* Copyright (c) 1989, 1993, 1994

/* $NetBSD: tsort.c,v 1.26 2021/02/06 16:02:16 dbj Exp $ */

/*
* Copyright (c) 1989, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Michael Rendell of Memorial University of Newfoundland.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
#if !defined(lint)
__COPYRIGHT("@(#) Copyright (c) 1989, 1993, 1994\
The Regents of the University of California. All rights reserved.");
#if 0
static char sccsid[] = "@(#)tsort.c 8.3 (Berkeley) 5/4/95";
#endif
__RCSID("$NetBSD: tsort.c,v 1.26 2021/02/06 16:02:16 dbj Exp $");
#endif /* not lint */

#include <sys/types.h>
#include <ctype.h>
#include <db.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#if !HAVE_NBTOOL_CONFIG_H
#include <util.h>
#endif

/*
* Topological sort. Input is a list of pairs of strings separated by
* white space (spaces, tabs, and/or newlines); strings are written to
* standard output in sorted order, one per line.
*
* usage:
* tsort [-l] [inputfile]
* If no input file is specified, standard input is read.
*
* Should be compatible with AT&T tsort HOWEVER the output is not identical
* (i.e. for most graphs there is more than one sorted order, and this tsort
* usually generates a different one than the AT&T tsort). Also, cycle
* reporting seems to be more accurate in this version (the AT&T tsort
* sometimes says a node is in a cycle when it isn't).
*
* Michael Rendell, [email protected] - Feb 26, '90
*/
#define HASHSIZE 53 /* doesn't need to be big */
#define NF_MARK 0x1 /* marker for cycle detection */
#define NF_ACYCLIC 0x2 /* this node is cycle free */
#define NF_NODEST 0x4 /* Unreachable */

typedef struct node_str NODE;

struct node_str {
NODE **n_prevp; /* pointer to previous node's n_next */
NODE *n_next; /* next node in graph */
NODE **n_arcs; /* array of arcs to other nodes */
size_t n_narcs; /* number of arcs in n_arcs[] */
size_t n_arcsize; /* size of n_arcs[] array */
size_t n_refcnt; /* # of arcs pointing to this node */
int n_flags; /* NF_* */
char n_name[1]; /* name of this node */
};

typedef struct _buf {
char *b_buf;
size_t b_bsize;
} BUF;

static DB *db;
static NODE *graph, **cycle_buf, **longest_cycle;
static int debug, longest, quiet, reverse;

static void add_arc(const char *, const char *);
static void clear_cycle(void);
static size_t find_cycle(NODE *, NODE *, size_t, size_t);
static NODE *get_node(const char *);
static void remove_node(NODE *);
static void tsort(void);
__dead static void usage(void);

int
main(int argc, char *argv[])
{
BUF *b;
int c, n, ch;
FILE *fp;
size_t bsize, nused;
BUF bufs[2];

setprogname(argv[0]);

fp = NULL;
while ((ch = getopt(argc, argv, "dlqr")) != -1)
switch (ch) {
case 'd':
debug = 1;
break;
case 'l':
longest = 1;
break;
case 'q':
quiet = 1;
break;
case 'r':
reverse = 1;
break;
case '?':
default:
usage();
}
argc -= optind;
argv += optind;

switch (argc) {
case 0:
fp = stdin;
break;
case 1:
if ((fp = fopen(*argv, "r")) == NULL)
err(EXIT_FAILURE, "%s", *argv);
break;
default:
usage();
}

for (b = bufs, n = 2; n-- > 0; b++)
b->b_buf = erealloc(NULL, b->b_bsize = 1024);

/* parse input and build the graph */
for (n = 0, c = getc(fp);;) {
while (c != EOF && isspace(c))
c = getc(fp);
if (c == EOF)
break;

nused = 0;
b = &bufs[n];
bsize = b->b_bsize;
do {
b->b_buf[nused++] = (char)c;
if (nused == bsize)
b->b_buf = erealloc(b->b_buf, bsize *= 2);
c = getc(fp);
} while (c != EOF && !isspace(c));

b->b_buf[nused] = '\0';
b->b_bsize = bsize;
if (n) {
if (reverse)
add_arc(bufs[1].b_buf, bufs[0].b_buf);
else
add_arc(bufs[0].b_buf, bufs[1].b_buf);
}
n = !n;
}
(void)fclose(fp);
if (n)
errx(EXIT_FAILURE, "odd data count");

/* do the sort */
tsort();
return EXIT_SUCCESS;
}

/*
* add an arc from node s1 to node s2 in the graph. If s1 or s2 are not in
* the graph, then add them.
*/
static void
add_arc(const char *s1, const char *s2)
{
NODE *n1;
NODE *n2;
size_t bsize, i;

n1 = get_node(s1);

if (strcmp(s1, s2) == 0)
return;

n2 = get_node(s2);

/*
* Check if this arc is already here.
*/
for (i = 0; i < n1->n_narcs; i++)
if (n1->n_arcs[i] == n2)
return;
/*
* Add it.
*/
if (n1->n_narcs == n1->n_arcsize) {
if (!n1->n_arcsize)
n1->n_arcsize = 10;
bsize = n1->n_arcsize * sizeof(*n1->n_arcs) * 2;
n1->n_arcs = erealloc(n1->n_arcs, bsize);
n1->n_arcsize = bsize / sizeof(*n1->n_arcs);
}
n1->n_arcs[n1->n_narcs++] = n2;
++n2->n_refcnt;
}

/* Find a node in the graph (insert if not found) and return a pointer to it. */
static NODE *
get_node(const char *name)
{
DBT data, key;
NODE *n;

if (db == NULL &&
(db = dbopen(NULL, O_RDWR, 0, DB_HASH, NULL)) == NULL)
err(EXIT_FAILURE, "db: %s", name);

key.data = __UNCONST(name);
key.size = strlen(name) + 1;

switch ((*db->get)(db, &key, &data, 0)) {
case 0:
(void)memmove(&n, data.data, sizeof(n));
return n;
case 1:
break;
default:
case -1:
err(EXIT_FAILURE, "db: %s", name);
}

n = emalloc(sizeof(NODE) + key.size);

n->n_narcs = 0;
n->n_arcsize = 0;
n->n_arcs = NULL;
n->n_refcnt = 0;
n->n_flags = 0;
(void)memmove(n->n_name, name, key.size);

/* Add to linked list. */
if ((n->n_next = graph) != NULL)
graph->n_prevp = &n->n_next;
n->n_prevp = &graph;
graph = n;

/* Add to hash table. */
data.data = &n;
data.size = sizeof(n);
if ((*db->put)(db, &key, &data, 0))
err(EXIT_FAILURE, "db: %s", name);
return n;
}

/*
* Clear the NODEST flag from all nodes.
*/
static void
clear_cycle(void)
{
NODE *n;

for (n = graph; n != NULL; n = n->n_next)
n->n_flags &= ~NF_NODEST;
}

/* do topological sort on graph */
static void
tsort(void)
{
NODE *n, *next;
size_t cnt, i;

while (graph != NULL) {
/*
* Keep getting rid of simple cases until there are none left,
* if there are any nodes still in the graph, then there is
* a cycle in it.
*/
do {
for (cnt = 0, n = graph; n != NULL; n = next) {
next = n->n_next;
if (n->n_refcnt == 0) {
remove_node(n);
++cnt;
}
}
} while (graph != NULL && cnt);

if (graph == NULL)
break;

if (!cycle_buf) {
/*
* Allocate space for two cycle logs - one to be used
* as scratch space, the other to save the longest
* cycle.
*/
for (cnt = 0, n = graph; n != NULL; n = n->n_next)
++cnt;
cycle_buf = ecalloc(cnt, sizeof(*cycle_buf));
longest_cycle = ecalloc(cnt, sizeof(*longest_cycle));
}
for (n = graph; n != NULL; n = n->n_next) {
if (!(n->n_flags & NF_ACYCLIC)) {
if ((cnt = find_cycle(n, n, 0, 0)) != 0) {
if (!quiet) {
warnx("cycle in data");
for (i = 0; i < cnt; i++)
warnx("%s",
longest_cycle[i]->n_name);
}
remove_node(n);
clear_cycle();
break;
} else {
/* to avoid further checks */
n->n_flags |= NF_ACYCLIC;
clear_cycle();
}
}
}
if (n == NULL)
errx(1, "internal error -- could not find cycle");
}
}

/* print node and remove from graph (does not actually free node) */
static void
remove_node(NODE *n)
{
NODE **np;
size_t i;

(void)printf("%s\n", n->n_name);
for (np = n->n_arcs, i = n->n_narcs; i-- > 0; np++)
--(*np)->n_refcnt;
n->n_narcs = 0;
*n->n_prevp = n->n_next;
if (n->n_next)
n->n_next->n_prevp = n->n_prevp;
}

/* look for the longest? cycle from node from to node to. */
static size_t
find_cycle(NODE *from, NODE *to, size_t longest_len, size_t depth)
{
NODE **np;
size_t i, len;

/*
* avoid infinite loops and ignore portions of the graph known
* to be acyclic
*/
if (from->n_flags & (NF_NODEST|NF_MARK|NF_ACYCLIC))
return 0;
from->n_flags |= NF_MARK;

for (np = from->n_arcs, i = from->n_narcs; i-- > 0; np++) {
cycle_buf[depth] = *np;
if (*np == to) {
if (depth + 1 > longest_len) {
longest_len = depth + 1;
(void)memcpy(longest_cycle, cycle_buf,
longest_len * sizeof(NODE *));
}
} else {
if ((*np)->n_flags & (NF_MARK|NF_ACYCLIC|NF_NODEST))
continue;
len = find_cycle(*np, to, longest_len, depth + 1);

if (debug)
(void)printf("%*s %s->%s %zu\n", (int)depth, "",
from->n_name, to->n_name, len);

if (len == 0)
(*np)->n_flags |= NF_NODEST;

if (len > longest_len)
longest_len = len;

if (len > 0 && !longest)
break;
}
}
from->n_flags &= ~NF_MARK;
return longest_len;
}

static void
usage(void)
{
(void)fprintf(stderr, "Usage: %s [-dlqr] [file]\n", getprogname());
exit(EXIT_FAILURE);
}