1PERLREAPI(1) Perl Programmers Reference Guide PERLREAPI(1)
2
6 perlreapi - Perl regular expression plugin interface
7
9 As of Perl 5.9.5 there is a new interface for plugging and using
10 regular expression engines other than the default one.
11 Each engine is supposed to provide access to a constant structure of
13 the following format:
14 typedef struct regexp_engine {
16 REGEXP* (*comp) (pTHX_
17 const SV * const pattern, const U32 flags);
18 I32 (*exec) (pTHX_
19 REGEXP * const rx,
20 char* stringarg,
21 char* strend, char* strbeg,
22 SSize_t minend, SV* sv,
23 void* data, U32 flags);
24 char* (*intuit) (pTHX_
25 REGEXP * const rx, SV *sv,
26 const char * const strbeg,
27 char *strpos, char *strend, U32 flags,
28 struct re_scream_pos_data_s *data);
29 SV* (*checkstr) (pTHX_ REGEXP * const rx);
30 void (*free) (pTHX_ REGEXP * const rx);
31 void (*numbered_buff_FETCH) (pTHX_
32 REGEXP * const rx,
33 const I32 paren,
34 SV * const sv);
35 void (*numbered_buff_STORE) (pTHX_
36 REGEXP * const rx,
37 const I32 paren,
38 SV const * const value);
39 I32 (*numbered_buff_LENGTH) (pTHX_
40 REGEXP * const rx,
41 const SV * const sv,
42 const I32 paren);
43 SV* (*named_buff) (pTHX_
44 REGEXP * const rx,
45 SV * const key,
46 SV * const value,
47 U32 flags);
48 SV* (*named_buff_iter) (pTHX_
49 REGEXP * const rx,
50 const SV * const lastkey,
51 const U32 flags);
52 SV* (*qr_package)(pTHX_ REGEXP * const rx);
53 #ifdef USE_ITHREADS
54 void* (*dupe) (pTHX_ REGEXP * const rx, CLONE_PARAMS *param);
55 #endif
56 REGEXP* (*op_comp) (...);
57 When a regexp is compiled, its "engine" field is then set to point at
59 the appropriate structure, so that when it needs to be used Perl can
60 find the right routines to do so.
61 In order to install a new regexp handler, $^H{regcomp} is set to an
63 integer which (when casted appropriately) resolves to one of these
64 structures. When compiling, the "comp" method is executed, and the
65 resulting "regexp" structure's engine field is expected to point back
66 at the same structure.
67 The pTHX_ symbol in the definition is a macro used by Perl under
69 threading to provide an extra argument to the routine holding a pointer
70 back to the interpreter that is executing the regexp. So under
71 threading all routines get an extra argument.
72
74 comp
75 REGEXP* comp(pTHX_ const SV * const pattern, const U32 flags);
76 Compile the pattern stored in "pattern" using the given "flags" and
78 return a pointer to a prepared "REGEXP" structure that can perform the
79 match. See "The REGEXP structure" below for an explanation of the
80 individual fields in the REGEXP struct.
81 The "pattern" parameter is the scalar that was used as the pattern.
83 Previous versions of Perl would pass two "char*" indicating the start
84 and end of the stringified pattern; the following snippet can be used
85 to get the old parameters:
86 STRLEN plen;
88 char* exp = SvPV(pattern, plen);
89 char* xend = exp + plen;
90 Since any scalar can be passed as a pattern, it's possible to implement
92 an engine that does something with an array (""ook" =~ [ qw/ eek hlagh
93 / ]") or with the non-stringified form of a compiled regular expression
94 (""ook" =~ qr/eek/"). Perl's own engine will always stringify
95 everything using the snippet above, but that doesn't mean other engines
96 have to.
97 The "flags" parameter is a bitfield which indicates which of the
99 "msixpn" flags the regex was compiled with. It also contains
100 additional info, such as if "use locale" is in effect.
101 The "eogc" flags are stripped out before being passed to the comp
103 routine. The regex engine does not need to know if any of these are
104 set, as those flags should only affect what Perl does with the pattern
105 and its match variables, not how it gets compiled and executed.
106 By the time the comp callback is called, some of these flags have
108 already had effect (noted below where applicable). However most of
109 their effect occurs after the comp callback has run, in routines that
110 read the "rx->extflags" field which it populates.
111 In general the flags should be preserved in "rx->extflags" after
113 compilation, although the regex engine might want to add or delete some
114 of them to invoke or disable some special behavior in Perl. The flags
115 along with any special behavior they cause are documented below:
116 The pattern modifiers:
118 "/m" - RXf_PMf_MULTILINE
120 If this is in "rx->extflags" it will be passed to "Perl_fbm_instr"
121 by "pp_split" which will treat the subject string as a multi-line
122 string.
123 "/s" - RXf_PMf_SINGLELINE
125 "/i" - RXf_PMf_FOLD
126 "/x" - RXf_PMf_EXTENDED
127 If present on a regex, "#" comments will be handled differently by
128 the tokenizer in some cases.
129 TODO: Document those cases.
131 "/p" - RXf_PMf_KEEPCOPY
133 TODO: Document this
134 Character set
136 The character set rules are determined by an enum that is contained
137 in this field. This is still experimental and subject to change,
138 but the current interface returns the rules by use of the in-line
139 function "get_regex_charset(const U32 flags)". The only currently
140 documented value returned from it is REGEX_LOCALE_CHARSET, which is
141 set if "use locale" is in effect. If present in "rx->extflags",
142 "split" will use the locale dependent definition of whitespace when
143 RXf_SKIPWHITE or RXf_WHITE is in effect. ASCII whitespace is
144 defined as per isSPACE, and by the internal macros "is_utf8_space"
145 under UTF-8, and "isSPACE_LC" under "use locale".
146 Additional flags:
148 RXf_SPLIT
150 This flag was removed in perl 5.18.0. "split ' '" is now special-
151 cased solely in the parser. RXf_SPLIT is still #defined, so you
152 can test for it. This is how it used to work:
153 If "split" is invoked as "split ' '" or with no arguments (which
155 really means "split(' ', $_)", see split), Perl will set this flag.
156 The regex engine can then check for it and set the SKIPWHITE and
157 WHITE extflags. To do this, the Perl engine does:
158 if (flags & RXf_SPLIT && r->prelen == 1 && r->precomp[0] == ' ')
160 r->extflags |= (RXf_SKIPWHITE|RXf_WHITE);
161 These flags can be set during compilation to enable optimizations in
163 the "split" operator.
164 RXf_SKIPWHITE
166 This flag was removed in perl 5.18.0. It is still #defined, so you
167 can set it, but doing so will have no effect. This is how it used
168 to work:
169 If the flag is present in "rx->extflags" "split" will delete
171 whitespace from the start of the subject string before it's
172 operated on. What is considered whitespace depends on if the
173 subject is a UTF-8 string and if the "RXf_PMf_LOCALE" flag is set.
174 If RXf_WHITE is set in addition to this flag, "split" will behave
176 like "split " "" under the Perl engine.
177 RXf_START_ONLY
179 Tells the split operator to split the target string on newlines
180 ("\n") without invoking the regex engine.
181 Perl's engine sets this if the pattern is "/^/" ("plen == 1 && *exp
183 == '^'"), even under "/^/s"; see split. Of course a different
184 regex engine might want to use the same optimizations with a
185 different syntax.
186 RXf_WHITE
188 Tells the split operator to split the target string on whitespace
189 without invoking the regex engine. The definition of whitespace
190 varies depending on if the target string is a UTF-8 string and on
191 if RXf_PMf_LOCALE is set.
192 Perl's engine sets this flag if the pattern is "\s+".
194 RXf_NULL
196 Tells the split operator to split the target string on characters.
197 The definition of character varies depending on if the target
198 string is a UTF-8 string.
199 Perl's engine sets this flag on empty patterns, this optimization
201 makes "split //" much faster than it would otherwise be. It's even
202 faster than "unpack".
203 RXf_NO_INPLACE_SUBST
205 Added in perl 5.18.0, this flag indicates that a regular expression
206 might perform an operation that would interfere with inplace
207 substitution. For instance it might contain lookbehind, or assign
208 to non-magical variables (such as $REGMARK and $REGERROR) during
209 matching. "s///" will skip certain optimisations when this is set.
210 exec
212 I32 exec(pTHX_ REGEXP * const rx,
213 char *stringarg, char* strend, char* strbeg,
214 SSize_t minend, SV* sv,
215 void* data, U32 flags);
216 Execute a regexp. The arguments are
218 rx The regular expression to execute.
220 sv This is the SV to be matched against. Note that the actual char
222 array to be matched against is supplied by the arguments described
223 below; the SV is just used to determine UTF8ness, "pos()" etc.
224 strbeg
226 Pointer to the physical start of the string.
227 strend
229 Pointer to the character following the physical end of the string
230 (i.e. the "\0", if any).
231 stringarg
233 Pointer to the position in the string where matching should start;
234 it might not be equal to "strbeg" (for example in a later iteration
235 of "/.../g").
236 minend
238 Minimum length of string (measured in bytes from "stringarg") that
239 must match; if the engine reaches the end of the match but hasn't
240 reached this position in the string, it should fail.
241 data
243 Optimisation data; subject to change.
244 flags
246 Optimisation flags; subject to change.
247 intuit
249 char* intuit(pTHX_
250 REGEXP * const rx,
251 SV *sv,
252 const char * const strbeg,
253 char *strpos,
254 char *strend,
255 const U32 flags,
256 struct re_scream_pos_data_s *data);
257 Find the start position where a regex match should be attempted, or
259 possibly if the regex engine should not be run because the pattern
260 can't match. This is called, as appropriate, by the core, depending on
261 the values of the "extflags" member of the "regexp" structure.
262 Arguments:
264 rx: the regex to match against
266 sv: the SV being matched: only used for utf8 flag; the string
267 itself is accessed via the pointers below. Note that on
268 something like an overloaded SV, SvPOK(sv) may be false
269 and the string pointers may point to something unrelated to
270 the SV itself.
271 strbeg: real beginning of string
272 strpos: the point in the string at which to begin matching
273 strend: pointer to the byte following the last char of the string
274 flags currently unused; set to 0
275 data: currently unused; set to NULL
276 checkstr
278 SV* checkstr(pTHX_ REGEXP * const rx);
279 Return a SV containing a string that must appear in the pattern. Used
281 by "split" for optimising matches.
282 free
284 void free(pTHX_ REGEXP * const rx);
285 Called by Perl when it is freeing a regexp pattern so that the engine
287 can release any resources pointed to by the "pprivate" member of the
288 "regexp" structure. This is only responsible for freeing private data;
289 Perl will handle releasing anything else contained in the "regexp"
290 structure.
291 Numbered capture callbacks
293 Called to get/set the value of "$`", "$'", $& and their named
294 equivalents, ${^PREMATCH}, ${^POSTMATCH} and ${^MATCH}, as well as the
295 numbered capture groups ($1, $2, ...).
296 The "paren" parameter will be 1 for $1, 2 for $2 and so forth, and have
298 these symbolic values for the special variables:
299 ${^PREMATCH} RX_BUFF_IDX_CARET_PREMATCH
301 ${^POSTMATCH} RX_BUFF_IDX_CARET_POSTMATCH
302 ${^MATCH} RX_BUFF_IDX_CARET_FULLMATCH
303 $` RX_BUFF_IDX_PREMATCH
304 $' RX_BUFF_IDX_POSTMATCH
305 $& RX_BUFF_IDX_FULLMATCH
306 Note that in Perl 5.17.3 and earlier, the last three constants were
308 also used for the caret variants of the variables.
309 The names have been chosen by analogy with Tie::Scalar methods names
311 with an additional LENGTH callback for efficiency. However named
312 capture variables are currently not tied internally but implemented via
313 magic.
314 numbered_buff_FETCH
316 void numbered_buff_FETCH(pTHX_ REGEXP * const rx, const I32 paren,
318 SV * const sv);
319 Fetch a specified numbered capture. "sv" should be set to the scalar
321 to return, the scalar is passed as an argument rather than being
322 returned from the function because when it's called Perl already has a
323 scalar to store the value, creating another one would be redundant.
324 The scalar can be set with "sv_setsv", "sv_setpvn" and friends, see
325 perlapi.
326 This callback is where Perl untaints its own capture variables under
328 taint mode (see perlsec). See the "Perl_reg_numbered_buff_fetch"
329 function in regcomp.c for how to untaint capture variables if that's
330 something you'd like your engine to do as well.
331 numbered_buff_STORE
333 void (*numbered_buff_STORE) (pTHX_
335 REGEXP * const rx,
336 const I32 paren,
337 SV const * const value);
338 Set the value of a numbered capture variable. "value" is the scalar
340 that is to be used as the new value. It's up to the engine to make
341 sure this is used as the new value (or reject it).
342 Example:
344 if ("ook" =~ /(o*)/) {
346 # 'paren' will be '1' and 'value' will be 'ee'
347 $1 =~ tr/o/e/;
348 }
349 Perl's own engine will croak on any attempt to modify the capture
351 variables, to do this in another engine use the following callback
352 (copied from "Perl_reg_numbered_buff_store"):
353 void
355 Example_reg_numbered_buff_store(pTHX_
356 REGEXP * const rx,
357 const I32 paren,
358 SV const * const value)
359 {
360 PERL_UNUSED_ARG(rx);
361 PERL_UNUSED_ARG(paren);
362 PERL_UNUSED_ARG(value);
363 if (!PL_localizing)
365 Perl_croak(aTHX_ PL_no_modify);
366 }
367 Actually Perl will not always croak in a statement that looks like it
369 would modify a numbered capture variable. This is because the STORE
370 callback will not be called if Perl can determine that it doesn't have
371 to modify the value. This is exactly how tied variables behave in the
372 same situation:
373 package CaptureVar;
375 use parent 'Tie::Scalar';
376 sub TIESCALAR { bless [] }
378 sub FETCH { undef }
379 sub STORE { die "This doesn't get called" }
380 package main;
382 tie my $sv => "CaptureVar";
384 $sv =~ y/a/b/;
385 Because $sv is "undef" when the "y///" operator is applied to it, the
387 transliteration won't actually execute and the program won't "die".
388 This is different to how 5.8 and earlier versions behaved since the
389 capture variables were READONLY variables then; now they'll just die
390 when assigned to in the default engine.
391 numbered_buff_LENGTH
393 I32 numbered_buff_LENGTH (pTHX_
395 REGEXP * const rx,
396 const SV * const sv,
397 const I32 paren);
398 Get the "length" of a capture variable. There's a special callback for
400 this so that Perl doesn't have to do a FETCH and run "length" on the
401 result, since the length is (in Perl's case) known from an offset
402 stored in "rx->offs", this is much more efficient:
403 I32 s1 = rx->offs[paren].start;
405 I32 s2 = rx->offs[paren].end;
406 I32 len = t1 - s1;
407 This is a little bit more complex in the case of UTF-8, see what
409 "Perl_reg_numbered_buff_length" does with is_utf8_string_loclen.
410 Named capture callbacks
412 Called to get/set the value of "%+" and "%-", as well as by some
413 utility functions in re.
414 There are two callbacks, "named_buff" is called in all the cases the
416 FETCH, STORE, DELETE, CLEAR, EXISTS and SCALAR Tie::Hash callbacks
417 would be on changes to "%+" and "%-" and "named_buff_iter" in the same
418 cases as FIRSTKEY and NEXTKEY.
419 The "flags" parameter can be used to determine which of these
421 operations the callbacks should respond to. The following flags are
422 currently defined:
423 Which Tie::Hash operation is being performed from the Perl level on
425 "%+" or "%+", if any:
426 RXapif_FETCH
428 RXapif_STORE
429 RXapif_DELETE
430 RXapif_CLEAR
431 RXapif_EXISTS
432 RXapif_SCALAR
433 RXapif_FIRSTKEY
434 RXapif_NEXTKEY
435 If "%+" or "%-" is being operated on, if any.
437 RXapif_ONE /* %+ */
439 RXapif_ALL /* %- */
440 If this is being called as "re::regname", "re::regnames" or
442 "re::regnames_count", if any. The first two will be combined with
443 "RXapif_ONE" or "RXapif_ALL".
444 RXapif_REGNAME
446 RXapif_REGNAMES
447 RXapif_REGNAMES_COUNT
448 Internally "%+" and "%-" are implemented with a real tied interface via
450 Tie::Hash::NamedCapture. The methods in that package will call back
451 into these functions. However the usage of Tie::Hash::NamedCapture for
452 this purpose might change in future releases. For instance this might
453 be implemented by magic instead (would need an extension to mgvtbl).
454 named_buff
456 SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key,
458 SV * const value, U32 flags);
459 named_buff_iter
461 SV* (*named_buff_iter) (pTHX_
463 REGEXP * const rx,
464 const SV * const lastkey,
465 const U32 flags);
466 qr_package
468 SV* qr_package(pTHX_ REGEXP * const rx);
469 The package the qr// magic object is blessed into (as seen by "ref
471 qr//"). It is recommended that engines change this to their package
472 name for identification regardless of if they implement methods on the
473 object.
474 The package this method returns should also have the internal "Regexp"
476 package in its @ISA. "qr//->isa("Regexp")" should always be true
477 regardless of what engine is being used.
478 Example implementation might be:
480 SV*
482 Example_qr_package(pTHX_ REGEXP * const rx)
483 {
484 PERL_UNUSED_ARG(rx);
485 return newSVpvs("re::engine::Example");
486 }
487 Any method calls on an object created with "qr//" will be dispatched to
489 the package as a normal object.
490 use re::engine::Example;
492 my $re = qr//;
493 $re->meth; # dispatched to re::engine::Example::meth()
494 To retrieve the "REGEXP" object from the scalar in an XS function use
496 the "SvRX" macro, see "REGEXP Functions" in perlapi.
497 void meth(SV * rv)
499 PPCODE:
500 REGEXP * re = SvRX(sv);
501 dupe
503 void* dupe(pTHX_ REGEXP * const rx, CLONE_PARAMS *param);
504 On threaded builds a regexp may need to be duplicated so that the
506 pattern can be used by multiple threads. This routine is expected to
507 handle the duplication of any private data pointed to by the "pprivate"
508 member of the "regexp" structure. It will be called with the
509 preconstructed new "regexp" structure as an argument, the "pprivate"
510 member will point at the old private structure, and it is this
511 routine's responsibility to construct a copy and return a pointer to it
512 (which Perl will then use to overwrite the field as passed to this
513 routine.)
514 This allows the engine to dupe its private data but also if necessary
516 modify the final structure if it really must.
517 On unthreaded builds this field doesn't exist.
519 op_comp
521 This is private to the Perl core and subject to change. Should be left
522 null.
523
525 The REGEXP struct is defined in regexp.h. All regex engines must be
526 able to correctly build such a structure in their "comp" routine.
527 The REGEXP structure contains all the data that Perl needs to be aware
529 of to properly work with the regular expression. It includes data
530 about optimisations that Perl can use to determine if the regex engine
531 should really be used, and various other control info that is needed to
532 properly execute patterns in various contexts, such as if the pattern
533 anchored in some way, or what flags were used during the compile, or if
534 the program contains special constructs that Perl needs to be aware of.
535 In addition it contains two fields that are intended for the private
537 use of the regex engine that compiled the pattern. These are the
538 "intflags" and "pprivate" members. "pprivate" is a void pointer to an
539 arbitrary structure, whose use and management is the responsibility of
540 the compiling engine. Perl will never modify either of these values.
541 typedef struct regexp {
543 /* what engine created this regexp? */
544 const struct regexp_engine* engine;
545 /* what re is this a lightweight copy of? */
547 struct regexp* mother_re;
548 /* Information about the match that the Perl core uses to manage
550 * things */
551 U32 extflags; /* Flags used both externally and internally */
552 I32 minlen; /* mininum possible number of chars in */
553 string to match */
554 I32 minlenret; /* mininum possible number of chars in $& */
555 U32 gofs; /* chars left of pos that we search from */
556 /* substring data about strings that must appear
558 in the final match, used for optimisations */
559 struct reg_substr_data *substrs;
560 U32 nparens; /* number of capture groups */
562 /* private engine specific data */
564 U32 intflags; /* Engine Specific Internal flags */
565 void *pprivate; /* Data private to the regex engine which
566 created this object. */
567 /* Data about the last/current match. These are modified during
569 * matching*/
570 U32 lastparen; /* highest close paren matched ($+) */
571 U32 lastcloseparen; /* last close paren matched ($^N) */
572 regexp_paren_pair *offs; /* Array of offsets for (@-) and
573 (@+) */
574 char *subbeg; /* saved or original string so \digit works
576 forever. */
577 SV_SAVED_COPY /* If non-NULL, SV which is COW from original */
578 I32 sublen; /* Length of string pointed by subbeg */
579 I32 suboffset; /* byte offset of subbeg from logical start of
580 str */
581 I32 subcoffset; /* suboffset equiv, but in chars (for @-/@+) */
582 /* Information about the match that isn't often used */
584 I32 prelen; /* length of precomp */
585 const char *precomp; /* pre-compilation regular expression */
586 char *wrapped; /* wrapped version of the pattern */
588 I32 wraplen; /* length of wrapped */
589 I32 seen_evals; /* number of eval groups in the pattern - for
591 security checks */
592 HV *paren_names; /* Optional hash of paren names */
593 /* Refcount of this regexp */
595 I32 refcnt; /* Refcount of this regexp */
596 } regexp;
597 The fields are discussed in more detail below:
599 "engine"
601 This field points at a "regexp_engine" structure which contains
602 pointers to the subroutines that are to be used for performing a match.
603 It is the compiling routine's responsibility to populate this field
604 before returning the regexp object.
605 Internally this is set to "NULL" unless a custom engine is specified in
607 $^H{regcomp}, Perl's own set of callbacks can be accessed in the struct
608 pointed to by "RE_ENGINE_PTR".
609 "mother_re"
611 TODO, see commit 28d8d7f41a.
612 "extflags"
614 This will be used by Perl to see what flags the regexp was compiled
615 with, this will normally be set to the value of the flags parameter by
616 the comp callback. See the comp documentation for valid flags.
617 "minlen" "minlenret"
619 The minimum string length (in characters) required for the pattern to
620 match. This is used to prune the search space by not bothering to
621 match any closer to the end of a string than would allow a match. For
622 instance there is no point in even starting the regex engine if the
623 minlen is 10 but the string is only 5 characters long. There is no way
624 that the pattern can match.
625 "minlenret" is the minimum length (in characters) of the string that
627 would be found in $& after a match.
628 The difference between "minlen" and "minlenret" can be seen in the
630 following pattern:
631 /ns(?=\d)/
633 where the "minlen" would be 3 but "minlenret" would only be 2 as the \d
635 is required to match but is not actually included in the matched
636 content. This distinction is particularly important as the
637 substitution logic uses the "minlenret" to tell if it can do in-place
638 substitutions (these can result in considerable speed-up).
639 "gofs"
641 Left offset from pos() to start match at.
642 "substrs"
644 Substring data about strings that must appear in the final match. This
645 is currently only used internally by Perl's engine, but might be used
646 in the future for all engines for optimisations.
647 "nparens", "lastparen", and "lastcloseparen"
649 These fields are used to keep track of: how many paren capture groups
650 there are in the pattern; which was the highest paren to be closed (see
651 "$+" in perlvar); and which was the most recent paren to be closed (see
652 "$^N" in perlvar).
653 "intflags"
655 The engine's private copy of the flags the pattern was compiled with.
656 Usually this is the same as "extflags" unless the engine chose to
657 modify one of them.
658 "pprivate"
660 A void* pointing to an engine-defined data structure. The Perl engine
661 uses the "regexp_internal" structure (see "Base Structures" in
662 perlreguts) but a custom engine should use something else.
663 "offs"
665 A "regexp_paren_pair" structure which defines offsets into the string
666 being matched which correspond to the $& and $1, $2 etc. captures, the
667 "regexp_paren_pair" struct is defined as follows:
668 typedef struct regexp_paren_pair {
670 I32 start;
671 I32 end;
672 } regexp_paren_pair;
673 If "->offs[num].start" or "->offs[num].end" is "-1" then that capture
675 group did not match. "->offs[0].start/end" represents $& (or
676 "${^MATCH}" under "/p") and "->offs[paren].end" matches $$paren where
677 $paren = 1>.
678 "precomp" "prelen"
680 Used for optimisations. "precomp" holds a copy of the pattern that was
681 compiled and "prelen" its length. When a new pattern is to be compiled
682 (such as inside a loop) the internal "regcomp" operator checks if the
683 last compiled "REGEXP"'s "precomp" and "prelen" are equivalent to the
684 new one, and if so uses the old pattern instead of compiling a new one.
685 The relevant snippet from "Perl_pp_regcomp":
687 if (!re || !re->precomp || re->prelen != (I32)len ||
689 memNE(re->precomp, t, len))
690 /* Compile a new pattern */
691 "paren_names"
693 This is a hash used internally to track named capture groups and their
694 offsets. The keys are the names of the buffers the values are
695 dualvars, with the IV slot holding the number of buffers with the given
696 name and the pv being an embedded array of I32. The values may also be
697 contained independently in the data array in cases where named
698 backreferences are used.
699 "substrs"
701 Holds information on the longest string that must occur at a fixed
702 offset from the start of the pattern, and the longest string that must
703 occur at a floating offset from the start of the pattern. Used to do
704 Fast-Boyer-Moore searches on the string to find out if its worth using
705 the regex engine at all, and if so where in the string to search.
706 "subbeg" "sublen" "saved_copy" "suboffset" "subcoffset"
708 Used during the execution phase for managing search and replace
709 patterns, and for providing the text for $&, $1 etc. "subbeg" points to
710 a buffer (either the original string, or a copy in the case of
711 "RX_MATCH_COPIED(rx)"), and "sublen" is the length of the buffer. The
712 "RX_OFFS" start and end indices index into this buffer.
713 In the presence of the "REXEC_COPY_STR" flag, but with the addition of
715 the "REXEC_COPY_SKIP_PRE" or "REXEC_COPY_SKIP_POST" flags, an engine
716 can choose not to copy the full buffer (although it must still do so in
717 the presence of "RXf_PMf_KEEPCOPY" or the relevant bits being set in
718 "PL_sawampersand"). In this case, it may set "suboffset" to indicate
719 the number of bytes from the logical start of the buffer to the
720 physical start (i.e. "subbeg"). It should also set "subcoffset", the
721 number of characters in the offset. The latter is needed to support
722 "@-" and "@+" which work in characters, not bytes.
723 "wrapped" "wraplen"
725 Stores the string "qr//" stringifies to. The Perl engine for example
726 stores "(?^:eek)" in the case of "qr/eek/".
727 When using a custom engine that doesn't support the "(?:)" construct
729 for inline modifiers, it's probably best to have "qr//" stringify to
730 the supplied pattern, note that this will create undesired patterns in
731 cases such as:
732 my $x = qr/a|b/; # "a|b"
734 my $y = qr/c/i; # "c"
735 my $z = qr/$x$y/; # "a|bc"
736 There's no solution for this problem other than making the custom
738 engine understand a construct like "(?:)".
739 "seen_evals"
741 This stores the number of eval groups in the pattern. This is used for
742 security purposes when embedding compiled regexes into larger patterns
743 with "qr//".
744 "refcnt"
746 The number of times the structure is referenced. When this falls to 0,
747 the regexp is automatically freed by a call to "pregfree". This should
748 be set to 1 in each engine's "comp" routine.
749
751 Originally part of perlreguts.
752
754 Originally written by Yves Orton, expanded by AEvar Arnfjoerd`
755 Bjarmason.
756
758 Copyright 2006 Yves Orton and 2007 AEvar Arnfjoerd` Bjarmason.
759 This program is free software; you can redistribute it and/or modify it
761 under the same terms as Perl itself.
762perl v5.36.3 2023-11-30 PERLREAPI(1)