c5301
YO
74
75sub _load_unload {
76 my ($on)= @_;
77 if ($on) {
ec781434
NC
78 # We call install() every time, as if we didn't, we wouldn't
79 # "see" any changes to the color environment var since
80 # the last time it was called.
81
82 # install() returns an integer, which if casted properly
99cc5cc6 83 # in C resolves to a structure containing the regexp
ec781434
NC
84 # hooks. Setting it to a random integer will guarantee
85 # segfaults.
86 $^H{regcomp} = install();
de8c5301
YO
87 } else {
88 delete $^H{regcomp};
89 }
90}
91
92sub bits {
93 my $on = shift;
94 my $bits = 0;
95 unless (@_) {
96 require Carp;
97 Carp::carp("Useless use of \"re\" pragma");
98 }
99 foreach my $idx (0..$#_){
100 my $s=$_[$idx];
101 if ($s eq 'Debug' or $s eq 'Debugcolor') {
102 setcolor() if $s =~/color/i;
103 ${^RE_DEBUG_FLAGS} = 0 unless defined ${^RE_DEBUG_FLAGS};
104 for my $idx ($idx+1..$#_) {
105 if ($flags{$_[$idx]}) {
106 if ($on) {
107 ${^RE_DEBUG_FLAGS} |= $flags{$_[$idx]};
108 } else {
109 ${^RE_DEBUG_FLAGS} &= ~ $flags{$_[$idx]};
110 }
111 } else {
112 require Carp;
113 Carp::carp("Unknown \"re\" Debug flag '$_[$idx]', possible flags: ",
114 join(", ",sort keys %flags ) );
115 }
116 }
117 _load_unload($on ? 1 : ${^RE_DEBUG_FLAGS});
118 last;
119 } elsif ($s eq 'debug' or $s eq 'debugcolor') {
120 setcolor() if $s =~/color/i;
121 _load_unload($on);
66e6b4c5 122 last;
de8c5301
YO
123 } elsif (exists $bitmask{$s}) {
124 $bits |= $bitmask{$s};
125 } elsif ($EXPORT_OK{$s}) {
de8c5301
YO
126 require Exporter;
127 re->export_to_level(2, 're', $s);
128 } else {
129 require Carp;
130 Carp::carp("Unknown \"re\" subpragma '$s' (known ones are: ",
131 join(', ', map {qq('$_')} 'debug', 'debugcolor', sort keys %bitmask),
132 ")");
133 }
134 }
135 $bits;
136}
137
138sub import {
139 shift;
140 $^H |= bits(1, @_);
141}
142
143sub unimport {
144 shift;
145 $^H &= ~ bits(0, @_);
146}
147
1481;
149
150__END__
56953603 151
b3eb6a9b
GS
152=head1 NAME
153
154re - Perl pragma to alter regular expression behaviour
155
156=head1 SYNOPSIS
157
e4d48cc9
GS
158 use re 'taint';
159 ($x) = ($^X =~ /^(.*)$/s); # $x is tainted here
b3eb6a9b 160
2cd61cdb 161 $pat = '(?{ $foo = 1 })';
e4d48cc9 162 use re 'eval';
2cd61cdb 163 /foo${pat}bar/; # won't fail (when not under -T switch)
e4d48cc9
GS
164
165 {
166 no re 'taint'; # the default
167 ($x) = ($^X =~ /^(.*)$/s); # $x is not tainted here
168
169 no re 'eval'; # the default
2cd61cdb 170 /foo${pat}bar/; # disallowed (with or without -T switch)
e4d48cc9 171 }
b3eb6a9b 172
1e2e3d02
YO
173 use re 'debug'; # output debugging info during
174 /^(.*)$/s; # compile and run time
175
2cd61cdb 176
02ea72ae
IZ
177 use re 'debugcolor'; # same as 'debug', but with colored output
178 ...
179
a3621e74 180 use re qw(Debug All); # Finer tuned debugging options.
4ee9a43f 181 use re qw(Debug More);
fe759410 182 no re qw(Debug ALL); # Turn of all re debugging in this scope
4ee9a43f 183
de8c5301
YO
184 use re qw(is_regexp regexp_pattern); # import utility functions
185 my ($pat,$mods)=regexp_pattern(qr/foo/i);
186 if (is_regexp($obj)) {
187 print "Got regexp: ",
188 scalar regexp_pattern($obj); # just as perl would stringify it
189 } # but no hassle with blessed re's.
a3621e74 190
3ffabb8c
GS
191(We use $^X in these examples because it's tainted by default.)
192
b3eb6a9b
GS
193=head1 DESCRIPTION
194
de8c5301
YO
195=head2 'taint' mode
196
b3eb6a9b 197When C<use re 'taint'> is in effect, and a tainted string is the target
99cc5cc6
A
198of a regexp, the regexp memories (or values returned by the m// operator
199in list context) are tainted. This feature is useful when regexp operations
e4d48cc9
GS
200on tainted data aren't meant to extract safe substrings, but to perform
201other transformations.
b3eb6a9b 202
de8c5301
YO
203=head2 'eval' mode
204
99cc5cc6 205When C<use re 'eval'> is in effect, a regexp is allowed to contain
0b370c0a
A
206C<(?{ ... })> zero-width assertions and C<(??{ ... })> postponed
207subexpressions, even if the regular expression contains
ffbc6a93 208variable interpolation. That is normally disallowed, since it is a
2cd61cdb
IZ
209potential security risk. Note that this pragma is ignored when the regular
210expression is obtained from tainted data, i.e. evaluation is always
0b370c0a 211disallowed with tainted regular expressions. See L<perlre/(?{ code })>
bb1773de 212and L<perlre/(??{ code })>.
2cd61cdb 213
ffbc6a93 214For the purpose of this pragma, interpolation of precompiled regular
0a92e3a8
GS
215expressions (i.e., the result of C<qr//>) is I<not> considered variable
216interpolation. Thus:
2cd61cdb
IZ
217
218 /foo${pat}bar/
219
ffbc6a93 220I<is> allowed if $pat is a precompiled regular expression, even
0b370c0a 221if $pat contains C<(?{ ... })> assertions or C<(??{ ... })> subexpressions.
2cd61cdb 222
de8c5301
YO
223=head2 'debug' mode
224
ffbc6a93 225When C<use re 'debug'> is in effect, perl emits debugging messages when
2cd61cdb
IZ
226compiling and using regular expressions. The output is the same as that
227obtained by running a C<-DDEBUGGING>-enabled perl interpreter with the
228B<-Dr> switch. It may be quite voluminous depending on the complexity
02ea72ae
IZ
229of the match. Using C<debugcolor> instead of C<debug> enables a
230form of output that can be used to get a colorful display on terminals
231that understand termcap color sequences. Set C<$ENV{PERL_RE_TC}> to a
232comma-separated list of C<termcap> properties to use for highlighting
ffbc6a93 233strings on/off, pre-point part on/off.
2cd61cdb
IZ
234See L<perldebug/"Debugging regular expressions"> for additional info.
235
de8c5301
YO
236As of 5.9.5 the directive C<use re 'debug'> and its equivalents are
237lexically scoped, as the other directives are. However they have both
238compile-time and run-time effects.
239
240See L<perlmodlib/Pragmatic Modules>.
241
242=head2 'Debug' mode
243
a3621e74
YO
244Similarly C<use re 'Debug'> produces debugging output, the difference
245being that it allows the fine tuning of what debugging output will be
be8e71aa
YO
246emitted. Options are divided into three groups, those related to
247compilation, those related to execution and those related to special
248purposes. The options are as follows:
249
250=over 4
251
252=item Compile related options
253
254=over 4
255
256=item COMPILE
257
258Turns on all compile related debug options.
259
260=item PARSE
261
262Turns on debug output related to the process of parsing the pattern.
263
264=item OPTIMISE
265
266Enables output related to the optimisation phase of compilation.
267
24b23f37 268=item TRIEC
be8e71aa
YO
269
270Detailed info about trie compilation.
271
272=item DUMP
273
274Dump the final program out after it is compiled and optimised.
275
be8e71aa
YO
276=back
277
278=item Execute related options
279
280=over 4
281
282=item EXECUTE
283
284Turns on all execute related debug options.
285
286=item MATCH
287
288Turns on debugging of the main matching loop.
289
24b23f37 290=item TRIEE
be8e71aa
YO
291
292Extra debugging of how tries execute.
293
294=item INTUIT
295
296Enable debugging of start point optimisations.
297
298=back
299
300=item Extra debugging options
301
302=over 4
303
304=item EXTRA
305
306Turns on all "extra" debugging options.
307
e7707071
YO
308=item BUFFERS
309
c27a5cfe 310Enable debugging the capture group storage during match. Warning,
e7707071
YO
311this can potentially produce extremely large output.
312
24b23f37
YO
313=item TRIEM
314
315Enable enhanced TRIE debugging. Enhances both TRIEE
316and TRIEC.
317
318=item STATE
319
4ee9a43f 320Enable debugging of states in the engine.
24b23f37
YO
321
322=item STACK
be8e71aa 323
24b23f37
YO
324Enable debugging of the recursion stack in the engine. Enabling
325or disabling this option automatically does the same for debugging
326states as well. This output from this can be quite large.
327
328=item OPTIMISEM
329
330Enable enhanced optimisation debugging and start point optimisations.
99cc5cc6 331Probably not useful except when debugging the regexp engine itself.
24b23f37
YO
332
333=item OFFSETS
334
335Dump offset information. This can be used to see how regops correlate
336to the pattern. Output format is
337
338 NODENUM:POSITION[LENGTH]
339
340Where 1 is the position of the first char in the string. Note that position
341can be 0, or larger than the actual length of the pattern, likewise length
342can be zero.
be8e71aa 343
24b23f37 344=item OFFSETSDBG
be8e71aa
YO
345
346Enable debugging of offsets information. This emits copious
fe759410 347amounts of trace information and doesn't mesh well with other
be8e71aa
YO
348debug options.
349
fe759410 350Almost definitely only useful to people hacking
be8e71aa
YO
351on the offsets part of the debug engine.
352
353=back
354
355=item Other useful flags
356
357These are useful shortcuts to save on the typing.
358
359=over 4
360
361=item ALL
362
e7707071 363Enable all options at once except OFFSETS, OFFSETSDBG and BUFFERS
be8e71aa
YO
364
365=item All
366
fe759410 367Enable DUMP and all execute options. Equivalent to:
be8e71aa
YO
368
369 use re 'debug';
370
371=item MORE
372
373=item More
374
24b23f37 375Enable TRIEM and all execute compile and execute options.
be8e71aa 376
dba3f186 377=back
be8e71aa 378
dba3f186 379=back
a3621e74 380
1e2e3d02 381As of 5.9.5 the directive C<use re 'debug'> and its equivalents are
4ee9a43f 382lexically scoped, as the other directives are. However they have both
1e2e3d02 383compile-time and run-time effects.
b3eb6a9b 384
de8c5301 385=head2 Exportable Functions
b3eb6a9b 386
de8c5301 387As of perl 5.9.5 're' debug contains a number of utility functions that
4ee9a43f 388may be optionally exported into the caller's namespace. They are listed
de8c5301 389below.
b3eb6a9b 390
de8c5301 391=over 4
b3eb6a9b 392
de8c5301 393=item is_regexp($ref)
02ea72ae 394
de8c5301 395Returns true if the argument is a compiled regular expression as returned
4ee9a43f 396by C<qr//>, false if it is not.
02ea72ae 397
4ee9a43f
RGS
398This function will not be confused by overloading or blessing. In
399internals terms, this extracts the regexp pointer out of the
de8c5301 400PERL_MAGIC_qr structure so it it cannot be fooled.
894be9b7 401
de8c5301 402=item regexp_pattern($ref)
02ea72ae 403
4ee9a43f
RGS
404If the argument is a compiled regular expression as returned by C<qr//>,
405then this function returns the pattern.
be8e71aa 406
4ee9a43f
RGS
407In list context it returns a two element list, the first element
408containing the pattern and the second containing the modifiers used when
409the pattern was compiled.
be8e71aa 410
4ee9a43f 411 my ($pat, $mods) = regexp_pattern($ref);
a3621e74 412
99cc5cc6 413In scalar context it returns the same as perl would when stringifying a raw
4ee9a43f
RGS
414C<qr//> with the same pattern inside. If the argument is not a compiled
415reference then this routine returns false but defined in scalar context,
416and the empty list in list context. Thus the following
f9f4320a 417
dff5e0c4 418 if (regexp_pattern($ref) eq '(?^i:foo)')
dba3f186 419
de8c5301 420will be warning free regardless of what $ref actually is.
380e0b81 421
4ee9a43f
RGS
422Like C<is_regexp> this function will not be confused by overloading
423or blessing of the object.
b3eb6a9b 424
256ddcd0
YO
425=item regmust($ref)
426
432acd5f 427If the argument is a compiled regular expression as returned by C<qr//>,
99cc5cc6 428then this function returns what the optimiser considers to be the longest
432acd5f
RGS
429anchored fixed string and longest floating fixed string in the pattern.
430
431A I<fixed string> is defined as being a substring that must appear for the
432pattern to match. An I<anchored fixed string> is a fixed string that must
433appear at a particular offset from the beginning of the match. A I<floating
434fixed string> is defined as a fixed string that can appear at any point in
435a range of positions relative to the start of the match. For example,
436
437 my $qr = qr/here .* there/x;
438 my ($anchored, $floating) = regmust($qr);
256ddcd0 439 print "anchored:'$anchored'\nfloating:'$floating'\n";
432acd5f 440
256ddcd0
YO
441results in
442
443 anchored:'here'
444 floating:'there'
445
432acd5f
RGS
446Because the C<here> is before the C<.*> in the pattern, its position
447can be determined exactly. That's not true, however, for the C<there>;
448it could appear at any point after where the anchored string appeared.
256ddcd0
YO
449Perl uses both for its optimisations, prefering the longer, or, if they are
450equal, the floating.
451
452B<NOTE:> This may not necessarily be the definitive longest anchored and
432acd5f 453floating string. This will be what the optimiser of the Perl that you
256ddcd0
YO
454are using thinks is the longest. If you believe that the result is wrong
455please report it via the L<perlbug> utility.
456
28d8d7f4 457=item regname($name,$all)
44a2ac75 458
28d8d7f4
YO
459Returns the contents of a named buffer of the last successful match. If
460$all is true, then returns an array ref containing one entry per buffer,
44a2ac75
YO
461otherwise returns the first defined buffer.
462
28d8d7f4 463=item regnames($all)
44a2ac75 464
28d8d7f4
YO
465Returns a list of all of the named buffers defined in the last successful
466match. If $all is true, then it returns all names defined, if not it returns
467only names which were involved in the match.
44a2ac75 468
28d8d7f4 469=item regnames_count()
44a2ac75 470
28d8d7f4
YO
471Returns the number of distinct names defined in the pattern used
472for the last successful match.
44a2ac75 473
28d8d7f4
YO
474B<Note:> this result is always the actual number of distinct
475named buffers defined, it may not actually match that which is
476returned by C<regnames()> and related routines when those routines
477have not been called with the $all parameter set.
44a2ac75 478
de8c5301 479=back
b3eb6a9b 480
de8c5301 481=head1 SEE ALSO
b3eb6a9b 482
de8c5301
YO
483L<perlmodlib/Pragmatic Modules>.
484
485=cut