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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 using other regexp engines than |
8 | the default one. Each engine is supposed to provide access to a constant |
9 | structure of the following format: |
10 | |
11 | typedef struct regexp_engine { |
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12 | REGEXP* (*comp) (pTHX_ const SV * const pattern, const U32 flags); |
49d7dfbc |
13 | I32 (*exec) (pTHX_ REGEXP * const rx, char* stringarg, char* strend, |
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14 | char* strbeg, I32 minend, SV* screamer, |
15 | void* data, U32 flags); |
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16 | char* (*intuit) (pTHX_ REGEXP * const rx, SV *sv, char *strpos, |
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17 | char *strend, U32 flags, |
18 | struct re_scream_pos_data_s *data); |
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19 | SV* (*checkstr) (pTHX_ REGEXP * const rx); |
20 | void (*free) (pTHX_ REGEXP * const rx); |
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21 | void (*numbered_buff_FETCH) (pTHX_ REGEXP * const rx, const I32 paren, |
22 | SV * const sv); |
23 | void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren, |
24 | SV const * const value); |
25 | I32 (*numbered_buff_LENGTH) (pTHX_ REGEXP * const rx, const SV * const sv, |
26 | const I32 paren); |
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27 | SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key, |
28 | SV * const value, U32 flags); |
29 | SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey, |
30 | const U32 flags); |
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31 | SV* (*qr_package)(pTHX_ REGEXP * const rx); |
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32 | #ifdef USE_ITHREADS |
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33 | void* (*dupe) (pTHX_ REGEXP * const rx, CLONE_PARAMS *param); |
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34 | #endif |
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35 | |
36 | When a regexp is compiled, its C<engine> field is then set to point at |
37 | the appropriate structure so that when it needs to be used Perl can find |
38 | the right routines to do so. |
39 | |
40 | In order to install a new regexp handler, C<$^H{regcomp}> is set |
41 | to an integer which (when casted appropriately) resolves to one of these |
42 | structures. When compiling, the C<comp> method is executed, and the |
43 | resulting regexp structure's engine field is expected to point back at |
44 | the same structure. |
45 | |
46 | The pTHX_ symbol in the definition is a macro used by perl under threading |
47 | to provide an extra argument to the routine holding a pointer back to |
48 | the interpreter that is executing the regexp. So under threading all |
49 | routines get an extra argument. |
50 | |
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51 | =head1 Callbacks |
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52 | |
53 | =head2 comp |
54 | |
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55 | REGEXP* comp(pTHX_ const SV * const pattern, const U32 flags); |
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56 | |
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57 | Compile the pattern stored in C<pattern> using the given C<flags> and |
58 | return a pointer to a prepared C<REGEXP> structure that can perform |
59 | the match. See L</The REGEXP structure> below for an explanation of |
60 | the individual fields in the REGEXP struct. |
61 | |
62 | The C<pattern> parameter is the scalar that was used as the |
63 | pattern. previous versions of perl would pass two C<char*> indicating |
64 | the start and end of the stringifed pattern, the following snippet can |
65 | be used to get the old parameters: |
66 | |
67 | STRLEN plen; |
68 | char* exp = SvPV(pattern, plen); |
69 | char* xend = exp + plen; |
70 | |
71 | Since any scalar can be passed as a pattern it's possible to implement |
72 | an engine that does something with an array (C<< "ook" =~ [ qw/ eek |
73 | hlagh / ] >>) or with the non-stringified form of a compiled regular |
74 | expression (C<< "ook" =~ qr/eek/ >>). perl's own engine will always |
75 | stringify everything using the snippet above but that doesn't mean |
76 | other engines have to. |
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77 | |
78 | The C<flags> paramater is a bitfield which indicates which of the |
79 | C<msixk> flags the regex was compiled with. In addition it contains |
80 | info about whether C<use locale> is in effect and optimization info |
81 | for C<split>. A regex engine might want to use the same split |
82 | optimizations with a different syntax, for instance a Perl6 engine |
83 | would treat C<split /^^/> equivalently to perl's C<split /^/>, see |
84 | L<split documentation|perlfunc> and the relevant code in C<pp_split> |
85 | in F<pp.c> to find out whether your engine should be setting these. |
86 | |
87 | The C<eogc> flags are stripped out before being passed to the comp |
88 | routine. The regex engine does not need to know whether any of these |
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89 | are set as those flags should only affect what perl does with the |
90 | pattern and its match variables, not how it gets compiled & executed. |
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91 | |
92 | =over 4 |
93 | |
94 | =item RXf_SKIPWHITE |
95 | |
96 | C<split ' '> or C<split> with no arguments (which really means |
97 | C<split(' ', $_> see L<split|perlfunc>). |
98 | |
99 | =item RXf_START_ONLY |
100 | |
101 | Set if the pattern is C</^/> (C<<r->prelen == 1 && r->precomp[0] == |
102 | '^'>>). Will be used by the C<split> operator to split the given |
103 | string on C<\n> (even under C</^/s>, see L<split|perlfunc>). |
104 | |
105 | =item RXf_WHITE |
106 | |
107 | Set if the pattern is exactly C</\s+/> and used by C<split>, the |
108 | definition of whitespace varies depending on whether RXf_UTF8 or |
109 | RXf_PMf_LOCALE is set. |
110 | |
111 | =item RXf_PMf_LOCALE |
112 | |
113 | Makes C<split> use the locale dependant definition of whitespace under C<use |
114 | locale> when RXf_SKIPWHITE or RXf_WHITE is in effect. Under ASCII whitespace is |
115 | defined as per L<isSPACE|perlapi/ISSPACE>, and by the internal macros |
116 | C<is_utf8_space> under UTF-8 and C<isSPACE_LC> under C<use locale>. |
117 | |
118 | =item RXf_PMf_MULTILINE |
119 | |
120 | The C</m> flag, this ends up being passed to C<Perl_fbm_instr> by |
121 | C<pp_split> regardless of the engine. |
122 | |
123 | =item RXf_PMf_SINGLELINE |
124 | |
125 | The C</s> flag. Guaranteed not to be used outside the regex engine. |
126 | |
127 | =item RXf_PMf_FOLD |
128 | |
129 | The C</i> flag. Guaranteed not to be used outside the regex engine. |
130 | |
131 | =item RXf_PMf_EXTENDED |
132 | |
133 | The C</x> flag. Guaranteed not to be used outside the regex |
134 | engine. However if present on a regex C<#> comments will be stripped |
135 | by the tokenizer regardless of the engine currently in use. |
136 | |
137 | =item RXf_PMf_KEEPCOPY |
138 | |
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139 | The C</p> flag. |
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140 | |
141 | =item RXf_UTF8 |
142 | |
143 | Set if the pattern is L<SvUTF8()|perlapi/SvUTF8>, set by Perl_pmruntime. |
144 | |
145 | =back |
146 | |
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147 | In general these flags should be preserved in C<< rx->extflags >> |
148 | after compilation, although it is possible the regex includes |
149 | constructs that changes them. The perl engine for instance may upgrade |
150 | non-utf8 strings to utf8 if the pattern includes constructs such as |
151 | C<\x{...}> that can only match unicode values. RXf_SKIPWHITE should |
152 | always be preserved verbatim in C<< regex->extflags >>. |
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153 | |
154 | =head2 exec |
155 | |
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156 | I32 exec(pTHX_ REGEXP * const rx, |
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157 | char *stringarg, char* strend, char* strbeg, |
158 | I32 minend, SV* screamer, |
159 | void* data, U32 flags); |
160 | |
161 | Execute a regexp. |
162 | |
163 | =head2 intuit |
164 | |
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165 | char* intuit(pTHX_ REGEXP * const rx, |
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166 | SV *sv, char *strpos, char *strend, |
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167 | const U32 flags, struct re_scream_pos_data_s *data); |
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168 | |
169 | Find the start position where a regex match should be attempted, |
170 | or possibly whether the regex engine should not be run because the |
171 | pattern can't match. This is called as appropriate by the core |
172 | depending on the values of the extflags member of the regexp |
173 | structure. |
174 | |
175 | =head2 checkstr |
176 | |
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177 | SV* checkstr(pTHX_ REGEXP * const rx); |
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178 | |
179 | Return a SV containing a string that must appear in the pattern. Used |
180 | by C<split> for optimising matches. |
181 | |
182 | =head2 free |
183 | |
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184 | void free(pTHX_ REGEXP * const rx); |
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185 | |
186 | Called by perl when it is freeing a regexp pattern so that the engine |
187 | can release any resources pointed to by the C<pprivate> member of the |
188 | regexp structure. This is only responsible for freeing private data; |
189 | perl will handle releasing anything else contained in the regexp structure. |
190 | |
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191 | =head2 Numbered capture callbacks |
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192 | |
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193 | Called to get/set the value of C<$`>, C<$'>, C<$&> and their named |
194 | equivalents, ${^PREMATCH}, ${^POSTMATCH} and $^{MATCH}, as well as the |
195 | numbered capture buffers (C<$1>, C<$2>, ...). |
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196 | |
197 | The C<paren> paramater will be C<-2> for C<$`>, C<-1> for C<$'>, C<0> |
198 | for C<$&>, C<1> for C<$1> and so forth. |
199 | |
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200 | The names have been chosen by analogy with L<Tie::Scalar> methods |
201 | names with an additional B<LENGTH> callback for efficiency. However |
202 | named capture variables are currently not tied internally but |
203 | implemented via magic. |
204 | |
205 | =head3 numbered_buff_FETCH |
206 | |
207 | void numbered_buff_FETCH(pTHX_ REGEXP * const rx, const I32 paren, |
208 | SV * const sv); |
209 | |
210 | Fetch a specified numbered capture. C<sv> should be set to the scalar |
211 | to return, the scalar is passed as an argument rather than being |
212 | returned from the function because when it's called perl already has a |
213 | scalar to store the value, creating another one would be |
214 | redundant. The scalar can be set with C<sv_setsv>, C<sv_setpvn> and |
215 | friends, see L<perlapi>. |
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216 | |
217 | This callback is where perl untaints its own capture variables under |
218 | taint mode (see L<perlsec>). See the C<Perl_reg_numbered_buff_get> |
219 | function in F<regcomp.c> for how to untaint capture variables if |
220 | that's something you'd like your engine to do as well. |
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221 | |
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222 | =head3 numbered_buff_STORE |
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223 | |
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224 | void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren, |
225 | SV const * const value); |
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226 | |
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227 | Set the value of a numbered capture variable. C<value> is the scalar |
228 | that is to be used as the new value. It's up to the engine to make |
229 | sure this is used as the new value (or reject it). |
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230 | |
231 | Example: |
232 | |
233 | if ("ook" =~ /(o*)/) { |
234 | # `paren' will be `1' and `value' will be `ee' |
235 | $1 =~ tr/o/e/; |
236 | } |
237 | |
238 | Perl's own engine will croak on any attempt to modify the capture |
239 | variables, to do this in another engine use the following callack |
240 | (copied from C<Perl_reg_numbered_buff_store>): |
241 | |
242 | void |
243 | Example_reg_numbered_buff_store(pTHX_ REGEXP * const rx, const I32 paren, |
244 | SV const * const value) |
245 | { |
246 | PERL_UNUSED_ARG(rx); |
247 | PERL_UNUSED_ARG(paren); |
248 | PERL_UNUSED_ARG(value); |
249 | |
250 | if (!PL_localizing) |
251 | Perl_croak(aTHX_ PL_no_modify); |
252 | } |
253 | |
254 | Actually perl 5.10 will not I<always> croak in a statement that looks |
255 | like it would modify a numbered capture variable. This is because the |
256 | STORE callback will not be called if perl can determine that it |
257 | doesn't have to modify the value. This is exactly how tied variables |
258 | behave in the same situation: |
259 | |
260 | package CaptureVar; |
261 | use base 'Tie::Scalar'; |
262 | |
263 | sub TIESCALAR { bless [] } |
264 | sub FETCH { undef } |
265 | sub STORE { die "This doesn't get called" } |
266 | |
267 | package main; |
268 | |
269 | tie my $sv => "CatptureVar"; |
270 | $sv =~ y/a/b/; |
271 | |
272 | Because C<$sv> is C<undef> when the C<y///> operator is applied to it |
273 | the transliteration won't actually execute and the program won't |
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274 | C<die>. This is different to how 5.8 and earlier versions behaved |
275 | since the capture variables were READONLY variables then, now they'll |
276 | just die when assigned to in the default engine. |
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277 | |
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278 | =head3 numbered_buff_LENGTH |
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279 | |
280 | I32 numbered_buff_LENGTH (pTHX_ REGEXP * const rx, const SV * const sv, |
281 | const I32 paren); |
282 | |
283 | Get the C<length> of a capture variable. There's a special callback |
284 | for this so that perl doesn't have to do a FETCH and run C<length> on |
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285 | the result, since the length is (in perl's case) known from an offset |
286 | stored in C<<rx->offs> this is much more efficient: |
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287 | |
288 | I32 s1 = rx->offs[paren].start; |
289 | I32 s2 = rx->offs[paren].end; |
290 | I32 len = t1 - s1; |
291 | |
292 | This is a little bit more complex in the case of UTF-8, see what |
293 | C<Perl_reg_numbered_buff_length> does with |
294 | L<is_utf8_string_loclen|perlapi/is_utf8_string_loclen>. |
295 | |
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296 | =head2 Named capture callbacks |
297 | |
298 | Called to get/set the value of C<%+> and C<%-> as well as by some |
299 | utility functions in L<re>. |
300 | |
301 | There are two callbacks, C<named_buff> is called in all the cases the |
302 | FETCH, STORE, DELETE, CLEAR, EXISTS and SCALAR L<Tie::Hash> callbacks |
303 | would be on changes to C<%+> and C<%-> and C<named_buff_iter> in the |
304 | same cases as FIRSTKEY and NEXTKEY. |
305 | |
306 | The C<flags> parameter can be used to determine which of these |
307 | operations the callbacks should respond to, the following flags are |
308 | currently defined: |
309 | |
310 | Which L<Tie::Hash> operation is being performed from the Perl level on |
311 | C<%+> or C<%+>, if any: |
312 | |
313 | RXf_HASH_FETCH |
314 | RXf_HASH_STORE |
315 | RXf_HASH_DELETE |
316 | RXf_HASH_CLEAR |
317 | RXf_HASH_EXISTS |
318 | RXf_HASH_SCALAR |
319 | RXf_HASH_FIRSTKEY |
320 | RXf_HASH_NEXTKEY |
321 | |
322 | Whether C<%+> or C<%-> is being operated on, if any. |
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323 | |
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324 | RXf_HASH_ONE /* %+ */ |
325 | RXf_HASH_ALL /* %- */ |
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326 | |
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327 | Whether this is being called as C<re::regname>, C<re::regnames> or |
328 | C<C<re::regnames_count>, if any. The first two will be combined with |
329 | C<RXf_HASH_ONE> or C<RXf_HASH_ALL>. |
330 | |
331 | RXf_HASH_REGNAME |
332 | RXf_HASH_REGNAMES |
333 | RXf_HASH_REGNAMES_COUNT |
334 | |
335 | Internally C<%+> and C<%-> are implemented with a real tied interface |
336 | via L<Tie::Hash::NamedCapture>. The methods in that package will call |
337 | back into these functions. However the usage of |
338 | L<Tie::Hash::NamedCapture> for this purpose might change in future |
339 | releases. For instance this might be implemented by magic instead |
340 | (would need an extension to mgvtbl). |
341 | |
342 | =head3 named_buff |
343 | |
344 | SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key, |
345 | SV * const value, U32 flags); |
346 | |
347 | =head3 named_buff_iter |
348 | |
349 | SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey, |
350 | const U32 flags); |
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351 | |
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352 | =head2 qr_package |
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353 | |
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354 | SV* qr_package(pTHX_ REGEXP * const rx); |
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355 | |
356 | The package the qr// magic object is blessed into (as seen by C<ref |
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357 | qr//>). It is recommended that engines change this to their package |
358 | name for identification regardless of whether they implement methods |
359 | on the object. |
360 | |
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361 | The package this method returns should also have the internal |
362 | C<Regexp> package in its C<@ISA>. C<qr//->isa("Regexp")> should always |
363 | be true regardless of what engine is being used. |
364 | |
365 | Example implementation might be: |
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366 | |
367 | SV* |
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368 | Example_qr_package(pTHX_ REGEXP * const rx) |
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369 | { |
370 | PERL_UNUSED_ARG(rx); |
371 | return newSVpvs("re::engine::Example"); |
372 | } |
373 | |
374 | Any method calls on an object created with C<qr//> will be dispatched to the |
375 | package as a normal object. |
376 | |
377 | use re::engine::Example; |
378 | my $re = qr//; |
379 | $re->meth; # dispatched to re::engine::Example::meth() |
380 | |
381 | To retrieve the C<REGEXP> object from the scalar in an XS function use the |
382 | following snippet: |
383 | |
384 | void meth(SV * rv) |
385 | PPCODE: |
386 | MAGIC * mg; |
387 | REGEXP * re; |
388 | |
389 | if (SvMAGICAL(sv)) |
390 | mg_get(sv); |
391 | if (SvROK(sv) && |
392 | (sv = (SV*)SvRV(sv)) && /* assignment deliberate */ |
393 | SvTYPE(sv) == SVt_PVMG && |
394 | (mg = mg_find(sv, PERL_MAGIC_qr))) /* assignment deliberate */ |
395 | { |
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396 | re = (REGEXP *)mg->mg_obj; |
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397 | } |
398 | |
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399 | =head2 dupe |
400 | |
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401 | void* dupe(pTHX_ REGEXP * const rx, CLONE_PARAMS *param); |
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402 | |
403 | On threaded builds a regexp may need to be duplicated so that the pattern |
404 | can be used by mutiple threads. This routine is expected to handle the |
405 | duplication of any private data pointed to by the C<pprivate> member of |
406 | the regexp structure. It will be called with the preconstructed new |
407 | regexp structure as an argument, the C<pprivate> member will point at |
408 | the B<old> private structue, and it is this routine's responsibility to |
409 | construct a copy and return a pointer to it (which perl will then use to |
410 | overwrite the field as passed to this routine.) |
411 | |
412 | This allows the engine to dupe its private data but also if necessary |
413 | modify the final structure if it really must. |
414 | |
415 | On unthreaded builds this field doesn't exist. |
416 | |
417 | =head1 The REGEXP structure |
418 | |
419 | The REGEXP struct is defined in F<regexp.h>. All regex engines must be able to |
420 | correctly build such a structure in their L</comp> routine. |
421 | |
422 | The REGEXP structure contains all the data that perl needs to be aware of |
423 | to properly work with the regular expression. It includes data about |
424 | optimisations that perl can use to determine if the regex engine should |
425 | really be used, and various other control info that is needed to properly |
426 | execute patterns in various contexts such as is the pattern anchored in |
427 | some way, or what flags were used during the compile, or whether the |
428 | program contains special constructs that perl needs to be aware of. |
429 | |
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430 | In addition it contains two fields that are intended for the private |
431 | use of the regex engine that compiled the pattern. These are the |
432 | C<intflags> and C<pprivate> members. C<pprivate> is a void pointer to |
433 | an arbitrary structure whose use and management is the responsibility |
434 | of the compiling engine. perl will never modify either of these |
435 | values. |
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436 | |
437 | typedef struct regexp { |
438 | /* what engine created this regexp? */ |
439 | const struct regexp_engine* engine; |
440 | |
441 | /* what re is this a lightweight copy of? */ |
442 | struct regexp* mother_re; |
443 | |
444 | /* Information about the match that the perl core uses to manage things */ |
445 | U32 extflags; /* Flags used both externally and internally */ |
446 | I32 minlen; /* mininum possible length of string to match */ |
447 | I32 minlenret; /* mininum possible length of $& */ |
448 | U32 gofs; /* chars left of pos that we search from */ |
449 | |
450 | /* substring data about strings that must appear |
451 | in the final match, used for optimisations */ |
452 | struct reg_substr_data *substrs; |
453 | |
454 | U32 nparens; /* number of capture buffers */ |
455 | |
456 | /* private engine specific data */ |
457 | U32 intflags; /* Engine Specific Internal flags */ |
458 | void *pprivate; /* Data private to the regex engine which |
459 | created this object. */ |
460 | |
461 | /* Data about the last/current match. These are modified during matching*/ |
462 | U32 lastparen; /* last open paren matched */ |
463 | U32 lastcloseparen; /* last close paren matched */ |
464 | regexp_paren_pair *swap; /* Swap copy of *offs */ |
465 | regexp_paren_pair *offs; /* Array of offsets for (@-) and (@+) */ |
466 | |
467 | char *subbeg; /* saved or original string so \digit works forever. */ |
468 | SV_SAVED_COPY /* If non-NULL, SV which is COW from original */ |
469 | I32 sublen; /* Length of string pointed by subbeg */ |
470 | |
471 | /* Information about the match that isn't often used */ |
472 | I32 prelen; /* length of precomp */ |
473 | const char *precomp; /* pre-compilation regular expression */ |
474 | |
475 | /* wrapped can't be const char*, as it is returned by sv_2pv_flags */ |
476 | char *wrapped; /* wrapped version of the pattern */ |
477 | I32 wraplen; /* length of wrapped */ |
478 | |
479 | I32 seen_evals; /* number of eval groups in the pattern - for security checks */ |
480 | HV *paren_names; /* Optional hash of paren names */ |
481 | |
482 | /* Refcount of this regexp */ |
483 | I32 refcnt; /* Refcount of this regexp */ |
484 | } regexp; |
485 | |
486 | The fields are discussed in more detail below: |
487 | |
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488 | =head2 C<engine> |
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489 | |
490 | This field points at a regexp_engine structure which contains pointers |
491 | to the subroutines that are to be used for performing a match. It |
492 | is the compiling routine's responsibility to populate this field before |
493 | returning the regexp object. |
494 | |
495 | Internally this is set to C<NULL> unless a custom engine is specified in |
496 | C<$^H{regcomp}>, perl's own set of callbacks can be accessed in the struct |
497 | pointed to by C<RE_ENGINE_PTR>. |
498 | |
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499 | =head2 C<mother_re> |
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500 | |
501 | TODO, see L<http://www.mail-archive.com/perl5-changes@perl.org/msg17328.html> |
502 | |
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503 | =head2 C<extflags> |
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504 | |
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505 | This will be used by perl to see what flags the regexp was compiled |
506 | with, this will normally be set to the value of the flags parameter by |
507 | the L<comp|/comp> callback. |
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508 | |
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509 | =head2 C<minlen> C<minlenret> |
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510 | |
511 | The minimum string length required for the pattern to match. This is used to |
512 | prune the search space by not bothering to match any closer to the end of a |
513 | string than would allow a match. For instance there is no point in even |
514 | starting the regex engine if the minlen is 10 but the string is only 5 |
515 | characters long. There is no way that the pattern can match. |
516 | |
517 | C<minlenret> is the minimum length of the string that would be found |
518 | in $& after a match. |
519 | |
520 | The difference between C<minlen> and C<minlenret> can be seen in the |
521 | following pattern: |
522 | |
523 | /ns(?=\d)/ |
524 | |
525 | where the C<minlen> would be 3 but C<minlenret> would only be 2 as the \d is |
526 | required to match but is not actually included in the matched content. This |
527 | distinction is particularly important as the substitution logic uses the |
528 | C<minlenret> to tell whether it can do in-place substition which can result in |
529 | considerable speedup. |
530 | |
882227b7 |
531 | =head2 C<gofs> |
108003db |
532 | |
533 | Left offset from pos() to start match at. |
534 | |
882227b7 |
535 | =head2 C<substrs> |
108003db |
536 | |
192b9cd1 |
537 | Substring data about strings that must appear in the final match. This |
538 | is currently only used internally by perl's engine for but might be |
539 | used in the future for all engines for optimisations like C<minlen>. |
108003db |
540 | |
882227b7 |
541 | =head2 C<nparens>, C<lasparen>, and C<lastcloseparen> |
108003db |
542 | |
543 | These fields are used to keep track of how many paren groups could be matched |
544 | in the pattern, which was the last open paren to be entered, and which was |
545 | the last close paren to be entered. |
546 | |
882227b7 |
547 | =head2 C<intflags> |
108003db |
548 | |
549 | The engine's private copy of the flags the pattern was compiled with. Usually |
192b9cd1 |
550 | this is the same as C<extflags> unless the engine chose to modify one of them. |
108003db |
551 | |
882227b7 |
552 | =head2 C<pprivate> |
108003db |
553 | |
554 | A void* pointing to an engine-defined data structure. The perl engine uses the |
555 | C<regexp_internal> structure (see L<perlreguts/Base Structures>) but a custom |
556 | engine should use something else. |
557 | |
882227b7 |
558 | =head2 C<swap> |
108003db |
559 | |
560 | TODO: document |
561 | |
882227b7 |
562 | =head2 C<offs> |
108003db |
563 | |
564 | A C<regexp_paren_pair> structure which defines offsets into the string being |
565 | matched which correspond to the C<$&> and C<$1>, C<$2> etc. captures, the |
566 | C<regexp_paren_pair> struct is defined as follows: |
567 | |
568 | typedef struct regexp_paren_pair { |
569 | I32 start; |
570 | I32 end; |
571 | } regexp_paren_pair; |
572 | |
573 | If C<< ->offs[num].start >> or C<< ->offs[num].end >> is C<-1> then that |
574 | capture buffer did not match. C<< ->offs[0].start/end >> represents C<$&> (or |
575 | C<${^MATCH> under C<//p>) and C<< ->offs[paren].end >> matches C<$$paren> where |
576 | C<$paren >= 1>. |
577 | |
882227b7 |
578 | =head2 C<precomp> C<prelen> |
108003db |
579 | |
192b9cd1 |
580 | Used for optimisations. C<precomp> holds a copy of the pattern that |
581 | was compiled and C<prelen> its length. When a new pattern is to be |
582 | compiled (such as inside a loop) the internal C<regcomp> operator |
583 | checks whether the last compiled C<REGEXP>'s C<precomp> and C<prelen> |
584 | are equivalent to the new one, and if so uses the old pattern instead |
585 | of compiling a new one. |
586 | |
587 | The relevant snippet from C<Perl_pp_regcomp>: |
588 | |
589 | if (!re || !re->precomp || re->prelen != (I32)len || |
590 | memNE(re->precomp, t, len)) |
591 | /* Compile a new pattern */ |
108003db |
592 | |
882227b7 |
593 | =head2 C<paren_names> |
108003db |
594 | |
595 | This is a hash used internally to track named capture buffers and their |
596 | offsets. The keys are the names of the buffers the values are dualvars, |
597 | with the IV slot holding the number of buffers with the given name and the |
598 | pv being an embedded array of I32. The values may also be contained |
599 | independently in the data array in cases where named backreferences are |
600 | used. |
601 | |
882227b7 |
602 | =head2 C<reg_substr_data> |
108003db |
603 | |
604 | Holds information on the longest string that must occur at a fixed |
605 | offset from the start of the pattern, and the longest string that must |
606 | occur at a floating offset from the start of the pattern. Used to do |
607 | Fast-Boyer-Moore searches on the string to find out if its worth using |
608 | the regex engine at all, and if so where in the string to search. |
609 | |
882227b7 |
610 | =head2 C<subbeg> C<sublen> C<saved_copy> |
108003db |
611 | |
612 | #define SAVEPVN(p,n) ((p) ? savepvn(p,n) : NULL) |
613 | if (RX_MATCH_COPIED(ret)) |
614 | ret->subbeg = SAVEPVN(ret->subbeg, ret->sublen); |
615 | else |
616 | ret->subbeg = NULL; |
617 | |
618 | C<PL_sawampersand || rx->extflags & RXf_PMf_KEEPCOPY> |
619 | |
620 | These are used during execution phase for managing search and replace |
621 | patterns. |
622 | |
882227b7 |
623 | =head2 C<wrapped> C<wraplen> |
108003db |
624 | |
625 | Stores the string C<qr//> stringifies to, for example C<(?-xism:eek)> |
626 | in the case of C<qr/eek/>. |
627 | |
628 | When using a custom engine that doesn't support the C<(?:)> construct for |
629 | inline modifiers it's best to have C<qr//> stringify to the supplied pattern, |
630 | note that this will create invalid patterns in cases such as: |
631 | |
632 | my $x = qr/a|b/; # "a|b" |
192b9cd1 |
633 | my $y = qr/c/i; # "c" |
108003db |
634 | my $z = qr/$x$y/; # "a|bc" |
635 | |
192b9cd1 |
636 | There's no solution for this problem other than making the custom |
637 | engine understand a construct like C<(?:)>. |
108003db |
638 | |
639 | The C<Perl_reg_stringify> in F<regcomp.c> does the stringification work. |
640 | |
882227b7 |
641 | =head2 C<seen_evals> |
108003db |
642 | |
643 | This stores the number of eval groups in the pattern. This is used for security |
644 | purposes when embedding compiled regexes into larger patterns with C<qr//>. |
645 | |
882227b7 |
646 | =head2 C<refcnt> |
108003db |
647 | |
648 | The number of times the structure is referenced. When this falls to 0 the |
649 | regexp is automatically freed by a call to pregfree. This should be set to 1 in |
650 | each engine's L</comp> routine. |
651 | |
108003db |
652 | =head1 HISTORY |
653 | |
654 | Originally part of L<perlreguts>. |
655 | |
656 | =head1 AUTHORS |
657 | |
658 | Originally written by Yves Orton, expanded by E<AElig>var ArnfjE<ouml>rE<eth> |
659 | Bjarmason. |
660 | |
661 | =head1 LICENSE |
662 | |
663 | Copyright 2006 Yves Orton and 2007 E<AElig>var ArnfjE<ouml>rE<eth> Bjarmason. |
664 | |
665 | This program is free software; you can redistribute it and/or modify it under |
666 | the same terms as Perl itself. |
667 | |
668 | =cut |