regcomp.c

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/*  $OpenBSD: regcomp.c,v 1.20 2010/11/21 00:02:30 tedu Exp $ */
/*-
 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
 * Copyright (c) 1992, 1993, 1994
 *  The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Henry Spencer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *  @(#)regcomp.c   8.5 (Berkeley) 3/20/94
 */
 
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include "rz_regex.h"
#include "rz_util/rz_str.h"
#include "rz_util/rz_assert.h"
 
#include "utils.h"
#include "regex2.h"
 
#include "cclass.h"
#include "cname.h"
 
/*
 * parse structure, passed up and down to avoid global variables and
 * other clumsinesses
 */
struct parse {
    char *next; /* next character in RE */
    char *end; /* end of string (-> NUL normally) */
    int error; /* has an error been seen? */
    sop *strip; /* malloced strip */
    sopno ssize; /* malloced strip size (allocated) */
    sopno slen; /* malloced strip length (used) */
    int ncsalloc; /* number of csets allocated */
    struct re_guts *g;
#define NPAREN 10 /* we need to remember () 1-9 for back refs */
    sopno pbegin[NPAREN]; /* -> ( ([0] unused) */
    sopno pend[NPAREN]; /* -> ) ([0] unused) */
};
 
static void p_ere(struct parse *, int);
static void p_ere_exp(struct parse *);
static void p_str(struct parse *);
static void p_bre(struct parse *, int, int);
static int p_simp_re(struct parse *, int);
static int p_count(struct parse *);
static void p_bracket(struct parse *);
static void p_b_term(struct parse *, cset *);
static void p_b_cclass(struct parse *, cset *);
static void p_b_eclass(struct parse *, cset *);
static char p_b_symbol(struct parse *);
static char p_b_coll_elem(struct parse *, int);
static char othercase(int);
static void bothcases(struct parse *, int);
static void ordinary(struct parse *, int);
static void special(struct parse *, int);
static void nonnewline(struct parse *);
static void repeat(struct parse *, sopno, int, int);
static int seterr(struct parse *, int);
static cset *allocset(struct parse *);
static void freeset(struct parse *, cset *);
static int freezeset(struct parse *, cset *);
static int firstch(struct parse *, cset *);
static int nch(struct parse *, cset *);
static void mcadd(struct parse *, cset *, char *);
static void mcinvert(struct parse *, cset *);
static void mccase(struct parse *, cset *);
static int isinsets(struct re_guts *, int);
static int samesets(struct re_guts *, int, int);
static void categorize(struct parse *, struct re_guts *);
static sopno dupl(struct parse *, sopno, sopno);
static void doemit(struct parse *, sop, size_t);
static void doinsert(struct parse *, sop, size_t, sopno);
static void dofwd(struct parse *, sopno, sop);
static void enlarge(struct parse *, sopno);
static void stripsnug(struct parse *, struct re_guts *);
static void findmust(struct parse *, struct re_guts *);
static sopno pluscount(struct parse *, struct re_guts *);
 
static char nuls[10]; /* place to point scanner in event of error */
 
/*
 * macros for use with parse structure
 * BEWARE:  these know that the parse structure is named `p' !!!
 */
#define PEEK()           (*p->next)
#define PEEK2()          (*(p->next + 1))
#define MORE()           (p->next < p->end)
#define MORE2()          (p->next + 1 < p->end)
#define SEE(c)           (MORE() && PEEK() == (c))
#define SEETWO(a, b)     (MORE() && MORE2() && PEEK() == (a) && PEEK2() == (b))
#define EAT(c)           ((SEE(c)) ? (NEXT(), 1) : 0)
#define EATTWO(a, b)     ((SEETWO(a, b)) ? (NEXT2(), 1) : 0)
#define NEXT()           (p->next++)
#define NEXT2()          (p->next += 2)
#define NEXTn(n)         (p->next += (n))
#define GETNEXT()        (*p->next++)
#define SETERROR(e)      seterr(p, (e))
#define REQUIRE(co, e)   (void)((co) || SETERROR(e))
#define MUSTSEE(c, e)    (REQUIRE(MORE() && PEEK() == (c), e))
#define MUSTEAT(c, e)    (REQUIRE(MORE() && GETNEXT() == (c), e))
#define MUSTNOTSEE(c, e) (REQUIRE(!MORE() || PEEK() != (c), e))
#define EMIT(op, sopnd)  doemit(p, (sop)(op), (size_t)(sopnd))
#define INSERT(op, pos)  doinsert(p, (sop)(op), HERE() - (pos) + 1, pos)
#define AHEAD(pos)       dofwd(p, pos, HERE() - (pos))
#define ASTERN(sop, pos) EMIT(sop, HERE() - (pos))
#define HERE()           (p->slen)
#define THERE()          (p->slen - 1)
#define THERETHERE()     (p->slen - 2)
#define DROP(n)          (p->slen -= (n))
 
RZ_API int rz_regex_match(const char *pattern, const char *flags, const char *text) {
    int ret;
    RzRegex rx;
    int re_flags = rz_regex_flags(flags);
    if (rz_regex_comp(&rx, pattern, re_flags)) {
        eprintf("FAIL TO COMPILE %s\n", pattern);
        return 0;
    }
    ret = rz_regex_exec(&rx, text, 0, 0, re_flags);
    rz_regex_fini(&rx);
    return ret ? 0 : 1;
}
 
RZ_API RzList *rz_regex_get_match_list(const char *pattern, const char *flags, const char *text) {
    RzList *list = rz_list_newf(free);
    RzRegex rx;
    RzRegexMatch match;
    char *entry;
    size_t entry_len = 0;
    int re_flags = rz_regex_flags(flags);
    if (rz_regex_comp(&rx, pattern, re_flags)) {
        eprintf("Failed to compile regexp: %s\n", pattern);
        return NULL;
    }
 
    /* Initialize the boundaries for RZ_REGEX_STARTEND */
    match.rm_so = 0;
    match.rm_eo = strlen(text);
    while (!rz_regex_exec(&rx, text, 1, &match, re_flags | RZ_REGEX_STARTEND)) {
        entry_len = match.rm_eo - match.rm_so + 1;
        entry = RZ_NEWS0(char, entry_len);
        rz_str_ncpy(entry, text + match.rm_so, entry_len);
        rz_list_append(list, entry);
        /* Update the boundaries for RZ_REGEX_STARTEND */
        match.rm_so = match.rm_eo;
        match.rm_eo = strlen(text);
    }
    rz_regex_fini(&rx);
    return list;
}
 
RZ_API RzRegex *rz_regex_new(const char *pattern, const char *flags) {
    rz_return_val_if_fail(pattern, NULL);
    RzRegex *r, rx = { 0 };
    if (rz_regex_comp(&rx, pattern, rz_regex_flags(flags))) {
        return NULL;
    }
    r = RZ_NEW(RzRegex);
    if (!r) {
        return NULL;
    }
    memcpy(r, &rx, sizeof(RzRegex));
    return r;
}
 
RZ_API int rz_regex_flags(const char *f) {
    int flags = 0;
    if (!f || !*f) {
        return 0;
    }
    if (strchr(f, 'e')) {
        flags |= RZ_REGEX_EXTENDED;
    }
    if (strchr(f, 'i')) {
        flags |= RZ_REGEX_ICASE;
    }
    if (strchr(f, 's')) {
        flags |= RZ_REGEX_NOSUB;
    }
    if (strchr(f, 'n')) {
        flags |= RZ_REGEX_NEWLINE;
    }
    if (strchr(f, 'N')) {
        flags |= RZ_REGEX_NOSPEC;
    }
    if (strchr(f, 'p')) {
        flags |= RZ_REGEX_PEND;
    }
    if (strchr(f, 'd')) {
        flags |= RZ_REGEX_DUMP;
    }
    return flags;
}
 
RZ_API void rz_regex_fini(RzRegex *preg) {
    struct re_guts *g;
    if (!preg) {
        return;
    }
    if (preg->re_magic != MAGIC1) { /* oops */
        return; /* nice to complain, but hard */
    }
 
    g = preg->re_g;
    if (!g || g->magic != MAGIC2) { /* oops again */
        return;
    }
    preg->re_magic = 0; /* mark it invalid */
    g->magic = 0; /* mark it invalid */
 
    free(g->strip);
    free(g->sets);
    free(g->setbits);
    free(g->must);
    free(g);
}
 
RZ_API void rz_regex_free(RzRegex *preg) {
    rz_regex_fini(preg);
    free(preg);
}
 
/*
 - regcomp - interface for parser and compilation
 - 0 success, otherwise RZ_REGEX_something
 */
RZ_API int rz_regex_comp(RzRegex *preg, const char *pattern, int cflags) {
    struct parse pa;
    struct re_guts *g;
    struct parse *p = &pa;
    int i;
    size_t len;
#ifdef REDEBUG
#define GOODFLAGS(f) (f)
#else
#define GOODFLAGS(f) ((f) & ~RZ_REGEX_DUMP)
#endif
    cflags = GOODFLAGS(cflags);
    if (!preg || ((cflags & RZ_REGEX_EXTENDED) && (cflags & RZ_REGEX_NOSPEC))) {
        return RZ_REGEX_INVARG;
    }
    if (cflags & RZ_REGEX_PEND) {
        if (preg->re_endp < pattern) {
            return RZ_REGEX_INVARG;
        }
        len = preg->re_endp - pattern;
    } else {
        len = strlen((char *)pattern);
    }
    /* do the mallocs early so failure handling is easy */
    g = calloc(1, sizeof(struct re_guts) + (NC - 1));
    if (!g) {
        return RZ_REGEX_ESPACE;
    }
    /*
     * Limit the pattern space to avoid a 32-bit overflow on buffer
     * extension.  Also avoid any signed overflow in case of conversion
     * so make the real limit based on a 31-bit overflow.
     *
     * Likely not applicable on 64-bit systems but handle the case
     * generically (who are we to stop people from using ~715MB+
     * patterns?).
     */
    size_t maxlen = ((size_t)-1 >> 1) / sizeof(sop) * 2 / 3;
    if (len >= maxlen) {
        free(g);
        return RZ_REGEX_ESPACE;
    }
    preg->re_flags = cflags;
    p->ssize = len / (size_t)2 * (size_t)3 + (size_t)1; /* ugh */
    if (p->ssize < len) {
        free(g);
        return RZ_REGEX_ESPACE;
    }
 
    p->strip = (sop *)calloc(p->ssize, sizeof(sop));
    if (!p->strip) {
        free(g);
        return RZ_REGEX_ESPACE;
    }
    p->slen = 0;
    if (!p->strip) {
        free(g);
        return RZ_REGEX_ESPACE;
    }
 
    /* set things up */
    p->g = g;
    p->next = (char *)pattern; /* convenience; we do not modify it */
    p->end = p->next + len;
    p->error = 0;
    p->ncsalloc = 0;
    for (i = 0; i < NPAREN; i++) {
        p->pbegin[i] = 0;
        p->pend[i] = 0;
    }
    g->csetsize = NC;
    g->sets = NULL;
    g->setbits = NULL;
    g->ncsets = 0;
    g->cflags = cflags;
    g->iflags = 0;
    g->nbol = 0;
    g->neol = 0;
    g->must = NULL;
    g->mlen = 0;
    g->nsub = 0;
    g->ncategories = 1; /* category 0 is "everything else" */
    g->categories = &g->catspace[-(CHAR_MIN)];
    (void)memset((char *)g->catspace, 0, NC * sizeof(cat_t));
    g->backrefs = 0;
 
    /* do it */
    EMIT(OEND, 0);
    g->firststate = THERE();
    if (cflags & RZ_REGEX_EXTENDED) {
        p_ere(p, OUT);
    } else if (cflags & RZ_REGEX_NOSPEC) {
        p_str(p);
    } else {
        p_bre(p, OUT, OUT);
    }
    EMIT(OEND, 0);
    g->laststate = THERE();
 
    /* tidy up loose ends and fill things in */
    categorize(p, g);
    stripsnug(p, g);
    findmust(p, g);
    g->nplus = pluscount(p, g);
    g->magic = MAGIC2;
    preg->re_nsub = g->nsub;
    preg->re_g = g;
    preg->re_magic = MAGIC1;
#ifndef REDEBUG
    /* not debugging, so can't rely on the asssert() in regexec() */
    if (g->iflags & BAD) {
        SETERROR(RZ_REGEX_ASSERT);
    }
#endif
    if (p->error) {
        rz_regex_fini(preg);
    }
    return p->error;
}
 
/*
 - p_ere - ERE parser top level, concatenation and alternation
 */
static void p_ere(struct parse *p, int stop) { /* character this ERE should end at */
    bool isFirst = true;
    sopno prevback = 0;
    sopno prevfwd = 0;
    sopno conc = 0;
    char c;
 
    for (;;) {
        /* do a bunch of concatenated expressions */
        conc = HERE();
        while (MORE() && (c = PEEK()) != '|' && c != stop) {
            p_ere_exp(p);
        }
        REQUIRE(HERE() != conc, RZ_REGEX_EMPTY); /* require nonempty */
 
        if (!EAT('|')) {
            break; /* NOTE BREAK OUT */
        }
        if (isFirst) {
            INSERT(OCH_, conc); /* offset is wrong */
            prevfwd = conc;
            prevback = conc;
            isFirst = false;
        }
        ASTERN(OOR1, prevback);
        prevback = THERE();
        AHEAD(prevfwd); /* fix previous offset */
        prevfwd = HERE();
        EMIT(OOR2, 0); /* offset is very wrong */
    }
 
    if (!isFirst) { /* tail-end fixups */
        AHEAD(prevfwd);
        ASTERN(O_CH, prevback);
    }
    // asert(!MORE() || SEE(stop));
}
 
/*
 - p_ere_exp - parse one subERE, an atom possibly followed by a repetition op
 */
static void p_ere_exp(struct parse *p) {
    char c;
    sopno pos;
    int count;
    int count2;
    sopno subno;
    int wascaret = 0;
 
    if (!MORE()) { /* caller should have ensured this */
        return;
    }
    c = GETNEXT();
 
    pos = HERE();
    switch (c) {
    case '(':
        REQUIRE(MORE(), RZ_REGEX_EPAREN);
        p->g->nsub++;
        subno = p->g->nsub;
        if (subno < NPAREN) {
            p->pbegin[subno] = HERE();
        }
        EMIT(OLPAREN, subno);
        if (!SEE(')')) {
            p_ere(p, ')');
        }
        if (subno < NPAREN) {
            p->pend[subno] = HERE();
            if (!p->pend[subno]) {
                break;
            }
        }
        EMIT(ORPAREN, subno);
        MUSTEAT(')', RZ_REGEX_EPAREN);
        break;
    case '^':
        EMIT(OBOL, 0);
        p->g->iflags |= USEBOL;
        p->g->nbol++;
        wascaret = 1;
        break;
    case '$':
        EMIT(OEOL, 0);
        p->g->iflags |= USEEOL;
        p->g->neol++;
        break;
    case '|':
        SETERROR(RZ_REGEX_EMPTY);
        break;
    case '*':
    case '+':
    case '?':
        SETERROR(RZ_REGEX_BADRPT);
        break;
    case '.':
        if (p->g->cflags & RZ_REGEX_NEWLINE) {
            nonnewline(p);
        } else {
            EMIT(OANY, 0);
        }
        break;
    case '[':
        p_bracket(p);
        break;
    case '\\':
        REQUIRE(MORE(), RZ_REGEX_EESCAPE);
        c = GETNEXT();
        if (!isalpha(c)) {
            ordinary(p, c);
        } else {
            special(p, c);
        }
        break;
    case '{': /* okay as ordinary except if digit follows */
        REQUIRE(!MORE() || !isdigit((ut8)PEEK()), RZ_REGEX_BADRPT);
        /* FALLTHROUGH */
    default:
        ordinary(p, c);
        break;
    }
 
    if (!MORE()) {
        return;
    }
    c = PEEK();
    /* we call { a repetition if followed by a digit */
    if (!(c == '*' || c == '+' || c == '?' ||
            (c == '{' && MORE2() && isdigit((ut8)PEEK2())))) {
        return; /* no repetition, we're done */
    }
    NEXT();
 
    REQUIRE(!wascaret, RZ_REGEX_BADRPT);
    switch (c) {
    case '*': /* implemented as +? */
        /* this case does not require the (y|) trick, noKLUDGE */
        INSERT(OPLUS_, pos);
        ASTERN(O_PLUS, pos);
        INSERT(OQUEST_, pos);
        ASTERN(O_QUEST, pos);
        break;
    case '+':
        INSERT(OPLUS_, pos);
        ASTERN(O_PLUS, pos);
        break;
    case '?':
        /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
        INSERT(OCH_, pos); /* offset slightly wrong */
        ASTERN(OOR1, pos); /* this one's right */
        AHEAD(pos); /* fix the OCH_ */
        EMIT(OOR2, 0); /* offset very wrong... */
        AHEAD(THERE()); /* ...so fix it */
        ASTERN(O_CH, THERETHERE());
        break;
    case '{':
        count = p_count(p);
        if (EAT(',')) {
            if (isdigit((ut8)PEEK())) {
                count2 = p_count(p);
                REQUIRE(count <= count2, RZ_REGEX_BADBR);
            } else { /* single number with comma */
                count2 = INTFINITY;
            }
        } else { /* just a single number */
            count2 = count;
        }
        repeat(p, pos, count, count2);
        if (!EAT('}')) { /* error heuristics */
            while (MORE() && PEEK() != '}') {
                NEXT();
            }
            REQUIRE(MORE(), RZ_REGEX_EBRACE);
            SETERROR(RZ_REGEX_BADBR);
        }
        break;
    }
 
    if (!MORE()) {
        return;
    }
    c = PEEK();
    if (!(c == '*' || c == '+' || c == '?' ||
            (c == '{' && MORE2() && isdigit((ut8)PEEK2())))) {
        return;
    }
    SETERROR(RZ_REGEX_BADRPT);
}
 
/*
 - p_str - string (no metacharacters) "parser"
 */
static void p_str(struct parse *p) {
    REQUIRE(MORE(), RZ_REGEX_EMPTY);
    while (MORE()) {
        ordinary(p, GETNEXT());
    }
}
 
/*
 - p_bre - BRE parser top level, anchoring and concatenation
 * Giving end1 as OUT essentially eliminates the end1/end2 check.
 *
 * This implementation is a bit of a kludge, in that a trailing $ is first
 * taken as an ordinary character and then revised to be an anchor.  The
 * only undesirable side effect is that '$' gets included as a character
 * category in such cases.  This is fairly harmless; not worth fixing.
 * The amount of lookahead needed to avoid this kludge is excessive.
 */
static void p_bre(struct parse *p,
    int end1, /* first terminating character */
    int end2) /* second terminating character */
{
    sopno start = HERE();
    int first = 1; /* first subexpression? */
    int wasdollar = 0;
 
    if (EAT('^')) {
        EMIT(OBOL, 0);
        p->g->iflags |= USEBOL;
        p->g->nbol++;
    }
    while (MORE() && !SEETWO(end1, end2)) {
        wasdollar = p_simp_re(p, first);
        first = 0;
    }
    if (wasdollar) { /* oops, that was a trailing anchor */
        DROP(1);
        EMIT(OEOL, 0);
        p->g->iflags |= USEEOL;
        p->g->neol++;
    }
 
    REQUIRE(HERE() != start, RZ_REGEX_EMPTY); /* require nonempty */
}
 
/*
 - p_simp_re - parse a simple RE, an atom possibly followed by a repetition
 */
static int /* was the simple RE an unbackslashed $? */
p_simp_re(struct parse *p,
    int starordinary) /* is a leading * an ordinary character? */
{
    int c;
    int count;
    int count2;
    sopno pos;
    int i;
    sopno subno;
#define BACKSL (1 << CHAR_BIT)
 
    pos = HERE(); /* repetion op, if any, covers from here */
 
    if (!MORE()) { /* caller should have ensured this */
        return 0;
    }
    c = GETNEXT();
    if (c == '\\') {
        REQUIRE(MORE(), RZ_REGEX_EESCAPE);
        c = BACKSL | GETNEXT();
    }
    switch (c) {
    case '.':
        if (p->g->cflags & RZ_REGEX_NEWLINE) {
            nonnewline(p);
        } else {
            EMIT(OANY, 0);
        }
        break;
    case '[':
        p_bracket(p);
        break;
    case BACKSL | '{':
        SETERROR(RZ_REGEX_BADRPT);
        break;
    case BACKSL | '(':
        p->g->nsub++;
        subno = p->g->nsub;
        if (subno < NPAREN) {
            p->pbegin[subno] = HERE();
        }
        EMIT(OLPAREN, subno);
        /* the MORE here is an error heuristic */
        if (MORE() && !SEETWO('\\', ')')) {
            p_bre(p, '\\', ')');
        }
        if (subno < NPAREN) {
            p->pend[subno] = HERE();
            if (!p->pend[subno]) {
                break;
            }
        }
        EMIT(ORPAREN, subno);
        REQUIRE(EATTWO('\\', ')'), RZ_REGEX_EPAREN);
        break;
    case BACKSL | ')': /* should not get here -- must be user */
    case BACKSL | '}':
        SETERROR(RZ_REGEX_EPAREN);
        break;
    case BACKSL | '1':
    case BACKSL | '2':
    case BACKSL | '3':
    case BACKSL | '4':
    case BACKSL | '5':
    case BACKSL | '6':
    case BACKSL | '7':
    case BACKSL | '8':
    case BACKSL | '9':
        i = (c & ~BACKSL) - '0';
        if (p->pend[i] != 0) {
            if (i <= p->g->nsub) {
                EMIT(OBACK_, i);
                if (p->pbegin[i] != 0 && OP(p->strip[p->pbegin[i]]) == OLPAREN &&
                    OP(p->strip[p->pend[i]]) == ORPAREN) {
                    (void)dupl(p, p->pbegin[i] + 1, p->pend[i]);
                    EMIT(O_BACK, i);
                }
            }
        } else {
            SETERROR(RZ_REGEX_ESUBREG);
        }
        p->g->backrefs = 1;
        break;
    case '*':
        REQUIRE(starordinary, RZ_REGEX_BADRPT);
        /* FALLTHROUGH */
    default:
        ordinary(p, (char)c);
        break;
    }
 
    if (EAT('*')) { /* implemented as +? */
        /* this case does not require the (y|) trick, noKLUDGE */
        INSERT(OPLUS_, pos);
        ASTERN(O_PLUS, pos);
        INSERT(OQUEST_, pos);
        ASTERN(O_QUEST, pos);
    } else if (EATTWO('\\', '{')) {
        count = p_count(p);
        if (EAT(',')) {
            if (MORE() && isdigit((ut8)PEEK())) {
                count2 = p_count(p);
                REQUIRE(count <= count2, RZ_REGEX_BADBR);
            } else { /* single number with comma */
                count2 = INTFINITY;
            }
        } else { /* just a single number */
            count2 = count;
        }
        repeat(p, pos, count, count2);
        if (!EATTWO('\\', '}')) { /* error heuristics */
            while (MORE() && !SEETWO('\\', '}')) {
                NEXT();
            }
            REQUIRE(MORE(), RZ_REGEX_EBRACE);
            SETERROR(RZ_REGEX_BADBR);
        }
    } else if (c == '$') { /* $ (but not \$) ends it */
        return (1);
    }
 
    return (0);
}
 
/*
 - p_count - parse a repetition count
 */
static int /* the value */
p_count(struct parse *p) {
    int count = 0;
    int ndigits = 0;
 
    while (MORE() && isdigit((ut8)PEEK()) && count <= DUPMAX) {
        count = count * 10 + (GETNEXT() - '0');
        ndigits++;
    }
 
    REQUIRE(ndigits > 0 && count <= DUPMAX, RZ_REGEX_BADBR);
    return (count);
}
 
/*
 - p_bracket - parse a bracketed character list
 *
 * Note a significant property of this code:  if the allocset() did SETERROR,
 * no set operations are done.
 */
static void p_bracket(struct parse *p) {
    cset *cs;
    int invert = 0;
 
    /* Dept of Truly Sickening Special-Case Kludges */
    if (p->next + 5 < p->end && strncmp(p->next, "[:<:]]", 6) == 0) {
        EMIT(OBOW, 0);
        NEXTn(6);
        return;
    }
    if (p->next + 5 < p->end && strncmp(p->next, "[:>:]]", 6) == 0) {
        EMIT(OEOW, 0);
        NEXTn(6);
        return;
    }
 
    if (!(cs = allocset(p))) {
        /* allocset did set error status in p */
        return;
    }
 
    if (EAT('^')) {
        invert++; /* make note to invert set at end */
    }
    if (EAT(']')) {
        CHadd(cs, ']');
    } else if (EAT('-')) {
        CHadd(cs, '-');
    }
    while (MORE() && PEEK() != ']' && !SEETWO('-', ']')) {
        p_b_term(p, cs);
    }
    if (EAT('-')) {
        CHadd(cs, '-');
    }
    MUSTEAT(']', RZ_REGEX_EBRACK);
 
    if (p->error != 0) { /* don't mess things up further */
        freeset(p, cs);
        return;
    }
 
    if (p->g->cflags & RZ_REGEX_ICASE) {
        int i;
        int ci;
 
        for (i = p->g->csetsize - 1; i >= 0; i--) {
            if (CHIN(cs, i) && isalpha(i)) {
                ci = othercase(i);
                if (ci != i) {
                    CHadd(cs, ci);
                }
            }
        }
        if (cs->multis != NULL) {
            mccase(p, cs);
        }
    }
    if (invert) {
        int i;
 
        for (i = p->g->csetsize - 1; i >= 0; i--) {
            if (CHIN(cs, i)) {
                CHsub(cs, i);
            } else {
                CHadd(cs, i);
            }
        }
        if (p->g->cflags & RZ_REGEX_NEWLINE) {
            CHsub(cs, '\n');
        }
        if (cs->multis != NULL) {
            mcinvert(p, cs);
        }
    }
 
    if (cs->multis) { /* xxx */
        return;
    }
 
    if (nch(p, cs) == 1) { /* optimize singleton sets */
        ordinary(p, firstch(p, cs));
        freeset(p, cs);
    } else {
        EMIT(OANYOF, freezeset(p, cs));
    }
}
 
/*
 - p_b_term - parse one term of a bracketed character list
 */
static void p_b_term(struct parse *p, cset *cs) {
    char c;
    char start = 0, finish;
    int i;
 
    /* classify what we've got */
    switch ((MORE()) ? PEEK() : '\0') {
    case '[':
        c = (MORE2()) ? PEEK2() : '\0';
        break;
    case '-':
        SETERROR(RZ_REGEX_ERANGE);
        return; /* NOTE RETURN */
        break;
    default:
        c = '\0';
        break;
    }
 
    switch (c) {
    case ':': /* character class */
        NEXT2();
        REQUIRE(MORE(), RZ_REGEX_EBRACK);
        c = PEEK();
        REQUIRE(c != '-' && c != ']', RZ_REGEX_ECTYPE);
        p_b_cclass(p, cs);
        REQUIRE(MORE(), RZ_REGEX_EBRACK);
        REQUIRE(EATTWO(':', ']'), RZ_REGEX_ECTYPE);
        break;
    case '=': /* equivalence class */
        NEXT2();
        REQUIRE(MORE(), RZ_REGEX_EBRACK);
        c = PEEK();
        REQUIRE(c != '-' && c != ']', RZ_REGEX_ECOLLATE);
        p_b_eclass(p, cs);
        REQUIRE(MORE(), RZ_REGEX_EBRACK);
        REQUIRE(EATTWO('=', ']'), RZ_REGEX_ECOLLATE);
        break;
    default: /* symbol, ordinary character, or range */
        /* xxx revision needed for multichar stuff */
        start = p_b_symbol(p);
        if (SEE('-') && MORE2() && PEEK2() != ']') {
            /* range */
            NEXT();
            if (EAT('-')) {
                finish = '-';
            } else {
                finish = p_b_symbol(p);
            }
        } else {
            finish = start;
        }
        /* xxx what about signed chars here... */
        REQUIRE(start <= finish, RZ_REGEX_ERANGE);
        for (i = start; i <= finish; i++) {
            CHadd(cs, i);
        }
        break;
    }
}
 
/*
 - p_b_cclass - parse a character-class name and deal with it
 */
static void p_b_cclass(struct parse *p, cset *cs) {
    char *sp = p->next;
    struct cclass *cp;
    size_t len;
    char *u;
    char c;
 
    while (MORE() && isalpha((unsigned char)PEEK())) {
        NEXT();
    }
    len = p->next - sp;
    for (cp = cclasses; cp->name != NULL; cp++) {
        if (strncmp(cp->name, sp, len) == 0 && cp->name[len] == '\0') {
            break;
        }
    }
    if (!cp->name) {
        /* oops, didn't find it */
        SETERROR(RZ_REGEX_ECTYPE);
        return;
    }
 
    u = cp->chars;
    while ((c = *u++) != '\0') {
        CHadd(cs, c);
    }
    for (u = cp->multis; *u != '\0'; u += strlen(u) + 1) {
        MCadd(p, cs, u);
    }
}
 
/*
 - p_b_eclass - parse an equivalence-class name and deal with it
 *
 * This implementation is incomplete. xxx
 */
static void p_b_eclass(struct parse *p, cset *cs) {
    char c;
 
    c = p_b_coll_elem(p, '=');
    CHadd(cs, c);
}
 
/*
 - p_b_symbol - parse a character or [..]ed multicharacter collating symbol
 */
static char /* value of symbol */
p_b_symbol(struct parse *p) {
    char value;
 
    REQUIRE(MORE(), RZ_REGEX_EBRACK);
    if (!EATTWO('[', '.')) {
        return (GETNEXT());
    }
 
    /* collating symbol */
    value = p_b_coll_elem(p, '.');
    REQUIRE(EATTWO('.', ']'), RZ_REGEX_ECOLLATE);
    return (value);
}
 
/*
 - p_b_coll_elem - parse a collating-element name and look it up
 */
static char /* value of collating element */
p_b_coll_elem(struct parse *p,
    int endc) /* name ended by endc,']' */
{
    char *sp = p->next;
    struct cname *cp;
    int len;
 
    while (MORE() && !SEETWO(endc, ']')) {
        NEXT();
    }
    if (!MORE()) {
        SETERROR(RZ_REGEX_EBRACK);
        return (0);
    }
    len = p->next - sp;
    for (cp = cnames; cp->name != NULL; cp++) {
        if (strncmp(cp->name, sp, len) == 0 && cp->name[len] == '\0') {
            return (cp->code); /* known name */
        }
    }
    if (len == 1) {
        return (*sp); /* single character */
    }
    SETERROR(RZ_REGEX_ECOLLATE); /* neither */
    return (0);
}
 
/*
 - othercase - return the case counterpart of an alphabetic
 */
static char /* if no counterpart, return ch */
othercase(int ch) {
    ch = (ut8)ch;
    if (isalpha(ch)) {
        if (isupper(ch)) {
            return ((ut8)tolower(ch));
        } else if (islower(ch)) {
            return ((ut8)toupper(ch));
        } else { /* peculiar, but could happen */
            return (ch);
        }
    }
    return ch;
}
 
/*
 - bothcases - emit a dualcase version of a two-case character
 *
 * Boy, is this implementation ever a kludge...
 */
static void bothcases(struct parse *p, int ch) {
    char *oldnext = p->next;
    char *oldend = p->end;
    char bracket[3];
 
    ch = (ut8)ch;
    if (othercase(ch) != ch) { /* p_bracket() would recurse */
        p->next = bracket;
        p->end = bracket + 2;
        bracket[0] = ch;
        bracket[1] = ']';
        bracket[2] = '\0';
        p_bracket(p);
        if (p->next == bracket + 2) {
            p->next = oldnext;
            p->end = oldend;
        }
    }
}
 
/*
 - ordinary - emit an ordinary character
 */
static void
ordinary(struct parse *p, int ch) {
    cat_t *cap = p->g->categories;
 
    if ((p->g->cflags & RZ_REGEX_ICASE) && isalpha((ut8)ch) && othercase(ch) != ch) {
        bothcases(p, ch);
    } else {
        EMIT(OCHAR, (ut8)ch);
        if (cap[ch] == 0) {
            cap[ch] = p->g->ncategories++;
        }
    }
}
 
static void
special(struct parse *p, int ch) {
    char *oldnext = p->next;
    char *oldend = p->end;
    char bracket[16] = { 0 };
    char digits[3] = { 0 };
    char c;
    int num = 0;
    switch (ch) {
    case 'x':
        digits[0] = GETNEXT();
        digits[1] = GETNEXT();
        c = (char)strtol(digits, NULL, 16);
        ordinary(p, c);
        return;
    case 'n':
        ordinary(p, '\n');
        return;
    case 't':
        ordinary(p, '\t');
        return;
    case 'r':
        ordinary(p, '\r');
        return;
    case 's':
        num = 5;
        memcpy(bracket, "\t\r\n ]", num);
        break;
    case 'd':
        num = 4;
        memcpy(bracket, "0-9]", num);
        break;
    case 'w':
        num = 4;
        memcpy(bracket, "a-z]", num);
        break;
    default:
        SETERROR(RZ_REGEX_INVARG);
        return;
    }
 
    p->next = bracket;
    p->end = bracket + num;
 
    p_bracket(p);
 
    if (p->next == bracket + num) {
        p->next = oldnext;
        p->end = oldend;
    }
}
 
/*
 - nonnewline - emit RZ_REGEX_NEWLINE version of OANY
 *
 * Boy, is this implementation ever a kludge...
 */
static void
nonnewline(struct parse *p) {
    char *oldnext = p->next;
    char *oldend = p->end;
    char bracket[4];
 
    p->next = bracket;
    p->end = bracket + 3;
    bracket[0] = '^';
    bracket[1] = '\n';
    bracket[2] = ']';
    bracket[3] = '\0';
    p_bracket(p);
    if (p->next == bracket + 3) {
        p->next = oldnext;
        p->end = oldend;
    }
}
 
/*
 - repeat - generate code for a bounded repetition, recursively if needed
 */
static void
repeat(struct parse *p,
    sopno start, /* operand from here to end of strip */
    int from, /* repeated from this number */
    int to) /* to this number of times (maybe INTFINITY) */
{
    sopno finish = HERE();
#define N         2
#define INF       3
#define REP(f, t) ((f)*8 + (t))
#define MAP(n)    (((n) <= 1) ? (n) : ((n) == INTFINITY) ? INF \
                             : N)
    sopno copy;
 
    if (p->error != 0) { /* head off possible runaway recursion */
        return;
    }
 
    if (from > to) {
        return;
    }
 
    switch (REP(MAP(from), MAP(to))) {
    case REP(0, 0): /* must be user doing this */
        DROP(finish - start); /* drop the operand */
        break;
    case REP(0, 1): /* as x{1,1}? */
    case REP(0, N): /* as x{1,n}? */
    case REP(0, INF): /* as x{1,}? */
        /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
        INSERT(OCH_, start); /* offset is wrong... */
        repeat(p, start + 1, 1, to);
        ASTERN(OOR1, start);
        AHEAD(start); /* ... fix it */
        EMIT(OOR2, 0);
        AHEAD(THERE());
        ASTERN(O_CH, THERETHERE());
        break;
    case REP(1, 1): /* trivial case */
        /* done */
        break;
    case REP(1, N): /* as x?x{1,n-1} */
        /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
        INSERT(OCH_, start);
        ASTERN(OOR1, start);
        AHEAD(start);
        EMIT(OOR2, 0); /* offset very wrong... */
        AHEAD(THERE()); /* ...so fix it */
        ASTERN(O_CH, THERETHERE());
        copy = dupl(p, start + 1, finish + 1);
        if (copy == finish + 4) {
            repeat(p, copy, 1, to - 1);
        }
        break;
    case REP(1, INF): /* as x+ */
        INSERT(OPLUS_, start);
        ASTERN(O_PLUS, start);
        break;
    case REP(N, N): /* as xx{m-1,n-1} */
        copy = dupl(p, start, finish);
        repeat(p, copy, from - 1, to - 1);
        break;
    case REP(N, INF): /* as xx{n-1,INF} */
        copy = dupl(p, start, finish);
        repeat(p, copy, from - 1, to);
        break;
    default: /* "can't happen" */
        SETERROR(RZ_REGEX_ASSERT); /* just in case */
        break;
    }
}
 
/*
 - seterr - set an error condition
 */
static int /* useless but makes type checking happy */
seterr(struct parse *p, int e) {
    if (p->error == 0) { /* keep earliest error condition */
        p->error = e;
    }
    p->next = nuls; /* try to bring things to a halt */
    p->end = nuls;
    return (0); /* make the return value well-defined */
}
 
/*
 - allocset - allocate a set of characters for []
 */
static cset *allocset(struct parse *p) {
    int no = p->g->ncsets++;
    size_t nc;
    size_t nbytes;
    cset *cs;
    size_t css = (size_t)p->g->csetsize;
    int i;
 
    if (no >= p->ncsalloc) { /* need another column of space */
        void *ptr;
 
        p->ncsalloc += CHAR_BIT;
        nc = p->ncsalloc;
        if (nc % CHAR_BIT) {
            goto nomem;
        }
        nbytes = nc / CHAR_BIT * css;
 
        ptr = (cset *)realloc((char *)p->g->sets, nc * sizeof(cset));
        if (!ptr) {
            goto nomem;
        }
        p->g->sets = ptr;
 
        ptr = (ut8 *)realloc((char *)p->g->setbits, nbytes);
        if (!ptr) {
            goto nomem;
        }
        p->g->setbits = ptr;
 
        for (i = 0; i < no; i++) {
            p->g->sets[i].ptr = p->g->setbits + css * (i / CHAR_BIT);
        }
 
        (void)memset((char *)p->g->setbits + (nbytes - css), 0, css);
    }
    /* XXX should not happen */
    if (!p->g->sets || !p->g->setbits) {
        goto nomem;
    }
 
    cs = &p->g->sets[no];
    cs->ptr = p->g->setbits + css * ((no) / CHAR_BIT);
    cs->mask = 1 << ((no) % CHAR_BIT);
    cs->hash = 0;
    cs->smultis = 0;
    cs->multis = NULL;
 
    return (cs);
nomem:
    RZ_FREE(p->g->sets);
    RZ_FREE(p->g->setbits);
 
    SETERROR(RZ_REGEX_ESPACE);
    /* caller's responsibility not to do set ops */
    return (NULL);
}
 
/*
 - freeset - free a now-unused set
 */
static void freeset(struct parse *p, cset *cs) {
    int i;
    cset *top = &p->g->sets[p->g->ncsets];
    size_t css = (size_t)p->g->csetsize;
 
    for (i = 0; i < css; i++) {
        CHsub(cs, i);
    }
    if (cs == top - 1) { /* recover only the easy case */
        p->g->ncsets--;
    }
}
 
/*
 - freezeset - final processing on a set of characters
 *
 * The main task here is merging identical sets.  This is usually a waste
 * of time (although the hash code minimizes the overhead), but can win
 * big if RZ_REGEX_ICASE is being used.  RZ_REGEX_ICASE, by the way, is why the hash
 * is done using addition rather than xor -- all ASCII [aA] sets xor to
 * the same value!
 */
static int /* set number */
freezeset(struct parse *p, cset *cs) {
    ut8 h = cs->hash;
    int i;
    cset *top = &p->g->sets[p->g->ncsets];
    cset *cs2;
    size_t css = (size_t)p->g->csetsize;
 
    /* look for an earlier one which is the same */
    for (cs2 = &p->g->sets[0]; cs2 < top; cs2++) {
        if (cs2->hash == h && cs2 != cs) {
            /* maybe */
            for (i = 0; i < css; i++) {
                if (!!CHIN(cs2, i) != !!CHIN(cs, i)) {
                    break; /* no */
                }
            }
            if (i == css) {
                break; /* yes */
            }
        }
    }
 
    if (cs2 < top) { /* found one */
        freeset(p, cs);
        cs = cs2;
    }
 
    return ((int)(cs - p->g->sets));
}
 
/*
 - firstch - return first character in a set (which must have at least one)
 */
static int /* character; there is no "none" value */
firstch(struct parse *p, cset *cs) {
    int i;
    size_t css = (size_t)p->g->csetsize;
 
    for (i = 0; i < css; i++) {
        if (CHIN(cs, i)) {
            return ((char)i);
        }
    }
    return (0); /* arbitrary */
}
 
/*
 - nch - number of characters in a set
 */
static int nch(struct parse *p, cset *cs) {
    int i;
    size_t css = (size_t)p->g->csetsize;
    int n = 0;
 
    for (i = 0; i < css; i++) {
        if (CHIN(cs, i)) {
            n++;
        }
    }
    return (n);
}
 
/*
 - mcadd - add a collating element to a cset
 */
static void mcadd(struct parse *p, cset *cs, char *cp) {
    size_t oldend = cs->smultis;
    void *np;
 
    cs->smultis += strlen(cp) + 1;
    np = realloc(cs->multis, cs->smultis);
    if (!np) {
        if (cs->multis) {
            free(cs->multis);
        }
        cs->multis = NULL;
        SETERROR(RZ_REGEX_ESPACE);
        return;
    }
    cs->multis = np;
 
    STRLCPY(cs->multis + oldend - 1, cp, cs->smultis - oldend + 1);
}
 
/*
 - mcinvert - invert the list of collating elements in a cset
 *
 * This would have to know the set of possibilities.  Implementation
 * is deferred.
 */
/* ARGSUSED */
static void mcinvert(struct parse *p, cset *cs) {
    // asert(!cs->multis);  /* xxx */
    return;
}
 
/*
 - mccase - add case counterparts of the list of collating elements in a cset
 *
 * This would have to know the set of possibilities.  Implementation
 * is deferred.
 */
/* ARGSUSED */
static void mccase(struct parse *p, cset *cs) {
    // asert(!cs->multis);  /* xxx */
    return;
}
 
/*
 - isinsets - is this character in any sets?
 */
static int /* predicate */
isinsets(struct re_guts *g, int c) {
    ut8 *col;
    int i;
    int ncols = (g->ncsets + (CHAR_BIT - 1)) / CHAR_BIT;
    unsigned uc = (ut8)c;
 
    for (i = 0, col = g->setbits; i < ncols; i++, col += g->csetsize) {
        if (col[uc] != 0) {
            return (1);
        }
    }
    return (0);
}
 
/*
 - samesets - are these two characters in exactly the same sets?
 */
static int /* predicate */
samesets(struct re_guts *g, int c1, int c2) {
    ut8 *col;
    int i;
    int ncols = (g->ncsets + (CHAR_BIT - 1)) / CHAR_BIT;
    unsigned uc1 = (ut8)c1;
    unsigned uc2 = (ut8)c2;
 
    for (i = 0, col = g->setbits; i < ncols; i++, col += g->csetsize) {
        if (col[uc1] != col[uc2]) {
            return (0);
        }
    }
    return (1);
}
 
/*
 - categorize - sort out character categories
 */
static void
categorize(struct parse *p, struct re_guts *g) {
    cat_t *cats = g ? g->categories : NULL;
    int c;
    int c2;
    cat_t cat;
 
    /* avoid making error situations worse */
    if (!p || p->error != 0 || !cats) {
        return;
    }
 
    for (c = CHAR_MIN; c <= CHAR_MAX; c++) {
        if (*(cats + c) && isinsets(g, c)) {
            cat = g->ncategories++;
            cats[c] = cat;
            for (c2 = c + 1; c2 <= CHAR_MAX; c2++) {
                if (cats[c2] == 0 && samesets(g, c, c2)) {
                    cats[c2] = cat;
                }
            }
        }
    }
}
 
/*
 - dupl - emit a duplicate of a bunch of sops
 */
static sopno /* start of duplicate */
dupl(struct parse *p,
    sopno start, /* from here */
    sopno finish) /* to this less one */
{
    sopno ret = HERE();
    sopno len = finish - start;
 
    if (finish >= start) {
        if (len == 0) {
            return (ret);
        }
        enlarge(p, p->ssize + len); /* this many unexpected additions */
        if (p->ssize >= p->slen + len) {
            (void)memcpy((char *)(p->strip + p->slen),
                (char *)(p->strip + start), (size_t)len * sizeof(sop));
            p->slen += len;
            return (ret);
        }
    }
    return ret;
}
 
/*
 - doemit - emit a strip operator
 *
 * It might seem better to implement this as a macro with a function as
 * hard-case backup, but it's just too big and messy unless there are
 * some changes to the data structures.  Maybe later.
 */
static void
doemit(struct parse *p, sop op, size_t opnd) {
    /* avoid making error situations worse */
    if (p->error != 0) {
        return;
    }
 
    /* deal with oversize operands ("can't happen", more or less) */
    if (opnd < 1 << OPSHIFT) {
 
        /* deal with undersized strip */
        if (p->slen >= p->ssize) {
            enlarge(p, (p->ssize + 1) / 2 * 3); /* +50% */
        }
        if (p->slen < p->ssize) {
            /* finally, it's all reduced to the easy case */
            p->strip[p->slen++] = SOP(op, opnd);
        }
    }
}
 
/*
 - doinsert - insert a sop into the strip
 */
static void
doinsert(struct parse *p, sop op, size_t opnd, sopno pos) {
    sopno sn;
    sop s;
    int i;
 
    /* avoid making error situations worse */
    if (p->error != 0) {
        return;
    }
 
    sn = HERE();
    EMIT(op, opnd); /* do checks, ensure space */
    if (HERE() != sn + 1) {
        return;
    }
    s = p->strip[sn];
 
    /* adjust paren pointers */
    if (pos > 0) {
        for (i = 1; i < NPAREN; i++) {
            if (p->pbegin[i] >= pos) {
                p->pbegin[i]++;
            }
            if (p->pend[i] >= pos) {
                p->pend[i]++;
            }
        }
    }
 
    memmove((char *)&p->strip[pos + 1], (char *)&p->strip[pos],
        (HERE() - pos - 1) * sizeof(sop));
    p->strip[pos] = s;
}
 
/*
 - dofwd - complete a forward reference
 */
static void
dofwd(struct parse *p, sopno pos, sop value) {
    /* avoid making error situations worse */
    if (p->error != 0) {
        return;
    }
 
    if (value < 1 << OPSHIFT) {
        p->strip[pos] = OP(p->strip[pos]) | value;
    }
}
 
/*
 - enlarge - enlarge the strip
 */
static void
enlarge(struct parse *p, sopno size) {
    sop *sp;
 
    if (p->ssize >= size) {
        return;
    }
 
    sp = (sop *)realloc(p->strip, size * sizeof(sop));
    if (!sp) {
        SETERROR(RZ_REGEX_ESPACE);
        return;
    }
    p->strip = sp;
    p->ssize = size;
}
 
/*
 - stripsnug - compact the strip
 */
static void
stripsnug(struct parse *p, struct re_guts *g) {
    g->nstates = p->slen;
    g->strip = (sop *)realloc((char *)p->strip, p->slen * sizeof(sop));
    if (!g->strip) {
        SETERROR(RZ_REGEX_ESPACE);
        g->strip = p->strip;
    }
}
 
/*
 - findmust - fill in must and mlen with longest mandatory literal string
 *
 * This algorithm could do fancy things like analyzing the operands of |
 * for common subsequences.  Someday.  This code is simple and finds most
 * of the interesting cases.
 *
 * Note that must and mlen got initialized during setup.
 */
static void
findmust(struct parse *p, struct re_guts *g) {
    sop *scan;
    sop *start = NULL; /* start initialized in the default case, after that */
    sop *newstart = NULL; /* newstart was initialized in the OCHAR case */
    sopno newlen;
    sop s;
    char *cp;
    sopno i;
 
    /* avoid making error situations worse */
    if (p->error != 0) {
        return;
    }
 
    /* find the longest OCHAR sequence in strip */
    newlen = 0;
    start = scan = g->strip + 1;
    do {
        s = *scan++;
        switch (OP(s)) {
        case OCHAR: /* sequence member */
            if (newlen == 0) { /* new sequence */
                newstart = scan - 1;
            }
            newlen++;
            break;
        case OPLUS_: /* things that don't break one */
        case OLPAREN:
        case ORPAREN:
            break;
        case OQUEST_: /* things that must be skipped */
        case OCH_:
            scan--;
            do {
                scan += OPND(s);
                s = *scan;
                /* asert() interferes w debug printouts */
                if (OP(s) != O_QUEST && OP(s) != O_CH &&
                    OP(s) != OOR2) {
                    g->iflags |= BAD;
                    return;
                }
            } while (OP(s) != O_QUEST && OP(s) != O_CH);
            /* fallthrough */
        default: /* things that break a sequence */
            if (newlen > g->mlen) { /* ends one */
                start = newstart;
                g->mlen = newlen;
            }
            newlen = 0;
            break;
        }
    } while (OP(s) != OEND);
 
    if (g->mlen == 0) { /* there isn't one */
        return;
    }
 
    /* turn it into a character string */
    g->must = malloc((size_t)g->mlen + 1);
    if (!g->must) { /* argh; just forget it */
        g->mlen = 0;
        return;
    }
    cp = g->must;
    scan = start;
    for (i = g->mlen; i > 0; i--) {
        while (OP(s = *scan++) != OCHAR) {
            continue;
        }
        if (cp < g->must + g->mlen) {
            *cp++ = (char)OPND(s);
        }
    }
    if (cp == g->must + g->mlen) {
        *cp++ = '\0'; /* just on general principles */
    }
}
 
/*
 - pluscount - count + nesting
 */
static sopno /* nesting depth */
pluscount(struct parse *p, struct re_guts *g) {
    sop *scan;
    sop s;
    sopno plusnest = 0;
    sopno maxnest = 0;
 
    if (p->error != 0) {
        return (0); /* there may not be an OEND */
    }
 
    scan = g->strip + 1;
    do {
        s = *scan++;
        switch (OP(s)) {
        case OPLUS_:
            plusnest++;
            break;
        case O_PLUS:
            if (plusnest > maxnest) {
                maxnest = plusnest;
            }
            plusnest--;
            break;
        }
    } while (OP(s) != OEND);
    if (plusnest != 0) {
        g->iflags |= BAD;
    }
    return (maxnest);
}