| 1 | =head1 NAME |
| 2 | |
| 3 | perlreapi - perl regular expression plugin interface |
| 4 | |
| 5 | =head1 DESCRIPTION |
| 6 | |
| 7 | As of Perl 5.9.5 there is a new interface for plugging and using other |
| 8 | regular expression engines than the default one. |
| 9 | |
| 10 | Each engine is supposed to provide access to a constant structure of the |
| 11 | following format: |
| 12 | |
| 13 | typedef struct regexp_engine { |
| 14 | REGEXP* (*comp) (pTHX_ const SV * const pattern, const U32 flags); |
| 15 | I32 (*exec) (pTHX_ REGEXP * const rx, char* stringarg, char* strend, |
| 16 | char* strbeg, I32 minend, SV* screamer, |
| 17 | void* data, U32 flags); |
| 18 | char* (*intuit) (pTHX_ REGEXP * const rx, SV *sv, char *strpos, |
| 19 | char *strend, U32 flags, |
| 20 | struct re_scream_pos_data_s *data); |
| 21 | SV* (*checkstr) (pTHX_ REGEXP * const rx); |
| 22 | void (*free) (pTHX_ REGEXP * const rx); |
| 23 | void (*numbered_buff_FETCH) (pTHX_ REGEXP * const rx, const I32 paren, |
| 24 | SV * const sv); |
| 25 | void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren, |
| 26 | SV const * const value); |
| 27 | I32 (*numbered_buff_LENGTH) (pTHX_ REGEXP * const rx, const SV * const sv, |
| 28 | const I32 paren); |
| 29 | SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key, |
| 30 | SV * const value, U32 flags); |
| 31 | SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey, |
| 32 | const U32 flags); |
| 33 | SV* (*qr_package)(pTHX_ REGEXP * const rx); |
| 34 | #ifdef USE_ITHREADS |
| 35 | void* (*dupe) (pTHX_ REGEXP * const rx, CLONE_PARAMS *param); |
| 36 | #endif |
| 37 | |
| 38 | When a regexp is compiled, its C<engine> field is then set to point at |
| 39 | the appropriate structure, so that when it needs to be used Perl can find |
| 40 | the right routines to do so. |
| 41 | |
| 42 | In order to install a new regexp handler, C<$^H{regcomp}> is set |
| 43 | to an integer which (when casted appropriately) resolves to one of these |
| 44 | structures. When compiling, the C<comp> method is executed, and the |
| 45 | resulting regexp structure's engine field is expected to point back at |
| 46 | the same structure. |
| 47 | |
| 48 | The pTHX_ symbol in the definition is a macro used by perl under threading |
| 49 | to provide an extra argument to the routine holding a pointer back to |
| 50 | the interpreter that is executing the regexp. So under threading all |
| 51 | routines get an extra argument. |
| 52 | |
| 53 | =head1 Callbacks |
| 54 | |
| 55 | =head2 comp |
| 56 | |
| 57 | REGEXP* comp(pTHX_ const SV * const pattern, const U32 flags); |
| 58 | |
| 59 | Compile the pattern stored in C<pattern> using the given C<flags> and |
| 60 | return a pointer to a prepared C<REGEXP> structure that can perform |
| 61 | the match. See L</The REGEXP structure> below for an explanation of |
| 62 | the individual fields in the REGEXP struct. |
| 63 | |
| 64 | The C<pattern> parameter is the scalar that was used as the |
| 65 | pattern. previous versions of perl would pass two C<char*> indicating |
| 66 | the start and end of the stringified pattern, the following snippet can |
| 67 | be used to get the old parameters: |
| 68 | |
| 69 | STRLEN plen; |
| 70 | char* exp = SvPV(pattern, plen); |
| 71 | char* xend = exp + plen; |
| 72 | |
| 73 | Since any scalar can be passed as a pattern it's possible to implement |
| 74 | an engine that does something with an array (C<< "ook" =~ [ qw/ eek |
| 75 | hlagh / ] >>) or with the non-stringified form of a compiled regular |
| 76 | expression (C<< "ook" =~ qr/eek/ >>). perl's own engine will always |
| 77 | stringify everything using the snippet above but that doesn't mean |
| 78 | other engines have to. |
| 79 | |
| 80 | The C<flags> parameter is a bitfield which indicates which of the |
| 81 | C<msixp> flags the regex was compiled with. It also contains |
| 82 | additional info such as whether C<use locale> is in effect. |
| 83 | |
| 84 | The C<eogc> flags are stripped out before being passed to the comp |
| 85 | routine. The regex engine does not need to know whether any of these |
| 86 | are set as those flags should only affect what perl does with the |
| 87 | pattern and its match variables, not how it gets compiled and |
| 88 | executed. |
| 89 | |
| 90 | By the time the comp callback is called, some of these flags have |
| 91 | already had effect (noted below where applicable). However most of |
| 92 | their effect occurs after the comp callback has run in routines that |
| 93 | read the C<< rx->extflags >> field which it populates. |
| 94 | |
| 95 | In general the flags should be preserved in C<< rx->extflags >> after |
| 96 | compilation, although the regex engine might want to add or delete |
| 97 | some of them to invoke or disable some special behavior in perl. The |
| 98 | flags along with any special behavior they cause are documented below: |
| 99 | |
| 100 | The pattern modifiers: |
| 101 | |
| 102 | =over 4 |
| 103 | |
| 104 | =item C</m> - RXf_PMf_MULTILINE |
| 105 | |
| 106 | If this is in C<< rx->extflags >> it will be passed to |
| 107 | C<Perl_fbm_instr> by C<pp_split> which will treat the subject string |
| 108 | as a multi-line string. |
| 109 | |
| 110 | =item C</s> - RXf_PMf_SINGLELINE |
| 111 | |
| 112 | =item C</i> - RXf_PMf_FOLD |
| 113 | |
| 114 | =item C</x> - RXf_PMf_EXTENDED |
| 115 | |
| 116 | If present on a regex C<#> comments will be handled differently by the |
| 117 | tokenizer in some cases. |
| 118 | |
| 119 | TODO: Document those cases. |
| 120 | |
| 121 | =item C</p> - RXf_PMf_KEEPCOPY |
| 122 | |
| 123 | TODO: Document this |
| 124 | |
| 125 | =item Character set |
| 126 | |
| 127 | The character set semantics are determined by an enum that is contained |
| 128 | in this field. This is still experimental and subject to change, but |
| 129 | the current interface returns the rules by use of the in-line function |
| 130 | C<get_regex_charset(const U32 flags)>. The only currently documented |
| 131 | value returned from it is REGEX_LOCALE_CHARSET, which is set if |
| 132 | C<use locale> is in effect. If present in C<< rx->extflags >>, |
| 133 | C<split> will use the locale dependent definition of whitespace |
| 134 | when RXf_SKIPWHITE or RXf_WHITE is in effect. ASCII whitespace |
| 135 | is defined as per L<isSPACE|perlapi/isSPACE>, and by the internal |
| 136 | macros C<is_utf8_space> under UTF-8, and C<isSPACE_LC> under C<use |
| 137 | locale>. |
| 138 | |
| 139 | =back |
| 140 | |
| 141 | Additional flags: |
| 142 | |
| 143 | =over 4 |
| 144 | |
| 145 | =item RXf_UTF8 |
| 146 | |
| 147 | Set if the pattern is L<SvUTF8()|perlapi/SvUTF8>, set by Perl_pmruntime. |
| 148 | |
| 149 | A regex engine may want to set or disable this flag during |
| 150 | compilation. The perl engine for instance may upgrade non-UTF-8 |
| 151 | strings to UTF-8 if the pattern includes constructs such as C<\x{...}> |
| 152 | that can only match Unicode values. |
| 153 | |
| 154 | =item RXf_SPLIT |
| 155 | |
| 156 | If C<split> is invoked as C<split ' '> or with no arguments (which |
| 157 | really means C<split(' ', $_)>, see L<split|perlfunc/split>), perl will |
| 158 | set this flag. The regex engine can then check for it and set the |
| 159 | SKIPWHITE and WHITE extflags. To do this the perl engine does: |
| 160 | |
| 161 | if (flags & RXf_SPLIT && r->prelen == 1 && r->precomp[0] == ' ') |
| 162 | r->extflags |= (RXf_SKIPWHITE|RXf_WHITE); |
| 163 | |
| 164 | =back |
| 165 | |
| 166 | These flags can be set during compilation to enable optimizations in |
| 167 | the C<split> operator. |
| 168 | |
| 169 | =over 4 |
| 170 | |
| 171 | =item RXf_SKIPWHITE |
| 172 | |
| 173 | If the flag is present in C<< rx->extflags >> C<split> will delete |
| 174 | whitespace from the start of the subject string before it's operated |
| 175 | on. What is considered whitespace depends on whether the subject is a |
| 176 | UTF-8 string and whether the C<RXf_PMf_LOCALE> flag is set. |
| 177 | |
| 178 | If RXf_WHITE is set in addition to this flag C<split> will behave like |
| 179 | C<split " "> under the perl engine. |
| 180 | |
| 181 | =item RXf_START_ONLY |
| 182 | |
| 183 | Tells the split operator to split the target string on newlines |
| 184 | (C<\n>) without invoking the regex engine. |
| 185 | |
| 186 | Perl's engine sets this if the pattern is C</^/> (C<plen == 1 && *exp |
| 187 | == '^'>), even under C</^/s>, see L<split|perlfunc>. Of course a |
| 188 | different regex engine might want to use the same optimizations |
| 189 | with a different syntax. |
| 190 | |
| 191 | =item RXf_WHITE |
| 192 | |
| 193 | Tells the split operator to split the target string on whitespace |
| 194 | without invoking the regex engine. The definition of whitespace varies |
| 195 | depending on whether the target string is a UTF-8 string and on |
| 196 | whether RXf_PMf_LOCALE is set. |
| 197 | |
| 198 | Perl's engine sets this flag if the pattern is C<\s+>. |
| 199 | |
| 200 | =item RXf_NULL |
| 201 | |
| 202 | Tells the split operator to split the target string on |
| 203 | characters. The definition of character varies depending on whether |
| 204 | the target string is a UTF-8 string. |
| 205 | |
| 206 | Perl's engine sets this flag on empty patterns, this optimization |
| 207 | makes C<split //> much faster than it would otherwise be. It's even |
| 208 | faster than C<unpack>. |
| 209 | |
| 210 | =back |
| 211 | |
| 212 | =head2 exec |
| 213 | |
| 214 | I32 exec(pTHX_ REGEXP * const rx, |
| 215 | char *stringarg, char* strend, char* strbeg, |
| 216 | I32 minend, SV* screamer, |
| 217 | void* data, U32 flags); |
| 218 | |
| 219 | Execute a regexp. |
| 220 | |
| 221 | =head2 intuit |
| 222 | |
| 223 | char* intuit(pTHX_ REGEXP * const rx, |
| 224 | SV *sv, char *strpos, char *strend, |
| 225 | const U32 flags, struct re_scream_pos_data_s *data); |
| 226 | |
| 227 | Find the start position where a regex match should be attempted, |
| 228 | or possibly whether the regex engine should not be run because the |
| 229 | pattern can't match. This is called as appropriate by the core |
| 230 | depending on the values of the extflags member of the regexp |
| 231 | structure. |
| 232 | |
| 233 | =head2 checkstr |
| 234 | |
| 235 | SV* checkstr(pTHX_ REGEXP * const rx); |
| 236 | |
| 237 | Return a SV containing a string that must appear in the pattern. Used |
| 238 | by C<split> for optimising matches. |
| 239 | |
| 240 | =head2 free |
| 241 | |
| 242 | void free(pTHX_ REGEXP * const rx); |
| 243 | |
| 244 | Called by perl when it is freeing a regexp pattern so that the engine |
| 245 | can release any resources pointed to by the C<pprivate> member of the |
| 246 | regexp structure. This is only responsible for freeing private data; |
| 247 | perl will handle releasing anything else contained in the regexp structure. |
| 248 | |
| 249 | =head2 Numbered capture callbacks |
| 250 | |
| 251 | Called to get/set the value of C<$`>, C<$'>, C<$&> and their named |
| 252 | equivalents, ${^PREMATCH}, ${^POSTMATCH} and $^{MATCH}, as well as the |
| 253 | numbered capture groups (C<$1>, C<$2>, ...). |
| 254 | |
| 255 | The C<paren> parameter will be C<-2> for C<$`>, C<-1> for C<$'>, C<0> |
| 256 | for C<$&>, C<1> for C<$1> and so forth. |
| 257 | |
| 258 | The names have been chosen by analogy with L<Tie::Scalar> methods |
| 259 | names with an additional B<LENGTH> callback for efficiency. However |
| 260 | named capture variables are currently not tied internally but |
| 261 | implemented via magic. |
| 262 | |
| 263 | =head3 numbered_buff_FETCH |
| 264 | |
| 265 | void numbered_buff_FETCH(pTHX_ REGEXP * const rx, const I32 paren, |
| 266 | SV * const sv); |
| 267 | |
| 268 | Fetch a specified numbered capture. C<sv> should be set to the scalar |
| 269 | to return, the scalar is passed as an argument rather than being |
| 270 | returned from the function because when it's called perl already has a |
| 271 | scalar to store the value, creating another one would be |
| 272 | redundant. The scalar can be set with C<sv_setsv>, C<sv_setpvn> and |
| 273 | friends, see L<perlapi>. |
| 274 | |
| 275 | This callback is where perl untaints its own capture variables under |
| 276 | taint mode (see L<perlsec>). See the C<Perl_reg_numbered_buff_fetch> |
| 277 | function in F<regcomp.c> for how to untaint capture variables if |
| 278 | that's something you'd like your engine to do as well. |
| 279 | |
| 280 | =head3 numbered_buff_STORE |
| 281 | |
| 282 | void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren, |
| 283 | SV const * const value); |
| 284 | |
| 285 | Set the value of a numbered capture variable. C<value> is the scalar |
| 286 | that is to be used as the new value. It's up to the engine to make |
| 287 | sure this is used as the new value (or reject it). |
| 288 | |
| 289 | Example: |
| 290 | |
| 291 | if ("ook" =~ /(o*)/) { |
| 292 | # 'paren' will be '1' and 'value' will be 'ee' |
| 293 | $1 =~ tr/o/e/; |
| 294 | } |
| 295 | |
| 296 | Perl's own engine will croak on any attempt to modify the capture |
| 297 | variables, to do this in another engine use the following callback |
| 298 | (copied from C<Perl_reg_numbered_buff_store>): |
| 299 | |
| 300 | void |
| 301 | Example_reg_numbered_buff_store(pTHX_ REGEXP * const rx, const I32 paren, |
| 302 | SV const * const value) |
| 303 | { |
| 304 | PERL_UNUSED_ARG(rx); |
| 305 | PERL_UNUSED_ARG(paren); |
| 306 | PERL_UNUSED_ARG(value); |
| 307 | |
| 308 | if (!PL_localizing) |
| 309 | Perl_croak(aTHX_ PL_no_modify); |
| 310 | } |
| 311 | |
| 312 | Actually perl will not I<always> croak in a statement that looks |
| 313 | like it would modify a numbered capture variable. This is because the |
| 314 | STORE callback will not be called if perl can determine that it |
| 315 | doesn't have to modify the value. This is exactly how tied variables |
| 316 | behave in the same situation: |
| 317 | |
| 318 | package CaptureVar; |
| 319 | use base 'Tie::Scalar'; |
| 320 | |
| 321 | sub TIESCALAR { bless [] } |
| 322 | sub FETCH { undef } |
| 323 | sub STORE { die "This doesn't get called" } |
| 324 | |
| 325 | package main; |
| 326 | |
| 327 | tie my $sv => "CaptureVar"; |
| 328 | $sv =~ y/a/b/; |
| 329 | |
| 330 | Because C<$sv> is C<undef> when the C<y///> operator is applied to it |
| 331 | the transliteration won't actually execute and the program won't |
| 332 | C<die>. This is different to how 5.8 and earlier versions behaved |
| 333 | since the capture variables were READONLY variables then, now they'll |
| 334 | just die when assigned to in the default engine. |
| 335 | |
| 336 | =head3 numbered_buff_LENGTH |
| 337 | |
| 338 | I32 numbered_buff_LENGTH (pTHX_ REGEXP * const rx, const SV * const sv, |
| 339 | const I32 paren); |
| 340 | |
| 341 | Get the C<length> of a capture variable. There's a special callback |
| 342 | for this so that perl doesn't have to do a FETCH and run C<length> on |
| 343 | the result, since the length is (in perl's case) known from an offset |
| 344 | stored in C<< rx->offs >> this is much more efficient: |
| 345 | |
| 346 | I32 s1 = rx->offs[paren].start; |
| 347 | I32 s2 = rx->offs[paren].end; |
| 348 | I32 len = t1 - s1; |
| 349 | |
| 350 | This is a little bit more complex in the case of UTF-8, see what |
| 351 | C<Perl_reg_numbered_buff_length> does with |
| 352 | L<is_utf8_string_loclen|perlapi/is_utf8_string_loclen>. |
| 353 | |
| 354 | =head2 Named capture callbacks |
| 355 | |
| 356 | Called to get/set the value of C<%+> and C<%-> as well as by some |
| 357 | utility functions in L<re>. |
| 358 | |
| 359 | There are two callbacks, C<named_buff> is called in all the cases the |
| 360 | FETCH, STORE, DELETE, CLEAR, EXISTS and SCALAR L<Tie::Hash> callbacks |
| 361 | would be on changes to C<%+> and C<%-> and C<named_buff_iter> in the |
| 362 | same cases as FIRSTKEY and NEXTKEY. |
| 363 | |
| 364 | The C<flags> parameter can be used to determine which of these |
| 365 | operations the callbacks should respond to, the following flags are |
| 366 | currently defined: |
| 367 | |
| 368 | Which L<Tie::Hash> operation is being performed from the Perl level on |
| 369 | C<%+> or C<%+>, if any: |
| 370 | |
| 371 | RXapif_FETCH |
| 372 | RXapif_STORE |
| 373 | RXapif_DELETE |
| 374 | RXapif_CLEAR |
| 375 | RXapif_EXISTS |
| 376 | RXapif_SCALAR |
| 377 | RXapif_FIRSTKEY |
| 378 | RXapif_NEXTKEY |
| 379 | |
| 380 | Whether C<%+> or C<%-> is being operated on, if any. |
| 381 | |
| 382 | RXapif_ONE /* %+ */ |
| 383 | RXapif_ALL /* %- */ |
| 384 | |
| 385 | Whether this is being called as C<re::regname>, C<re::regnames> or |
| 386 | C<re::regnames_count>, if any. The first two will be combined with |
| 387 | C<RXapif_ONE> or C<RXapif_ALL>. |
| 388 | |
| 389 | RXapif_REGNAME |
| 390 | RXapif_REGNAMES |
| 391 | RXapif_REGNAMES_COUNT |
| 392 | |
| 393 | Internally C<%+> and C<%-> are implemented with a real tied interface |
| 394 | via L<Tie::Hash::NamedCapture>. The methods in that package will call |
| 395 | back into these functions. However the usage of |
| 396 | L<Tie::Hash::NamedCapture> for this purpose might change in future |
| 397 | releases. For instance this might be implemented by magic instead |
| 398 | (would need an extension to mgvtbl). |
| 399 | |
| 400 | =head3 named_buff |
| 401 | |
| 402 | SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key, |
| 403 | SV * const value, U32 flags); |
| 404 | |
| 405 | =head3 named_buff_iter |
| 406 | |
| 407 | SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey, |
| 408 | const U32 flags); |
| 409 | |
| 410 | =head2 qr_package |
| 411 | |
| 412 | SV* qr_package(pTHX_ REGEXP * const rx); |
| 413 | |
| 414 | The package the qr// magic object is blessed into (as seen by C<ref |
| 415 | qr//>). It is recommended that engines change this to their package |
| 416 | name for identification regardless of whether they implement methods |
| 417 | on the object. |
| 418 | |
| 419 | The package this method returns should also have the internal |
| 420 | C<Regexp> package in its C<@ISA>. C<< qr//->isa("Regexp") >> should always |
| 421 | be true regardless of what engine is being used. |
| 422 | |
| 423 | Example implementation might be: |
| 424 | |
| 425 | SV* |
| 426 | Example_qr_package(pTHX_ REGEXP * const rx) |
| 427 | { |
| 428 | PERL_UNUSED_ARG(rx); |
| 429 | return newSVpvs("re::engine::Example"); |
| 430 | } |
| 431 | |
| 432 | Any method calls on an object created with C<qr//> will be dispatched to the |
| 433 | package as a normal object. |
| 434 | |
| 435 | use re::engine::Example; |
| 436 | my $re = qr//; |
| 437 | $re->meth; # dispatched to re::engine::Example::meth() |
| 438 | |
| 439 | To retrieve the C<REGEXP> object from the scalar in an XS function use |
| 440 | the C<SvRX> macro, see L<"REGEXP Functions" in perlapi|perlapi/REGEXP |
| 441 | Functions>. |
| 442 | |
| 443 | void meth(SV * rv) |
| 444 | PPCODE: |
| 445 | REGEXP * re = SvRX(sv); |
| 446 | |
| 447 | =head2 dupe |
| 448 | |
| 449 | void* dupe(pTHX_ REGEXP * const rx, CLONE_PARAMS *param); |
| 450 | |
| 451 | On threaded builds a regexp may need to be duplicated so that the pattern |
| 452 | can be used by multiple threads. This routine is expected to handle the |
| 453 | duplication of any private data pointed to by the C<pprivate> member of |
| 454 | the regexp structure. It will be called with the preconstructed new |
| 455 | regexp structure as an argument, the C<pprivate> member will point at |
| 456 | the B<old> private structure, and it is this routine's responsibility to |
| 457 | construct a copy and return a pointer to it (which perl will then use to |
| 458 | overwrite the field as passed to this routine.) |
| 459 | |
| 460 | This allows the engine to dupe its private data but also if necessary |
| 461 | modify the final structure if it really must. |
| 462 | |
| 463 | On unthreaded builds this field doesn't exist. |
| 464 | |
| 465 | =head1 The REGEXP structure |
| 466 | |
| 467 | The REGEXP struct is defined in F<regexp.h>. All regex engines must be able to |
| 468 | correctly build such a structure in their L</comp> routine. |
| 469 | |
| 470 | The REGEXP structure contains all the data that perl needs to be aware of |
| 471 | to properly work with the regular expression. It includes data about |
| 472 | optimisations that perl can use to determine if the regex engine should |
| 473 | really be used, and various other control info that is needed to properly |
| 474 | execute patterns in various contexts such as is the pattern anchored in |
| 475 | some way, or what flags were used during the compile, or whether the |
| 476 | program contains special constructs that perl needs to be aware of. |
| 477 | |
| 478 | In addition it contains two fields that are intended for the private |
| 479 | use of the regex engine that compiled the pattern. These are the |
| 480 | C<intflags> and C<pprivate> members. C<pprivate> is a void pointer to |
| 481 | an arbitrary structure whose use and management is the responsibility |
| 482 | of the compiling engine. perl will never modify either of these |
| 483 | values. |
| 484 | |
| 485 | typedef struct regexp { |
| 486 | /* what engine created this regexp? */ |
| 487 | const struct regexp_engine* engine; |
| 488 | |
| 489 | /* what re is this a lightweight copy of? */ |
| 490 | struct regexp* mother_re; |
| 491 | |
| 492 | /* Information about the match that the perl core uses to manage things */ |
| 493 | U32 extflags; /* Flags used both externally and internally */ |
| 494 | I32 minlen; /* mininum possible length of string to match */ |
| 495 | I32 minlenret; /* mininum possible length of $& */ |
| 496 | U32 gofs; /* chars left of pos that we search from */ |
| 497 | |
| 498 | /* substring data about strings that must appear |
| 499 | in the final match, used for optimisations */ |
| 500 | struct reg_substr_data *substrs; |
| 501 | |
| 502 | U32 nparens; /* number of capture groups */ |
| 503 | |
| 504 | /* private engine specific data */ |
| 505 | U32 intflags; /* Engine Specific Internal flags */ |
| 506 | void *pprivate; /* Data private to the regex engine which |
| 507 | created this object. */ |
| 508 | |
| 509 | /* Data about the last/current match. These are modified during matching*/ |
| 510 | U32 lastparen; /* last open paren matched */ |
| 511 | U32 lastcloseparen; /* last close paren matched */ |
| 512 | regexp_paren_pair *swap; /* Swap copy of *offs */ |
| 513 | regexp_paren_pair *offs; /* Array of offsets for (@-) and (@+) */ |
| 514 | |
| 515 | char *subbeg; /* saved or original string so \digit works forever. */ |
| 516 | SV_SAVED_COPY /* If non-NULL, SV which is COW from original */ |
| 517 | I32 sublen; /* Length of string pointed by subbeg */ |
| 518 | |
| 519 | /* Information about the match that isn't often used */ |
| 520 | I32 prelen; /* length of precomp */ |
| 521 | const char *precomp; /* pre-compilation regular expression */ |
| 522 | |
| 523 | char *wrapped; /* wrapped version of the pattern */ |
| 524 | I32 wraplen; /* length of wrapped */ |
| 525 | |
| 526 | I32 seen_evals; /* number of eval groups in the pattern - for security checks */ |
| 527 | HV *paren_names; /* Optional hash of paren names */ |
| 528 | |
| 529 | /* Refcount of this regexp */ |
| 530 | I32 refcnt; /* Refcount of this regexp */ |
| 531 | } regexp; |
| 532 | |
| 533 | The fields are discussed in more detail below: |
| 534 | |
| 535 | =head2 C<engine> |
| 536 | |
| 537 | This field points at a regexp_engine structure which contains pointers |
| 538 | to the subroutines that are to be used for performing a match. It |
| 539 | is the compiling routine's responsibility to populate this field before |
| 540 | returning the regexp object. |
| 541 | |
| 542 | Internally this is set to C<NULL> unless a custom engine is specified in |
| 543 | C<$^H{regcomp}>, perl's own set of callbacks can be accessed in the struct |
| 544 | pointed to by C<RE_ENGINE_PTR>. |
| 545 | |
| 546 | =head2 C<mother_re> |
| 547 | |
| 548 | TODO, see L<http://www.mail-archive.com/perl5-changes@perl.org/msg17328.html> |
| 549 | |
| 550 | =head2 C<extflags> |
| 551 | |
| 552 | This will be used by perl to see what flags the regexp was compiled |
| 553 | with, this will normally be set to the value of the flags parameter by |
| 554 | the L<comp|/comp> callback. See the L<comp|/comp> documentation for |
| 555 | valid flags. |
| 556 | |
| 557 | =head2 C<minlen> C<minlenret> |
| 558 | |
| 559 | The minimum string length required for the pattern to match. This is used to |
| 560 | prune the search space by not bothering to match any closer to the end of a |
| 561 | string than would allow a match. For instance there is no point in even |
| 562 | starting the regex engine if the minlen is 10 but the string is only 5 |
| 563 | characters long. There is no way that the pattern can match. |
| 564 | |
| 565 | C<minlenret> is the minimum length of the string that would be found |
| 566 | in $& after a match. |
| 567 | |
| 568 | The difference between C<minlen> and C<minlenret> can be seen in the |
| 569 | following pattern: |
| 570 | |
| 571 | /ns(?=\d)/ |
| 572 | |
| 573 | where the C<minlen> would be 3 but C<minlenret> would only be 2 as the \d is |
| 574 | required to match but is not actually included in the matched content. This |
| 575 | distinction is particularly important as the substitution logic uses the |
| 576 | C<minlenret> to tell whether it can do in-place substitution which can result in |
| 577 | considerable speedup. |
| 578 | |
| 579 | =head2 C<gofs> |
| 580 | |
| 581 | Left offset from pos() to start match at. |
| 582 | |
| 583 | =head2 C<substrs> |
| 584 | |
| 585 | Substring data about strings that must appear in the final match. This |
| 586 | is currently only used internally by perl's engine for but might be |
| 587 | used in the future for all engines for optimisations. |
| 588 | |
| 589 | =head2 C<nparens>, C<lastparen>, and C<lastcloseparen> |
| 590 | |
| 591 | These fields are used to keep track of how many paren groups could be matched |
| 592 | in the pattern, which was the last open paren to be entered, and which was |
| 593 | the last close paren to be entered. |
| 594 | |
| 595 | =head2 C<intflags> |
| 596 | |
| 597 | The engine's private copy of the flags the pattern was compiled with. Usually |
| 598 | this is the same as C<extflags> unless the engine chose to modify one of them. |
| 599 | |
| 600 | =head2 C<pprivate> |
| 601 | |
| 602 | A void* pointing to an engine-defined data structure. The perl engine uses the |
| 603 | C<regexp_internal> structure (see L<perlreguts/Base Structures>) but a custom |
| 604 | engine should use something else. |
| 605 | |
| 606 | =head2 C<swap> |
| 607 | |
| 608 | Unused. Left in for compatibility with perl 5.10.0. |
| 609 | |
| 610 | =head2 C<offs> |
| 611 | |
| 612 | A C<regexp_paren_pair> structure which defines offsets into the string being |
| 613 | matched which correspond to the C<$&> and C<$1>, C<$2> etc. captures, the |
| 614 | C<regexp_paren_pair> struct is defined as follows: |
| 615 | |
| 616 | typedef struct regexp_paren_pair { |
| 617 | I32 start; |
| 618 | I32 end; |
| 619 | } regexp_paren_pair; |
| 620 | |
| 621 | If C<< ->offs[num].start >> or C<< ->offs[num].end >> is C<-1> then that |
| 622 | capture group did not match. C<< ->offs[0].start/end >> represents C<$&> (or |
| 623 | C<${^MATCH> under C<//p>) and C<< ->offs[paren].end >> matches C<$$paren> where |
| 624 | C<$paren >= 1>. |
| 625 | |
| 626 | =head2 C<precomp> C<prelen> |
| 627 | |
| 628 | Used for optimisations. C<precomp> holds a copy of the pattern that |
| 629 | was compiled and C<prelen> its length. When a new pattern is to be |
| 630 | compiled (such as inside a loop) the internal C<regcomp> operator |
| 631 | checks whether the last compiled C<REGEXP>'s C<precomp> and C<prelen> |
| 632 | are equivalent to the new one, and if so uses the old pattern instead |
| 633 | of compiling a new one. |
| 634 | |
| 635 | The relevant snippet from C<Perl_pp_regcomp>: |
| 636 | |
| 637 | if (!re || !re->precomp || re->prelen != (I32)len || |
| 638 | memNE(re->precomp, t, len)) |
| 639 | /* Compile a new pattern */ |
| 640 | |
| 641 | =head2 C<paren_names> |
| 642 | |
| 643 | This is a hash used internally to track named capture groups and their |
| 644 | offsets. The keys are the names of the buffers the values are dualvars, |
| 645 | with the IV slot holding the number of buffers with the given name and the |
| 646 | pv being an embedded array of I32. The values may also be contained |
| 647 | independently in the data array in cases where named backreferences are |
| 648 | used. |
| 649 | |
| 650 | =head2 C<substrs> |
| 651 | |
| 652 | Holds information on the longest string that must occur at a fixed |
| 653 | offset from the start of the pattern, and the longest string that must |
| 654 | occur at a floating offset from the start of the pattern. Used to do |
| 655 | Fast-Boyer-Moore searches on the string to find out if its worth using |
| 656 | the regex engine at all, and if so where in the string to search. |
| 657 | |
| 658 | =head2 C<subbeg> C<sublen> C<saved_copy> |
| 659 | |
| 660 | Used during execution phase for managing search and replace patterns. |
| 661 | |
| 662 | =head2 C<wrapped> C<wraplen> |
| 663 | |
| 664 | Stores the string C<qr//> stringifies to. The perl engine for example |
| 665 | stores C<(?^:eek)> in the case of C<qr/eek/>. |
| 666 | |
| 667 | When using a custom engine that doesn't support the C<(?:)> construct |
| 668 | for inline modifiers, it's probably best to have C<qr//> stringify to |
| 669 | the supplied pattern, note that this will create undesired patterns in |
| 670 | cases such as: |
| 671 | |
| 672 | my $x = qr/a|b/; # "a|b" |
| 673 | my $y = qr/c/i; # "c" |
| 674 | my $z = qr/$x$y/; # "a|bc" |
| 675 | |
| 676 | There's no solution for this problem other than making the custom |
| 677 | engine understand a construct like C<(?:)>. |
| 678 | |
| 679 | =head2 C<seen_evals> |
| 680 | |
| 681 | This stores the number of eval groups in the pattern. This is used for security |
| 682 | purposes when embedding compiled regexes into larger patterns with C<qr//>. |
| 683 | |
| 684 | =head2 C<refcnt> |
| 685 | |
| 686 | The number of times the structure is referenced. When this falls to 0 the |
| 687 | regexp is automatically freed by a call to pregfree. This should be set to 1 in |
| 688 | each engine's L</comp> routine. |
| 689 | |
| 690 | =head1 HISTORY |
| 691 | |
| 692 | Originally part of L<perlreguts>. |
| 693 | |
| 694 | =head1 AUTHORS |
| 695 | |
| 696 | Originally written by Yves Orton, expanded by E<AElig>var ArnfjE<ouml>rE<eth> |
| 697 | Bjarmason. |
| 698 | |
| 699 | =head1 LICENSE |
| 700 | |
| 701 | Copyright 2006 Yves Orton and 2007 E<AElig>var ArnfjE<ouml>rE<eth> Bjarmason. |
| 702 | |
| 703 | This program is free software; you can redistribute it and/or modify it under |
| 704 | the same terms as Perl itself. |
| 705 | |
| 706 | =cut |