regcomp.c

早期freebsd实现

/* NOTE: this is derived from Henry Spencer's regexp code, and should not
 * confused with the original package (see point 3 below).  Thanks, Henry!
 */

/* Additional note: this code is very heavily munged from Henry's version
 * in places.  In some spots I've traded clarity for efficiency, so don't
 * blame Henry for some of the lack of readability.
 */

/* $RCSfile: regcomp.c,v $$Revision: 4.0.1.5 $$Date: 92/06/08 15:23:36 $
 *
 * $Log:	regcomp.c,v $
 * Revision 4.0.1.5  92/06/08  15:23:36  lwall
 * patch20: Perl now distinguishes overlapped copies from non-overlapped
 * patch20: /^stuff/ wrongly assumed an implicit $* == 1
 * patch20: /x{0}/ was wrongly interpreted as /x{0,}/
 * patch20: added \W, \S and \D inside /[...]/
 * 
 * Revision 4.0.1.4  91/11/05  22:55:14  lwall
 * patch11: Erratum
 * 
 * Revision 4.0.1.3  91/11/05  18:22:28  lwall
 * patch11: minimum match length calculation in regexp is now cumulative
 * patch11: initial .* in pattern had dependency on value of $*
 * patch11: certain patterns made use of garbage pointers from uncleared memory
 * patch11: prepared for ctype implementations that don't define isascii()
 * 
 * Revision 4.0.1.2  91/06/07  11:48:24  lwall
 * patch4: new copyright notice
 * patch4: /(x+) \1/ incorrectly optimized to not match "xxx xx"
 * patch4: // wouldn't use previous pattern if it started with a null character
 * 
 * Revision 4.0.1.1  91/04/12  09:04:45  lwall
 * patch1: random cleanup in cpp namespace
 * 
 * Revision 4.0  91/03/20  01:39:01  lwall
 * 4.0 baseline.
 * 
 */
/*SUPPRESS 112*/
/*
 * regcomp and regexec -- regsub and regerror are not used in perl
 *
 *	Copyright (c) 1986 by University of Toronto.
 *	Written by Henry Spencer.  Not derived from licensed software.
 *
 *	Permission is granted to anyone to use this software for any
 *	purpose on any computer system, and to redistribute it freely,
 *	subject to the following restrictions:
 *
 *	1. The author is not responsible for the consequences of use of
 *		this software, no matter how awful, even if they arise
 *		from defects in it.
 *
 *	2. The origin of this software must not be misrepresented, either
 *		by explicit claim or by omission.
 *
 *	3. Altered versions must be plainly marked as such, and must not
 *		be misrepresented as being the original software.
 *
 *
 ****    Alterations to Henry's code are...
 ****
 ****    Copyright (c) 1991, Larry Wall
 ****
 ****    You may distribute under the terms of either the GNU General Public
 ****    License or the Artistic License, as specified in the README file.

 *
 * Beware that some of this code is subtly aware of the way operator
 * precedence is structured in regular expressions.  Serious changes in
 * regular-expression syntax might require a total rethink.
 */
#include "EXTERN.h"
#include "perl.h"
#include "INTERN.h"
#include "regcomp.h"

#ifdef MSDOS
# if defined(BUGGY_MSC6)
 /* MSC 6.00A breaks on op/regexp.t test 85 unless we turn this off */
 # pragma optimize("a",off)
 /* But MSC 6.00A is happy with 'w', for aliases only across function calls*/
 # pragma optimize("w",on )
# endif /* BUGGY_MSC6 */
#endif /* MSDOS */

#ifndef STATIC
#define	STATIC	static
#endif

#define	ISMULT1(c)	((c) == '*' || (c) == '+' || (c) == '?')
#define	ISMULT2(s)	((*s) == '*' || (*s) == '+' || (*s) == '?' || \
	((*s) == '{' && regcurly(s)))
#ifdef atarist
#define	PERL_META	"^$.[()|?+*\\"
#else
#define	META	"^$.[()|?+*\\"
#endif

#ifdef SPSTART
#undef SPSTART		/* dratted cpp namespace... */
#endif
/*
 * Flags to be passed up and down.
 */
#define	HASWIDTH	01	/* Known never to match null string. */
#define	SIMPLE		02	/* Simple enough to be STAR/PLUS operand. */
#define	SPSTART		04	/* Starts with * or +. */
#define	WORST		0	/* Worst case. */

/*
 * Global work variables for regcomp().
 */
static char *regprecomp;		/* uncompiled string. */
static char *regparse;		/* Input-scan pointer. */
static char *regxend;		/* End of input for compile */
static int regnpar;		/* () count. */
static char *regcode;		/* Code-emit pointer; &regdummy = don't. */
static long regsize;		/* Code size. */
static int regfold;
static int regsawbracket;	/* Did we do {d,d} trick? */
static int regsawback;		/* Did we see \1, ...? */

/*
 * Forward declarations for regcomp()'s friends.
 */
STATIC int regcurly();
STATIC char *reg();
STATIC char *regbranch();
STATIC char *regpiece();
STATIC char *regatom();
STATIC char *regclass();
STATIC char *regnode();
STATIC char *reganode();
STATIC void regc();
STATIC void reginsert();
STATIC void regtail();
STATIC void regoptail();

/*
 - regcomp - compile a regular expression into internal code
 *
 * We can't allocate space until we know how big the compiled form will be,
 * but we can't compile it (and thus know how big it is) until we've got a
 * place to put the code.  So we cheat:  we compile it twice, once with code
 * generation turned off and size counting turned on, and once "for real".
 * This also means that we don't allocate space until we are sure that the
 * thing really will compile successfully, and we never have to move the
 * code and thus invalidate pointers into it.  (Note that it has to be in
 * one piece because free() must be able to free it all.) [NB: not true in perl]
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.  [I'll say.]
 */
regexp *
regcomp(exp,xend,fold)
char *exp;
char *xend;
int fold;
{
	register regexp *r;
	register char *scan;
	register STR *longish;
	STR *longest;
	register int len;
	register char *first;
	int flags;
	int backish;
	int backest;
	int curback;
	int minlen;
	int sawplus = 0;
	int sawopen = 0;

	if (exp == NULL)
		fatal("NULL regexp argument");

	/* First pass: determine size, legality. */
	regfold = fold;
	regparse = exp;
	regxend = xend;
	regprecomp = nsavestr(exp,xend-exp);
	regsawbracket = 0;
	regsawback = 0;
	regnpar = 1;
	regsize = 0L;
	regcode = &regdummy;
	regc((char)MAGIC);
	if (reg(0, &flags) == NULL) {
		Safefree(regprecomp);
		regprecomp = Nullch;
		return(NULL);
	}

	/* Small enough for pointer-storage convention? */
	if (regsize >= 32767L)		/* Probably could be 65535L. */
		FAIL("regexp too big");

	/* Allocate space. */
	Newc(1001, r, sizeof(regexp) + (unsigned)regsize, char, regexp);
	if (r == NULL)
		FAIL("regexp out of space");

	/* Second pass: emit code. */
	if (regsawbracket)
	    Copy(regprecomp,exp,xend-exp,char);
	r->prelen = xend-exp;
	r->precomp = regprecomp;
	r->subbeg = r->subbase = NULL;
	regparse = exp;
	regnpar = 1;
	regcode = r->program;
	regc((char)MAGIC);
	if (reg(0, &flags) == NULL)
		return(NULL);

	/* Dig out information for optimizations. */
	r->regstart = Nullstr;	/* Worst-case defaults. */
	r->reganch = 0;
	r->regmust = Nullstr;
	r->regback = -1;
	r->regstclass = Nullch;
	scan = r->program+1;			/* First BRANCH. */
	if (OP(regnext(scan)) == END) {/* Only one top-level choice. */
		scan = NEXTOPER(scan);

		first = scan;
		while ((OP(first) == OPEN && (sawopen = 1)) ||
		    (OP(first) == BRANCH && OP(regnext(first)) != BRANCH) ||
		    (OP(first) == PLUS) ||
		    (OP(first) == CURLY && ARG1(first) > 0) ) {
			if (OP(first) == PLUS)
			    sawplus = 1;
			else
			    first += regarglen[OP(first)];
			first = NEXTOPER(first);
		}

		/* Starting-point info. */
	    again:
		if (OP(first) == EXACTLY) {
			r->regstart =
			    str_make(OPERAND(first)+1,*OPERAND(first));
			if (r->regstart->str_cur > !(sawstudy|fold))
				fbmcompile(r->regstart,fold);
		}
		else if ((exp = index(simple,OP(first))) && exp > simple)
			r->regstclass = first;
		else if (OP(first) == BOUND || OP(first) == NBOUND)
			r->regstclass = first;
		else if (OP(first) == BOL) {
			r->reganch = ROPT_ANCH;
			first = NEXTOPER(first);
		    	goto again;
		}
		else if ((OP(first) == STAR && OP(NEXTOPER(first)) == ANY) &&
			 !(r->reganch & ROPT_ANCH) ) {
			/* turn .* into ^.* with an implied $*=1 */
			r->reganch = ROPT_ANCH | ROPT_IMPLICIT;
			first = NEXTOPER(first);
		    	goto again;
		}
		if (sawplus && (!sawopen || !regsawback))
		    r->reganch |= ROPT_SKIP;	/* x+ must match 1st of run */

#ifdef DEBUGGING
		if (debug & 512)
		    fprintf(stderr,"first %d next %d offset %d\n",
		      OP(first), OP(NEXTOPER(first)), first - scan);
#endif
		/*
		 * If there's something expensive in the r.e., find the
		 * longest literal string that must appear and make it the
		 * regmust.  Resolve ties in favor of later strings, since
		 * the regstart check works with the beginning of the r.e.
		 * and avoiding duplication strengthens checking.  Not a
		 * strong reason, but sufficient in the absence of others.
		 * [Now we resolve ties in favor of the earlier string if
		 * it happens that curback has been invalidated, since the
		 * earlier string may buy us something the later one won't.]
		 */
		longish = str_make("",0);
		longest = str_make("",0);
		len = 0;
		minlen = 0;
		curback = 0;
		backish = 0;
		backest = 0;
		while (OP(scan) != END) {
			if (OP(scan) == BRANCH) {
			    if (OP(regnext(scan)) == BRANCH) {
				curback = -30000;
				while (OP(scan) == BRANCH)
				    scan = regnext(scan);
			    }
			    else	/* single branch is ok */
				scan = NEXTOPER(scan);
			}
			if (OP(scan) == EXACTLY) {
			    char *t;

			    first = scan;
			    while (OP(t = regnext(scan)) == CLOSE)
				scan = t;
			    minlen += *OPERAND(first);
			    if (curback - backish == len) {
				str_ncat(longish, OPERAND(first)+1,
				    *OPERAND(first));
				len += *OPERAND(first);
				curback += *OPERAND(first);
				first = regnext(scan);
			    }
			    else if (*OPERAND(first) >= len + (curback >= 0)) {
				len = *OPERAND(first);
				str_nset(longish, OPERAND(first)+1,len);
				backish = curback;
				curback += len;
				first = regnext(scan);
			    }
			    else
				curback += *OPERAND(first);
			}
			else if (index(varies,OP(scan))) {
			    curback = -30000;
			    len = 0;
			    if (longish->str_cur > longest->str_cur) {
				str_sset(longest,longish);
				backest = backish;
			    }
			    str_nset(longish,"",0);
			    if (OP(scan) == PLUS &&
			      index(simple,OP(NEXTOPER(scan))))
				minlen++;
			    else if (OP(scan) == CURLY &&
			      index(simple,OP(NEXTOPER(scan)+4)))
				minlen += ARG1(scan);
			}
			else if (index(simple,OP(scan))) {
			    curback++;
			    minlen++;
			    len = 0;
			    if (longish->str_cur > longest->str_cur) {
				str_sset(longest,longish);
				backest = backish;
			    }
			    str_nset(longish,"",0);
			}
			scan = regnext(scan);
		}

		/* Prefer earlier on tie, unless we can tail match latter */

		if (longish->str_cur + (OP(first) == EOL) > longest->str_cur) {
		    str_sset(longest,longish);
		    backest = backish;
		}
		else
		    str_nset(longish,"",0);
		if (longest->str_cur
		    &&
		    (!r->regstart
		     ||
		     !fbminstr((unsigned char*) r->regstart->str_ptr,
			  (unsigned char *) r->regstart->str_ptr
			    + r->regstart->str_cur,
			  longest)
		    )
		   )
		{
			r->regmust = longest;
			if (backest < 0)
				backest = -1;
			r->regback = backest;
			if (longest->str_cur
			  > !(sawstudy || fold || OP(first) == EOL) )
				fbmcompile(r->regmust,fold);
			r->regmust->str_u.str_useful = 100;
			if (OP(first) == EOL && longish->str_cur)
			    r->regmust->str_pok |= SP_TAIL;
		}
		else {
			str_free(longest);
			longest = Nullstr;
		}
		str_free(longish);
	}

	r->do_folding = fold;
	r->nparens = regnpar - 1;
	r->minlen = minlen;
	Newz(1002, r->startp, regnpar, char*);
	Newz(1002, r->endp, regnpar, char*);
#ifdef DEBUGGING
	if (debug & 512)
		regdump(r);
#endif
	return(r);
}

/*
 - reg - regular expression, i.e. main body or parenthesized thing
 *
 * Caller must absorb opening parenthesis.
 *
 * Combining parenthesis handling with the base level of regular expression
 * is a trifle forced, but the need to tie the tails of the branches to what
 * follows makes it hard to avoid.
 */
static char *
reg(paren, flagp)
int paren;			/* Parenthesized? */
int *flagp;
{
	register char *ret;
	register char *br;
	register char *ender;
	register int parno;
	int flags;

	*flagp = HASWIDTH;	/* Tentatively. */

	/* Make an OPEN node, if parenthesized. */
	if (paren) {
		parno = regnpar;
		regnpar++;
		ret = reganode(OPEN, parno);
	} else
		ret = NULL;

	/* Pick up the branches, linking them together. */
	br = regbranch(&flags);
	if (br == NULL)
		return(NULL);
	if (ret != NULL)
		regtail(ret, br);	/* OPEN -> first. */
	else
		ret = br;
	if (!(flags&HASWIDTH))
		*flagp &= ~HASWIDTH;
	*flagp |= flags&SPSTART;
	while (*regparse == '|') {
		regparse++;
		br = regbranch(&flags);
		if (br == NULL)
			return(NULL);
		regtail(ret, br);	/* BRANCH -> BRANCH. */
		if (!(flags&HASWIDTH))
			*flagp &= ~HASWIDTH;
		*flagp |= flags&SPSTART;
	}

	/* Make a closing node, and hook it on the end. */
	if (paren)
	    ender = reganode(CLOSE, parno);
	else
	    ender = regnode(END);
	regtail(ret, ender);

	/* Hook the tails of the branches to the closing node. */
	for (br = ret; br != NULL; br = regnext(br))
		regoptail(br, ender);

	/* Check for proper termination. */
	if (paren && *regparse++ != ')') {
		FAIL("unmatched () in regexp");
	} else if (!paren && regparse < regxend) {
		if (*regparse == ')') {
			FAIL("unmatched () in regexp");
		} else
			FAIL("junk on end of regexp");	/* "Can't happen". */
		/* NOTREACHED */
	}

	return(ret);
}

/*
 - regbranch - one alternative of an | operator
 *
 * Implements the concatenation operator.
 */
static char *
regbranch(flagp)
int *flagp;
{
	register char *ret;
	register char *chain;
	register char *latest;
	int flags;

	*flagp = WORST;		/* Tentatively. */