364 lines
14 KiB
C++
364 lines
14 KiB
C++
/* dfa.h - declarations for GNU deterministic regexp compiler
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Copyright (C) 1988 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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$Id: dfa.h,v 1.3 1993/08/02 17:41:24 mycroft Exp $
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*/
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/* Written June, 1988 by Mike Haertel */
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/* FIXME:
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2. We should not export so much of the DFA internals.
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In addition to clobbering modularity, we eat up valuable
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name space. */
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/* Number of bits in an unsigned char. */
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#define CHARBITS 8
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/* First integer value that is greater than any character code. */
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#define NOTCHAR (1 << CHARBITS)
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/* INTBITS need not be exact, just a lower bound. */
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#define INTBITS (CHARBITS * sizeof (int))
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/* Number of ints required to hold a bit for every character. */
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#define CHARCLASS_INTS ((NOTCHAR + INTBITS - 1) / INTBITS)
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/* Sets of unsigned characters are stored as bit vectors in arrays of ints. */
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typedef int charclass[CHARCLASS_INTS];
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/* The regexp is parsed into an array of tokens in postfix form. Some tokens
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are operators and others are terminal symbols. Most (but not all) of these
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codes are returned by the lexical analyzer. */
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typedef enum
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{
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END = -1, /* END is a terminal symbol that matches the
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end of input; any value of END or less in
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the parse tree is such a symbol. Accepting
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states of the DFA are those that would have
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a transition on END. */
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/* Ordinary character values are terminal symbols that match themselves. */
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EMPTY = NOTCHAR, /* EMPTY is a terminal symbol that matches
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the empty string. */
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BACKREF, /* BACKREF is generated by \<digit>; it
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it not completely handled. If the scanner
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detects a transition on backref, it returns
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a kind of "semi-success" indicating that
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the match will have to be verified with
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a backtracking matcher. */
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BEGLINE, /* BEGLINE is a terminal symbol that matches
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the empty string if it is at the beginning
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of a line. */
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ENDLINE, /* ENDLINE is a terminal symbol that matches
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the empty string if it is at the end of
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a line. */
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BEGWORD, /* BEGWORD is a terminal symbol that matches
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the empty string if it is at the beginning
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of a word. */
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ENDWORD, /* ENDWORD is a terminal symbol that matches
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the empty string if it is at the end of
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a word. */
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LIMWORD, /* LIMWORD is a terminal symbol that matches
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the empty string if it is at the beginning
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or the end of a word. */
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NOTLIMWORD, /* NOTLIMWORD is a terminal symbol that
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matches the empty string if it is not at
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the beginning or end of a word. */
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QMARK, /* QMARK is an operator of one argument that
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matches zero or one occurences of its
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argument. */
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STAR, /* STAR is an operator of one argument that
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matches the Kleene closure (zero or more
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occurrences) of its argument. */
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PLUS, /* PLUS is an operator of one argument that
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matches the positive closure (one or more
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occurrences) of its argument. */
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REPMN, /* REPMN is a lexical token corresponding
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to the {m,n} construct. REPMN never
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appears in the compiled token vector. */
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CAT, /* CAT is an operator of two arguments that
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matches the concatenation of its
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arguments. CAT is never returned by the
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lexical analyzer. */
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OR, /* OR is an operator of two arguments that
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matches either of its arguments. */
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ORTOP, /* OR at the toplevel in the parse tree.
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This is used for a boyer-moore heuristic. */
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LPAREN, /* LPAREN never appears in the parse tree,
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it is only a lexeme. */
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RPAREN, /* RPAREN never appears in the parse tree. */
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CSET /* CSET and (and any value greater) is a
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terminal symbol that matches any of a
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class of characters. */
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} token;
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/* Sets are stored in an array in the compiled dfa; the index of the
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array corresponding to a given set token is given by SET_INDEX(t). */
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#define SET_INDEX(t) ((t) - CSET)
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/* Sometimes characters can only be matched depending on the surrounding
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context. Such context decisions depend on what the previous character
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was, and the value of the current (lookahead) character. Context
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dependent constraints are encoded as 8 bit integers. Each bit that
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is set indicates that the constraint succeeds in the corresponding
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context.
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bit 7 - previous and current are newlines
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bit 6 - previous was newline, current isn't
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bit 5 - previous wasn't newline, current is
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bit 4 - neither previous nor current is a newline
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bit 3 - previous and current are word-constituents
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bit 2 - previous was word-constituent, current isn't
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bit 1 - previous wasn't word-constituent, current is
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bit 0 - neither previous nor current is word-constituent
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Word-constituent characters are those that satisfy isalnum().
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The macro SUCCEEDS_IN_CONTEXT determines whether a a given constraint
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succeeds in a particular context. Prevn is true if the previous character
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was a newline, currn is true if the lookahead character is a newline.
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Prevl and currl similarly depend upon whether the previous and current
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characters are word-constituent letters. */
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#define MATCHES_NEWLINE_CONTEXT(constraint, prevn, currn) \
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((constraint) & 1 << (((prevn) ? 2 : 0) + ((currn) ? 1 : 0) + 4))
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#define MATCHES_LETTER_CONTEXT(constraint, prevl, currl) \
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((constraint) & 1 << (((prevl) ? 2 : 0) + ((currl) ? 1 : 0)))
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#define SUCCEEDS_IN_CONTEXT(constraint, prevn, currn, prevl, currl) \
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(MATCHES_NEWLINE_CONTEXT(constraint, prevn, currn) \
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&& MATCHES_LETTER_CONTEXT(constraint, prevl, currl))
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/* The following macros give information about what a constraint depends on. */
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#define PREV_NEWLINE_DEPENDENT(constraint) \
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(((constraint) & 0xc0) >> 2 != ((constraint) & 0x30))
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#define PREV_LETTER_DEPENDENT(constraint) \
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(((constraint) & 0x0c) >> 2 != ((constraint) & 0x03))
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/* Tokens that match the empty string subject to some constraint actually
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work by applying that constraint to determine what may follow them,
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taking into account what has gone before. The following values are
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the constraints corresponding to the special tokens previously defined. */
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#define NO_CONSTRAINT 0xff
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#define BEGLINE_CONSTRAINT 0xcf
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#define ENDLINE_CONSTRAINT 0xaf
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#define BEGWORD_CONSTRAINT 0xf2
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#define ENDWORD_CONSTRAINT 0xf4
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#define LIMWORD_CONSTRAINT 0xf6
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#define NOTLIMWORD_CONSTRAINT 0xf9
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/* States of the recognizer correspond to sets of positions in the parse
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tree, together with the constraints under which they may be matched.
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So a position is encoded as an index into the parse tree together with
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a constraint. */
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typedef struct
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{
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unsigned index; /* Index into the parse array. */
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unsigned constraint; /* Constraint for matching this position. */
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} position;
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/* Sets of positions are stored as arrays. */
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typedef struct
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{
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position *elems; /* Elements of this position set. */
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int nelem; /* Number of elements in this set. */
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} position_set;
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/* A state of the dfa consists of a set of positions, some flags,
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and the token value of the lowest-numbered position of the state that
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contains an END token. */
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typedef struct
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{
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int hash; /* Hash of the positions of this state. */
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position_set elems; /* Positions this state could match. */
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char newline; /* True if previous state matched newline. */
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char letter; /* True if previous state matched a letter. */
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char backref; /* True if this state matches a \<digit>. */
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unsigned char constraint; /* Constraint for this state to accept. */
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int first_end; /* Token value of the first END in elems. */
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} dfa_state;
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/* Element of a list of strings, at least one of which is known to
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appear in any R.E. matching the DFA. */
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struct dfamust
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{
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int exact;
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char *must;
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struct dfamust *next;
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};
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/* A compiled regular expression. */
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struct dfa
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{
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/* Stuff built by the scanner. */
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charclass *charclasses; /* Array of character sets for CSET tokens. */
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int cindex; /* Index for adding new charclasses. */
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int calloc; /* Number of charclasses currently allocated. */
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/* Stuff built by the parser. */
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token *tokens; /* Postfix parse array. */
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int tindex; /* Index for adding new tokens. */
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int talloc; /* Number of tokens currently allocated. */
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int depth; /* Depth required of an evaluation stack
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used for depth-first traversal of the
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parse tree. */
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int nleaves; /* Number of leaves on the parse tree. */
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int nregexps; /* Count of parallel regexps being built
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with dfaparse(). */
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/* Stuff owned by the state builder. */
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dfa_state *states; /* States of the dfa. */
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int sindex; /* Index for adding new states. */
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int salloc; /* Number of states currently allocated. */
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/* Stuff built by the structure analyzer. */
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position_set *follows; /* Array of follow sets, indexed by position
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index. The follow of a position is the set
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of positions containing characters that
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could conceivably follow a character
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matching the given position in a string
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matching the regexp. Allocated to the
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maximum possible position index. */
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int searchflag; /* True if we are supposed to build a searching
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as opposed to an exact matcher. A searching
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matcher finds the first and shortest string
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matching a regexp anywhere in the buffer,
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whereas an exact matcher finds the longest
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string matching, but anchored to the
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beginning of the buffer. */
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/* Stuff owned by the executor. */
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int tralloc; /* Number of transition tables that have
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slots so far. */
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int trcount; /* Number of transition tables that have
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actually been built. */
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int **trans; /* Transition tables for states that can
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never accept. If the transitions for a
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state have not yet been computed, or the
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state could possibly accept, its entry in
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this table is NULL. */
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int **realtrans; /* Trans always points to realtrans + 1; this
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is so trans[-1] can contain NULL. */
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int **fails; /* Transition tables after failing to accept
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on a state that potentially could do so. */
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int *success; /* Table of acceptance conditions used in
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dfaexec and computed in build_state. */
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int *newlines; /* Transitions on newlines. The entry for a
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newline in any transition table is always
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-1 so we can count lines without wasting
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too many cycles. The transition for a
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newline is stored separately and handled
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as a special case. Newline is also used
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as a sentinel at the end of the buffer. */
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struct dfamust *musts; /* List of strings, at least one of which
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is known to appear in any r.e. matching
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the dfa. */
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};
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/* Some macros for user access to dfa internals. */
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/* ACCEPTING returns true if s could possibly be an accepting state of r. */
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#define ACCEPTING(s, r) ((r).states[s].constraint)
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/* ACCEPTS_IN_CONTEXT returns true if the given state accepts in the
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specified context. */
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#define ACCEPTS_IN_CONTEXT(prevn, currn, prevl, currl, state, dfa) \
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SUCCEEDS_IN_CONTEXT((dfa).states[state].constraint, \
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prevn, currn, prevl, currl)
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/* FIRST_MATCHING_REGEXP returns the index number of the first of parallel
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regexps that a given state could accept. Parallel regexps are numbered
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starting at 1. */
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#define FIRST_MATCHING_REGEXP(state, dfa) (-(dfa).states[state].first_end)
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/* Entry points. */
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#if __STDC__
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/* dfasyntax() takes two arguments; the first sets the syntax bits described
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earlier in this file, and the second sets the case-folding flag. */
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extern void dfasyntax(int, int);
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/* Compile the given string of the given length into the given struct dfa.
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Final argument is a flag specifying whether to build a searching or an
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exact matcher. */
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extern void dfacomp(char *, size_t, struct dfa *, int);
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/* Execute the given struct dfa on the buffer of characters. The
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first char * points to the beginning, and the second points to the
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first character after the end of the buffer, which must be a writable
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place so a sentinel end-of-buffer marker can be stored there. The
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second-to-last argument is a flag telling whether to allow newlines to
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be part of a string matching the regexp. The next-to-last argument,
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if non-NULL, points to a place to increment every time we see a
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newline. The final argument, if non-NULL, points to a flag that will
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be set if further examination by a backtracking matcher is needed in
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order to verify backreferencing; otherwise the flag will be cleared.
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Returns NULL if no match is found, or a pointer to the first
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character after the first & shortest matching string in the buffer. */
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extern char *dfaexec(struct dfa *, char *, char *, int, int *, int *);
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/* Free the storage held by the components of a struct dfa. */
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extern void dfafree(struct dfa *);
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/* Entry points for people who know what they're doing. */
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/* Initialize the components of a struct dfa. */
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extern void dfainit(struct dfa *);
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/* Incrementally parse a string of given length into a struct dfa. */
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extern void dfaparse(char *, size_t, struct dfa *);
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/* Analyze a parsed regexp; second argument tells whether to build a searching
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or an exact matcher. */
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extern void dfaanalyze(struct dfa *, int);
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/* Compute, for each possible character, the transitions out of a given
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state, storing them in an array of integers. */
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extern void dfastate(int, struct dfa *, int []);
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/* Error handling. */
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/* dfaerror() is called by the regexp routines whenever an error occurs. It
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takes a single argument, a NUL-terminated string describing the error.
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The default dfaerror() prints the error message to stderr and exits.
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The user can provide a different dfafree() if so desired. */
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extern void dfaerror(char *);
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#else /* ! __STDC__ */
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extern void dfasyntax(), dfacomp(), dfafree(), dfainit(), dfaparse();
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extern void dfaanalyze(), dfastate(), dfaerror();
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extern char *dfaexec();
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#endif /* ! __STDC__ */
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