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C/C++ Source or Header | 1999-10-06 | 14.5 KB | 370 lines

/* dfa.h - declarations for GNU deterministic regexp compiler Copyright (C) 1988 Free Software Foundation, Inc. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ /* Written June, 1988 by Mike Haertel */ /* FIXME: 2. We should not export so much of the DFA internals. In addition to clobbering modularity, we eat up valuable name space. */ #ifndef PARAMS # if __STDC__ typedef void *ptr_t; # define PARAMS(x) x # else typedef char *ptr_t; # ifndef const # define const # endif # define PARAMS(x) () # endif #endif /* Number of bits in an unsigned char. */ #ifndef CHARBITS #define CHARBITS 8 #endif /* First integer value that is greater than any character code. */ #define NOTCHAR (1 << CHARBITS) /* INTBITS need not be exact, just a lower bound. */ #ifndef INTBITS #define INTBITS (CHARBITS * sizeof (int)) #endif /* Number of ints required to hold a bit for every character. */ #define CHARCLASS_INTS ((NOTCHAR + INTBITS - 1) / INTBITS) /* Sets of unsigned characters are stored as bit vectors in arrays of ints. */ typedef int charclass[CHARCLASS_INTS]; /* The regexp is parsed into an array of tokens in postfix form. Some tokens are operators and others are terminal symbols. Most (but not all) of these codes are returned by the lexical analyzer. */ typedef enum { END = -1, /* END is a terminal symbol that matches the end of input; any value of END or less in the parse tree is such a symbol. Accepting states of the DFA are those that would have a transition on END. */ /* Ordinary character values are terminal symbols that match themselves. */ EMPTY = NOTCHAR, /* EMPTY is a terminal symbol that matches the empty string. */ BACKREF, /* BACKREF is generated by \<digit>; it it not completely handled. If the scanner detects a transition on backref, it returns a kind of "semi-success" indicating that the match will have to be verified with a backtracking matcher. */ BEGLINE, /* BEGLINE is a terminal symbol that matches the empty string if it is at the beginning of a line. */ ENDLINE, /* ENDLINE is a terminal symbol that matches the empty string if it is at the end of a line. */ BEGWORD, /* BEGWORD is a terminal symbol that matches the empty string if it is at the beginning of a word. */ ENDWORD, /* ENDWORD is a terminal symbol that matches the empty string if it is at the end of a word. */ LIMWORD, /* LIMWORD is a terminal symbol that matches the empty string if it is at the beginning or the end of a word. */ NOTLIMWORD, /* NOTLIMWORD is a terminal symbol that matches the empty string if it is not at the beginning or end of a word. */ QMARK, /* QMARK is an operator of one argument that matches zero or one occurences of its argument. */ STAR, /* STAR is an operator of one argument that matches the Kleene closure (zero or more occurrences) of its argument. */ PLUS, /* PLUS is an operator of one argument that matches the positive closure (one or more occurrences) of its argument. */ REPMN, /* REPMN is a lexical token corresponding to the {m,n} construct. REPMN never appears in the compiled token vector. */ CAT, /* CAT is an operator of two arguments that matches the concatenation of its arguments. CAT is never returned by the lexical analyzer. */ OR, /* OR is an operator of two arguments that matches either of its arguments. */ ORTOP, /* OR at the toplevel in the parse tree. This is used for a boyer-moore heuristic. */ LPAREN, /* LPAREN never appears in the parse tree, it is only a lexeme. */ RPAREN, /* RPAREN never appears in the parse tree. */ CSET /* CSET and (and any value greater) is a terminal symbol that matches any of a class of characters. */ } token; /* Sets are stored in an array in the compiled dfa; the index of the array corresponding to a given set token is given by SET_INDEX(t). */ #define SET_INDEX(t) ((t) - CSET) /* Sometimes characters can only be matched depending on the surrounding context. Such context decisions depend on what the previous character was, and the value of the current (lookahead) character. Context dependent constraints are encoded as 8 bit integers. Each bit that is set indicates that the constraint succeeds in the corresponding context. bit 7 - previous and current are newlines bit 6 - previous was newline, current isn't bit 5 - previous wasn't newline, current is bit 4 - neither previous nor current is a newline bit 3 - previous and current are word-constituents bit 2 - previous was word-constituent, current isn't bit 1 - previous wasn't word-constituent, current is bit 0 - neither previous nor current is word-constituent Word-constituent characters are those that satisfy isalnum(). The macro SUCCEEDS_IN_CONTEXT determines whether a a given constraint succeeds in a particular context. Prevn is true if the previous character was a newline, currn is true if the lookahead character is a newline. Prevl and currl similarly depend upon whether the previous and current characters are word-constituent letters. */ #define MATCHES_NEWLINE_CONTEXT(constraint, prevn, currn) \ ((constraint) & 1 << (((prevn) ? 2 : 0) + ((currn) ? 1 : 0) + 4)) #define MATCHES_LETTER_CONTEXT(constraint, prevl, currl) \ ((constraint) & 1 << (((prevl) ? 2 : 0) + ((currl) ? 1 : 0))) #define SUCCEEDS_IN_CONTEXT(constraint, prevn, currn, prevl, currl) \ (MATCHES_NEWLINE_CONTEXT(constraint, prevn, currn) \ && MATCHES_LETTER_CONTEXT(constraint, prevl, currl)) /* The following macros give information about what a constraint depends on. */ #define PREV_NEWLINE_DEPENDENT(constraint) \ (((constraint) & 0xc0) >> 2 != ((constraint) & 0x30)) #define PREV_LETTER_DEPENDENT(constraint) \ (((constraint) & 0x0c) >> 2 != ((constraint) & 0x03)) /* Tokens that match the empty string subject to some constraint actually work by applying that constraint to determine what may follow them, taking into account what has gone before. The following values are the constraints corresponding to the special tokens previously defined. */ #define NO_CONSTRAINT 0xff #define BEGLINE_CONSTRAINT 0xcf #define ENDLINE_CONSTRAINT 0xaf #define BEGWORD_CONSTRAINT 0xf2 #define ENDWORD_CONSTRAINT 0xf4 #define LIMWORD_CONSTRAINT 0xf6 #define NOTLIMWORD_CONSTRAINT 0xf9 /* States of the recognizer correspond to sets of positions in the parse tree, together with the constraints under which they may be matched. So a position is encoded as an index into the parse tree together with a constraint. */ typedef struct { unsigned index; /* Index into the parse array. */ unsigned constraint; /* Constraint for matching this position. */ } position; /* Sets of positions are stored as arrays. */ typedef struct { position *elems; /* Elements of this position set. */ int nelem; /* Number of elements in this set. */ } position_set; /* A state of the dfa consists of a set of positions, some flags, and the token value of the lowest-numbered position of the state that contains an END token. */ typedef struct { int hash; /* Hash of the positions of this state. */ position_set elems; /* Positions this state could match. */ char newline; /* True if previous state matched newline. */ char letter; /* True if previous state matched a letter. */ char backref; /* True if this state matches a \<digit>. */ unsigned char constraint; /* Constraint for this state to accept. */ int first_end; /* Token value of the first END in elems. */ } dfa_state; /* Element of a list of strings, at least one of which is known to appear in any R.E. matching the DFA. */ struct dfamust { int exact; char *must; struct dfamust *next; }; /* A compiled regular expression. */ struct dfa { /* Stuff built by the scanner. */ charclass *charclasses; /* Array of character sets for CSET tokens. */ int cindex; /* Index for adding new charclasses. */ int calloc; /* Number of charclasses currently allocated. */ /* Stuff built by the parser. */ token *tokens; /* Postfix parse array. */ int tindex; /* Index for adding new tokens. */ int talloc; /* Number of tokens currently allocated. */ int depth; /* Depth required of an evaluation stack used for depth-first traversal of the parse tree. */ int nleaves; /* Number of leaves on the parse tree. */ int nregexps; /* Count of parallel regexps being built with dfaparse(). */ /* Stuff owned by the state builder. */ dfa_state *states; /* States of the dfa. */ int sindex; /* Index for adding new states. */ int salloc; /* Number of states currently allocated. */ /* Stuff built by the structure analyzer. */ position_set *follows; /* Array of follow sets, indexed by position index. The follow of a position is the set of positions containing characters that could conceivably follow a character matching the given position in a string matching the regexp. Allocated to the maximum possible position index. */ int searchflag; /* True if we are supposed to build a searching as opposed to an exact matcher. A searching matcher finds the first and shortest string matching a regexp anywhere in the buffer, whereas an exact matcher finds the longest string matching, but anchored to the beginning of the buffer. */ /* Stuff owned by the executor. */ int tralloc; /* Number of transition tables that have slots so far. */ int trcount; /* Number of transition tables that have actually been built. */ int **trans; /* Transition tables for states that can never accept. If the transitions for a state have not yet been computed, or the state could possibly accept, its entry in this table is NULL. */ int **realtrans; /* Trans always points to realtrans + 1; this is so trans[-1] can contain NULL. */ int **fails; /* Transition tables after failing to accept on a state that potentially could do so. */ int *success; /* Table of acceptance conditions used in dfaexec and computed in build_state. */ int *newlines; /* Transitions on newlines. The entry for a newline in any transition table is always -1 so we can count lines without wasting too many cycles. The transition for a newline is stored separately and handled as a special case. Newline is also used as a sentinel at the end of the buffer. */ struct dfamust *musts; /* List of strings, at least one of which is known to appear in any r.e. matching the dfa. */ }; /* Some macros for user access to dfa internals. */ /* ACCEPTING returns true if s could possibly be an accepting state of r. */ #define ACCEPTING(s, r) ((r).states[s].constraint) /* ACCEPTS_IN_CONTEXT returns true if the given state accepts in the specified context. */ #define ACCEPTS_IN_CONTEXT(prevn, currn, prevl, currl, state, dfa) \ SUCCEEDS_IN_CONTEXT((dfa).states[state].constraint, \ prevn, currn, prevl, currl) /* FIRST_MATCHING_REGEXP returns the index number of the first of parallel regexps that a given state could accept. Parallel regexps are numbered starting at 1. */ #define FIRST_MATCHING_REGEXP(state, dfa) (-(dfa).states[state].first_end) /* Entry points. */ /* dfasyntax() takes two arguments; the first sets the syntax bits described earlier in this file, and the second sets the case-folding flag. */ extern void dfasyntax PARAMS ((reg_syntax_t, int)); /* Compile the given string of the given length into the given struct dfa. Final argument is a flag specifying whether to build a searching or an exact matcher. */ extern void dfacomp PARAMS ((char *, size_t, struct dfa *, int)); /* Execute the given struct dfa on the buffer of characters. The first char * points to the beginning, and the second points to the first character after the end of the buffer, which must be a writable place so a sentinel end-of-buffer marker can be stored there. The second-to-last argument is a flag telling whether to allow newlines to be part of a string matching the regexp. The next-to-last argument, if non-NULL, points to a place to increment every time we see a newline. The final argument, if non-NULL, points to a flag that will be set if further examination by a backtracking matcher is needed in order to verify backreferencing; otherwise the flag will be cleared. Returns NULL if no match is found, or a pointer to the first character after the first & shortest matching string in the buffer. */ extern char *dfaexec PARAMS ((struct dfa *, char *, char *, int, int *, int *)); /* Free the storage held by the components of a struct dfa. */ extern void dfafree PARAMS ((struct dfa *)); /* Entry points for people who know what they're doing. */ /* Initialize the components of a struct dfa. */ extern void dfainit PARAMS ((struct dfa *)); /* Incrementally parse a string of given length into a struct dfa. */ extern void dfaparse PARAMS ((char *, size_t, struct dfa *)); /* Analyze a parsed regexp; second argument tells whether to build a searching or an exact matcher. */ extern void dfaanalyze PARAMS ((struct dfa *, int)); /* Compute, for each possible character, the transitions out of a given state, storing them in an array of integers. */ extern void dfastate PARAMS ((int, struct dfa *, int [])); /* Error handling. */ /* dfaerror() is called by the regexp routines whenever an error occurs. It takes a single argument, a NUL-terminated string describing the error. The default dfaerror() prints the error message to stderr and exits. The user can provide a different dfafree() if so desired. */ extern void dfaerror PARAMS ((const char *));