shared_source/c_tcl_base_7_5_w_mods/regexec.c

/* $Header$ */
/*
 * re_*exec and friends - match REs
 *
 * Copyright (c) 1998, 1999 Henry Spencer.  All rights reserved.
 * 
 * Development of this software was funded, in part, by Cray Research Inc.,
 * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
 * Corporation, none of whom are responsible for the results.  The author
 * thanks all of them. 
 * 
 * Redistribution and use in source and binary forms -- with or without
 * modification -- are permitted for any purpose, provided that
 * redistributions in source form retain this entire copyright notice and
 * indicate the origin and nature of any modifications.
 * 
 * I'd appreciate being given credit for this package in the documentation
 * of software which uses it, but that is not a requirement.
 * 
 * THIS SOFTWARE IS PROVIDED ``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
 * HENRY SPENCER 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.
 *
 */

#include "regguts.h"


/* lazy-DFA representation */
struct arcp {                   /* "pointer" to an outarc */
        struct sset *ss;
        color co;
};

struct sset {                   /* state set */
        unsigned *states;       /* pointer to bitvector */
        unsigned hash;          /* hash of bitvector */
#               define  HASH(bv, nw)    (((nw) == 1) ? *(bv) : hash(bv, nw))
#       define  HIT(h,bv,ss,nw) ((ss)->hash == (h) && ((nw) == 1 || \
                memcmp(VS(bv), VS((ss)->states), (nw)*sizeof(unsigned)) == 0))
        int flags;
#               define  STARTER         01      /* the initial state set */
#               define  POSTSTATE       02      /* includes the goal state */
#               define  LOCKED          04      /* locked in cache */
#               define  NOPROGRESS      010     /* zero-progress state set */
        struct arcp ins;        /* chain of inarcs pointing here */
        chr *lastseen;          /* last entered on arrival here */
        struct sset **outs;     /* outarc vector indexed by color */
        struct arcp *inchain;   /* chain-pointer vector for outarcs */
};

struct dfa {
        int nssets;             /* size of cache */
        int nssused;            /* how many entries occupied yet */
        int nstates;            /* number of states */
        int ncolors;            /* length of outarc and inchain vectors */
        int wordsper;           /* length of state-set bitvectors */
        struct sset *ssets;     /* state-set cache */
        unsigned *statesarea;   /* bitvector storage */
        unsigned *work;         /* pointer to work area within statesarea */
        struct sset **outsarea; /* outarc-vector storage */
        struct arcp *incarea;   /* inchain storage */
        struct cnfa *cnfa;
        struct colormap *cm;
        chr *lastpost;          /* location of last cache-flushed success */
        chr *lastnopr;          /* location of last cache-flushed NOPROGRESS */
        struct sset *search;    /* replacement-search-pointer memory */
        int cptsmalloced;       /* were the areas individually malloced? */
        char *mallocarea;       /* self, or master malloced area, or NULL */
};

#define WORK    1               /* number of work bitvectors needed */

/* setup for non-malloc allocation for small cases */
#define FEWSTATES       20      /* must be less than UBITS */
#define FEWCOLORS       15
struct smalldfa {
        struct dfa dfa;
        struct sset ssets[FEWSTATES*2];
        unsigned statesarea[FEWSTATES*2 + WORK];
        struct sset *outsarea[FEWSTATES*2 * FEWCOLORS];
        struct arcp incarea[FEWSTATES*2 * FEWCOLORS];
};
#define DOMALLOC        ((struct smalldfa *)NULL)       /* force malloc */


/* internal variables, bundled for easy passing around */
struct vars {
        regex_t *re;
        struct guts *g;
        int eflags;             /* copies of arguments */
        size_t nmatch;
        regmatch_t *pmatch;
        rm_detail_t *details;
        chr *start;             /* start of string */
        chr *stop;              /* just past end of string */
        int err;                /* error code if any (0 none) */
        regoff_t *mem;          /* memory vector for backtracking */
        struct smalldfa dfa1;
        struct smalldfa dfa2;
};
#define VISERR(vv)      ((vv)->err != 0)        /* have we seen an error yet? */
#define ISERR() VISERR(v)
#define VERR(vv,e)      (((vv)->err) ? (vv)->err : ((vv)->err = (e)))
#define ERR(e)  VERR(v, e)              /* record an error */
#define NOERR() {if (ISERR()) return v->err;}   /* if error seen, return it */
#define OFF(p)  ((p) - v->start)
#define LOFF(p) ((long)OFF(p))


/*
 * forward declarations
 */
/* =====^!^===== begin forwards =====^!^===== */
/* automatically gathered by fwd; do not hand-edit */
/* === regexec.c === */
int exec _ANSI_ARGS_((regex_t *, CONST chr *, size_t, rm_detail_t *, size_t, regmatch_t [], int));
static int find _ANSI_ARGS_((struct vars *, struct cnfa *, struct colormap *));
static int cfind _ANSI_ARGS_((struct vars *, struct cnfa *, struct colormap *));
static int cfindloop _ANSI_ARGS_((struct vars *, struct cnfa *, struct colormap *, struct dfa *, struct dfa *, chr **));
static VOID zapsubs _ANSI_ARGS_((regmatch_t *, size_t));
static VOID zapmem _ANSI_ARGS_((struct vars *, struct subre *));
static VOID subset _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int dissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int condissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int altdissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int cdissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int ccondissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int crevdissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int cbrdissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
static int caltdissect _ANSI_ARGS_((struct vars *, struct subre *, chr *, chr *));
/* === rege_dfa.c === */
static chr *longest _ANSI_ARGS_((struct vars *, struct dfa *, chr *, chr *, int *));
static chr *shortest _ANSI_ARGS_((struct vars *, struct dfa *, chr *, chr *, chr *, chr **, int *));
static chr *lastcold _ANSI_ARGS_((struct vars *, struct dfa *));
static struct dfa *newdfa _ANSI_ARGS_((struct vars *, struct cnfa *, struct colormap *, struct smalldfa *));
static VOID freedfa _ANSI_ARGS_((struct dfa *));
static unsigned hash _ANSI_ARGS_((unsigned *, int));
static struct sset *initialize _ANSI_ARGS_((struct vars *, struct dfa *, chr *));
static struct sset *miss _ANSI_ARGS_((struct vars *, struct dfa *, struct sset *, pcolor, chr *, chr *));
static int lacon _ANSI_ARGS_((struct vars *, struct cnfa *, chr *, pcolor));
static struct sset *getvacant _ANSI_ARGS_((struct vars *, struct dfa *, chr *, chr *));
static struct sset *pickss _ANSI_ARGS_((struct vars *, struct dfa *, chr *, chr *));
/* automatically gathered by fwd; do not hand-edit */
/* =====^!^===== end forwards =====^!^===== */


/*
 - exec - match regular expression
 ^ int exec(regex_t *, CONST chr *, size_t, rm_detail_t *,
 ^                                      size_t, regmatch_t [], int);
 */
int
exec(re, string, len, details, nmatch, pmatch, flags)
regex_t *re;
CONST chr *string;
size_t len;
rm_detail_t *details;
size_t nmatch;
regmatch_t pmatch[];
int flags;
{
        struct vars var;
        register struct vars *v = &var;
        int st;
        size_t n;
        int backref;
#       define  LOCALMAT        20
        regmatch_t mat[LOCALMAT];
#       define  LOCALMEM        40
        regoff_t mem[LOCALMEM];

        /* sanity checks */
        if (re == NULL || string == NULL || re->re_magic != REMAGIC)
                return REG_INVARG;
        if (re->re_csize != sizeof(chr))
                return REG_MIXED;

        /* setup */
        v->re = re;
        v->g = (struct guts *)re->re_guts;
        if ((v->g->cflags&REG_EXPECT) && details == NULL)
                return REG_INVARG;
        if (v->g->info&REG_UIMPOSSIBLE)
                return REG_NOMATCH;
        backref = (v->g->info&REG_UBACKREF) ? 1 : 0;
        v->eflags = flags;
        if (v->g->cflags&REG_NOSUB)
                nmatch = 0;             /* override client */
        v->nmatch = nmatch;
        if (backref) {
                /* need work area */
                if (v->g->nsub + 1 <= LOCALMAT)
                        v->pmatch = mat;
                else
                        v->pmatch = (regmatch_t *)MALLOC((v->g->nsub + 1) *
                                                        sizeof(regmatch_t));
                if (v->pmatch == NULL)
                        return REG_ESPACE;
                v->nmatch = v->g->nsub + 1;
        } else
                v->pmatch = pmatch;
        v->details = details;
        v->start = (chr *)string;
        v->stop = (chr *)string + len;
        v->err = 0;
        if (backref) {
                /* need retry memory */
                assert(v->g->ntree >= 0);
                n = (size_t)v->g->ntree;
                if (n <= LOCALMEM)
                        v->mem = mem;
                else
                        v->mem = (regoff_t *)MALLOC(n*sizeof(regoff_t));
                if (v->mem == NULL) {
                        if (v->pmatch != pmatch && v->pmatch != mat)
                                FREE(v->pmatch);
                        return REG_ESPACE;
                }
        } else
                v->mem = NULL;

        /* do it */
        assert(v->g->tree != NULL);
        if (backref)
                st = cfind(v, &v->g->tree->cnfa, &v->g->cmap);
        else
                st = find(v, &v->g->tree->cnfa, &v->g->cmap);

        /* copy (portion of) match vector over if necessary */
        if (st == REG_OKAY && v->pmatch != pmatch && nmatch > 0) {
                zapsubs(pmatch, nmatch);
                n = (nmatch < v->nmatch) ? nmatch : v->nmatch;
                memcpy(VS(pmatch), VS(v->pmatch), n*sizeof(regmatch_t));
        }

        /* clean up */
        if (v->pmatch != pmatch && v->pmatch != mat)
                FREE(v->pmatch);
        if (v->mem != NULL && v->mem != mem)
                FREE(v->mem);
        return st;
}

/*
 - find - find a match for the main NFA (no-complications case)
 ^ static int find(struct vars *, struct cnfa *, struct colormap *);
 */
static int
find(v, cnfa, cm)
struct vars *v;
struct cnfa *cnfa;
struct colormap *cm;
{
        struct dfa *s;
        struct dfa *d;
        chr *begin;
        chr *end = NULL;
        chr *cold;
        chr *open;              /* open and close of range of possible starts */
        chr *close;
        int hitend;
        int shorter = (v->g->tree->flags&SHORTER) ? 1 : 0;

        /* first, a shot with the search RE */
        s = newdfa(v, &v->g->search, cm, &v->dfa1);
        assert(!(ISERR() && s != NULL));
        NOERR();
        MDEBUG(("\nsearch at %ld\n", LOFF(v->start)));
        cold = NULL;
        close = shortest(v, s, v->start, v->start, v->stop, &cold, (int *)NULL);
        freedfa(s);
        NOERR();
        if (v->g->cflags&REG_EXPECT) {
                assert(v->details != NULL);
                if (cold != NULL)
                        v->details->rm_extend.rm_so = OFF(cold);
                else
                        v->details->rm_extend.rm_so = OFF(v->stop);
                v->details->rm_extend.rm_eo = OFF(v->stop);     /* unknown */
        }
        if (close == NULL)              /* not found */
                return REG_NOMATCH;
        if (v->nmatch == 0)             /* found, don't need exact location */
                return REG_OKAY;

        /* find starting point and match */
        assert(cold != NULL);
        open = cold;
        cold = NULL;
        MDEBUG(("between %ld and %ld\n", LOFF(open), LOFF(close)));
        d = newdfa(v, cnfa, cm, &v->dfa1);
        assert(!(ISERR() && d != NULL));
        NOERR();
        for (begin = open; begin <= close; begin++) {
                MDEBUG(("\nfind trying at %ld\n", LOFF(begin)));
                if (shorter)
                        end = shortest(v, d, begin, begin, v->stop,
                                                        (chr **)NULL, &hitend);
                else
                        end = longest(v, d, begin, v->stop, &hitend);
                NOERR();
                if (hitend && cold == NULL)
                        cold = begin;
                if (end != NULL)
                        break;          /* NOTE BREAK OUT */
        }
        assert(end != NULL);            /* search RE succeeded so loop should */
        freedfa(d);

        /* and pin down details */
        assert(v->nmatch > 0);
        v->pmatch[0].rm_so = OFF(begin);
        v->pmatch[0].rm_eo = OFF(end);
        if (v->g->cflags&REG_EXPECT) {
                if (cold != NULL)
                        v->details->rm_extend.rm_so = OFF(cold);
                else
                        v->details->rm_extend.rm_so = OFF(v->stop);
                v->details->rm_extend.rm_eo = OFF(v->stop);     /* unknown */
        }
        if (v->nmatch == 1)             /* no need for submatches */
                return REG_OKAY;

        /* submatches */
        zapsubs(v->pmatch, v->nmatch);
        return dissect(v, v->g->tree, begin, end);
}

/*
 - cfind - find a match for the main NFA (with complications)
 ^ static int cfind(struct vars *, struct cnfa *, struct colormap *);
 */
static int
cfind(v, cnfa, cm)
struct vars *v;
struct cnfa *cnfa;
struct colormap *cm;
{
        struct dfa *s;
        struct dfa *d;
        chr *cold;
        int ret;

        s = newdfa(v, &v->g->search, cm, &v->dfa1);
        NOERR();
        d = newdfa(v, cnfa, cm, &v->dfa2);
        if (ISERR()) {
                assert(d == NULL);
                freedfa(s);
                return v->err;
        }

        ret = cfindloop(v, cnfa, cm, d, s, &cold);

        freedfa(d);
        freedfa(s);
        NOERR();
        if (v->g->cflags&REG_EXPECT) {
                assert(v->details != NULL);
                if (cold != NULL)
                        v->details->rm_extend.rm_so = OFF(cold);
                else
                        v->details->rm_extend.rm_so = OFF(v->stop);
                v->details->rm_extend.rm_eo = OFF(v->stop);     /* unknown */
        }
        return ret;
}

/*
 - cfindloop - the heart of cfind
 ^ static int cfindloop(struct vars *, struct cnfa *, struct colormap *,
 ^      struct dfa *, struct dfa *, chr **);
 */
static int
cfindloop(v, cnfa, cm, d, s, coldp)
struct vars *v;
struct cnfa *cnfa;
struct colormap *cm;
struct dfa *d;
struct dfa *s;
chr **coldp;                    /* where to put coldstart pointer */
{
        chr *begin;
        chr *end;
        chr *cold;
        chr *open;              /* open and close of range of possible starts */
        chr *close;
        chr *estart;
        chr *estop;
        int er;
        int shorter = v->g->tree->flags&SHORTER;
        int hitend;

        assert(d != NULL && s != NULL);
        cold = NULL;
        close = v->start;
        do {
                MDEBUG(("\ncsearch at %ld\n", LOFF(close)));
                close = shortest(v, s, close, close, v->stop, &cold, (int *)NULL);
                if (close == NULL)
                        break;                          /* NOTE BREAK */
                assert(cold != NULL);
                open = cold;
                cold = NULL;
                MDEBUG(("cbetween %ld and %ld\n", LOFF(open), LOFF(close)));
                for (begin = open; begin <= close; begin++) {
                        MDEBUG(("\ncfind trying at %ld\n", LOFF(begin)));
                        estart = begin;
                        estop = v->stop;
                        for (;;) {
                                if (shorter)
                                        end = shortest(v, d, begin, estart,
                                                estop, (chr **)NULL, &hitend);
                                else
                                        end = longest(v, d, begin, estop,
                                                                &hitend);
                                if (hitend && cold == NULL)
                                        cold = begin;
                                if (end == NULL)
                                        break;          /* NOTE BREAK OUT */
                                MDEBUG(("tentative end %ld\n", LOFF(end)));
                                zapsubs(v->pmatch, v->nmatch);
                                zapmem(v, v->g->tree);
                                er = cdissect(v, v->g->tree, begin, end);
                                if (er == REG_OKAY) {
                                        if (v->nmatch > 0) {
                                                v->pmatch[0].rm_so = OFF(begin);
                                                v->pmatch[0].rm_eo = OFF(end);
                                        }
                                        *coldp = cold;
                                        return REG_OKAY;
                                }
                                if (er != REG_NOMATCH) {
                                        ERR(er);
                                        return er;
                                }
                                if ((shorter) ? end == estop : end == begin) {
                                        /* no point in trying again */
                                        *coldp = cold;
                                        return REG_NOMATCH;
                                }
                                /* go around and try again */
                                if (shorter)
                                        estart = end + 1;
                                else
                                        estop = end - 1;
                        }
                }
        } while (close < v->stop);

        *coldp = cold;
        return REG_NOMATCH;
}

/*
 - zapsubs - initialize the subexpression matches to "no match"
 ^ static VOID zapsubs(regmatch_t *, size_t);
 */
static VOID
zapsubs(p, n)
regmatch_t *p;
size_t n;
{
        size_t i;

        for (i = n-1; i > 0; i--) {
                p[i].rm_so = -1;
                p[i].rm_eo = -1;
        }
}

/*
 - zapmem - initialize the retry memory of a subtree to zeros
 ^ static VOID zapmem(struct vars *, struct subre *);
 */
static VOID
zapmem(v, t)
struct vars *v;
struct subre *t;
{
        if (t == NULL)
                return;

        assert(v->mem != NULL);
        v->mem[t->retry] = 0;
        if (t->op == '(') {
                assert(t->subno > 0);
                v->pmatch[t->subno].rm_so = -1;
                v->pmatch[t->subno].rm_eo = -1;
        }

        if (t->left != NULL)
                zapmem(v, t->left);
        if (t->right != NULL)
                zapmem(v, t->right);
}

/*
 - subset - set any subexpression relevant to a successful subre
 ^ static VOID subset(struct vars *, struct subre *, chr *, chr *);
 */
static VOID
subset(v, sub, begin, end)
struct vars *v;
struct subre *sub;
chr *begin;
chr *end;
{
        int n = sub->subno;

        assert(n > 0);
        if ((size_t)n >= v->nmatch)
                return;

        MDEBUG(("setting %d\n", n));
        v->pmatch[n].rm_so = OFF(begin);
        v->pmatch[n].rm_eo = OFF(end);
}

/*
 - dissect - determine subexpression matches (uncomplicated case)
 ^ static int dissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
dissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        assert(t != NULL);
        MDEBUG(("dissect %ld-%ld\n", LOFF(begin), LOFF(end)));

        switch (t->op) {
        case '=':               /* terminal node */
                assert(t->left == NULL && t->right == NULL);
                return REG_OKAY;        /* no action, parent did the work */
                break;
        case '|':               /* alternation */
                assert(t->left != NULL);
                return altdissect(v, t, begin, end);
                break;
        case 'b':               /* back ref -- shouldn't be calling us! */
                return REG_ASSERT;
                break;
        case '.':               /* concatenation */
                assert(t->left != NULL && t->right != NULL);
                return condissect(v, t, begin, end);
                break;
        case '(':               /* capturing */
                assert(t->left != NULL && t->right == NULL);
                assert(t->subno > 0);
                subset(v, t, begin, end);
                return dissect(v, t->left, begin, end);
                break;
        default:
                return REG_ASSERT;
                break;
        }
}

/*
 - condissect - determine concatenation subexpression matches (uncomplicated)
 ^ static int condissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
condissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        struct dfa *d;
        struct dfa *d2;
        chr *mid;
        int i;
        int shorter = (t->left->flags&SHORTER) ? 1 : 0;
        chr *stop = (shorter) ? end : begin;

        assert(t->op == '.');
        assert(t->left != NULL && t->left->cnfa.nstates > 0);
        assert(t->right != NULL && t->right->cnfa.nstates > 0);

        d = newdfa(v, &t->left->cnfa, &v->g->cmap, &v->dfa1);
        NOERR();
        d2 = newdfa(v, &t->right->cnfa, &v->g->cmap, &v->dfa2);
        if (ISERR()) {
                assert(d2 == NULL);
                freedfa(d);
                return v->err;
        }

        /* pick a tentative midpoint */
        if (shorter)
                mid = shortest(v, d, begin, begin, end, (chr **)NULL,
                                                                (int *)NULL);
        else
                mid = longest(v, d, begin, end, (int *)NULL);
        if (mid == NULL) {
                freedfa(d);
                freedfa(d2);
                return REG_ASSERT;
        }
        MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));

        /* iterate until satisfaction or failure */
        while (longest(v, d2, mid, end, (int *)NULL) != end) {
                /* that midpoint didn't work, find a new one */
                if (mid == stop) {
                        /* all possibilities exhausted! */
                        MDEBUG(("no midpoint!\n"));
                        freedfa(d);
                        freedfa(d2);
                        return REG_ASSERT;
                }
                if (shorter)
                        mid = shortest(v, d, begin, mid+1, end, (chr **)NULL,
                                                                (int *)NULL);
                else
                        mid = longest(v, d, begin, mid-1, (int *)NULL);
                if (mid == NULL) {
                        /* failed to find a new one! */
                        MDEBUG(("failed midpoint!\n"));
                        freedfa(d);
                        freedfa(d2);
                        return REG_ASSERT;
                }
                MDEBUG(("new midpoint %ld\n", LOFF(mid)));
        }

        /* satisfaction */
        MDEBUG(("successful\n"));
        freedfa(d);
        freedfa(d2);
        i = dissect(v, t->left, begin, mid);
        if (i != REG_OKAY)
                return i;
        return dissect(v, t->right, mid, end);
}

/*
 - altdissect - determine alternative subexpression matches (uncomplicated)
 ^ static int altdissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
altdissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        struct dfa *d;
        int i;

        assert(t != NULL);
        assert(t->op == '|');

        for (i = 0; t != NULL; t = t->right, i++) {
                MDEBUG(("trying %dth\n", i));
                assert(t->left != NULL && t->left->cnfa.nstates > 0);
                d = newdfa(v, &t->left->cnfa, &v->g->cmap, &v->dfa1);
                if (ISERR())
                        return v->err;
                if (longest(v, d, begin, end, (int *)NULL) == end) {
                        MDEBUG(("success\n"));
                        freedfa(d);
                        return dissect(v, t->left, begin, end);
                }
                freedfa(d);
        }
        return REG_ASSERT;      /* none of them matched?!? */
}

/*
 - cdissect - determine subexpression matches (with complications)
 * The retry memory stores the offset of the trial midpoint from begin, 
 * plus 1 so that 0 uniquely means "clean slate".
 ^ static int cdissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
cdissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        int er;

        assert(t != NULL);
        MDEBUG(("cdissect %ld-%ld %c\n", LOFF(begin), LOFF(end), t->op));

        switch (t->op) {
        case '=':               /* terminal node */
                assert(t->left == NULL && t->right == NULL);
                return REG_OKAY;        /* no action, parent did the work */
                break;
        case '|':               /* alternation */
                assert(t->left != NULL);
                return caltdissect(v, t, begin, end);
                break;
        case 'b':               /* back ref -- shouldn't be calling us! */
                assert(t->left == NULL && t->right == NULL);
                return cbrdissect(v, t, begin, end);
                break;
        case '.':               /* concatenation */
                assert(t->left != NULL && t->right != NULL);
                return ccondissect(v, t, begin, end);
                break;
        case '(':               /* capturing */
                assert(t->left != NULL && t->right == NULL);
                assert(t->subno > 0);
                er = cdissect(v, t->left, begin, end);
                if (er == REG_OKAY)
                        subset(v, t, begin, end);
                return er;
                break;
        default:
                return REG_ASSERT;
                break;
        }
}

/*
 - ccondissect - concatenation subexpression matches (with complications)
 * The retry memory stores the offset of the trial midpoint from begin, 
 * plus 1 so that 0 uniquely means "clean slate".
 ^ static int ccondissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
ccondissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        struct dfa *d;
        struct dfa *d2;
        chr *mid;
        int er;

        assert(t->op == '.');
        assert(t->left != NULL && t->left->cnfa.nstates > 0);
        assert(t->right != NULL && t->right->cnfa.nstates > 0);

        if (t->left->flags&SHORTER)             /* reverse scan */
                return crevdissect(v, t, begin, end);

        d = newdfa(v, &t->left->cnfa, &v->g->cmap, DOMALLOC);
        if (ISERR())
                return v->err;
        d2 = newdfa(v, &t->right->cnfa, &v->g->cmap, DOMALLOC);
        if (ISERR()) {
                freedfa(d);
                return v->err;
        }
        MDEBUG(("cconcat %d\n", t->retry));

        /* pick a tentative midpoint */
        if (v->mem[t->retry] == 0) {
                mid = longest(v, d, begin, end, (int *)NULL);
                if (mid == NULL) {
                        freedfa(d);
                        freedfa(d2);
                        return REG_NOMATCH;
                }
                MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));
                v->mem[t->retry] = (mid - begin) + 1;
        } else {
                mid = begin + (v->mem[t->retry] - 1);
                MDEBUG(("working midpoint %ld\n", LOFF(mid)));
        }

        /* iterate until satisfaction or failure */
        for (;;) {
                /* try this midpoint on for size */
                er = cdissect(v, t->left, begin, mid);
                if (er == REG_OKAY &&
                                longest(v, d2, mid, end, (int *)NULL) == end &&
                                (er = cdissect(v, t->right, mid, end)) == 
                                                                REG_OKAY)
                        break;                  /* NOTE BREAK OUT */
                if (er != REG_OKAY && er != REG_NOMATCH) {
                        freedfa(d);
                        freedfa(d2);
                        return er;
                }

                /* that midpoint didn't work, find a new one */
                if (mid == begin) {
                        /* all possibilities exhausted */
                        MDEBUG(("%d no midpoint\n", t->retry));
                        freedfa(d);
                        freedfa(d2);
                        return REG_NOMATCH;
                }
                mid = longest(v, d, begin, mid-1, (int *)NULL);
                if (mid == NULL) {
                        /* failed to find a new one */
                        MDEBUG(("%d failed midpoint\n", t->retry));
                        freedfa(d);
                        freedfa(d2);
                        return REG_NOMATCH;
                }
                MDEBUG(("%d: new midpoint %ld\n", t->retry, LOFF(mid)));
                v->mem[t->retry] = (mid - begin) + 1;
                zapmem(v, t->left);
                zapmem(v, t->right);
        }

        /* satisfaction */
        MDEBUG(("successful\n"));
        freedfa(d);
        freedfa(d2);
        return REG_OKAY;
}

/*
 - crevdissect - determine backref shortest-first subexpression matches
 * The retry memory stores the offset of the trial midpoint from begin, 
 * plus 1 so that 0 uniquely means "clean slate".
 ^ static int crevdissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
crevdissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        struct dfa *d;
        struct dfa *d2;
        chr *mid;
        int er;

        assert(t->op == '.');
        assert(t->left != NULL && t->left->cnfa.nstates > 0);
        assert(t->right != NULL && t->right->cnfa.nstates > 0);
        assert(t->left->flags&SHORTER);

        /* concatenation -- need to split the substring between parts */
        d = newdfa(v, &t->left->cnfa, &v->g->cmap, DOMALLOC);
        if (ISERR())
                return v->err;
        d2 = newdfa(v, &t->right->cnfa, &v->g->cmap, DOMALLOC);
        if (ISERR()) {
                freedfa(d);
                return v->err;
        }
        MDEBUG(("crev %d\n", t->retry));

        /* pick a tentative midpoint */
        if (v->mem[t->retry] == 0) {
                mid = shortest(v, d, begin, begin, end, (chr **)NULL, (int *)NULL);
                if (mid == NULL) {
                        freedfa(d);
                        freedfa(d2);
                        return REG_NOMATCH;
                }
                MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));
                v->mem[t->retry] = (mid - begin) + 1;
        } else {
                mid = begin + (v->mem[t->retry] - 1);
                MDEBUG(("working midpoint %ld\n", LOFF(mid)));
        }

        /* iterate until satisfaction or failure */
        for (;;) {
                /* try this midpoint on for size */
                er = cdissect(v, t->left, begin, mid);
                if (er == REG_OKAY &&
                                longest(v, d2, mid, end, (int *)NULL) == end &&
                                (er = cdissect(v, t->right, mid, end)) == 
                                                                REG_OKAY)
                        break;                  /* NOTE BREAK OUT */
                if (er != REG_OKAY && er != REG_NOMATCH) {
                        freedfa(d);
                        freedfa(d2);
                        return er;
                }

                /* that midpoint didn't work, find a new one */
                if (mid == end) {
                        /* all possibilities exhausted */
                        MDEBUG(("%d no midpoint\n", t->retry));
                        freedfa(d);
                        freedfa(d2);
                        return REG_NOMATCH;
                }
                mid = shortest(v, d, begin, mid+1, end, (chr **)NULL, (int *)NULL);
                if (mid == NULL) {
                        /* failed to find a new one */
                        MDEBUG(("%d failed midpoint\n", t->retry));
                        freedfa(d);
                        freedfa(d2);
                        return REG_NOMATCH;
                }
                MDEBUG(("%d: new midpoint %ld\n", t->retry, LOFF(mid)));
                v->mem[t->retry] = (mid - begin) + 1;
                zapmem(v, t->left);
                zapmem(v, t->right);
        }

        /* satisfaction */
        MDEBUG(("successful\n"));
        freedfa(d);
        freedfa(d2);
        return REG_OKAY;
}

/*
 - cbrdissect - determine backref subexpression matches
 ^ static int cbrdissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
cbrdissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        int i;
        int n = t->subno;
        size_t len;
        chr *paren;
        chr *p;
        chr *stop;
        int min = t->min;
        int max = t->max;

        assert(t != NULL);
        assert(t->op == 'b');
        assert(n >= 0);
        assert((size_t)n < v->nmatch);

        MDEBUG(("cbackref n%d %d{%d-%d}\n", t->retry, n, min, max));

        if (v->pmatch[n].rm_so == -1)
                return REG_NOMATCH;
        paren = v->start + v->pmatch[n].rm_so;
        len = v->pmatch[n].rm_eo - v->pmatch[n].rm_so;

        /* no room to maneuver -- retries are pointless */
        if (v->mem[t->retry])
                return REG_NOMATCH;
        v->mem[t->retry] = 1;

        /* special-case zero-length string */
        if (len == 0) {
                if (begin == end)
                        return REG_OKAY;
                return REG_NOMATCH;
        }

        /* and too-short string */
        assert(end >= begin);
        if ((size_t)(end - begin) < len)
                return REG_NOMATCH;
        stop = end - len;

        /* count occurrences */
        i = 0;
        for (p = begin; p <= stop && (i < max || max == INFINITY); p += len) {
                if ((*v->g->compare)(paren, p, len) != 0)
                                break;
                i++;
        }
        MDEBUG(("cbackref found %d\n", i));

        /* and sort it out */
        if (p != end)                   /* didn't consume all of it */
                return REG_NOMATCH;
        if (min <= i && (i <= max || max == INFINITY))
                return REG_OKAY;
        return REG_NOMATCH;             /* out of range */
}

/*
 - caltdissect - determine alternative subexpression matches (w. complications)
 ^ static int caltdissect(struct vars *, struct subre *, chr *, chr *);
 */
static int                      /* regexec return code */
caltdissect(v, t, begin, end)
struct vars *v;
struct subre *t;
chr *begin;                     /* beginning of relevant substring */
chr *end;                       /* end of same */
{
        struct dfa *d;
        int er;
#       define  UNTRIED 0       /* not yet tried at all */
#       define  TRYING  1       /* top matched, trying submatches */
#       define  TRIED   2       /* top didn't match or submatches exhausted */

        if (t == NULL)
                return REG_NOMATCH;
        assert(t->op == '|');
        if (v->mem[t->retry] == TRIED)
                return caltdissect(v, t->right, begin, end);

        MDEBUG(("calt n%d\n", t->retry));
        assert(t->left != NULL);

        if (v->mem[t->retry] == UNTRIED) {
                d = newdfa(v, &t->left->cnfa, &v->g->cmap, DOMALLOC);
                if (ISERR())
                        return v->err;
                if (longest(v, d, begin, end, (int *)NULL) != end) {
                        freedfa(d);
                        v->mem[t->retry] = TRIED;
                        return caltdissect(v, t->right, begin, end);
                }
                freedfa(d);
                MDEBUG(("calt matched\n"));
                v->mem[t->retry] = TRYING;
        }

        er = cdissect(v, t->left, begin, end);
        if (er != REG_NOMATCH)
                return er;

        v->mem[t->retry] = TRIED;
        return caltdissect(v, t->right, begin, end);
}


#include "rege_dfa.c"

/* End of regexec.c */