/* $OpenBSD: tsort.c,v 1.38 2024/01/18 15:34:29 espie Exp $ */
/* ex:ts=8 sw=4:
 *
 * Copyright (c) 1999-2004 Marc Espie <espie@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <assert.h>
#include <ctype.h>
#include <err.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ohash.h>

/* The complexity of topological sorting is O(e), where e is the
 * size of input.  While reading input, vertices have to be identified,
 * thus add the complexity of e keys retrieval among v keys using
 * an appropriate data structure.  This program uses open double hashing
 * for that purpose.  See Knuth for the expected complexity of double
 * hashing (Brent variation should probably be used if v << e, as a user
 * option).
 *
 * The algorithm used for longest cycle reporting is accurate, but somewhat
 * expensive.  It may need to build all free paths of the graph (a free
 * path is a path that never goes twice through the same node), whose
 * number can be as high as O(2^e).  Usually, the number of free paths is
 * much smaller though.  This program's author does not believe that a
 * significantly better worst-case complexity algorithm exists.
 *
 * In case of a hints file, the set of minimal nodes is maintained as a
 * heap.  The resulting complexity is O(e+v log v) for the worst case.
 * The average should actually be near O(e).
 *
 * If the hints file is incomplete, there is some extra complexity incurred
 * by make_transparent, which does propagate order values to unmarked
 * nodes. In the worst case, make_transparent is  O(e u),
 * where u is the number of originally unmarked nodes.
 * In practice, it is much faster.
 *
 * The simple topological sort algorithm detects cycles.  This program
 * goes further, breaking cycles through the use of simple heuristics.
 * Each cycle break checks the whole set of nodes, hence if c cycles break
 * are needed, this is an extra cost of O(c v).
 *
 * Possible heuristics are as follows:
 * - break cycle at node with lowest number of predecessors (default case),
 * - break longest cycle at node with lowest number of predecessors,
 * - break cycle at next node from the hints file.
 *
 * Except for the hints file case, which sets an explicit constraint on
 * which cycle to break, those heuristics locally result in the smallest
 * number of broken edges.
 *
 * Those are admittedly greedy strategies, as is the selection of the next
 * node from the hints file amongst equivalent candidates that is used for
 * `stable' topological sorting.
 */

#ifdef __GNUC__
#define UNUSED  __attribute__((unused))
#else
#define UNUSED
#endif

struct node;

/* The set of arcs from a given node is stored as a linked list.  */
struct link {
        struct link *next;
        struct node *node;
};

#define NO_ORDER        UINT_MAX

struct node {
        unsigned int refs;      /* Number of arcs left, coming into this node.
                                 * Note that nodes with a null count can't
                                 * be part of cycles.  */
        unsigned int order;     /* Order of nodes according to a hint file.  */

        struct link  *arcs;     /* List of forward arcs.  */

        /* Cycle detection algorithms build a free path of nodes.  */
        struct node  *from;     /* Previous node in the current path.  */
        struct link  *traverse; /* Next link to traverse when backtracking.  */
        unsigned int mark;      /* Mark processed nodes in cycle discovery.  */

        char         k[1];      /* Name of this node.  */
};

#define HASH_START 9

struct array {
        unsigned int entries;
        struct node  **t;
};

static void nodes_init(struct ohash *);
static struct node *node_lookup(struct ohash *, const char *, const char *);
static __dead void usage(void);
static struct node *new_node(const char *, const char *);

static unsigned int read_pairs(FILE *, struct ohash *, int,
    const char *, unsigned int, int);
static void split_nodes(struct ohash *, struct array *, struct array *);
static void make_transparent(struct ohash *);
static void insert_arc(struct node *, struct node *);

#ifdef DEBUG
static void dump_node(struct node *);
static void dump_array(struct array *);
static void dump_hash(struct ohash *);
#endif
static unsigned int read_hints(FILE *, struct ohash *, int,
    const char *, unsigned int);
static struct node *find_smallest_node(struct array *);
static struct node *find_good_cycle_break(struct array *);
static void print_cycle(struct array *);
static struct node *find_cycle_from(struct node *, struct array *);
static struct node *find_predecessor(struct array *, struct node *);
static unsigned int traverse_node(struct node *, unsigned int, struct array *);
static struct node *find_longest_cycle(struct array *, struct array *);
static struct node *find_normal_cycle(struct array *, struct array *);

static void heap_down(struct array *, unsigned int);
static void heapify(struct array *, int);
static struct node *dequeue(struct array *);
static void enqueue(struct array *, struct node *);



static void *hash_calloc(size_t, size_t, void *);
static void hash_free(void *, void *);
static void* entry_alloc(size_t, void *);
static void *ereallocarray(void *, size_t, size_t);
static void *emem(void *);
#define DEBUG_TRAVERSE 0
static struct ohash_info node_info = {
        offsetof(struct node, k), NULL, hash_calloc, hash_free, entry_alloc };
static void parse_args(int, char *[], struct ohash *);
static int tsort(struct ohash *);

static int              quiet_flag, long_flag,
                        warn_flag, hints_flag, verbose_flag;


int main(int, char *[]);

/***
 *** Memory handling.
 ***/

static void *
emem(void *p)
{
        if (p)
                return p;
        else
                errx(1, "Memory exhausted");
}

static void *
hash_calloc(size_t n, size_t s, void *u UNUSED)
{
        return emem(calloc(n, s));
}

static void
hash_free(void *p, void *u UNUSED)
{
        free(p);
}

static void *
entry_alloc(size_t s, void *u UNUSED)
{
        return ereallocarray(NULL, 1, s);
}

static void *
ereallocarray(void *p, size_t n, size_t s)
{
        return emem(reallocarray(p, n, s));
}


/***
 *** Hash table.
 ***/

/* Inserting and finding nodes in the hash structure.
 * We handle interval strings for efficiency wrt fgetln.  */
static struct node *
new_node(const char *start, const char *end)
{
        struct node     *n;

        n = ohash_create_entry(&node_info, start, &end);
        n->from = NULL;
        n->arcs = NULL;
        n->refs = 0;
        n->mark = 0;
        n->order = NO_ORDER;
        n->traverse = NULL;
        return n;
}


static void
nodes_init(struct ohash *h)
{
        ohash_init(h, HASH_START, &node_info);
}

static struct node *
node_lookup(struct ohash *h, const char *start, const char *end)
{
        unsigned int    i;
        struct node *   n;

        i = ohash_qlookupi(h, start, &end);

        n = ohash_find(h, i);
        if (n == NULL)
                n = ohash_insert(h, i, new_node(start, end));
        return n;
}

#ifdef DEBUG
static void
dump_node(struct node *n)
{
        struct link     *l;

        if (n->refs == 0)
                return;
        printf("%s (%u/%u): ", n->k, n->order, n->refs);
        for (l = n->arcs; l != NULL; l = l->next)
                if (n->refs != 0)
                printf("%s(%u/%u) ", l->node->k, l->node->order, l->node->refs);
        putchar('\n');
}

static void
dump_array(struct array *a)
{
        unsigned int    i;

        for (i = 0; i < a->entries; i++)
                dump_node(a->t[i]);
}

static void
dump_hash(struct ohash *h)
{
        unsigned int    i;
        struct node     *n;

        for (n = ohash_first(h, &i); n != NULL; n = ohash_next(h, &i))
                dump_node(n);
}
#endif

/***
 *** Reading data.
 ***/

static void
insert_arc(struct node *a, struct node *b)
{
        struct link     *l;

        /* Check that this arc is not already present.  */
        for (l = a->arcs; l != NULL; l = l->next) {
                if (l->node == b)
                        return;
        }
        b->refs++;
        l = ereallocarray(NULL, 1, sizeof(struct link));
        l->node = b;
        l->next = a->arcs;
        a->arcs = l;
}

static unsigned int
read_pairs(FILE *f, struct ohash *h, int reverse, const char *name,
    unsigned int order, int hint)
{
        int             toggle;
        struct node     *a;
        size_t          size;
        char            *str;

        toggle = 1;
        a = NULL;

        while ((str = fgetln(f, &size)) != NULL) {
                char *sentinel;

                sentinel = str + size;
                for (;;) {
                        char *e;

                        while (str < sentinel &&
                            isspace((unsigned char)*str))
                                str++;
                        if (str == sentinel)
                                break;
                        for (e = str;
                            e < sentinel && !isspace((unsigned char)*e); e++)
                                continue;
                        if (toggle) {
                                a = node_lookup(h, str, e);
                                if (a->order == NO_ORDER && hint)
                                        a->order = order++;
                        } else {
                                struct node *b;

                                b = node_lookup(h, str, e);
                                assert(a != NULL);
                                if (b != a) {
                                        if (reverse)
                                                insert_arc(b, a);
                                        else
                                                insert_arc(a, b);
                                }
                        }
                        toggle = !toggle;
                        str = e;
                }
        }
        if (toggle == 0)
                errx(1, "odd number of node names in %s", name);
        if (!feof(f))
                err(1, "error reading %s", name);
        return order;
}

static unsigned int
read_hints(FILE *f, struct ohash *h, int quiet, const char *name,
    unsigned int order)
{
        char            *str;
        size_t          size;

        while ((str = fgetln(f, &size)) != NULL) {
                char *sentinel;

                sentinel = str + size;
                for (;;) {
                        char *e;
                        struct node *a;

                        while (str < sentinel && isspace((unsigned char)*str))
                                str++;
                        if (str == sentinel)
                                break;
                        for (e = str;
                            e < sentinel && !isspace((unsigned char)*e); e++)
                                continue;
                        a = node_lookup(h, str, e);
                        if (a->order != NO_ORDER) {
                                if (!quiet)
                                    warnx(
                                        "duplicate node %s in hints file %s",
                                        a->k, name);
                        } else
                                a->order = order++;
                        str = e;
                }
        }
        if (!feof(f))
                err(1, "error reading %s", name);
        return order;
}


/***
 *** Standard heap handling routines.
 ***/

static void
heap_down(struct array *h, unsigned int i)
{
        unsigned int    j;
        struct node     *swap;

        for (; (j=2*i+1) < h->entries; i = j) {
                if (j+1 < h->entries && h->t[j+1]->order < h->t[j]->order)
                        j++;
                if (h->t[i]->order <= h->t[j]->order)
                        break;
                swap = h->t[i];
                h->t[i] = h->t[j];
                h->t[j] = swap;
        }
}

static void
heapify(struct array *h, int verbose)
{
        unsigned int    i;

        for (i = h->entries; i != 0;) {
                if (h->t[--i]->order == NO_ORDER && verbose)
                        warnx("node %s absent from hints file", h->t[i]->k);
                heap_down(h, i);
        }
}

#define DEQUEUE(h) ( hints_flag ? dequeue(h) : (h)->t[--(h)->entries] )

static struct node *
dequeue(struct array *h)
{
        struct node     *n;

        if (h->entries == 0)
                n = NULL;
        else {
                n = h->t[0];
                if (--h->entries != 0) {
                    h->t[0] = h->t[h->entries];
                    heap_down(h, 0);
                }
        }
        return n;
}

#define ENQUEUE(h, n) do {                      \
        if (hints_flag)                         \
                enqueue((h), (n));              \
        else                                    \
                (h)->t[(h)->entries++] = (n);   \
        } while(0)

static void
enqueue(struct array *h, struct node *n)
{
        unsigned int    i, j;
        struct node     *swap;

        h->t[h->entries++] = n;
        for (i = h->entries-1; i > 0; i = j) {
                j = (i-1)/2;
                if (h->t[j]->order < h->t[i]->order)
                        break;
                swap = h->t[j];
                h->t[j] = h->t[i];
                h->t[i] = swap;
        }
}

/* Nodes without order should not hinder direct dependencies.
 * Iterate until no nodes are left.
 */
static void
make_transparent(struct ohash *hash)
{
        struct node     *n;
        unsigned int    i;
        struct link     *l;
        int             adjusted;
        int             bad;
        unsigned int    min;

        /* first try to solve complete nodes */
        do {
                adjusted = 0;
                bad = 0;
                for (n = ohash_first(hash, &i); n != NULL;
                    n = ohash_next(hash, &i)) {
                        if (n->order == NO_ORDER) {
                                min = NO_ORDER;

                                for (l = n->arcs; l != NULL; l = l->next) {
                                        /* unsolved node -> delay resolution */
                                        if (l->node->order == NO_ORDER) {
                                                bad = 1;
                                                break;
                                        } else if (l->node->order < min)
                                                min = l->node->order;
                                }
                                if (min < NO_ORDER && l == NULL) {
                                        n->order = min;
                                        adjusted = 1;
                                }
                        }
                }

        } while (adjusted);

        /* then, if incomplete nodes are left, do them */
        if (bad) do {
                adjusted = 0;
                for (n = ohash_first(hash, &i); n != NULL;
                    n = ohash_next(hash, &i))
                        if (n->order == NO_ORDER)
                                for (l = n->arcs; l != NULL; l = l->next)
                                        if (l->node->order < n->order) {
                                                n->order = l->node->order;
                                                adjusted = 1;
                                        }
        } while (adjusted);
}


/***
 *** Search through hash array for nodes.
 ***/

/* Split nodes into unrefed nodes/live nodes.  */
static void
split_nodes(struct ohash *hash, struct array *heap, struct array *remaining)
{

        struct node *n;
        unsigned int i;

        heap->t = ereallocarray(NULL, ohash_entries(hash),
            sizeof(struct node *));
        remaining->t = ereallocarray(NULL, ohash_entries(hash),
            sizeof(struct node *));
        heap->entries = 0;
        remaining->entries = 0;

        for (n = ohash_first(hash, &i); n != NULL; n = ohash_next(hash, &i)) {
                if (n->refs == 0)
                        heap->t[heap->entries++] = n;
                else
                        remaining->t[remaining->entries++] = n;
        }
}

/* Good point to break a cycle: live node with as few refs as possible. */
static struct node *
find_good_cycle_break(struct array *h)
{
        unsigned int    i;
        unsigned int    best;
        struct node     *u;

        best = UINT_MAX;
        u = NULL;

        assert(h->entries != 0);
        for (i = 0; i < h->entries; i++) {
                struct node *n = h->t[i];
                /* No need to look further. */
                if (n->refs == 1)
                        return n;
                if (n->refs != 0 && n->refs < best) {
                        best = n->refs;
                        u = n;
                }
        }
        assert(u != NULL);
        return u;
}

/*  Retrieve the node with the smallest order.  */
static struct node *
find_smallest_node(struct array *h)
{
        unsigned int    i;
        unsigned int    best;
        struct node     *u;

        best = UINT_MAX;
        u = NULL;

        assert(h->entries != 0);
        for (i = 0; i < h->entries; i++) {
                struct node *n = h->t[i];
                if (n->refs != 0 && n->order < best) {
                        best = n->order;
                        u = n;
                }
        }
        assert(u != NULL);
        return u;
}


/***
 *** Graph algorithms.
 ***/

/* Explore the nodes reachable from i to find a cycle, store it in c.
 * This may fail.  */
static struct node *
find_cycle_from(struct node *i, struct array *c)
{
        struct node     *n;

        n = i;
        /* XXX Previous cycle findings may have left this pointer non-null.  */
        i->from = NULL;

        for (;;) {
                /* Note that all marks are reversed before this code exits.  */
                n->mark = 1;
                if (n->traverse)
                        n->traverse = n->traverse->next;
                else
                        n->traverse = n->arcs;
                /* Skip over dead nodes.  */
                while (n->traverse && n->traverse->node->refs == 0)
                        n->traverse = n->traverse->next;
                if (n->traverse) {
                        struct node *go = n->traverse->node;

                        if (go->mark) {
                                c->entries = 0;
                                for (; n != NULL && n != go; n = n->from) {
                                        c->t[c->entries++] = n;
                                        n->mark = 0;
                                }
                                for (; n != NULL; n = n->from)
                                        n->mark = 0;
                                c->t[c->entries++] = go;
                                return go;
                        } else {
                            go->from = n;
                            n = go;
                        }
                } else {
                        n->mark = 0;
                        n = n->from;
                        if (n == NULL)
                                return NULL;
                }
        }
}

/* Find a live predecessor of node n.  This is a slow routine, as it needs
 * to go through the whole array, but it is not needed often.
 */
static struct node *
find_predecessor(struct array *a, struct node *n)
{
        unsigned int i;

        for (i = 0; i < a->entries; i++) {
                struct node *m;

                m = a->t[i];
                if (m->refs != 0) {
                        struct link *l;

                        for (l = m->arcs; l != NULL; l = l->next)
                                if (l->node == n)
                                        return m;
                }
        }
        assert(1 == 0);
        return NULL;
}

/* Traverse all strongly connected components reachable from node n.
   Start numbering them at o. Return the maximum order reached.
   Update the largest cycle found so far.
 */
static unsigned int
traverse_node(struct node *n, unsigned int o, struct array *c)
{
        unsigned int    min, max;

        n->from = NULL;
        min = o;
        max = ++o;

        for (;;) {
                n->mark = o;
                if (DEBUG_TRAVERSE)
                        printf("%s(%u) ", n->k, n->mark);
                /* Find next arc to explore.  */
                if (n->traverse)
                        n->traverse = n->traverse->next;
                else
                        n->traverse = n->arcs;
                /* Skip over dead nodes.  */
                while (n->traverse && n->traverse->node->refs == 0)
                        n->traverse = n->traverse->next;
                /* If arc left.  */
                if (n->traverse) {
                        struct node     *go;

                        go = n->traverse->node;
                        /* Optimisation: if go->mark < min, we already
                         * visited this strongly-connected component in
                         * a previous pass.  Hence, this can yield no new
                         * cycle.  */

                        /* Not part of the current path: go for it.  */
                        if (go->mark == 0 || go->mark == min) {
                                go->from = n;
                                n = go;
                                o++;
                                if (o > max)
                                        max = o;
                        /* Part of the current path: check cycle length.  */
                        } else if (go->mark > min) {
                                if (DEBUG_TRAVERSE)
                                        printf("%d\n", o - go->mark + 1);
                                if (o - go->mark + 1 > c->entries) {
                                        struct node *t;
                                        unsigned int i;

                                        c->entries = o - go->mark + 1;
                                        i = 0;
                                        c->t[i++] = go;
                                        for (t = n; t != go; t = t->from)
                                                c->t[i++] = t;
                                }
                        }

                /* No arc left: backtrack.  */
                } else {
                        n->mark = min;
                        n = n->from;
                        if (!n)
                                return max;
                        o--;
                }
        }
}

static void
print_cycle(struct array *c)
{
        unsigned int    i;

        /* Printing in reverse order, since cycle discoveries finds reverse
         * edges.  */
        for (i = c->entries; i != 0;) {
                i--;
                warnx("%s", c->t[i]->k);
        }
}

static struct node *
find_longest_cycle(struct array *h, struct array *c)
{
        unsigned int    i;
        unsigned int    o;
        unsigned int    best;
        struct node     *n;
        static int      notfirst = 0;

        assert(h->entries != 0);

        /* No cycle found yet.  */
        c->entries = 0;

        /* Reset the set of marks, except the first time around.  */
        if (notfirst) {
                for (i = 0; i < h->entries; i++)
                        h->t[i]->mark = 0;
        } else
                notfirst = 1;

        o = 0;

        /* Traverse the array.  Each unmarked, live node heralds a
         * new set of strongly connected components.  */
        for (i = 0; i < h->entries; i++) {
                n = h->t[i];
                if (n->refs != 0 && n->mark == 0) {
                        /* Each call to traverse_node uses a separate
                         * interval of numbers to mark nodes.  */
                        o++;
                        o = traverse_node(n, o, c);
                }
        }

        assert(c->entries != 0);
        n = c->t[0];
        best = n->refs;
        for (i = 0; i < c->entries; i++) {
                if (c->t[i]->refs < best) {
                        n = c->t[i];
                        best = n->refs;
                }
        }
        return n;
}

static struct node *
find_normal_cycle(struct array *h, struct array *c)
{
        struct node *b, *n;

        if (hints_flag)
                n = find_smallest_node(h);
        else
                n = find_good_cycle_break(h);
        while ((b = find_cycle_from(n, c)) == NULL)
                n = find_predecessor(h, n);
        return b;
}


#define plural(n) ((n) > 1 ? "s" : "")

static void 
parse_args(int argc, char *argv[], struct ohash *pairs)
{
        int c;
        unsigned int    order;
        int reverse_flag;
        const char **files;
        int i, j;

        i = 0;

        reverse_flag = quiet_flag = long_flag =
                warn_flag = hints_flag = verbose_flag = 0;
        /* argc is good enough, as we start at argv[1] */
        files = ereallocarray(NULL, argc, sizeof (char *));
        while ((c = getopt(argc, argv, "h:flqrvw")) != -1) {
                switch(c) {
                case 'h':
                        files[i++] = optarg;
                        hints_flag = 1;
                        break;
                        /*FALLTHRU*/
                case 'f':
                        hints_flag = 2;
                        break;
                case 'l':
                        long_flag = 1;
                        break;
                case 'q':
                        quiet_flag = 1;
                        break;
                case 'r':
                        reverse_flag = 1;
                        break;
                case 'v':
                        verbose_flag = 1;
                        break;
                case 'w':
                        warn_flag = 1;
                        break;
                default:
                        usage();
                }
        }

        argc -= optind;
        argv += optind;

        switch(argc) {
        case 1:
                files[i++] = argv[0];
                break;
        case 0:
                break;
        default:
                usage();
        }

        files[i] = NULL;

        nodes_init(pairs);
        order = 0;
                
        for (j = 0; j != i-argc; j++) {
                FILE *f;

                f = fopen(files[j], "r");
                if (f == NULL)
                        err(1, "Can't open hint file %s", files[i]);
                order = read_hints(f, pairs, quiet_flag, files[i], order);
                fclose(f);
        }
        free(files);

        if (argc == 1) {
                FILE *f;

                f = fopen(argv[0], "r");
                if (f == NULL)
                        err(1, "Can't open file %s", argv[0]);
                order = read_pairs(f, pairs, reverse_flag, argv[0], order,
                    hints_flag == 2);
                fclose(f);
        } else {
                order = read_pairs(stdin, pairs, reverse_flag, "stdin",
                    order, hints_flag == 2);
        }
}

static int
tsort(struct ohash *pairs)
{
            struct array        aux;    /* Unrefed nodes/cycle reporting.  */
            struct array        remaining;
            unsigned int        broken_arcs, broken_cycles;
            unsigned int        left;

            broken_arcs = 0;
            broken_cycles = 0;

            if (hints_flag)
                    make_transparent(pairs);
            split_nodes(pairs, &aux, &remaining);
            ohash_delete(pairs);

            if (hints_flag)
                    heapify(&aux, verbose_flag);

            left = remaining.entries + aux.entries;
            while (left != 0) {

                    /* Standard topological sort.  */
                    while (aux.entries) {
                            struct link *l;
                            struct node *n;

                            n = DEQUEUE(&aux);
                            printf("%s\n", n->k);
                            left--;
                            /* We can't free nodes, as we don't know which
                             * entry we can remove in the hash table.  We
                             * rely on refs == 0 to recognize live nodes.
                             * Decrease ref count of live nodes, enter new
                             * candidates into the unrefed list.  */
                            for (l = n->arcs; l != NULL; l = l->next)
                                    if (l->node->refs != 0 &&
                                        --l->node->refs == 0) {
                                            ENQUEUE(&aux, l->node);
                                    }
                    }
                    /* There are still cycles to break.  */
                    if (left != 0) {
                            struct node *n;

                            broken_cycles++;
                            /* XXX Simple cycle detection and long cycle
                             * detection are mutually exclusive.  */

                            if (long_flag)
                                    n = find_longest_cycle(&remaining, &aux);
                            else
                                    n = find_normal_cycle(&remaining, &aux);

                            if (!quiet_flag) {
                                    warnx("cycle in data");
                                    print_cycle(&aux);
                            }

                            if (verbose_flag)
                                    warnx("%u edge%s broken", n->refs,
                                        plural(n->refs));
                            broken_arcs += n->refs;
                            n->refs = 0;
                            /* Reinitialization, cycle reporting uses aux.  */
                            aux.t[0] = n;
                            aux.entries = 1;
                    }
            }
            if (verbose_flag && broken_cycles != 0)
                    warnx("%u cycle%s broken, for a total of %u edge%s",
                        broken_cycles, plural(broken_cycles),
                        broken_arcs, plural(broken_arcs));
            if (warn_flag)
                    return (broken_cycles < 256 ? broken_cycles : 255);
            else
                    return (0);
}

int
main(int argc, char *argv[])
{
        struct ohash    pairs;

        if (pledge("stdio rpath", NULL) == -1)
                err(1, "pledge");

        parse_args(argc, argv, &pairs);

        if (pledge("stdio", NULL) == -1)
                err(1, "pledge");

        return tsort(&pairs);
}


extern char *__progname;

static void
usage(void)
{
        fprintf(stderr, "Usage: %s [-flqrvw] [-h file] [file]\n", __progname);
        exit(1);
}