C++ regnext函数代码示例

/*
 - regtail - set the next-pointer at the end of a node chain
 */
static void
regtail(
	char *p,
	char *val )
{
	register char *scan;
	register char *temp;
	register int offset;

	if (p == &regdummy)
		return;

	/* Find last node. */
	scan = p;
	for (;;) {
		temp = regnext(scan);
		if (temp == NULL)
			break;
		scan = temp;
	}

	if (OP(scan) == BACK)
		offset = scan - val;
	else
		offset = val - scan;
	*(scan+1) = (offset>>8)&0377;
	*(scan+2) = offset&0377;
}

static int regmatchsimplerepeat(regex_t *preg, int scan, int matchmin)
{
	int nextch = '\0';
	const char *save;
	int no;
	int c;

	int max = preg->program[scan + 2];
	int min = preg->program[scan + 3];
	int next = regnext(preg, scan);

	/*
	 * Lookahead to avoid useless match attempts
	 * when we know what character comes next.
	 */
	if (OP(preg, next) == EXACTLY) {
		nextch = preg->program[OPERAND(next)];
	}
	save = preg->reginput;
	no = regrepeat(preg, scan + 5, max);
	if (no < min) {
		return 0;
	}
	if (matchmin) {
		/* from min up to no */
		max = no;
		no = min;
	}
	/* else from no down to min */
	while (1) {
		if (matchmin) {
			if (no > max) {
				break;
			}
		}
		else {
			if (no < min) {
				break;
			}
		}
		preg->reginput = save + utf8_index(save, no);
		reg_utf8_tounicode_case(preg->reginput, &c, (preg->cflags & REG_ICASE));
		/* If it could work, try it. */
		if (reg_iseol(preg, nextch) || c == nextch) {
			if (regmatch(preg, next)) {
				return(1);
			}
		}
		if (matchmin) {
			/* Couldn't or didn't, add one more */
			no++;
		}
		else {
			/* Couldn't or didn't -- back up. */
			no--;
		}
	}
	return(0);
}

static int regmatchrepeat(regex_t *preg, int scan, int matchmin)
{
	int *scanpt = preg->program + scan;

	int max = scanpt[2];
	int min = scanpt[3];

	/* Have we reached min? */
	if (scanpt[4] < min) {
		/* No, so get another one */
		scanpt[4]++;
		if (regmatch(preg, scan + 5)) {
			return 1;
		}
		scanpt[4]--;
		return 0;
	}
	if (scanpt[4] > max) {
		return 0;
	}

	if (matchmin) {
		/* minimal, so try other branch first */
		if (regmatch(preg, regnext(preg, scan))) {
			return 1;
		}
		/* No, so try one more */
		scanpt[4]++;
		if (regmatch(preg, scan + 5)) {
			return 1;
		}
		scanpt[4]--;
		return 0;
	}
	/* maximal, so try this branch again */
	if (scanpt[4] < max) {
		scanpt[4]++;
		if (regmatch(preg, scan + 5)) {
			return 1;
		}
		scanpt[4]--;
	}
	/* At this point we are at max with no match. Try the other branch */
	return regmatch(preg, regnext(preg, scan));
}

void CRegExp::regtail(TCHAR *p, TCHAR *val)
{
	TCHAR *scan;
	TCHAR *temp;
//	int offset;

	if (!bEmitCode)
		return;

	// Find last node.
	for (scan = p; (temp = regnext(scan)) != NULL; scan = temp)
		continue;

	*((short *)(scan+1)) = (OP(scan) == BACK) ? scan - val : val - scan;
}

/*
 - regdump - dump a SRE onto stdout in vaguely comprehensible form
 */
void
regdump(SRE *r)
{
	register char *s;
	register char op = EXACTLY;	/* Arbitrary non-END op. */
	register char *next;
	extern char *strchr();


	s = r->program + 1;
	while (op != END) {	/* While that wasn't END last time... */
		op = OP(s);
		printf("%2d%s", s-r->program, regprop(s));	/* Where, what. */
		next = regnext(s);
		if (next == NULL) {		/* Next ptr. */
			printf("(0)");
		} else {
			printf("(%d)", (s-r->program)+(next-s));
		}
		s += 3;
		if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
			/* Literal string, where present. */
			while (*s != '\0') {
				putchar(*s);
				s++;
			}
			s++;
		}
		putchar('\n');
	}

	/* Header fields of interest. */
	if (r->regstart != '\0') {
		printf("start `%c' ", r->regstart);
	}
	if (r->reganch) {
		printf("anchored ");
	}
	if (r->regmust != NULL) {
		printf("must have \"%s\"", r->regmust);
	}
	printf("\n");
}

/*
 - regdump - dump a regexp onto stdout in vaguely comprehensible form
 */
void regdump (regexp * r)
{
    register char *s;
    register char op = EXACTLY; /* Arbitrary non-END op. */
    register char *nxt;

#ifdef _AIX
    extern char *strchr();

#endif                          /* _AIX */

    s = r->program + 1;
    while (op != END) {         /* While that wasn't END last time... */
        op = OP(s);
        printf("%2ld%s", (s - r->program), regprop(s));    /* Where, what. */
        nxt = regnext(s);
        if (nxt == (char *) NULL)       /* nxt ptr. */
            printf("(0)");
        else
            printf("(%ld)", ((s - r->program) + (nxt - s)));
        s += 3;
        if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
            /* Literal string, where present. */
            while (*s != '\0') {
                putchar(*s);
                s++;
            }
            s++;
        }
        putchar('\n');
    }

    /* Header fields of interest. */
    if (r->regstart != '\0')
        printf("start `%c' ", r->regstart);
    if (r->reganch)
        printf("anchored ");
    if (r->regmust != (char *) NULL)
        printf("must have \"%s\"", r->regmust);
    printf("\n");
}

/*
 - regtail - set the next-pointer at the end of a node chain
 */
static void regtail(regex_t *preg, int p, int val)
{
	int scan;
	int temp;
	int offset;

	/* Find last node. */
	scan = p;
	for (;;) {
		temp = regnext(preg, scan);
		if (temp == 0)
			break;
		scan = temp;
	}

	if (OP(preg, scan) == BACK)
		offset = scan - val;
	else
		offset = val - scan;

	preg->program[scan + 1] = offset;
}

/*
 - regtail - set the next-pointer at the end of a node chain
 */
void ossimRegExp::regtail (char* p, const char* val) {
    char* scan;
    char* temp;
    int   offset;

    if (p == &regdummy)
        return;

    // Find last node.
    scan = p;
    for (;;) {
        temp = regnext(scan);
        if (temp == NULL)
            break;
        scan = temp;
    }

    if (OP(scan) == BACK)
        offset = (const char*)scan - val;
    else
        offset = val - scan;
    *(scan + 1) = (offset >> 8) & 0377;
    *(scan + 2) = offset & 0377;
}

/*
 - 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.)
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.
 */
regexp *
regcomp( const char *exp )
{
	register regexp *r;
	register char *scan;
	register char *longest;
	register unsigned len;
	int flags;

	if (exp == NULL)
		FAIL("NULL argument");

	/* First pass: determine size, legality. */
#ifdef notdef
	if (exp[0] == '.' && exp[1] == '*') exp += 2;  /* aid grep */
#endif
	regparse = (char *)exp;
	regnpar = 1;
	regsize = 0L;
	regcode = &regdummy;
	regc(MAGIC);
	if (reg(0, &flags) == NULL)
		return(NULL);

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

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

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

	/* Dig out information for optimizations. */
	r->regstart = '\0';	/* Worst-case defaults. */
	r->reganch = 0;
	r->regmust = NULL;
	r->regmlen = 0;
	scan = r->program+1;			/* First BRANCH. */
	if (OP(regnext(scan)) == END) {		/* Only one top-level choice. */
		scan = OPERAND(scan);

		/* Starting-point info. */
		if (OP(scan) == EXACTLY)
			r->regstart = *OPERAND(scan);
		else if (OP(scan) == BOL)
			r->reganch++;

		/*
		 * 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.
		 */
		if (flags&SPSTART) {
			longest = NULL;
			len = 0;
			for (; scan != NULL; scan = regnext(scan))
				if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
					longest = OPERAND(scan);
					len = strlen(OPERAND(scan));
				}
			r->regmust = longest;
			r->regmlen = len;
		}
	}

	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( int paren, int *flagp )
{
    char        *ret, *br, *ender;
    int         flags;
    char        parno = 0;

    *flagp = HASWIDTH;      /* Tentatively. */

    /* Make an OPEN node, if parenthesized. */
    if( paren ) {
        if( regnpar >= NSUBEXP ) {
            FAIL( ERR_RE_TOO_MANY_ROUND_BRACKETS );
        }
        parno = regnpar;
        regnpar++;
        ret = regnode( 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. */
    ender = regnode( ( paren ) ? CLOSE + parno : 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( ERR_RE_UNMATCHED_ROUND_BRACKETS );
    } else if( !paren && *regparse != '\0' ) {
        if( *regparse == ')' ) {
            FAIL( ERR_RE_UNMATCHED_ROUND_BRACKETS );
        } else {
            FAIL( ERR_RE_INTERNAL_FOULUP );    /* "Can't happen". */
        }
    }

    return( ret );
}

int	CRegExp::regmatch(TCHAR *prog)
{
	TCHAR *scan;	// Current node.
	TCHAR *next;		// Next node.

	for (scan = prog; scan != NULL; scan = next) {
		next = regnext(scan);

		switch (OP(scan)) {
		case BOL:
			if (reginput != regbol)
				return(0);
			break;
		case EOL:
			if (*reginput != _T('\0'))
				return(0);
			break;
		case ANY:
			if (*reginput == _T('\0'))
				return(0);
			reginput++;
			break;
		case EXACTLY: {
			size_t len;
			TCHAR *const opnd = OPERAND(scan);

			// Inline the first character, for speed.
			if (*opnd != *reginput)
				return(0);
			len = _tcslen(opnd);
			if (len > 1 && _tcsncmp(opnd, reginput, len) != 0)
				return(0);
			reginput += len;
			break;
			}
		case ANYOF:
			if (*reginput == _T('\0') ||
					_tcschr(OPERAND(scan), *reginput) == NULL)
				return(0);
			reginput++;
			break;
		case ANYBUT:
			if (*reginput == _T('\0') ||
					_tcschr(OPERAND(scan), *reginput) != NULL)
				return(0);
			reginput++;
			break;
		case NOTHING:
			break;
		case BACK:
			break;
		case OPEN+1: case OPEN+2: case OPEN+3:
		case OPEN+4: case OPEN+5: case OPEN+6:
		case OPEN+7: case OPEN+8: case OPEN+9: {
			const int no = OP(scan) - OPEN;
			TCHAR *const input = reginput;

			if (regmatch(next)) {
				// Don't set startp if some later
				// invocation of the same parentheses
				// already has.

				if (startp[no] == NULL)
					startp[no] = input;
				return(1);
			} else
				return(0);
			break;
			}
		case CLOSE+1: case CLOSE+2: case CLOSE+3:
		case CLOSE+4: case CLOSE+5: case CLOSE+6:
		case CLOSE+7: case CLOSE+8: case CLOSE+9: {
			const int no = OP(scan) - CLOSE;
			TCHAR *const input = reginput;

			if (regmatch(next)) {
				// Don't set endp if some later
				// invocation of the same parentheses
				// already has.

				if (endp[no] == NULL)
					endp[no] = input;
				return(1);
			} else
				return(0);
			break;
			}
		case BRANCH: {
			TCHAR *const save = reginput;

			if (OP(next) != BRANCH)		// No choice.
				next = OPERAND(scan);	// Avoid recursion.
			else {
				while (OP(scan) == BRANCH) {
					if (regmatch(OPERAND(scan)))
						return(1);
					reginput = save;
					scan = regnext(scan);
				}
				return(0);
//.........这里部分代码省略.........

/*
 - regdump - dump a regexp onto stdout in vaguely comprehensible form
 */
static void regdump(regex_t *preg)
{
	int s;
	int op = EXACTLY;	/* Arbitrary non-END op. */
	int next;
	char buf[MAX_UTF8_LEN + 1];

	int i;
	for (i = 1; i < preg->p; i++) {
		printf("%02x ", (unsigned char)preg->program[i]);
		if (i % 16 == 0) {
			printf("\n");
		}
	}
	printf("\n");

	s = 1;
	while (op != END && s < preg->p) {	/* While that wasn't END last time... */
		op = OP(preg, s);
		printf("%3d: %s", s, regprop(op));	/* Where, what. */
		next = regnext(preg, s);
		if (next == 0)		/* Next ptr. */
			printf("(0)");
		else
			printf("(%d)", next);
		s += 2;
		if (op == REP || op == REPMIN || op == REPX || op == REPXMIN) {
			int max = preg->program[s];
			int min = preg->program[s + 1];
			if (max == 65535) {
				printf("{%d,*}", min);
			}
			else {
				printf("{%d,%d}", min, max);
			}
			printf(" %d", preg->program[s + 2]);
			s += 3;
		}
		else if (op == ANYOF || op == ANYBUT) {
			/* set of ranges */

			while (preg->program[s]) {
				int len = preg->program[s++];
				int first = preg->program[s++];
				buf[utf8_getchars(buf, first)] = 0;
				printf("%s", buf);
				if (len > 1) {
					buf[utf8_getchars(buf, first + len - 1)] = 0;
					printf("-%s", buf);
				}
			}
			s++;
		}
		else if (op == EXACTLY) {
			/* Literal string, where present. */

			while (preg->program[s]) {
				buf[utf8_getchars(buf, preg->program[s])] = 0;
				printf("%s", buf);
				s++;
			}
			s++;
		}
		putchar('\n');
	}

	if (op == END) {
		/* Header fields of interest. */
		if (preg->regstart) {
			buf[utf8_getchars(buf, preg->regstart)] = 0;
			printf("start '%s' ", buf);
		}
		if (preg->reganch)
			printf("anchored ");
		if (preg->regmust != 0) {
			int i;
			printf("must have:");
			for (i = 0; i < preg->regmlen; i++) {
				putchar(preg->program[preg->regmust + i]);
			}
			putchar('\n');
		}
	}
	printf("\n");
}

/* 0 failure, 1 success */
static int regmatch(regex_t *preg, int prog)
{
	int scan;	/* Current node. */
	int next;		/* Next node. */
	const char *save;

	scan = prog;

#ifdef DEBUG
	if (scan != 0 && regnarrate)
		fprintf(stderr, "%s(\n", regprop(scan));
#endif
	while (scan != 0) {
		int n;
		int c;
#ifdef DEBUG
		if (regnarrate) {
			fprintf(stderr, "%3d: %s...\n", scan, regprop(OP(preg, scan)));	/* Where, what. */
		}
#endif
		next = regnext(preg, scan);
		n = reg_utf8_tounicode_case(preg->reginput, &c, (preg->cflags & REG_ICASE));

		switch (OP(preg, scan)) {
		case BOL:
			if (preg->reginput != preg->regbol)
				return(0);
			break;
		case EOL:
			if (!reg_iseol(preg, c)) {
				return(0);
			}
			break;
		case WORDA:
			/* Must be looking at a letter, digit, or _ */
			if ((!isalnum(UCHAR(c))) && c != '_')
				return(0);
			/* Prev must be BOL or nonword */
			if (preg->reginput > preg->regbol &&
				(isalnum(UCHAR(preg->reginput[-1])) || preg->reginput[-1] == '_'))
				return(0);
			break;
		case WORDZ:
			/* Can't match at BOL */
			if (preg->reginput > preg->regbol) {
				/* Current must be EOL or nonword */
				if (reg_iseol(preg, c) || !isalnum(UCHAR(c)) || c != '_') {
					c = preg->reginput[-1];
					/* Previous must be word */
					if (isalnum(UCHAR(c)) || c == '_') {
						break;
					}
				}
			}
			/* No */
			return(0);

		case ANY:
			if (reg_iseol(preg, c))
				return 0;
			preg->reginput += n;
			break;
		case EXACTLY: {
				int opnd;
				int len;
				int slen;

				opnd = OPERAND(scan);
				len = str_int_len(preg->program + opnd);

				slen = prefix_cmp(preg->program + opnd, len, preg->reginput, preg->cflags & REG_ICASE);
				if (slen < 0) {
					return(0);
				}
				preg->reginput += slen;
			}
			break;
		case ANYOF:
			if (reg_iseol(preg, c) || reg_range_find(preg->program + OPERAND(scan), c) == 0) {
				return(0);
			}
			preg->reginput += n;
			break;
		case ANYBUT:
			if (reg_iseol(preg, c) || reg_range_find(preg->program + OPERAND(scan), c) != 0) {
				return(0);
			}
			preg->reginput += n;
			break;
		case NOTHING:
			break;
		case BACK:
			break;
		case BRANCH:
			if (OP(preg, next) != BRANCH)		/* No choice. */
				next = OPERAND(scan);	/* Avoid recursion. */
			else {
				do {
					save = preg->reginput;
//.........这里部分代码省略.........

/*
 - regmatch - main matching routine
 *
 * Conceptually the strategy is simple:  check to see whether the current
 * node matches, call self recursively to see whether the rest matches,
 * and then act accordingly.  In practice we make some effort to avoid
 * recursion, in particular by going through "ordinary" nodes (that don't
 * need to know whether the rest of the match failed) by a loop instead of
 * by recursion.
 */
static int			/* 0 failure, 1 success */
regmatch(char *prog)
{
	register char *scan;	/* Current node. */
	char *next;		/* Next node. */
	extern char *strchr();

	scan = prog;
#ifdef DEBUG
	if (scan != NULL && regnarrate) {
		fprintf(stderr, "%s(\n", regprop(scan));
	}
#endif
	while (scan != NULL) {
#ifdef DEBUG
		if (regnarrate) {
			fprintf(stderr, "%s...\n", regprop(scan));
		}
#endif
		next = regnext(scan);

		switch (OP(scan)) {
		case BOL:
			if (reginput != regbol) {
				return(0);
			}
			break;
		case EOL:
			if (regpeek(0) != '\0' && regpeek(0) != '\n') {
				return(0);
			}
			break;
		case BEGWORD:
			/* Match if current char isident
			 * and previous char BOL or !ident */
			if ((regpeek(0) == 0 || !isident(regpeek(0))) ||
			    (reginput != regbol && isident(regpeek(-1)))) {
				return(0);
			}
			break;
		case ENDWORD:
			/* Match if previous char isident
			 * and current char EOL or !ident */
			if ((regpeek(0) != 0 && isident(regpeek(0))) ||
			    reginput == regbol ||
			    !isident(regpeek(-1))) {
 				return(0);
			}
 			break;
		case WHITESP:
			/* match single whitespace */
			if (regpeek(0) != 0 && !isspace(regpeek(0))) {
				return(0);
			}
			reginput++;
			break;
		case NWHITESP:
			/* don't match eol, or space or tab */
			if (regpeek(0) == 0 || isspace(regpeek(0))) {
				return(0);
			}
			reginput++;
			break;
		case ALNUM: /* includes _ */
			if (regpeek(0) == 0 || !isident(regpeek(0))) {
				return(0);
			}
			reginput++;
			break;
		case NALNUM:
			if (regpeek(0) == 0 || isident(regpeek(0))) {
				return(0);
			}
			reginput++;
			break;
		case DIGIT:
			if (regpeek(0) == 0 || !isdigit(regpeek(0))) {
				return(0);
			}
			reginput++;
			break;
		case NDIGIT:
			if (regpeek(0) == 0 || isdigit(regpeek(0))) {
				return(0);
			}
			reginput++;
			break;
		case PRINT:
			if (regpeek(0) == 0 ||
			    !(isprint(regpeek(0)) || isspace(regpeek(0)))) {
//.........这里部分代码省略.........

void ossimRegExp::compile (const char* exp) {
    const char* scan;
    const char* longest;
    unsigned long len;
    int         flags;

    if (exp == NULL) {
        //RAISE Error, SYM(ossimRegExp), SYM(No_Expr),
        printf ("ossimRegExp::compile(): No expression supplied.\n");
        return;
    }

    // First pass: determine size, legality.
    regparse = exp;
    regnpar = 1;
    regsize = 0L;
    regcode = &regdummy;
    regc(MAGIC);
    if(!reg(0, &flags))
    {
        printf ("ossimRegExp::compile(): Error in compile.\n");
        return;
    }
    this->startp[0] = this->endp[0] = this->searchstring = NULL;

    // Small enough for pointer-storage convention?
    if (regsize >= 32767L) {	// Probably could be 65535L.
        //RAISE Error, SYM(ossimRegExp), SYM(Expr_Too_Big),
        printf ("ossimRegExp::compile(): Expression too big.\n");
        return;
    }

    // Allocate space.
//#ifndef WIN32
    if (this->program != NULL) delete [] this->program;
//#endif
    this->program = new char[regsize];
    this->progsize = (int) regsize;

    if (this->program == NULL) {
        //RAISE Error, SYM(ossimRegExp), SYM(Out_Of_Memory),
        printf ("ossimRegExp::compile(): Out of memory.\n");
        return;
    }

    // Second pass: emit code.
    regparse = exp;
    regnpar = 1;
    regcode = this->program;
    regc(MAGIC);
    reg(0, &flags);

    // Dig out information for optimizations.
    this->regstart = '\0';		// Worst-case defaults.
    this->reganch = 0;
    this->regmust = NULL;
    this->regmlen = 0;
    scan = this->program + 1;	// First BRANCH.
    if (OP(regnext(scan)) == END) {	// Only one top-level choice.
        scan = OPERAND(scan);

        // Starting-point info.
        if (OP(scan) == EXACTLY)
            this->regstart = *OPERAND(scan);
        else if (OP(scan) == BOL)
            this->reganch++;

        //
        // 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.
        //
        if (flags & SPSTART) {
            longest = NULL;
            len = 0;
            for (; scan != NULL; scan = regnext(scan))
                if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
                    longest = OPERAND(scan);
                    len = (unsigned long)strlen(OPERAND(scan));
                }
            this->regmust = longest;
            this->regmlen = len;
        }
    }
}