1 /* dfa.h - declarations for GNU deterministic regexp compiler
2 Copyright (C) 1988 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */
18 /* Written June, 1988 by Mike Haertel */
21 2. We should not export so much of the DFA internals.
22 In addition to clobbering modularity, we eat up valuable
25 /* Number of bits in an unsigned char. */
30 /* First integer value that is greater than any character code. */
31 #define NOTCHAR (1 << CHARBITS)
33 /* INTBITS need not be exact, just a lower bound. */
35 #define INTBITS (CHARBITS * sizeof (int))
38 /* Number of ints required to hold a bit for every character. */
39 #define CHARCLASS_INTS ((NOTCHAR + INTBITS - 1) / INTBITS)
41 /* Sets of unsigned characters are stored as bit vectors in arrays of ints. */
42 typedef int charclass[CHARCLASS_INTS];
44 /* The regexp is parsed into an array of tokens in postfix form. Some tokens
45 are operators and others are terminal symbols. Most (but not all) of these
46 codes are returned by the lexical analyzer. */
50 END = -1, /* END is a terminal symbol that matches the
51 end of input; any value of END or less in
52 the parse tree is such a symbol. Accepting
53 states of the DFA are those that would have
54 a transition on END. */
56 /* Ordinary character values are terminal symbols that match themselves. */
58 EMPTY = NOTCHAR, /* EMPTY is a terminal symbol that matches
61 BACKREF, /* BACKREF is generated by \<digit>; it
62 it not completely handled. If the scanner
63 detects a transition on backref, it returns
64 a kind of "semi-success" indicating that
65 the match will have to be verified with
66 a backtracking matcher. */
68 BEGLINE, /* BEGLINE is a terminal symbol that matches
69 the empty string if it is at the beginning
72 ENDLINE, /* ENDLINE is a terminal symbol that matches
73 the empty string if it is at the end of
76 BEGWORD, /* BEGWORD is a terminal symbol that matches
77 the empty string if it is at the beginning
80 ENDWORD, /* ENDWORD is a terminal symbol that matches
81 the empty string if it is at the end of
84 LIMWORD, /* LIMWORD is a terminal symbol that matches
85 the empty string if it is at the beginning
86 or the end of a word. */
88 NOTLIMWORD, /* NOTLIMWORD is a terminal symbol that
89 matches the empty string if it is not at
90 the beginning or end of a word. */
92 QMARK, /* QMARK is an operator of one argument that
93 matches zero or one occurences of its
96 STAR, /* STAR is an operator of one argument that
97 matches the Kleene closure (zero or more
98 occurrences) of its argument. */
100 PLUS, /* PLUS is an operator of one argument that
101 matches the positive closure (one or more
102 occurrences) of its argument. */
104 REPMN, /* REPMN is a lexical token corresponding
105 to the {m,n} construct. REPMN never
106 appears in the compiled token vector. */
108 CAT, /* CAT is an operator of two arguments that
109 matches the concatenation of its
110 arguments. CAT is never returned by the
113 OR, /* OR is an operator of two arguments that
114 matches either of its arguments. */
116 ORTOP, /* OR at the toplevel in the parse tree.
117 This is used for a boyer-moore heuristic. */
119 LPAREN, /* LPAREN never appears in the parse tree,
120 it is only a lexeme. */
122 RPAREN, /* RPAREN never appears in the parse tree. */
124 CSET /* CSET and (and any value greater) is a
125 terminal symbol that matches any of a
126 class of characters. */
129 /* Sets are stored in an array in the compiled dfa; the index of the
130 array corresponding to a given set token is given by SET_INDEX(t). */
131 #define SET_INDEX(t) ((t) - CSET)
133 /* Sometimes characters can only be matched depending on the surrounding
134 context. Such context decisions depend on what the previous character
135 was, and the value of the current (lookahead) character. Context
136 dependent constraints are encoded as 8 bit integers. Each bit that
137 is set indicates that the constraint succeeds in the corresponding
140 bit 7 - previous and current are newlines
141 bit 6 - previous was newline, current isn't
142 bit 5 - previous wasn't newline, current is
143 bit 4 - neither previous nor current is a newline
144 bit 3 - previous and current are word-constituents
145 bit 2 - previous was word-constituent, current isn't
146 bit 1 - previous wasn't word-constituent, current is
147 bit 0 - neither previous nor current is word-constituent
149 Word-constituent characters are those that satisfy isalnum().
151 The macro SUCCEEDS_IN_CONTEXT determines whether a a given constraint
152 succeeds in a particular context. Prevn is true if the previous character
153 was a newline, currn is true if the lookahead character is a newline.
154 Prevl and currl similarly depend upon whether the previous and current
155 characters are word-constituent letters. */
156 #define MATCHES_NEWLINE_CONTEXT(constraint, prevn, currn) \
157 ((constraint) & 1 << (((prevn) ? 2 : 0) + ((currn) ? 1 : 0) + 4))
158 #define MATCHES_LETTER_CONTEXT(constraint, prevl, currl) \
159 ((constraint) & 1 << (((prevl) ? 2 : 0) + ((currl) ? 1 : 0)))
160 #define SUCCEEDS_IN_CONTEXT(constraint, prevn, currn, prevl, currl) \
161 (MATCHES_NEWLINE_CONTEXT(constraint, prevn, currn) \
162 && MATCHES_LETTER_CONTEXT(constraint, prevl, currl))
164 /* The following macros give information about what a constraint depends on. */
165 #define PREV_NEWLINE_DEPENDENT(constraint) \
166 (((constraint) & 0xc0) >> 2 != ((constraint) & 0x30))
167 #define PREV_LETTER_DEPENDENT(constraint) \
168 (((constraint) & 0x0c) >> 2 != ((constraint) & 0x03))
170 /* Tokens that match the empty string subject to some constraint actually
171 work by applying that constraint to determine what may follow them,
172 taking into account what has gone before. The following values are
173 the constraints corresponding to the special tokens previously defined. */
174 #define NO_CONSTRAINT 0xff
175 #define BEGLINE_CONSTRAINT 0xcf
176 #define ENDLINE_CONSTRAINT 0xaf
177 #define BEGWORD_CONSTRAINT 0xf2
178 #define ENDWORD_CONSTRAINT 0xf4
179 #define LIMWORD_CONSTRAINT 0xf6
180 #define NOTLIMWORD_CONSTRAINT 0xf9
182 /* States of the recognizer correspond to sets of positions in the parse
183 tree, together with the constraints under which they may be matched.
184 So a position is encoded as an index into the parse tree together with
188 unsigned index; /* Index into the parse array. */
189 unsigned constraint; /* Constraint for matching this position. */
192 /* Sets of positions are stored as arrays. */
195 position *elems; /* Elements of this position set. */
196 int nelem; /* Number of elements in this set. */
199 /* A state of the dfa consists of a set of positions, some flags,
200 and the token value of the lowest-numbered position of the state that
201 contains an END token. */
204 int hash; /* Hash of the positions of this state. */
205 position_set elems; /* Positions this state could match. */
206 char newline; /* True if previous state matched newline. */
207 char letter; /* True if previous state matched a letter. */
208 char backref; /* True if this state matches a \<digit>. */
209 unsigned char constraint; /* Constraint for this state to accept. */
210 int first_end; /* Token value of the first END in elems. */
213 /* Element of a list of strings, at least one of which is known to
214 appear in any R.E. matching the DFA. */
219 struct dfamust *next;
222 /* A compiled regular expression. */
225 /* Stuff built by the scanner. */
226 charclass *charclasses; /* Array of character sets for CSET tokens. */
227 int cindex; /* Index for adding new charclasses. */
228 int calloc; /* Number of charclasses currently allocated. */
230 /* Stuff built by the parser. */
231 token *tokens; /* Postfix parse array. */
232 int tindex; /* Index for adding new tokens. */
233 int talloc; /* Number of tokens currently allocated. */
234 int depth; /* Depth required of an evaluation stack
235 used for depth-first traversal of the
237 int nleaves; /* Number of leaves on the parse tree. */
238 int nregexps; /* Count of parallel regexps being built
241 /* Stuff owned by the state builder. */
242 dfa_state *states; /* States of the dfa. */
243 int sindex; /* Index for adding new states. */
244 int salloc; /* Number of states currently allocated. */
246 /* Stuff built by the structure analyzer. */
247 position_set *follows; /* Array of follow sets, indexed by position
248 index. The follow of a position is the set
249 of positions containing characters that
250 could conceivably follow a character
251 matching the given position in a string
252 matching the regexp. Allocated to the
253 maximum possible position index. */
254 int searchflag; /* True if we are supposed to build a searching
255 as opposed to an exact matcher. A searching
256 matcher finds the first and shortest string
257 matching a regexp anywhere in the buffer,
258 whereas an exact matcher finds the longest
259 string matching, but anchored to the
260 beginning of the buffer. */
262 /* Stuff owned by the executor. */
263 int tralloc; /* Number of transition tables that have
265 int trcount; /* Number of transition tables that have
266 actually been built. */
267 int **trans; /* Transition tables for states that can
268 never accept. If the transitions for a
269 state have not yet been computed, or the
270 state could possibly accept, its entry in
271 this table is NULL. */
272 int **realtrans; /* Trans always points to realtrans + 1; this
273 is so trans[-1] can contain NULL. */
274 int **fails; /* Transition tables after failing to accept
275 on a state that potentially could do so. */
276 int *success; /* Table of acceptance conditions used in
277 dfaexec and computed in build_state. */
278 int *newlines; /* Transitions on newlines. The entry for a
279 newline in any transition table is always
280 -1 so we can count lines without wasting
281 too many cycles. The transition for a
282 newline is stored separately and handled
283 as a special case. Newline is also used
284 as a sentinel at the end of the buffer. */
285 struct dfamust *musts; /* List of strings, at least one of which
286 is known to appear in any r.e. matching
290 /* Some macros for user access to dfa internals. */
292 /* ACCEPTING returns true if s could possibly be an accepting state of r. */
293 #define ACCEPTING(s, r) ((r).states[s].constraint)
295 /* ACCEPTS_IN_CONTEXT returns true if the given state accepts in the
296 specified context. */
297 #define ACCEPTS_IN_CONTEXT(prevn, currn, prevl, currl, state, dfa) \
298 SUCCEEDS_IN_CONTEXT((dfa).states[state].constraint, \
299 prevn, currn, prevl, currl)
301 /* FIRST_MATCHING_REGEXP returns the index number of the first of parallel
302 regexps that a given state could accept. Parallel regexps are numbered
304 #define FIRST_MATCHING_REGEXP(state, dfa) (-(dfa).states[state].first_end)
310 /* dfasyntax() takes two arguments; the first sets the syntax bits described
311 earlier in this file, and the second sets the case-folding flag. */
312 extern void dfasyntax(reg_syntax_t, int);
314 /* Compile the given string of the given length into the given struct dfa.
315 Final argument is a flag specifying whether to build a searching or an
317 extern void dfacomp(char *, size_t, struct dfa *, int);
319 /* Execute the given struct dfa on the buffer of characters. The
320 first char * points to the beginning, and the second points to the
321 first character after the end of the buffer, which must be a writable
322 place so a sentinel end-of-buffer marker can be stored there. The
323 second-to-last argument is a flag telling whether to allow newlines to
324 be part of a string matching the regexp. The next-to-last argument,
325 if non-NULL, points to a place to increment every time we see a
326 newline. The final argument, if non-NULL, points to a flag that will
327 be set if further examination by a backtracking matcher is needed in
328 order to verify backreferencing; otherwise the flag will be cleared.
329 Returns NULL if no match is found, or a pointer to the first
330 character after the first & shortest matching string in the buffer. */
331 extern char *dfaexec(struct dfa *, char *, char *, int, int *, int *);
333 /* Free the storage held by the components of a struct dfa. */
334 extern void dfafree(struct dfa *);
336 /* Entry points for people who know what they're doing. */
338 /* Initialize the components of a struct dfa. */
339 extern void dfainit(struct dfa *);
341 /* Incrementally parse a string of given length into a struct dfa. */
342 extern void dfaparse(char *, size_t, struct dfa *);
344 /* Analyze a parsed regexp; second argument tells whether to build a searching
345 or an exact matcher. */
346 extern void dfaanalyze(struct dfa *, int);
348 /* Compute, for each possible character, the transitions out of a given
349 state, storing them in an array of integers. */
350 extern void dfastate(int, struct dfa *, int []);
352 /* Error handling. */
354 /* dfaerror() is called by the regexp routines whenever an error occurs. It
355 takes a single argument, a NUL-terminated string describing the error.
356 The default dfaerror() prints the error message to stderr and exits.
357 The user can provide a different dfafree() if so desired. */
358 extern void dfaerror(const char *);
360 #else /* ! __STDC__ */
361 extern void dfasyntax(), dfacomp(), dfafree(), dfainit(), dfaparse();
362 extern void dfaanalyze(), dfastate(), dfaerror();
363 extern char *dfaexec();
364 #endif /* ! __STDC__ */