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1 | =head1 NAME |
2 | |
3 | perlreapi - perl regular expression plugin interface |
4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | As of Perl 5.9.5 there is a new interface for using other regexp |
8 | engines than the default one. Each engine is supposed to provide |
9 | access to a constant structure of the following format: |
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10 | |
11 | typedef struct regexp_engine { |
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12 | REGEXP* (*comp) (pTHX_ const SV * const pattern, const U32 flags); |
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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 |
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79 | C<msixp> flags the regex was compiled with. It also contains |
80 | additional info such as whether C<use locale> is in effect. |
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81 | |
82 | The C<eogc> flags are stripped out before being passed to the comp |
83 | routine. The regex engine does not need to know whether any of these |
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84 | are set as those flags should only affect what perl does with the |
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85 | pattern and its match variables, not how it gets compiled and |
86 | executed. |
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87 | |
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88 | By the time the comp callback is called, some of these flags have |
89 | already had effect (noted below where applicable). However most of |
90 | their effect occurs after the comp callback has run in routines that |
91 | read the C<< rx->extflags >> field which it populates. |
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92 | |
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93 | In general the flags should be preserved in C<< rx->extflags >> after |
94 | compilation, although the regex engine might want to add or delete |
95 | some of them to invoke or disable some special behavior in perl. The |
96 | flags along with any special behavior they cause are documented below: |
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97 | |
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98 | The pattern modifiers: |
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99 | |
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100 | =over 4 |
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101 | |
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102 | =item C</m> - RXf_PMf_MULTILINE |
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103 | |
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104 | If this is in C<< rx->extflags >> it will be passed to |
105 | C<Perl_fbm_instr> by C<pp_split> which will treat the subject string |
106 | as a multi-line string. |
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107 | |
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108 | =item C</s> - RXf_PMf_SINGLELINE |
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109 | |
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110 | =item C</i> - RXf_PMf_FOLD |
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111 | |
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112 | =item C</x> - RXf_PMf_EXTENDED |
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113 | |
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114 | If present on a regex C<#> comments will be handled differently by the |
115 | tokenizer in some cases. |
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116 | |
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117 | TODO: Document those cases. |
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118 | |
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119 | =item C</p> - RXf_PMf_KEEPCOPY |
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120 | |
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121 | =back |
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122 | |
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123 | Additional flags: |
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124 | |
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125 | =over 4 |
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126 | |
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127 | =item RXf_PMf_LOCALE |
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128 | |
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129 | Set if C<use locale> is in effect. If present in C<< rx->extflags >> |
130 | C<split> will use the locale dependant definition of whitespace under |
131 | when RXf_SKIPWHITE or RXf_WHITE are in effect. Under ASCII whitespace |
132 | is defined as per L<isSPACE|perlapi/ISSPACE>, and by the internal |
133 | macros C<is_utf8_space> under UTF-8 and C<isSPACE_LC> under C<use |
134 | locale>. |
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135 | |
136 | =item RXf_UTF8 |
137 | |
138 | Set if the pattern is L<SvUTF8()|perlapi/SvUTF8>, set by Perl_pmruntime. |
139 | |
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140 | A regex engine may want to set or disable this flag during |
141 | compilation. The perl engine for instance may upgrade non-UTF-8 |
142 | strings to UTF-8 if the pattern includes constructs such as C<\x{...}> |
143 | that can only match Unicode values. |
144 | |
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145 | =item RXf_SPLIT |
146 | |
147 | If C<split> is invoked as C<split ' '> or with no arguments (which |
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148 | really means C<split(' ', $_)>, see L<split|perlfunc/split>), perl will |
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149 | set this flag. The regex engine can then check for it and set the |
150 | SKIPWHITE and WHITE extflags. To do this the perl engine does: |
151 | |
152 | if (flags & RXf_SPLIT && r->prelen == 1 && r->precomp[0] == ' ') |
153 | r->extflags |= (RXf_SKIPWHITE|RXf_WHITE); |
154 | |
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155 | =back |
156 | |
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157 | These flags can be set during compilation to enable optimizations in |
158 | the C<split> operator. |
159 | |
160 | =over 4 |
161 | |
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162 | =item RXf_SKIPWHITE |
163 | |
164 | If the flag is present in C<< rx->extflags >> C<split> will delete |
165 | whitespace from the start of the subject string before it's operated |
166 | on. What is considered whitespace depends on whether the subject is a |
167 | UTF-8 string and whether the C<RXf_PMf_LOCALE> flag is set. |
168 | |
169 | If RXf_WHITE is set in addition to this flag C<split> will behave like |
170 | C<split " "> under the perl engine. |
171 | |
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172 | =item RXf_START_ONLY |
173 | |
174 | Tells the split operator to split the target string on newlines |
175 | (C<\n>) without invoking the regex engine. |
176 | |
177 | Perl's engine sets this if the pattern is C</^/> (C<plen == 1 && *exp |
178 | == '^'>), even under C</^/s>, see L<split|perlfunc>. Of course a |
179 | different regex engine might want to use the same optimizations |
180 | with a different syntax. |
181 | |
182 | =item RXf_WHITE |
183 | |
184 | Tells the split operator to split the target string on whitespace |
185 | without invoking the regex engine. The definition of whitespace varies |
186 | depending on whether the target string is a UTF-8 string and on |
187 | whether RXf_PMf_LOCALE is set. |
188 | |
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189 | Perl's engine sets this flag if the pattern is C<\s+>. |
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190 | |
191 | =back |
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192 | |
193 | =head2 exec |
194 | |
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195 | I32 exec(pTHX_ REGEXP * const rx, |
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196 | char *stringarg, char* strend, char* strbeg, |
197 | I32 minend, SV* screamer, |
198 | void* data, U32 flags); |
199 | |
200 | Execute a regexp. |
201 | |
202 | =head2 intuit |
203 | |
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204 | char* intuit(pTHX_ REGEXP * const rx, |
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205 | SV *sv, char *strpos, char *strend, |
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206 | const U32 flags, struct re_scream_pos_data_s *data); |
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207 | |
208 | Find the start position where a regex match should be attempted, |
209 | or possibly whether the regex engine should not be run because the |
210 | pattern can't match. This is called as appropriate by the core |
211 | depending on the values of the extflags member of the regexp |
212 | structure. |
213 | |
214 | =head2 checkstr |
215 | |
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216 | SV* checkstr(pTHX_ REGEXP * const rx); |
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217 | |
218 | Return a SV containing a string that must appear in the pattern. Used |
219 | by C<split> for optimising matches. |
220 | |
221 | =head2 free |
222 | |
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223 | void free(pTHX_ REGEXP * const rx); |
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224 | |
225 | Called by perl when it is freeing a regexp pattern so that the engine |
226 | can release any resources pointed to by the C<pprivate> member of the |
227 | regexp structure. This is only responsible for freeing private data; |
228 | perl will handle releasing anything else contained in the regexp structure. |
229 | |
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230 | =head2 Numbered capture callbacks |
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231 | |
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232 | Called to get/set the value of C<$`>, C<$'>, C<$&> and their named |
233 | equivalents, ${^PREMATCH}, ${^POSTMATCH} and $^{MATCH}, as well as the |
234 | numbered capture buffers (C<$1>, C<$2>, ...). |
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235 | |
236 | The C<paren> paramater will be C<-2> for C<$`>, C<-1> for C<$'>, C<0> |
237 | for C<$&>, C<1> for C<$1> and so forth. |
238 | |
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239 | The names have been chosen by analogy with L<Tie::Scalar> methods |
240 | names with an additional B<LENGTH> callback for efficiency. However |
241 | named capture variables are currently not tied internally but |
242 | implemented via magic. |
243 | |
244 | =head3 numbered_buff_FETCH |
245 | |
246 | void numbered_buff_FETCH(pTHX_ REGEXP * const rx, const I32 paren, |
247 | SV * const sv); |
248 | |
249 | Fetch a specified numbered capture. C<sv> should be set to the scalar |
250 | to return, the scalar is passed as an argument rather than being |
251 | returned from the function because when it's called perl already has a |
252 | scalar to store the value, creating another one would be |
253 | redundant. The scalar can be set with C<sv_setsv>, C<sv_setpvn> and |
254 | friends, see L<perlapi>. |
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255 | |
256 | This callback is where perl untaints its own capture variables under |
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257 | taint mode (see L<perlsec>). See the C<Perl_reg_numbered_buff_fetch> |
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258 | function in F<regcomp.c> for how to untaint capture variables if |
259 | that's something you'd like your engine to do as well. |
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260 | |
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261 | =head3 numbered_buff_STORE |
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262 | |
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263 | void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren, |
264 | SV const * const value); |
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265 | |
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266 | Set the value of a numbered capture variable. C<value> is the scalar |
267 | that is to be used as the new value. It's up to the engine to make |
268 | sure this is used as the new value (or reject it). |
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269 | |
270 | Example: |
271 | |
272 | if ("ook" =~ /(o*)/) { |
273 | # `paren' will be `1' and `value' will be `ee' |
274 | $1 =~ tr/o/e/; |
275 | } |
276 | |
277 | Perl's own engine will croak on any attempt to modify the capture |
278 | variables, to do this in another engine use the following callack |
279 | (copied from C<Perl_reg_numbered_buff_store>): |
280 | |
281 | void |
282 | Example_reg_numbered_buff_store(pTHX_ REGEXP * const rx, const I32 paren, |
283 | SV const * const value) |
284 | { |
285 | PERL_UNUSED_ARG(rx); |
286 | PERL_UNUSED_ARG(paren); |
287 | PERL_UNUSED_ARG(value); |
288 | |
289 | if (!PL_localizing) |
290 | Perl_croak(aTHX_ PL_no_modify); |
291 | } |
292 | |
293 | Actually perl 5.10 will not I<always> croak in a statement that looks |
294 | like it would modify a numbered capture variable. This is because the |
295 | STORE callback will not be called if perl can determine that it |
296 | doesn't have to modify the value. This is exactly how tied variables |
297 | behave in the same situation: |
298 | |
299 | package CaptureVar; |
300 | use base 'Tie::Scalar'; |
301 | |
302 | sub TIESCALAR { bless [] } |
303 | sub FETCH { undef } |
304 | sub STORE { die "This doesn't get called" } |
305 | |
306 | package main; |
307 | |
308 | tie my $sv => "CatptureVar"; |
309 | $sv =~ y/a/b/; |
310 | |
311 | Because C<$sv> is C<undef> when the C<y///> operator is applied to it |
312 | the transliteration won't actually execute and the program won't |
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313 | C<die>. This is different to how 5.8 and earlier versions behaved |
314 | since the capture variables were READONLY variables then, now they'll |
315 | just die when assigned to in the default engine. |
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316 | |
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317 | =head3 numbered_buff_LENGTH |
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318 | |
319 | I32 numbered_buff_LENGTH (pTHX_ REGEXP * const rx, const SV * const sv, |
320 | const I32 paren); |
321 | |
322 | Get the C<length> of a capture variable. There's a special callback |
323 | for this so that perl doesn't have to do a FETCH and run C<length> on |
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324 | the result, since the length is (in perl's case) known from an offset |
325 | stored in C<<rx->offs> this is much more efficient: |
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326 | |
327 | I32 s1 = rx->offs[paren].start; |
328 | I32 s2 = rx->offs[paren].end; |
329 | I32 len = t1 - s1; |
330 | |
331 | This is a little bit more complex in the case of UTF-8, see what |
332 | C<Perl_reg_numbered_buff_length> does with |
333 | L<is_utf8_string_loclen|perlapi/is_utf8_string_loclen>. |
334 | |
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335 | =head2 Named capture callbacks |
336 | |
337 | Called to get/set the value of C<%+> and C<%-> as well as by some |
338 | utility functions in L<re>. |
339 | |
340 | There are two callbacks, C<named_buff> is called in all the cases the |
341 | FETCH, STORE, DELETE, CLEAR, EXISTS and SCALAR L<Tie::Hash> callbacks |
342 | would be on changes to C<%+> and C<%-> and C<named_buff_iter> in the |
343 | same cases as FIRSTKEY and NEXTKEY. |
344 | |
345 | The C<flags> parameter can be used to determine which of these |
346 | operations the callbacks should respond to, the following flags are |
347 | currently defined: |
348 | |
349 | Which L<Tie::Hash> operation is being performed from the Perl level on |
350 | C<%+> or C<%+>, if any: |
351 | |
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352 | RXapif_FETCH |
353 | RXapif_STORE |
354 | RXapif_DELETE |
355 | RXapif_CLEAR |
356 | RXapif_EXISTS |
357 | RXapif_SCALAR |
358 | RXapif_FIRSTKEY |
359 | RXapif_NEXTKEY |
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360 | |
361 | Whether C<%+> or C<%-> is being operated on, if any. |
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362 | |
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363 | RXapif_ONE /* %+ */ |
364 | RXapif_ALL /* %- */ |
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365 | |
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366 | Whether this is being called as C<re::regname>, C<re::regnames> or |
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367 | C<re::regnames_count>, if any. The first two will be combined with |
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368 | C<RXapif_ONE> or C<RXapif_ALL>. |
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369 | |
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370 | RXapif_REGNAME |
371 | RXapif_REGNAMES |
372 | RXapif_REGNAMES_COUNT |
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373 | |
374 | Internally C<%+> and C<%-> are implemented with a real tied interface |
375 | via L<Tie::Hash::NamedCapture>. The methods in that package will call |
376 | back into these functions. However the usage of |
377 | L<Tie::Hash::NamedCapture> for this purpose might change in future |
378 | releases. For instance this might be implemented by magic instead |
379 | (would need an extension to mgvtbl). |
380 | |
381 | =head3 named_buff |
382 | |
383 | SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key, |
384 | SV * const value, U32 flags); |
385 | |
386 | =head3 named_buff_iter |
387 | |
388 | SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey, |
389 | const U32 flags); |
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390 | |
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391 | =head2 qr_package |
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392 | |
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393 | SV* qr_package(pTHX_ REGEXP * const rx); |
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394 | |
395 | The package the qr// magic object is blessed into (as seen by C<ref |
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396 | qr//>). It is recommended that engines change this to their package |
397 | name for identification regardless of whether they implement methods |
398 | on the object. |
399 | |
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400 | The package this method returns should also have the internal |
401 | C<Regexp> package in its C<@ISA>. C<qr//->isa("Regexp")> should always |
402 | be true regardless of what engine is being used. |
403 | |
404 | Example implementation might be: |
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405 | |
406 | SV* |
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407 | Example_qr_package(pTHX_ REGEXP * const rx) |
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408 | { |
409 | PERL_UNUSED_ARG(rx); |
410 | return newSVpvs("re::engine::Example"); |
411 | } |
412 | |
413 | Any method calls on an object created with C<qr//> will be dispatched to the |
414 | package as a normal object. |
415 | |
416 | use re::engine::Example; |
417 | my $re = qr//; |
418 | $re->meth; # dispatched to re::engine::Example::meth() |
419 | |
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420 | To retrieve the C<REGEXP> object from the scalar in an XS function use |
421 | the C<SvRX> macro, see L<"REGEXP Functions" in perlapi|perlapi/REGEXP |
422 | Functions>. |
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423 | |
424 | void meth(SV * rv) |
425 | PPCODE: |
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426 | REGEXP * re = SvRX(sv); |
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427 | |
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428 | =head2 dupe |
429 | |
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430 | void* dupe(pTHX_ REGEXP * const rx, CLONE_PARAMS *param); |
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431 | |
432 | On threaded builds a regexp may need to be duplicated so that the pattern |
433 | can be used by mutiple threads. This routine is expected to handle the |
434 | duplication of any private data pointed to by the C<pprivate> member of |
435 | the regexp structure. It will be called with the preconstructed new |
436 | regexp structure as an argument, the C<pprivate> member will point at |
437 | the B<old> private structue, and it is this routine's responsibility to |
438 | construct a copy and return a pointer to it (which perl will then use to |
439 | overwrite the field as passed to this routine.) |
440 | |
441 | This allows the engine to dupe its private data but also if necessary |
442 | modify the final structure if it really must. |
443 | |
444 | On unthreaded builds this field doesn't exist. |
445 | |
446 | =head1 The REGEXP structure |
447 | |
448 | The REGEXP struct is defined in F<regexp.h>. All regex engines must be able to |
449 | correctly build such a structure in their L</comp> routine. |
450 | |
451 | The REGEXP structure contains all the data that perl needs to be aware of |
452 | to properly work with the regular expression. It includes data about |
453 | optimisations that perl can use to determine if the regex engine should |
454 | really be used, and various other control info that is needed to properly |
455 | execute patterns in various contexts such as is the pattern anchored in |
456 | some way, or what flags were used during the compile, or whether the |
457 | program contains special constructs that perl needs to be aware of. |
458 | |
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459 | In addition it contains two fields that are intended for the private |
460 | use of the regex engine that compiled the pattern. These are the |
461 | C<intflags> and C<pprivate> members. C<pprivate> is a void pointer to |
462 | an arbitrary structure whose use and management is the responsibility |
463 | of the compiling engine. perl will never modify either of these |
464 | values. |
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465 | |
466 | typedef struct regexp { |
467 | /* what engine created this regexp? */ |
468 | const struct regexp_engine* engine; |
469 | |
470 | /* what re is this a lightweight copy of? */ |
471 | struct regexp* mother_re; |
472 | |
473 | /* Information about the match that the perl core uses to manage things */ |
474 | U32 extflags; /* Flags used both externally and internally */ |
475 | I32 minlen; /* mininum possible length of string to match */ |
476 | I32 minlenret; /* mininum possible length of $& */ |
477 | U32 gofs; /* chars left of pos that we search from */ |
478 | |
479 | /* substring data about strings that must appear |
480 | in the final match, used for optimisations */ |
481 | struct reg_substr_data *substrs; |
482 | |
483 | U32 nparens; /* number of capture buffers */ |
484 | |
485 | /* private engine specific data */ |
486 | U32 intflags; /* Engine Specific Internal flags */ |
487 | void *pprivate; /* Data private to the regex engine which |
488 | created this object. */ |
489 | |
490 | /* Data about the last/current match. These are modified during matching*/ |
491 | U32 lastparen; /* last open paren matched */ |
492 | U32 lastcloseparen; /* last close paren matched */ |
493 | regexp_paren_pair *swap; /* Swap copy of *offs */ |
494 | regexp_paren_pair *offs; /* Array of offsets for (@-) and (@+) */ |
495 | |
496 | char *subbeg; /* saved or original string so \digit works forever. */ |
497 | SV_SAVED_COPY /* If non-NULL, SV which is COW from original */ |
498 | I32 sublen; /* Length of string pointed by subbeg */ |
499 | |
500 | /* Information about the match that isn't often used */ |
501 | I32 prelen; /* length of precomp */ |
502 | const char *precomp; /* pre-compilation regular expression */ |
503 | |
108003db |
504 | char *wrapped; /* wrapped version of the pattern */ |
505 | I32 wraplen; /* length of wrapped */ |
506 | |
507 | I32 seen_evals; /* number of eval groups in the pattern - for security checks */ |
508 | HV *paren_names; /* Optional hash of paren names */ |
509 | |
510 | /* Refcount of this regexp */ |
511 | I32 refcnt; /* Refcount of this regexp */ |
512 | } regexp; |
513 | |
514 | The fields are discussed in more detail below: |
515 | |
882227b7 |
516 | =head2 C<engine> |
108003db |
517 | |
518 | This field points at a regexp_engine structure which contains pointers |
519 | to the subroutines that are to be used for performing a match. It |
520 | is the compiling routine's responsibility to populate this field before |
521 | returning the regexp object. |
522 | |
523 | Internally this is set to C<NULL> unless a custom engine is specified in |
524 | C<$^H{regcomp}>, perl's own set of callbacks can be accessed in the struct |
525 | pointed to by C<RE_ENGINE_PTR>. |
526 | |
882227b7 |
527 | =head2 C<mother_re> |
108003db |
528 | |
529 | TODO, see L<http://www.mail-archive.com/perl5-changes@perl.org/msg17328.html> |
530 | |
882227b7 |
531 | =head2 C<extflags> |
108003db |
532 | |
192b9cd1 |
533 | This will be used by perl to see what flags the regexp was compiled |
534 | with, this will normally be set to the value of the flags parameter by |
c998b245 |
535 | the L<comp|/comp> callback. See the L<comp|/comp> documentation for |
536 | valid flags. |
108003db |
537 | |
882227b7 |
538 | =head2 C<minlen> C<minlenret> |
108003db |
539 | |
540 | The minimum string length required for the pattern to match. This is used to |
541 | prune the search space by not bothering to match any closer to the end of a |
542 | string than would allow a match. For instance there is no point in even |
543 | starting the regex engine if the minlen is 10 but the string is only 5 |
544 | characters long. There is no way that the pattern can match. |
545 | |
546 | C<minlenret> is the minimum length of the string that would be found |
547 | in $& after a match. |
548 | |
549 | The difference between C<minlen> and C<minlenret> can be seen in the |
550 | following pattern: |
551 | |
552 | /ns(?=\d)/ |
553 | |
554 | where the C<minlen> would be 3 but C<minlenret> would only be 2 as the \d is |
555 | required to match but is not actually included in the matched content. This |
556 | distinction is particularly important as the substitution logic uses the |
557 | C<minlenret> to tell whether it can do in-place substition which can result in |
558 | considerable speedup. |
559 | |
882227b7 |
560 | =head2 C<gofs> |
108003db |
561 | |
562 | Left offset from pos() to start match at. |
563 | |
882227b7 |
564 | =head2 C<substrs> |
108003db |
565 | |
192b9cd1 |
566 | Substring data about strings that must appear in the final match. This |
567 | is currently only used internally by perl's engine for but might be |
c998b245 |
568 | used in the future for all engines for optimisations. |
108003db |
569 | |
882227b7 |
570 | =head2 C<nparens>, C<lasparen>, and C<lastcloseparen> |
108003db |
571 | |
572 | These fields are used to keep track of how many paren groups could be matched |
573 | in the pattern, which was the last open paren to be entered, and which was |
574 | the last close paren to be entered. |
575 | |
882227b7 |
576 | =head2 C<intflags> |
108003db |
577 | |
578 | The engine's private copy of the flags the pattern was compiled with. Usually |
192b9cd1 |
579 | this is the same as C<extflags> unless the engine chose to modify one of them. |
108003db |
580 | |
882227b7 |
581 | =head2 C<pprivate> |
108003db |
582 | |
583 | A void* pointing to an engine-defined data structure. The perl engine uses the |
584 | C<regexp_internal> structure (see L<perlreguts/Base Structures>) but a custom |
585 | engine should use something else. |
586 | |
882227b7 |
587 | =head2 C<swap> |
108003db |
588 | |
589 | TODO: document |
590 | |
882227b7 |
591 | =head2 C<offs> |
108003db |
592 | |
593 | A C<regexp_paren_pair> structure which defines offsets into the string being |
594 | matched which correspond to the C<$&> and C<$1>, C<$2> etc. captures, the |
595 | C<regexp_paren_pair> struct is defined as follows: |
596 | |
597 | typedef struct regexp_paren_pair { |
598 | I32 start; |
599 | I32 end; |
600 | } regexp_paren_pair; |
601 | |
602 | If C<< ->offs[num].start >> or C<< ->offs[num].end >> is C<-1> then that |
603 | capture buffer did not match. C<< ->offs[0].start/end >> represents C<$&> (or |
604 | C<${^MATCH> under C<//p>) and C<< ->offs[paren].end >> matches C<$$paren> where |
605 | C<$paren >= 1>. |
606 | |
882227b7 |
607 | =head2 C<precomp> C<prelen> |
108003db |
608 | |
192b9cd1 |
609 | Used for optimisations. C<precomp> holds a copy of the pattern that |
610 | was compiled and C<prelen> its length. When a new pattern is to be |
611 | compiled (such as inside a loop) the internal C<regcomp> operator |
612 | checks whether the last compiled C<REGEXP>'s C<precomp> and C<prelen> |
613 | are equivalent to the new one, and if so uses the old pattern instead |
614 | of compiling a new one. |
615 | |
616 | The relevant snippet from C<Perl_pp_regcomp>: |
617 | |
618 | if (!re || !re->precomp || re->prelen != (I32)len || |
619 | memNE(re->precomp, t, len)) |
620 | /* Compile a new pattern */ |
108003db |
621 | |
882227b7 |
622 | =head2 C<paren_names> |
108003db |
623 | |
624 | This is a hash used internally to track named capture buffers and their |
625 | offsets. The keys are the names of the buffers the values are dualvars, |
626 | with the IV slot holding the number of buffers with the given name and the |
627 | pv being an embedded array of I32. The values may also be contained |
628 | independently in the data array in cases where named backreferences are |
629 | used. |
630 | |
c998b245 |
631 | =head2 C<substrs> |
108003db |
632 | |
633 | Holds information on the longest string that must occur at a fixed |
634 | offset from the start of the pattern, and the longest string that must |
635 | occur at a floating offset from the start of the pattern. Used to do |
636 | Fast-Boyer-Moore searches on the string to find out if its worth using |
637 | the regex engine at all, and if so where in the string to search. |
638 | |
882227b7 |
639 | =head2 C<subbeg> C<sublen> C<saved_copy> |
108003db |
640 | |
c998b245 |
641 | Used during execution phase for managing search and replace patterns. |
108003db |
642 | |
882227b7 |
643 | =head2 C<wrapped> C<wraplen> |
108003db |
644 | |
c998b245 |
645 | Stores the string C<qr//> stringifies to. The perl engine for example |
646 | stores C<(?-xism:eek)> in the case of C<qr/eek/>. |
108003db |
647 | |
c998b245 |
648 | When using a custom engine that doesn't support the C<(?:)> construct |
649 | for inline modifiers, it's probably best to have C<qr//> stringify to |
650 | the supplied pattern, note that this will create undesired patterns in |
651 | cases such as: |
108003db |
652 | |
653 | my $x = qr/a|b/; # "a|b" |
192b9cd1 |
654 | my $y = qr/c/i; # "c" |
108003db |
655 | my $z = qr/$x$y/; # "a|bc" |
656 | |
192b9cd1 |
657 | There's no solution for this problem other than making the custom |
658 | engine understand a construct like C<(?:)>. |
108003db |
659 | |
882227b7 |
660 | =head2 C<seen_evals> |
108003db |
661 | |
662 | This stores the number of eval groups in the pattern. This is used for security |
663 | purposes when embedding compiled regexes into larger patterns with C<qr//>. |
664 | |
882227b7 |
665 | =head2 C<refcnt> |
108003db |
666 | |
667 | The number of times the structure is referenced. When this falls to 0 the |
668 | regexp is automatically freed by a call to pregfree. This should be set to 1 in |
669 | each engine's L</comp> routine. |
670 | |
108003db |
671 | =head1 HISTORY |
672 | |
673 | Originally part of L<perlreguts>. |
674 | |
675 | =head1 AUTHORS |
676 | |
677 | Originally written by Yves Orton, expanded by E<AElig>var ArnfjE<ouml>rE<eth> |
678 | Bjarmason. |
679 | |
680 | =head1 LICENSE |
681 | |
682 | Copyright 2006 Yves Orton and 2007 E<AElig>var ArnfjE<ouml>rE<eth> Bjarmason. |
683 | |
684 | This program is free software; you can redistribute it and/or modify it under |
685 | the same terms as Perl itself. |
686 | |
687 | =cut |