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