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C/C++ Source or Header | 1995-05-19 | 15.5 KB | 380 lines

#include <stdlib.h> #include <sys/types.h> #include <string.h> #include <malloc.h> extern char *bcopy(), *bzero(); #ifdef SOMEDAY #define ISALNUM(c) isalnum(c) #define ISALPHA(c) isalpha(c) #else #define ISALNUM(c) (isascii(c) && isalnum(c)) #define ISALPHA(c) (isascii(c) && isalpha(c)) #endif /* 1 means plain parentheses serve as grouping, and backslash parentheses are needed for literal searching. 0 means backslash-parentheses are grouping, and plain parentheses are for literal searching. */ #define RE_NO_BK_PARENS 1 /* 1 means plain | serves as the "or"-operator, and \| is a literal. 0 means \| serves as the "or"-operator, and | is a literal. */ #define RE_NO_BK_VBAR 2 /* 0 means plain + or ? serves as an operator, and \+, \? are literals. 1 means \+, \? are operators and plain +, ? are literals. */ #define RE_BK_PLUS_QM 4 /* 1 means | binds tighter than ^ or $. 0 means the contrary. */ #define RE_TIGHT_VBAR 8 /* 1 means treat \n as an _OR operator 0 means treat it as a normal character */ #define RE_NEWLINE_OR 16 /* 0 means that a special characters (such as *, ^, and $) always have their special meaning regardless of the surrounding context. 1 means that special characters may act as normal characters in some contexts. Specifically, this applies to: ^ - only special at the beginning, or after ( or | $ - only special at the end, or before ) or | *, +, ? - only special when not after the beginning, (, or | */ #define RE_CONTEXT_INDEP_OPS 32 /* Now define combinations of bits for the standard possibilities. */ #define RE_SYNTAX_AWK (RE_NO_BK_PARENS | RE_NO_BK_VBAR | RE_CONTEXT_INDEP_OPS) #define RE_SYNTAX_EGREP (RE_SYNTAX_AWK | RE_NEWLINE_OR) #define RE_SYNTAX_GREP (RE_BK_PLUS_QM | RE_NEWLINE_OR) #define RE_SYNTAX_EMACS 0 /* Number of bits in an unsigned char. */ #define CHARBITS 8 /* First integer value that is greater than any character code. */ #define _NOTCHAR (1 << CHARBITS) /* INTBITS need not be exact, just a lower bound. */ #define INTBITS (CHARBITS * sizeof (int)) /* Number of ints required to hold a bit for every character. */ #define _CHARSET_INTS ((_NOTCHAR + INTBITS - 1) / INTBITS) /* Sets of unsigned characters are stored as bit vectors in arrays of ints. */ typedef int _charset[_CHARSET_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. */ _ALLBEGLINE, /* _ALLBEGLINE is a terminal symbol that matches the empty string if it is at the beginning of a line; _ALLBEGLINE applies to the entire regexp and can only occur as the first token thereof. _ALLBEGLINE never appears in the parse tree; a _BEGLINE is prepended with _CAT to the entire regexp instead. */ _ENDLINE, /* _ENDLINE is a terminal symbol that matches the empty string if it is at the end of a line. */ _ALLENDLINE, /* _ALLENDLINE is to _ENDLINE as _ALLBEGLINE is to _BEGLINE. */ _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. */ _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. */ _LPAREN, /* _LPAREN never appears in the parse tree, it is only a lexeme. */ _RPAREN, /* _RPAREN never appears in the parse tree. */ _SET /* _SET 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 regexp; the index of the array corresponding to a given set token is given by _SET_INDEX(t). */ #define _SET_INDEX(t) ((t) - _SET) /* 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 { long index; /* Index into the parse array. */ int 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 regexp 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. */ unsigned newline:1, /* True if previous state matched newline. */ letter:1, /* True if previous state matched a letter. */ backref:1, /* True if this state matches a \<digit>. */ constraint:8; /* Constraint for this state to accept. */ int first_end; /* Token value of the first _END in elems. */ } _dfa_state; /* If an r.e. is at most MUST_MAX characters long, we look for a string which must appear in it; whatever's found is dropped into the struct reg. */ #define MUST_MAX 50 /* A compiled regular expression. */ struct regexp { /* Stuff built by the scanner. */ _charset *charsets; /* Array of character sets for _SET tokens. */ int cindex; /* Index for adding new charsets. */ int calloc; /* Number of charsets 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 regparse(). */ /* Stuff owned by the state builder. */ _dfa_state *states; /* States of the regexp. */ 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 regexecute 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. */ char must[MUST_MAX]; int mustn; }; /* Some macros for user access to regexp 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, reg) \ _SUCCEEDS_IN_CONTEXT((reg).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, reg) (-(reg).states[state].first_end) /* Entry points. */ /* Regsyntax() takes two arguments; the first sets the syntax bits described earlier in this file, and the second sets the case-folding flag. */ extern void regsyntax(int, int); /* Compile the given string of the given length into the given struct regexp. Final argument is a flag specifying whether to build a searching or an exact matcher. */ extern void regcompile(const char *, size_t, struct regexp *, int); /* Execute the given struct regexp 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 *regexecute(struct regexp *, char *, char *, int, int *, int *); /* Free the storage held by the components of a struct regexp. */ extern void regfree(struct regexp *); /* Entry points for people who know what they're doing. */ /* Initialize the components of a struct regexp. */ extern void reginit(struct regexp *); /* Incrementally parse a string of given length into a struct regexp. */ extern void regparse(const char *, size_t, struct regexp *); /* Analyze a parsed regexp; second argument tells whether to build a searching or an exact matcher. */ extern void reganalyze(struct regexp *, int); /* Compute, for each possible character, the transitions out of a given state, storing them in an array of integers. */ extern void regstate(int, struct regexp *, int []); /* Error handling. */ /* Regerror() is called by the regexp routines whenever an error occurs. It takes a single argument, a NUL-terminated string describing the error. The default regerror() prints the error message to stderr and exits. The user can provide a different regfree() if so desired. */ extern void regerror(const char *);