The R Project SVN R

/*-
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. 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.
 *
 *  @(#)engine.c    8.5 (Berkeley) 3/20/94
 */

/*
 * The matching engine and friends.  This file is #included by regexec.c
 * after suitable #defines of a variety of macros used herein, so that
 * different state representations can be used without duplicating masses
 * of code.
 */

#ifdef SNAMES
#define matcher smatcher
#define fast    sfast
#define slow    sslow
#define dissect sdissect
#define backref sbackref
#define step    sstep
#define print   sprint
#define at  sat
#define match   smat
#endif
#ifdef LNAMES
#define matcher lmatcher
#define fast    lfast
#define slow    lslow
#define dissect ldissect
#define backref lbackref
#define step    lstep
#define print   lprint
#define at  lat
#define match   lmat
#endif

/* another structure passed up and down to avoid zillions of parameters */
struct match {
    struct re_guts *g;
    int eflags;
    regmatch_t *pmatch; /* [nsub+1] (0 element unused) */
    char *offp;     /* offsets work from here */
    char *beginp;       /* start of string -- virtual NUL precedes */
    char *endp;     /* end of string -- virtual NUL here */
    char *coldp;        /* can be no match starting before here */
    char **lastpos;     /* [nplus+1] */
    STATEVARS;
    states st;      /* current states */
    states fresh;       /* states for a fresh start */
    states tmp;     /* temporary */
    states empty;       /* empty set of states */
};

/* ========= begin header generated by ./mkh ========= */
#ifdef __cplusplus
extern "C" {
#endif

/* === engine.c === */
static int matcher __P((struct re_guts *g, char *string, size_t nmatch, regmatch_t pmatch[], int eflags));
static char *dissect __P((struct match *m, char *start, char *stop, sopno startst, sopno stopst));
static char *backref __P((struct match *m, char *start, char *stop, sopno startst, sopno stopst, sopno lev));
static char *fast __P((struct match *m, char *start, char *stop, sopno startst, sopno stopst));
static char *slow __P((struct match *m, char *start, char *stop, sopno startst, sopno stopst));
static states step __P((struct re_guts *g, sopno start, sopno stop, states bef, int ch, states aft));
#define BOL (OUT+1)
#define EOL (BOL+1)
#define BOLEOL  (BOL+2)
#define NOTHING (BOL+3)
#define BOW (BOL+4)
#define EOW (BOL+5)
#define CODEMAX (BOL+5)     /* highest code used */
#define NONCHAR(c)  ((c) > CHAR_MAX)
#define NNONCHAR    (CODEMAX-CHAR_MAX)
#ifdef REDEBUG
static void print __P((struct match *m, char *caption, states st, int ch, FILE *d));
#endif
#ifdef REDEBUG
static void at __P((struct match *m, char *title, char *start, char *stop, sopno startst, sopno stopst));
#endif
#ifdef REDEBUG
static char *pchar __P((int ch));
#endif

#ifdef __cplusplus
}
#endif
/* ========= end header generated by ./mkh ========= */

#ifdef REDEBUG
#define SP(t, s, c) print(m, t, s, c, stdout)
#define AT(t, p1, p2, s1, s2)   at(m, t, p1, p2, s1, s2)
#define NOTE(str)   { if (m->eflags&REG_TRACE) printf("=%s\n", (str)); }
#else
#define SP(t, s, c) /* nothing */
#define AT(t, p1, p2, s1, s2)   /* nothing */
#define NOTE(s) /* nothing */
#endif

/*
 - matcher - the actual matching engine
 == static int matcher(register struct re_guts *g, char *string, \
 == size_t nmatch, regmatch_t pmatch[], int eflags);
 */
static int          /* 0 success, REG_NOMATCH failure */
matcher(g, string, nmatch, pmatch, eflags)
register struct re_guts *g;
char *string;
size_t nmatch;
regmatch_t pmatch[];
int eflags;
{
    register char *endp;
    register int i;
    struct match mv;
    register struct match *m = &mv;
    register char *dp;
    register const sopno gf = g->firststate+1;  /* +1 for OEND */
    register const sopno gl = g->laststate;
    char *start;
    char *stop;

    /* simplify the situation where possible */
    if (g->cflags&REG_NOSUB)
        nmatch = 0;
    if (eflags&REG_STARTEND) {
        start = string + pmatch[0].rm_so;
        stop = string + pmatch[0].rm_eo;
    } else {
        start = string;
        stop = start + strlen(start);
    }
    if (stop < start)
        return(REG_INVARG);

    /* prescreening; this does wonders for this rather slow code */
    if (g->must != NULL) {
        for (dp = start; dp < stop; dp++)
            if (*dp == g->must[0] && stop - dp >= g->mlen &&
                memcmp(dp, g->must, (size_t)g->mlen) == 0)
                break;
        if (dp == stop)     /* we didn't find g->must */
            return(REG_NOMATCH);
    }

    /* match struct setup */
    m->g = g;
    m->eflags = eflags;
    m->pmatch = NULL;
    m->lastpos = NULL;
    m->offp = string;
    m->beginp = start;
    m->endp = stop;
    STATESETUP(m, 4);
    SETUP(m->st);
    SETUP(m->fresh);
    SETUP(m->tmp);
    SETUP(m->empty);
    CLEAR(m->empty);

    /* this loop does only one repetition except for backrefs */
    for (;;) {
        endp = fast(m, start, stop, gf, gl);
        if (endp == NULL) {     /* a miss */
            STATETEARDOWN(m);
            return(REG_NOMATCH);
        }
        if (nmatch == 0 && !g->backrefs)
            break;      /* no further info needed */

        /* where? */
        assert(m->coldp != NULL);
        for (;;) {
            NOTE("finding start");
            endp = slow(m, m->coldp, stop, gf, gl);
            if (endp != NULL)
                break;
            assert(m->coldp < m->endp);
            m->coldp++;
        }
        if (nmatch == 1 && !g->backrefs)
            break;      /* no further info needed */

        /* oh my, he wants the subexpressions... */
        if (m->pmatch == NULL)
            m->pmatch = (regmatch_t *)malloc((m->g->nsub + 1) *
                            sizeof(regmatch_t));
        if (m->pmatch == NULL) {
            STATETEARDOWN(m);
            return(REG_ESPACE);
        }
        for (i = 1; i <= m->g->nsub; i++)
            m->pmatch[i].rm_so = m->pmatch[i].rm_eo = -1;
        if (!g->backrefs && !(m->eflags&REG_BACKR)) {
            NOTE("dissecting");
            dp = dissect(m, m->coldp, endp, gf, gl);
        } else {
            if (g->nplus > 0 && m->lastpos == NULL)
                m->lastpos = (char **)malloc((g->nplus+1) *
                            sizeof(char *));
            if (g->nplus > 0 && m->lastpos == NULL) {
                free(m->pmatch);
                STATETEARDOWN(m);
                return(REG_ESPACE);
            }
            NOTE("backref dissect");
            dp = backref(m, m->coldp, endp, gf, gl, (sopno)0);
        }
        if (dp != NULL)
            break;

        /* uh-oh... we couldn't find a subexpression-level match */
        assert(g->backrefs);    /* must be back references doing it */
        assert(g->nplus == 0 || m->lastpos != NULL);
        for (;;) {
            if (dp != NULL || endp <= m->coldp)
                break;      /* defeat */
            NOTE("backoff");
            endp = slow(m, m->coldp, endp-1, gf, gl);
            if (endp == NULL)
                break;      /* defeat */
            /* try it on a shorter possibility */
#ifndef NDEBUG
            for (i = 1; i <= m->g->nsub; i++) {
                assert(m->pmatch[i].rm_so == -1);
                assert(m->pmatch[i].rm_eo == -1);
            }
#endif
            NOTE("backoff dissect");
            dp = backref(m, m->coldp, endp, gf, gl, (sopno)0);
        }
        assert(dp == NULL || dp == endp);
        if (dp != NULL)     /* found a shorter one */
            break;

        /* despite initial appearances, there is no match here */
        NOTE("false alarm");
        start = m->coldp + 1;   /* recycle starting later */
        assert(start <= stop);
    }

    /* fill in the details if requested */
    if (nmatch > 0) {
        pmatch[0].rm_so = m->coldp - m->offp;
        pmatch[0].rm_eo = endp - m->offp;
    }
    if (nmatch > 1) {
        assert(m->pmatch != NULL);
        for (i = 1; i < nmatch; i++)
            if (i <= m->g->nsub)
                pmatch[i] = m->pmatch[i];
            else {
                pmatch[i].rm_so = -1;
                pmatch[i].rm_eo = -1;
            }
    }

    if (m->pmatch != NULL)
        free((char *)m->pmatch);
    if (m->lastpos != NULL)
        free((char *)m->lastpos);
    STATETEARDOWN(m);
    return(0);
}

/*
 - dissect - figure out what matched what, no back references
 == static char *dissect(register struct match *m, char *start, \
 == char *stop, sopno startst, sopno stopst);
 */
static char *           /* == stop (success) always */
dissect(m, start, stop, startst, stopst)
register struct match *m;
char *start;
char *stop;
sopno startst;
sopno stopst;
{
    register int i;
    register sopno ss;  /* start sop of current subRE */
    register sopno es;  /* end sop of current subRE */
    register char *sp;  /* start of string matched by it */
    register char *stp; /* string matched by it cannot pass here */
    register char *rest;    /* start of rest of string */
    register char *tail;    /* string unmatched by rest of RE */
    register sopno ssub;    /* start sop of subsubRE */
    register sopno esub;    /* end sop of subsubRE */
    register char *ssp; /* start of string matched by subsubRE */
    register char *sep; /* end of string matched by subsubRE */
    register char *oldssp;  /* previous ssp */
    register char *dp;

    AT("diss", start, stop, startst, stopst);
    sp = start;
    for (ss = startst; ss < stopst; ss = es) {
        /* identify end of subRE */
        es = ss;
        switch (OP(m->g->strip[es])) {
        case OPLUS_:
        case OQUEST_:
            es += OPND(m->g->strip[es]);
            break;
        case OCH_:
            while (OP(m->g->strip[es]) != O_CH)
                es += OPND(m->g->strip[es]);
            break;
        }
        es++;

        /* figure out what it matched */
        switch (OP(m->g->strip[ss])) {
        case OEND:
            assert(nope);
            break;
        case OCHAR:
            sp++;
            break;
        case OBOL:
        case OEOL:
        case OBOW:
        case OEOW:
            break;
        case OANY:
        case OANYOF:
            sp++;
            break;
        case OBACK_:
        case O_BACK:
            assert(nope);
            break;
        /* cases where length of match is hard to find */
        case OQUEST_:
            stp = stop;
            for (;;) {
                /* how long could this one be? */
                rest = slow(m, sp, stp, ss, es);
                assert(rest != NULL);   /* it did match */
                /* could the rest match the rest? */
                tail = slow(m, rest, stop, es, stopst);
                if (tail == stop)
                    break;      /* yes! */
                /* no -- try a shorter match for this one */
                stp = rest - 1;
                assert(stp >= sp);  /* it did work */
            }
            ssub = ss + 1;
            esub = es - 1;
            /* did innards match? */
            if (slow(m, sp, rest, ssub, esub) != NULL) {
                dp = dissect(m, sp, rest, ssub, esub);
                assert(dp == rest);
            } else      /* no */
                assert(sp == rest);
            sp = rest;
            break;
        case OPLUS_:
            stp = stop;
            for (;;) {
                /* how long could this one be? */
                rest = slow(m, sp, stp, ss, es);
                assert(rest != NULL);   /* it did match */
                /* could the rest match the rest? */
                tail = slow(m, rest, stop, es, stopst);
                if (tail == stop)
                    break;      /* yes! */
                /* no -- try a shorter match for this one */
                stp = rest - 1;
                assert(stp >= sp);  /* it did work */
            }
            ssub = ss + 1;
            esub = es - 1;
            ssp = sp;
            oldssp = ssp;
            for (;;) {  /* find last match of innards */
                sep = slow(m, ssp, rest, ssub, esub);
                if (sep == NULL || sep == ssp)
                    break;  /* failed or matched null */
                oldssp = ssp;   /* on to next try */
                ssp = sep;
            }
            if (sep == NULL) {
                /* last successful match */
                sep = ssp;
                ssp = oldssp;
            }
            assert(sep == rest);    /* must exhaust substring */
            assert(slow(m, ssp, sep, ssub, esub) == rest);
            dp = dissect(m, ssp, sep, ssub, esub);
            assert(dp == sep);
            sp = rest;
            break;
        case OCH_:
            stp = stop;
            for (;;) {
                /* how long could this one be? */
                rest = slow(m, sp, stp, ss, es);
                assert(rest != NULL);   /* it did match */
                /* could the rest match the rest? */
                tail = slow(m, rest, stop, es, stopst);
                if (tail == stop)
                    break;      /* yes! */
                /* no -- try a shorter match for this one */
                stp = rest - 1;
                assert(stp >= sp);  /* it did work */
            }
            ssub = ss + 1;
            esub = ss + OPND(m->g->strip[ss]) - 1;
            assert(OP(m->g->strip[esub]) == OOR1);
            for (;;) {  /* find first matching branch */
                if (slow(m, sp, rest, ssub, esub) == rest)
                    break;  /* it matched all of it */
                /* that one missed, try next one */
                assert(OP(m->g->strip[esub]) == OOR1);
                esub++;
                assert(OP(m->g->strip[esub]) == OOR2);
                ssub = esub + 1;
                esub += OPND(m->g->strip[esub]);
                if (OP(m->g->strip[esub]) == OOR2)
                    esub--;
                else
                    assert(OP(m->g->strip[esub]) == O_CH);
            }
            dp = dissect(m, sp, rest, ssub, esub);
            assert(dp == rest);
            sp = rest;
            break;
        case O_PLUS:
        case O_QUEST:
        case OOR1:
        case OOR2:
        case O_CH:
            assert(nope);
            break;
        case OLPAREN:
            i = OPND(m->g->strip[ss]);
            assert(0 < i && i <= m->g->nsub);
            m->pmatch[i].rm_so = sp - m->offp;
            break;
        case ORPAREN:
            i = OPND(m->g->strip[ss]);
            assert(0 < i && i <= m->g->nsub);
            m->pmatch[i].rm_eo = sp - m->offp;
            break;
        default:        /* uh oh */
            assert(nope);
            break;
        }
    }

    assert(sp == stop);
    return(sp);
}

/*
 - backref - figure out what matched what, figuring in back references
 == static char *backref(register struct match *m, char *start, \
 == char *stop, sopno startst, sopno stopst, sopno lev);
 */
static char *           /* == stop (success) or NULL (failure) */
backref(m, start, stop, startst, stopst, lev)
register struct match *m;
char *start;
char *stop;
sopno startst;
sopno stopst;
sopno lev;          /* PLUS nesting level */
{
    register int i;
    register sopno ss;  /* start sop of current subRE */
    register char *sp;  /* start of string matched by it */
    register sopno ssub;    /* start sop of subsubRE */
    register sopno esub;    /* end sop of subsubRE */
    register char *ssp; /* start of string matched by subsubRE */
    register char *dp;
    register size_t len;
    register int hard;
    register sop s;
    register regoff_t offsave;
    register cset *cs;

    AT("back", start, stop, startst, stopst);
    sp = start;

    /* get as far as we can with easy stuff */
    hard = 0;
    for (ss = startst; !hard && ss < stopst; ss++)
        switch (OP(s = m->g->strip[ss])) {
        case OCHAR:
            if (sp == stop || *sp++ != (char)OPND(s))
                return(NULL);
            break;
        case OANY:
            if (sp == stop)
                return(NULL);
            sp++;
            break;
        case OANYOF:
            cs = &m->g->sets[OPND(s)];
            if (sp == stop || !CHIN(cs, *sp++))
                return(NULL);
            break;
        case OBOL:
            if ( (sp == m->beginp && !(m->eflags&REG_NOTBOL)) ||
                    (sp < m->endp && *(sp-1) == '\n' &&
                        (m->g->cflags&REG_NEWLINE)) )
                { /* yes */ }
            else
                return(NULL);
            break;
        case OEOL:
            if ( (sp == m->endp && !(m->eflags&REG_NOTEOL)) ||
                    (sp < m->endp && *sp == '\n' &&
                        (m->g->cflags&REG_NEWLINE)) )
                { /* yes */ }
            else
                return(NULL);
            break;
        case OBOW:
            if (( (sp == m->beginp && !(m->eflags&REG_NOTBOL)) ||
                    (sp < m->endp && *(sp-1) == '\n' &&
                        (m->g->cflags&REG_NEWLINE)) ||
                    (sp > m->beginp &&
                            !ISWORD(*(sp-1))) ) &&
                    (sp < m->endp && ISWORD(*sp)) )
                { /* yes */ }
            else
                return(NULL);
            break;
        case OEOW:
            if (( (sp == m->endp && !(m->eflags&REG_NOTEOL)) ||
                    (sp < m->endp && *sp == '\n' &&
                        (m->g->cflags&REG_NEWLINE)) ||
                    (sp < m->endp && !ISWORD(*sp)) ) &&
                    (sp > m->beginp && ISWORD(*(sp-1))) )
                { /* yes */ }
            else
                return(NULL);
            break;
        case O_QUEST:
            break;
        case OOR1:  /* matches null but needs to skip */
            ss++;
            s = m->g->strip[ss];
            do {
                assert(OP(s) == OOR2);
                ss += OPND(s);
            } while (OP(s = m->g->strip[ss]) != O_CH);
            /* note that the ss++ gets us past the O_CH */
            break;
        default:    /* have to make a choice */
            hard = 1;
            break;
        }
    if (!hard) {        /* that was it! */
        if (sp != stop)
            return(NULL);
        return(sp);
    }
    ss--;           /* adjust for the for's final increment */

    /* the hard stuff */
    AT("hard", sp, stop, ss, stopst);
    s = m->g->strip[ss];
    switch (OP(s)) {
    case OBACK_:        /* the vilest depths */
        i = OPND(s);
        assert(0 < i && i <= m->g->nsub);
        if (m->pmatch[i].rm_eo == -1)
            return(NULL);
        assert(m->pmatch[i].rm_so != -1);
        len = m->pmatch[i].rm_eo - m->pmatch[i].rm_so;
        assert(stop - m->beginp >= len);
        if (sp > stop - len)
            return(NULL);   /* not enough left to match */
        ssp = m->offp + m->pmatch[i].rm_so;
        if (memcmp(sp, ssp, len) != 0)
            return(NULL);
        while (m->g->strip[ss] != SOP(O_BACK, i))
            ss++;
        return(backref(m, sp+len, stop, ss+1, stopst, lev));
        break;
    case OQUEST_:       /* to null or not */
        dp = backref(m, sp, stop, ss+1, stopst, lev);
        if (dp != NULL)
            return(dp); /* not */
        return(backref(m, sp, stop, ss+OPND(s)+1, stopst, lev));
        break;
    case OPLUS_:
        assert(m->lastpos != NULL);
        assert(lev+1 <= m->g->nplus);
        m->lastpos[lev+1] = sp;
        return(backref(m, sp, stop, ss+1, stopst, lev+1));
        break;
    case O_PLUS:
        if (sp == m->lastpos[lev])  /* last pass matched null */
            return(backref(m, sp, stop, ss+1, stopst, lev-1));
        /* try another pass */
        m->lastpos[lev] = sp;
        dp = backref(m, sp, stop, ss-OPND(s)+1, stopst, lev);
        if (dp == NULL)
            return(backref(m, sp, stop, ss+1, stopst, lev-1));
        else
            return(dp);
        break;
    case OCH_:      /* find the right one, if any */
        ssub = ss + 1;
        esub = ss + OPND(s) - 1;
        assert(OP(m->g->strip[esub]) == OOR1);
        for (;;) {  /* find first matching branch */
            dp = backref(m, sp, stop, ssub, esub, lev);
            if (dp != NULL)
                return(dp);
            /* that one missed, try next one */
            if (OP(m->g->strip[esub]) == O_CH)
                return(NULL);   /* there is none */
            esub++;
            assert(OP(m->g->strip[esub]) == OOR2);
            ssub = esub + 1;
            esub += OPND(m->g->strip[esub]);
            if (OP(m->g->strip[esub]) == OOR2)
                esub--;
            else
                assert(OP(m->g->strip[esub]) == O_CH);
        }
        break;
    case OLPAREN:       /* must undo assignment if rest fails */
        i = OPND(s);
        assert(0 < i && i <= m->g->nsub);
        offsave = m->pmatch[i].rm_so;
        m->pmatch[i].rm_so = sp - m->offp;
        dp = backref(m, sp, stop, ss+1, stopst, lev);
        if (dp != NULL)
            return(dp);
        m->pmatch[i].rm_so = offsave;
        return(NULL);
        break;
    case ORPAREN:       /* must undo assignment if rest fails */
        i = OPND(s);
        assert(0 < i && i <= m->g->nsub);
        offsave = m->pmatch[i].rm_eo;
        m->pmatch[i].rm_eo = sp - m->offp;
        dp = backref(m, sp, stop, ss+1, stopst, lev);
        if (dp != NULL)
            return(dp);
        m->pmatch[i].rm_eo = offsave;
        return(NULL);
        break;
    default:        /* uh oh */
        assert(nope);
        break;
    }

    /* "can't happen" */
    assert(nope);
    /* NOTREACHED */
    return "shut up gcc";
}

/*
 - fast - step through the string at top speed
 == static char *fast(register struct match *m, char *start, \
 == char *stop, sopno startst, sopno stopst);
 */
static char *           /* where tentative match ended, or NULL */
fast(m, start, stop, startst, stopst)
register struct match *m;
char *start;
char *stop;
sopno startst;
sopno stopst;
{
    register states st = m->st;
    register states fresh = m->fresh;
    register states tmp = m->tmp;
    register char *p = start;
    register int c = (start == m->beginp) ? OUT : *(start-1);
    register int lastc; /* previous c */
    register int flagch;
    register int i;
    register char *coldp;   /* last p after which no match was underway */

    CLEAR(st);
    SET1(st, startst);
    st = step(m->g, startst, stopst, st, NOTHING, st);
    ASSIGN(fresh, st);
    SP("start", st, *p);
    coldp = NULL;
    for (;;) {
        /* next character */
        lastc = c;
        c = (p == m->endp) ? OUT : *p;
        if (EQ(st, fresh))
            coldp = p;

        /* is there an EOL and/or BOL between lastc and c? */
        flagch = '\0';
        i = 0;
        if ( (lastc == '\n' && m->g->cflags&REG_NEWLINE) ||
                (lastc == OUT && !(m->eflags&REG_NOTBOL)) ) {
            flagch = BOL;
            i = m->g->nbol;
        }
        if ( (c == '\n' && m->g->cflags&REG_NEWLINE) ||
                (c == OUT && !(m->eflags&REG_NOTEOL)) ) {
            flagch = (flagch == BOL) ? BOLEOL : EOL;
            i += m->g->neol;
        }
        if (i != 0) {
            for (; i > 0; i--)
                st = step(m->g, startst, stopst, st, flagch, st);
            SP("boleol", st, c);
        }

        /* how about a word boundary? */
        if ( (flagch == BOL || (lastc != OUT && !ISWORD(lastc))) &&
                    (c != OUT && ISWORD(c)) ) {
            flagch = BOW;
        }
        if ( (lastc != OUT && ISWORD(lastc)) &&
                (flagch == EOL || (c != OUT && !ISWORD(c))) ) {
            flagch = EOW;
        }
        if (flagch == BOW || flagch == EOW) {
            st = step(m->g, startst, stopst, st, flagch, st);
            SP("boweow", st, c);
        }

        /* are we done? */
        if (ISSET(st, stopst) || p == stop)
            break;      /* NOTE BREAK OUT */

        /* no, we must deal with this character */
        ASSIGN(tmp, st);
        ASSIGN(st, fresh);
        assert(c != OUT);
        st = step(m->g, startst, stopst, tmp, c, st);
        SP("aft", st, c);
        assert(EQ(step(m->g, startst, stopst, st, NOTHING, st), st));
        p++;
    }

    assert(coldp != NULL);
    m->coldp = coldp;
    if (ISSET(st, stopst))
        return(p+1);
    else
        return(NULL);
}

/*
 - slow - step through the string more deliberately
 == static char *slow(register struct match *m, char *start, \
 == char *stop, sopno startst, sopno stopst);
 */
static char *           /* where it ended */
slow(m, start, stop, startst, stopst)
register struct match *m;
char *start;
char *stop;
sopno startst;
sopno stopst;
{
    register states st = m->st;
    register states empty = m->empty;
    register states tmp = m->tmp;
    register char *p = start;
    register int c = (start == m->beginp) ? OUT : *(start-1);
    register int lastc; /* previous c */
    register int flagch;
    register int i;
    register char *matchp;  /* last p at which a match ended */

    AT("slow", start, stop, startst, stopst);
    CLEAR(st);
    SET1(st, startst);
    SP("sstart", st, *p);
    st = step(m->g, startst, stopst, st, NOTHING, st);
    matchp = NULL;
    for (;;) {
        /* next character */
        lastc = c;
        c = (p == m->endp) ? OUT : *p;

        /* is there an EOL and/or BOL between lastc and c? */
        flagch = '\0';
        i = 0;
        if ( (lastc == '\n' && m->g->cflags&REG_NEWLINE) ||
                (lastc == OUT && !(m->eflags&REG_NOTBOL)) ) {
            flagch = BOL;
            i = m->g->nbol;
        }
        if ( (c == '\n' && m->g->cflags&REG_NEWLINE) ||
                (c == OUT && !(m->eflags&REG_NOTEOL)) ) {
            flagch = (flagch == BOL) ? BOLEOL : EOL;
            i += m->g->neol;
        }
        if (i != 0) {
            for (; i > 0; i--)
                st = step(m->g, startst, stopst, st, flagch, st);
            SP("sboleol", st, c);
        }

        /* how about a word boundary? */
        if ( (flagch == BOL || (lastc != OUT && !ISWORD(lastc))) &&
                    (c != OUT && ISWORD(c)) ) {
            flagch = BOW;
        }
        if ( (lastc != OUT && ISWORD(lastc)) &&
                (flagch == EOL || (c != OUT && !ISWORD(c))) ) {
            flagch = EOW;
        }
        if (flagch == BOW || flagch == EOW) {
            st = step(m->g, startst, stopst, st, flagch, st);
            SP("sboweow", st, c);
        }

        /* are we done? */
        if (ISSET(st, stopst))
            matchp = p;
        if (EQ(st, empty) || p == stop)
            break;      /* NOTE BREAK OUT */

        /* no, we must deal with this character */
        ASSIGN(tmp, st);
        ASSIGN(st, empty);
        assert(c != OUT);
        st = step(m->g, startst, stopst, tmp, c, st);
        SP("saft", st, c);
        assert(EQ(step(m->g, startst, stopst, st, NOTHING, st), st));
        p++;
    }

    return(matchp);
}


/*
 - step - map set of states reachable before char to set reachable after
 == static states step(register struct re_guts *g, sopno start, sopno stop, \
 == register states bef, int ch, register states aft);
 == #define BOL (OUT+1)
 == #define EOL (BOL+1)
 == #define BOLEOL  (BOL+2)
 == #define NOTHING (BOL+3)
 == #define BOW (BOL+4)
 == #define EOW (BOL+5)
 == #define CODEMAX (BOL+5)     // highest code used
 == #define NONCHAR(c)  ((c) > CHAR_MAX)
 == #define NNONCHAR    (CODEMAX-CHAR_MAX)
 */
static states
step(g, start, stop, bef, ch, aft)
register struct re_guts *g;
sopno start;            /* start state within strip */
sopno stop;         /* state after stop state within strip */
register states bef;        /* states reachable before */
int ch;             /* character or NONCHAR code */
register states aft;        /* states already known reachable after */
{
    register cset *cs;
    register sop s;
    register sopno pc;
    register onestate here;     /* note, macros know this name */
    register sopno look;
    register int i;

    for (pc = start, INIT(here, pc); pc != stop; pc++, INC(here)) {
        s = g->strip[pc];
        switch (OP(s)) {
        case OEND:
            assert(pc == stop-1);
            break;
        case OCHAR:
            /* only characters can match */
            assert(!NONCHAR(ch) || ch != (char)OPND(s));
            if (ch == (char)OPND(s))
                FWD(aft, bef, 1);
            break;
        case OBOL:
            if (ch == BOL || ch == BOLEOL)
                FWD(aft, bef, 1);
            break;
        case OEOL:
            if (ch == EOL || ch == BOLEOL)
                FWD(aft, bef, 1);
            break;
        case OBOW:
            if (ch == BOW)
                FWD(aft, bef, 1);
            break;
        case OEOW:
            if (ch == EOW)
                FWD(aft, bef, 1);
            break;
        case OANY:
            if (!NONCHAR(ch))
                FWD(aft, bef, 1);
            break;
        case OANYOF:
            cs = &g->sets[OPND(s)];
            if (!NONCHAR(ch) && CHIN(cs, ch))
                FWD(aft, bef, 1);
            break;
        case OBACK_:        /* ignored here */
        case O_BACK:
            FWD(aft, aft, 1);
            break;
        case OPLUS_:        /* forward, this is just an empty */
            FWD(aft, aft, 1);
            break;
        case O_PLUS:        /* both forward and back */
            FWD(aft, aft, 1);
            i = ISSETBACK(aft, OPND(s));
            BACK(aft, aft, OPND(s));
            if (!i && ISSETBACK(aft, OPND(s))) {
                /* oho, must reconsider loop body */
                pc -= OPND(s) + 1;
                INIT(here, pc);
            }
            break;
        case OQUEST_:       /* two branches, both forward */
            FWD(aft, aft, 1);
            FWD(aft, aft, OPND(s));
            break;
        case O_QUEST:       /* just an empty */
            FWD(aft, aft, 1);
            break;
        case OLPAREN:       /* not significant here */
        case ORPAREN:
            FWD(aft, aft, 1);
            break;
        case OCH_:      /* mark the first two branches */
            FWD(aft, aft, 1);
            assert(OP(g->strip[pc+OPND(s)]) == OOR2);
            FWD(aft, aft, OPND(s));
            break;
        case OOR1:      /* done a branch, find the O_CH */
            if (ISSTATEIN(aft, here)) {
                for (look = 1;
                        OP(s = g->strip[pc+look]) != O_CH;
                        look += OPND(s))
                    assert(OP(s) == OOR2);
                FWD(aft, aft, look);
            }
            break;
        case OOR2:      /* propagate OCH_'s marking */
            FWD(aft, aft, 1);
            if (OP(g->strip[pc+OPND(s)]) != O_CH) {
                assert(OP(g->strip[pc+OPND(s)]) == OOR2);
                FWD(aft, aft, OPND(s));
            }
            break;
        case O_CH:      /* just empty */
            FWD(aft, aft, 1);
            break;
        default:        /* ooooops... */
            assert(nope);
            break;
        }
    }

    return(aft);
}

#ifdef REDEBUG
/*
 - print - print a set of states
 == #ifdef REDEBUG
 == static void print(struct match *m, char *caption, states st, \
 == int ch, FILE *d);
 == #endif
 */
static void
print(m, caption, st, ch, d)
struct match *m;
char *caption;
states st;
int ch;
FILE *d;
{
    register struct re_guts *g = m->g;
    register int i;
    register int first = 1;

    if (!(m->eflags&REG_TRACE))
        return;

    fprintf(d, "%s", caption);
    if (ch != '\0')
        fprintf(d, " %s", pchar(ch));
    for (i = 0; i < g->nstates; i++)
        if (ISSET(st, i)) {
            fprintf(d, "%s%d", (first) ? "\t" : ", ", i);
            first = 0;
        }
    fprintf(d, "\n");
}

/*
 - at - print current situation
 == #ifdef REDEBUG
 == static void at(struct match *m, char *title, char *start, char *stop, \
 ==                     sopno startst, sopno stopst);
 == #endif
 */
static void
at(m, title, start, stop, startst, stopst)
struct match *m;
char *title;
char *start;
char *stop;
sopno startst;
sopno stopst;
{
    if (!(m->eflags&REG_TRACE))
        return;

    printf("%s %s-", title, pchar(*start));
    printf("%s ", pchar(*stop));
    printf("%ld-%ld\n", (long)startst, (long)stopst);
}

#ifndef PCHARDONE
#define PCHARDONE   /* never again */
/*
 - pchar - make a character printable
 == #ifdef REDEBUG
 == static char *pchar(int ch);
 == #endif
 *
 * Is this identical to regchar() over in debug.c?  Well, yes.  But a
 * duplicate here avoids having a debugging-capable regexec.o tied to
 * a matching debug.o, and this is convenient.  It all disappears in
 * the non-debug compilation anyway, so it doesn't matter much.
 */
static char *           /* -> representation */
pchar(ch)
int ch;
{
    static char pbuf[10];

    if (isprint((uch)ch) || ch == ' ')
        sprintf(pbuf, "%c", ch);
    else
        sprintf(pbuf, "\\%o", ch);
    return(pbuf);
}
#endif
#endif

#undef  matcher
#undef  fast
#undef  slow
#undef  dissect
#undef  backref
#undef  step
#undef  print
#undef  at
#undef  match