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revision 601 by ph10, Sun Oct 10 16:24:11 2010 UTC revision 602 by ph10, Wed May 25 08:29:03 2011 UTC
# Line 68  things I did for 6.8 was to fix Yet Anot Line 68  things I did for 6.8 was to fix Yet Anot
68  I had a flash of inspiration as to how I could run the real compile function in  I had a flash of inspiration as to how I could run the real compile function in
69  a "fake" mode that enables it to compute how much memory it would need, while  a "fake" mode that enables it to compute how much memory it would need, while
70  actually only ever using a few hundred bytes of working memory, and without too  actually only ever using a few hundred bytes of working memory, and without too
71  many tests of the mode that might slow it down. So I re-factored the compiling  many tests of the mode that might slow it down. So I refactored the compiling
72  functions to work this way. This got rid of about 600 lines of source. It  functions to work this way. This got rid of about 600 lines of source. It
73  should make future maintenance and development easier. As this was such a major  should make future maintenance and development easier. As this was such a major
74  change, I never released 6.8, instead upping the number to 7.0 (other quite  change, I never released 6.8, instead upping the number to 7.0 (other quite
# Line 108  needed at compile time to produce a trad Line 108  needed at compile time to produce a trad
108  ever active at once. I believe some other regex matchers work this way.  ever active at once. I believe some other regex matchers work this way.
109    
110    
111    Changeable options
112    ------------------
113    
114    The /i, /m, or /s options (PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL) may
115    change in the middle of patterns. From PCRE 8.13, their processing is handled
116    entirely at compile time by generating different opcodes for the different
117    settings. The runtime functions do not need to keep track of an options state
118    any more.
119    
120    
121  Format of compiled patterns  Format of compiled patterns
122  ---------------------------  ---------------------------
123    
# Line 124  greater than 64K are going to be process Line 134  greater than 64K are going to be process
134  "normal" compilation options. Data values that are counts (e.g. for  "normal" compilation options. Data values that are counts (e.g. for
135  quantifiers) are always just two bytes long.  quantifiers) are always just two bytes long.
136    
 A list of the opcodes follows:  
   
137  Opcodes with no following data  Opcodes with no following data
138  ------------------------------  ------------------------------
139    
# Line 138  These items are all just one byte long Line 146  These items are all just one byte long
146    OP_SOD                 match start of data: \A    OP_SOD                 match start of data: \A
147    OP_SOM,                start of match (subject + offset): \G    OP_SOM,                start of match (subject + offset): \G
148    OP_SET_SOM,            set start of match (\K)    OP_SET_SOM,            set start of match (\K)
149    OP_CIRC                ^ (start of data, or after \n in multiline)    OP_CIRC                ^ (start of data)
150      OP_CIRCM               ^ multiline mode (start of data or after newline)
151    OP_NOT_WORD_BOUNDARY   \W    OP_NOT_WORD_BOUNDARY   \W
152    OP_WORD_BOUNDARY       \w    OP_WORD_BOUNDARY       \w
153    OP_NOT_DIGIT           \D    OP_NOT_DIGIT           \D
# Line 153  These items are all just one byte long Line 162  These items are all just one byte long
162    OP_WORDCHAR            \w    OP_WORDCHAR            \w
163    OP_EODN                match end of data or \n at end: \Z    OP_EODN                match end of data or \n at end: \Z
164    OP_EOD                 match end of data: \z    OP_EOD                 match end of data: \z
165    OP_DOLL                $ (end of data, or before \n in multiline)    OP_DOLL                $ (end of data, or before final newline)
166      OP_DOLLM               $ multiline mode (end of data or before newline)
167    OP_EXTUNI              match an extended Unicode character    OP_EXTUNI              match an extended Unicode character
168    OP_ANYNL               match any Unicode newline sequence    OP_ANYNL               match any Unicode newline sequence
169    
# Line 177  two, the name follows immediately; for O Line 187  two, the name follows immediately; for O
187  offset value.  offset value.
188    
189    
190    Matching literal characters
191    ---------------------------
192    
193    The OP_CHAR opcode is followed by a single character that is to be matched
194    casefully. For caseless matching, OP_CHARI is used. In UTF-8 mode, the
195    character may be more than one byte long. (Earlier versions of PCRE used
196    multi-character strings, but this was changed to allow some new features to be
197    added.)
198    
199    
200  Repeating single characters  Repeating single characters
201  ---------------------------  ---------------------------
202    
203  The common repeats (*, +, ?) when applied to a single character use the  The common repeats (*, +, ?) when applied to a single character use the
204  following opcodes:  following opcodes, which come in caseful and caseless versions:
205    
206    OP_STAR    Caseful         Caseless
207    OP_MINSTAR    OP_STAR         OP_STARI
208    OP_POSSTAR    OP_MINSTAR      OP_MINSTARI
209    OP_PLUS    OP_POSSTAR      OP_POSSTARI
210    OP_MINPLUS    OP_PLUS         OP_PLUSI
211    OP_POSPLUS    OP_MINPLUS      OP_MINPLUSI
212    OP_QUERY    OP_POSPLUS      OP_POSPLUSI
213    OP_MINQUERY    OP_QUERY        OP_QUERYI
214    OP_POSQUERY    OP_MINQUERY     OP_MINQUERYI
215      OP_POSQUERY     OP_POSQUERYI
216    
217  In ASCII mode, these are two-byte items; in UTF-8 mode, the length is variable.  In ASCII mode, these are two-byte items; in UTF-8 mode, the length is variable.
218  Those with "MIN" in their name are the minimizing versions. Those with "POS" in  Those with "MIN" in their name are the minimizing versions. Those with "POS" in
219  their names are possessive versions. Each is followed by the character that is  their names are possessive versions. Each is followed by the character that is
220  to be repeated. Other repeats make use of  to be repeated. Other repeats make use of these opcodes:
221    
222    OP_UPTO    Caseful         Caseless
223    OP_MINUPTO    OP_UPTO         OP_UPTOI
224    OP_POSUPTO    OP_MINUPTO      OP_MINUPTOI
225    OP_EXACT    OP_POSUPTO      OP_POSUPTOI
226      OP_EXACT        OP_EXACTI
227    
228  which are followed by a two-byte count (most significant first) and the  Each of these is followed by a two-byte count (most significant first) and the
229  repeated character. OP_UPTO matches from 0 to the given number. A repeat with a  repeated character. OP_UPTO matches from 0 to the given number. A repeat with a
230  non-zero minimum and a fixed maximum is coded as an OP_EXACT followed by an  non-zero minimum and a fixed maximum is coded as an OP_EXACT followed by an
231  OP_UPTO (or OP_MINUPTO or OPT_POSUPTO).  OP_UPTO (or OP_MINUPTO or OPT_POSUPTO).
# Line 244  three bytes: OP_PROP or OP_NOTPROP and t Line 266  three bytes: OP_PROP or OP_NOTPROP and t
266  value.  value.
267    
268    
 Matching literal characters  
 ---------------------------  
   
 The OP_CHAR opcode is followed by a single character that is to be matched  
 casefully. For caseless matching, OP_CHARNC is used. In UTF-8 mode, the  
 character may be more than one byte long. (Earlier versions of PCRE used  
 multi-character strings, but this was changed to allow some new features to be  
 added.)  
   
   
269  Character classes  Character classes
270  -----------------  -----------------
271    
272  If there is only one character, OP_CHAR or OP_CHARNC is used for a positive  If there is only one character, OP_CHAR or OP_CHARI is used for a positive
273  class, and OP_NOT for a negative one (that is, for something like [^a]).  class, and OP_NOT or OP_NOTI for a negative one (that is, for something like
274  However, in UTF-8 mode, the use of OP_NOT applies only to characters with  [^a]). However, in UTF-8 mode, the use of OP_NOT[I] applies only to characters
275  values < 128, because OP_NOT is confined to single bytes.  with values < 128, because OP_NOT[I] is confined to single bytes.
276    
277  Another set of repeating opcodes (OP_NOTSTAR etc.) are used for a repeated,  Another set of 13 repeating opcodes (called OP_NOTSTAR etc.) are used for a
278  negated, single-character class. The normal ones (OP_STAR etc.) are used for a  repeated, negated, single-character class. The normal single-character opcodes
279  repeated positive single-character class.  (OP_STAR, etc.) are used for a repeated positive single-character class.
280    
281  When there's more than one character in a class and all the characters are less  When there is more than one character in a class and all the characters are
282  than 256, OP_CLASS is used for a positive class, and OP_NCLASS for a negative  less than 256, OP_CLASS is used for a positive class, and OP_NCLASS for a
283  one. In either case, the opcode is followed by a 32-byte bit map containing a 1  negative one. In either case, the opcode is followed by a 32-byte bit map
284  bit for every character that is acceptable. The bits are counted from the least  containing a 1 bit for every character that is acceptable. The bits are counted
285  significant end of each byte.  from the least significant end of each byte. In caseless mode, bits for both
286    cases are set.
287    
288  The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8 mode,  The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8 mode,
289  subject characters with values greater than 256 can be handled correctly. For  subject characters with values greater than 256 can be handled correctly. For
290  OP_CLASS they don't match, whereas for OP_NCLASS they do.  OP_CLASS they do not match, whereas for OP_NCLASS they do.
291    
292  For classes containing characters with values > 255, OP_XCLASS is used. It  For classes containing characters with values > 255, OP_XCLASS is used. It
293  optionally uses a bit map (if any characters lie within it), followed by a list  optionally uses a bit map (if any characters lie within it), followed by a list
294  of pairs and single characters. There is a flag character than indicates  of pairs (for a range) and single characters. In caseless mode, both cases are
295  whether it's a positive or a negative class.  explicitly listed. There is a flag character than indicates whether it is a
296    positive or a negative class.
297    
298    
299  Back references  Back references
300  ---------------  ---------------
301    
302  OP_REF is followed by two bytes containing the reference number.  OP_REF (caseful) or OP_REFI (caseless) is followed by two bytes containing the
303    reference number.
304    
305    
306  Repeating character classes and back references  Repeating character classes and back references
307  -----------------------------------------------  -----------------------------------------------
308    
309  Single-character classes are handled specially (see above). This section  Single-character classes are handled specially (see above). This section
310  applies to OP_CLASS and OP_REF. In both cases, the repeat information follows  applies to OP_CLASS and OP_REF[I]. In both cases, the repeat information
311  the base item. The matching code looks at the following opcode to see if it is  follows the base item. The matching code looks at the following opcode to see
312  one of  if it is one of
313    
314    OP_CRSTAR    OP_CRSTAR
315    OP_CRMINSTAR    OP_CRMINSTAR
# Line 423  start of the following item, and another Line 438  start of the following item, and another
438  next item.  next item.
439    
440    
 Changing options  
 ----------------  
   
 If any of the /i, /m, or /s options are changed within a pattern, an OP_OPT  
 opcode is compiled, followed by one byte containing the new settings of these  
 flags. If there are several alternatives, there is an occurrence of OP_OPT at  
 the start of all those following the first options change, to set appropriate  
 options for the start of the alternative. Immediately after the end of the  
 group there is another such item to reset the flags to their previous values. A  
 change of flag right at the very start of the pattern can be handled entirely  
 at compile time, and so does not cause anything to be put into the compiled  
 data.  
   
441  Philip Hazel  Philip Hazel
442  October 2010  May 2011

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