[unix-history] / usr.bin / tsort / tsort.c

/*
 * Copyright (c) 1989 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. 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.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1989 The Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)tsort.c	5.3 (Berkeley) 6/1/90";
#endif /* not lint */

#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>

/*
 *  Topological sort.  Input is a list of pairs of strings seperated by
 *  white space (spaces, tabs, and/or newlines); strings are written to
 *  standard output in sorted order, one per line.
 *
 *  usage:
 *     tsort [inputfile]
 *  If no input file is specified, standard input is read.
 *
 *  Should be compatable 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 then 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, michael@stretch.cs.mun.ca - 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 */

typedef struct node_str NODE;

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

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

NODE *add_node(), *find_node();
void add_arc(), no_memory(), remove_node(), tsort();
char *grow_buf(), *malloc();

extern int errno;
NODE *graph;
NODE *hashtable[HASHSIZE];
NODE **cycle_buf;
NODE **longest_cycle;

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

	if (argc < 2)
		fp = stdin;
	else if (argc > 2) {
		(void)fprintf(stderr, "usage: tsort [ inputfile ]\n");
		exit(1);
	} else if (!(fp = fopen(argv[1], "r"))) {
		(void)fprintf(stderr, "tsort: %s.\n", strerror(errno));
		exit(1);
	}

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

		b->b_buf[nused] = '\0';
		b->b_bsize = bsize;
		if (n)
			add_arc(bufs[0].b_buf, bufs[1].b_buf);
		n = !n;
	}
	(void)fclose(fp);
	if (n) {
		(void)fprintf(stderr, "tsort: odd data count.\n");
		exit(1);
	}

	/* do the sort */
	tsort();
	exit(0);
}

/* double the size of oldbuf and return a pointer to the new buffer. */
char *
grow_buf(bp, size)
	char *bp;
	int size;
{
	char *realloc();

	if (!(bp = realloc(bp, (u_int)size)))
		no_memory();
	return(bp);
}

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

	n1 = find_node(s1);
	if (!n1)
		n1 = add_node(s1);

	if (!strcmp(s1, s2))
		return;

	n2 = find_node(s2);
	if (!n2)
		n2 = add_node(s2);

	/*
	 * could check to see if this arc is here already, but it isn't
	 * worth the bother -- there usually isn't and it doesn't hurt if
	 * there is (I think :-).
	 */
	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 = (NODE **)grow_buf((char *)n1->n_arcs, bsize);
		n1->n_arcsize = bsize / sizeof(*n1->n_arcs);
	}
	n1->n_arcs[n1->n_narcs++] = n2;
	++n2->n_refcnt;
}

hash_string(s)
	char *s;
{
	register int hash, i;

	for (hash = 0, i = 1; *s; s++, i++)
		hash += *s * i;
	return(hash % HASHSIZE);
}

/*
 * find a node in the graph and return a pointer to it - returns null if not
 * found.
 */
NODE *
find_node(name)
	char *name;
{
	register NODE *n;

	for (n = hashtable[hash_string(name)]; n; n = n->n_hash)
		if (!strcmp(n->n_name, name))
			return(n);
	return((NODE *)NULL);
}

/* Add a node to the graph and return a pointer to it. */
NODE *
add_node(name)
	char *name;
{
	register NODE *n;
	int hash;

	if (!(n = (NODE *)malloc(sizeof(NODE))) || !(n->n_name = strdup(name)))
		no_memory();

	n->n_narcs = 0;
	n->n_arcsize = 0;
	n->n_arcs = (NODE **)NULL;
	n->n_refcnt = 0;
	n->n_flags = 0;

	/* add to linked list */
	if (n->n_next = graph)
		graph->n_prevp = &n->n_next;
	n->n_prevp = &graph;
	graph = n;

	/* add to hash table */
	hash = hash_string(name);
	n->n_hash = hashtable[hash];
	hashtable[hash] = n;
	return(n);
}

/* do topological sort on graph */
void
tsort()
{
	register NODE *n, *m, *next;
	register int cnt;

	while (graph) {
		/*
		 * 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; n = next) {
				next = n->n_next;
				if (n->n_refcnt == 0) {
					remove_node(n);
					++cnt;
				}
			}
		} while (graph && cnt);

		if (!graph)
			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; n = n->n_next)
				++cnt;
			cycle_buf =
			    (NODE **)malloc((u_int)sizeof(NODE *) * cnt);
			longest_cycle =
			    (NODE **)malloc((u_int)sizeof(NODE *) * cnt);
			if (!cycle_buf || !longest_cycle)
				no_memory();
		}
		for (n = graph; n; n = n->n_next)
			if (!(n->n_flags & NF_ACYCLIC)) {
				for (m=graph; m; m=m->n_next)
					m->n_flags &= ~NF_MARK;
				if (cnt = find_cycle(n, n, 0, 0)) {
					register int i;

					(void)fprintf(stderr,
					    "tsort: cycle in data.\n");
					for (i = 0; i < cnt; i++)
						(void)fprintf(stderr,
				"tsort: %s.\n", longest_cycle[i]->n_name);
					remove_node(n);
					break;
				} else
					/* to avoid further checks */
					n->n_flags  = NF_ACYCLIC;
			}

		if (!n) {
			(void)fprintf(stderr,
			    "tsort: internal error -- could not find cycle.\n");
			exit(1);
		}
	}
}

/* print node and remove from graph (does not actually free node) */
void
remove_node(n)
	register NODE *n;
{
	register NODE **np;
	register int 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 a path from node from to node to. */
find_cycle(from, to, longest_len, depth)
	NODE *from, *to;
	int depth, longest_len;
{
	register NODE **np;
	register int i, len;

	/*
	 * avoid infinite loops and ignore portions of the graph known
	 * to be acyclic
	 */
	if (from->n_flags & (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((char *)longest_cycle,
				    (char *)cycle_buf,
				    longest_len * sizeof(NODE *));
			}
		} else {
			len = find_cycle(*np, to, longest_len, depth + 1);
			if (len > longest_len) {
				longest_len = len;
				break;
			}
		}
	}
	return(longest_len);
}

void
no_memory()
{
	(void)fprintf(stderr, "tsort: %s.\n", strerror(ENOMEM));
	exit(1);
}
Commit	Line	Data
15637ed4 RG	1	/*
	2	* Copyright (c) 1989 The Regents of the University of California.
	3	* All rights reserved.
	4	*
	5	* This code is derived from software contributed to Berkeley by
	6	* Michael Rendell of Memorial University of Newfoundland.
	7	*
	8	* Redistribution and use in source and binary forms, with or without
	9	* modification, are permitted provided that the following conditions
	10	* are met:
	11	* 1. Redistributions of source code must retain the above copyright
	12	* notice, this list of conditions and the following disclaimer.
	13	* 2. Redistributions in binary form must reproduce the above copyright
	14	* notice, this list of conditions and the following disclaimer in the
	15	* documentation and/or other materials provided with the distribution.
	16	* 3. All advertising materials mentioning features or use of this software
	17	* must display the following acknowledgement:
	18	* This product includes software developed by the University of
	19	* California, Berkeley and its contributors.
	20	* 4. Neither the name of the University nor the names of its contributors
	21	* may be used to endorse or promote products derived from this software
	22	* without specific prior written permission.
	23	*
	24	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	25	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	26	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	27	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	28	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	29	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	30	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	31	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	32	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	33	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	34	* SUCH DAMAGE.
	35	*/
	36
	37	#ifndef lint
	38	char copyright[] =
	39	"@(#) Copyright (c) 1989 The Regents of the University of California.\n\
	40	All rights reserved.\n";
	41	#endif /* not lint */
	42
	43	#ifndef lint
	44	static char sccsid[] = "@(#)tsort.c 5.3 (Berkeley) 6/1/90";
	45	#endif /* not lint */
	46
	47	#include <sys/types.h>
	48	#include <errno.h>
	49	#include <stdio.h>
	50	#include <ctype.h>
	51	#include <string.h>
	52
	53	/*
	54	* Topological sort. Input is a list of pairs of strings seperated by
	55	* white space (spaces, tabs, and/or newlines); strings are written to
	56	* standard output in sorted order, one per line.
	57	*
	58	* usage:
	59	* tsort [inputfile]
	60	* If no input file is specified, standard input is read.
	61	*
	62	* Should be compatable with AT&T tsort HOWEVER the output is not identical
	63	* (i.e. for most graphs there is more than one sorted order, and this tsort
	64	* usually generates a different one then the AT&T tsort). Also, cycle
65	* reporting seems to be more accurate in this version (the AT&T tsort
66	* sometimes says a node is in a cycle when it isn't).
67	*
68	* Michael Rendell, michael@stretch.cs.mun.ca - Feb 26, '90
69	*/
70	#define HASHSIZE 53 /* doesn't need to be big */
71	#define NF_MARK 0x1 /* marker for cycle detection */
72	#define NF_ACYCLIC 0x2 /* this node is cycle free */
73
74	typedef struct node_str NODE;
75
76	struct node_str {
77	char n_name; / name of this node */
78	NODE *n_prevp; / pointer to previous node's n_next */
79	NODE n_next; / next node in graph */
80	NODE n_hash; / next node in hash table */
81	int n_narcs; /* number of arcs in n_arcs[] */
82	int n_arcsize; /* size of n_arcs[] array */
83	NODE *n_arcs; / array of arcs to other nodes */
84	int n_refcnt; /* # of arcs pointing to this node */
85	int n_flags; /* NF_* */
86	};
87
88	typedef struct _buf {
89	char *b_buf;
90	int b_bsize;
91	} BUF;
92
93	NODE add_node(), find_node();
94	void add_arc(), no_memory(), remove_node(), tsort();
95	char grow_buf(), malloc();
96
97	extern int errno;
98	NODE *graph;
99	NODE *hashtable[HASHSIZE];
100	NODE **cycle_buf;
101	NODE **longest_cycle;
102
103	main(argc, argv)
104	int argc;
105	char **argv;
106	{
107	register BUF *b;
108	register int c, n;
109	FILE *fp;
110	int bsize, nused;
111	BUF bufs[2];
112
113	if (argc < 2)
114	fp = stdin;
a6fe0c40	115	else if (argc > 2) {
15637ed4 RG	116	(void)fprintf(stderr, "usage: tsort [ inputfile ]\n");
	117	exit(1);
	118	} else if (!(fp = fopen(argv[1], "r"))) {
	119	(void)fprintf(stderr, "tsort: %s.\n", strerror(errno));
	120	exit(1);
	121	}
	122
	123	for (b = bufs, n = 2; --n >= 0; b++)
	124	b->b_buf = grow_buf((char *)NULL, b->b_bsize = 1024);
	125
	126	/* parse input and build the graph */
	127	for (n = 0, c = getc(fp);;) {
	128	while (c != EOF && isspace(c))
	129	c = getc(fp);
	130	if (c == EOF)
	131	break;
	132
	133	nused = 0;
	134	b = &bufs[n];
	135	bsize = b->b_bsize;
	136	do {
	137	b->b_buf[nused++] = c;
	138	if (nused == bsize) {
	139	bsize *= 2;
	140	b->b_buf = grow_buf(b->b_buf, bsize);
	141	}
	142	c = getc(fp);
	143	} while (c != EOF && !isspace(c));
	144
	145	b->b_buf[nused] = '\0';
	146	b->b_bsize = bsize;
	147	if (n)
	148	add_arc(bufs[0].b_buf, bufs[1].b_buf);
	149	n = !n;
	150	}
	151	(void)fclose(fp);
	152	if (n) {
	153	(void)fprintf(stderr, "tsort: odd data count.\n");
	154	exit(1);
	155	}
	156
	157	/* do the sort */
	158	tsort();
	159	exit(0);
	160	}
	161
	162	/* double the size of oldbuf and return a pointer to the new buffer. */
	163	char *
	164	grow_buf(bp, size)
	165	char *bp;
	166	int size;
	167	{
	168	char *realloc();
	169
	170	if (!(bp = realloc(bp, (u_int)size)))
	171	no_memory();
	172	return(bp);
	173	}
	174
	175	/*
	176	* add an arc from node s1 to node s2 in the graph. If s1 or s2 are not in
	177	* the graph, then add them.
	178	*/
	179	void
180	add_arc(s1, s2)
181	char s1, s2;
182	{
183	register NODE *n1;
184	NODE *n2;
185	int bsize;
186
187	n1 = find_node(s1);
188	if (!n1)
189	n1 = add_node(s1);
190
191	if (!strcmp(s1, s2))
192	return;
193
194	n2 = find_node(s2);
195	if (!n2)
196	n2 = add_node(s2);
197
198	/*
199	* could check to see if this arc is here already, but it isn't
200	* worth the bother -- there usually isn't and it doesn't hurt if
201	* there is (I think :-).
202	*/
203	if (n1->n_narcs == n1->n_arcsize) {
204	if (!n1->n_arcsize)
205	n1->n_arcsize = 10;
206	bsize = n1->n_arcsize * sizeof(n1->n_arcs) 2;
207	n1->n_arcs = (NODE *)grow_buf((char )n1->n_arcs, bsize);
208	n1->n_arcsize = bsize / sizeof(*n1->n_arcs);
209	}
210	n1->n_arcs[n1->n_narcs++] = n2;
211	++n2->n_refcnt;
212	}
213
214	hash_string(s)
215	char *s;
216	{
217	register int hash, i;
218
219	for (hash = 0, i = 1; *s; s++, i++)
220	hash += s i;
221	return(hash % HASHSIZE);
222	}
223
224	/*
225	* find a node in the graph and return a pointer to it - returns null if not
226	* found.
227	*/
228	NODE *
229	find_node(name)
230	char *name;
231	{
232	register NODE *n;
233
234	for (n = hashtable[hash_string(name)]; n; n = n->n_hash)
235	if (!strcmp(n->n_name, name))
236	return(n);
237	return((NODE *)NULL);
238	}
239
240	/* Add a node to the graph and return a pointer to it. */
241	NODE *
242	add_node(name)
243	char *name;
244	{
245	register NODE *n;
246	int hash;
247
248	if (!(n = (NODE *)malloc(sizeof(NODE))) \|\| !(n->n_name = strdup(name)))
249	no_memory();
250
251	n->n_narcs = 0;
252	n->n_arcsize = 0;
253	n->n_arcs = (NODE **)NULL;
254	n->n_refcnt = 0;
255	n->n_flags = 0;
256
257	/* add to linked list */
258	if (n->n_next = graph)
259	graph->n_prevp = &n->n_next;
260	n->n_prevp = &graph;
261	graph = n;
262
263	/* add to hash table */
264	hash = hash_string(name);
265	n->n_hash = hashtable[hash];
266	hashtable[hash] = n;
267	return(n);
268	}
269
270	/* do topological sort on graph */
271	void
272	tsort()
273	{
439c584a	274	register NODE n, m, *next;
15637ed4 RG	275	register int cnt;
	276
	277	while (graph) {
	278	/*
	279	* keep getting rid of simple cases until there are none left,
	280	* if there are any nodes still in the graph, then there is
	281	* a cycle in it.
	282	*/
	283	do {
	284	for (cnt = 0, n = graph; n; n = next) {
	285	next = n->n_next;
	286	if (n->n_refcnt == 0) {
	287	remove_node(n);
	288	++cnt;
	289	}
	290	}
	291	} while (graph && cnt);
	292
	293	if (!graph)
	294	break;
	295
	296	if (!cycle_buf) {
	297	/*
	298	* allocate space for two cycle logs - one to be used
	299	* as scratch space, the other to save the longest
	300	* cycle.
	301	*/
	302	for (cnt = 0, n = graph; n; n = n->n_next)
	303	++cnt;
	304	cycle_buf =
	305	(NODE *)malloc((u_int)sizeof(NODE ) * cnt);
	306	longest_cycle =
	307	(NODE *)malloc((u_int)sizeof(NODE ) * cnt);
	308	if (!cycle_buf \|\| !longest_cycle)
	309	no_memory();
	310	}
	311	for (n = graph; n; n = n->n_next)
	312	if (!(n->n_flags & NF_ACYCLIC)) {
439c584a JH	313	for (m=graph; m; m=m->n_next)
439c584a JH	314	m->n_flags &= ~NF_MARK;
15637ed4 RG	315	if (cnt = find_cycle(n, n, 0, 0)) {
	316	register int i;
	317
	318	(void)fprintf(stderr,
	319	"tsort: cycle in data.\n");
	320	for (i = 0; i < cnt; i++)
	321	(void)fprintf(stderr,
	322	"tsort: %s.\n", longest_cycle[i]->n_name);
	323	remove_node(n);
	324	break;
	325	} else
	326	/* to avoid further checks */
	327	n->n_flags = NF_ACYCLIC;
	328	}
	329
	330	if (!n) {
	331	(void)fprintf(stderr,
	332	"tsort: internal error -- could not find cycle.\n");
	333	exit(1);
	334	}
	335	}
	336	}
	337
	338	/* print node and remove from graph (does not actually free node) */
	339	void
	340	remove_node(n)
	341	register NODE *n;
	342	{
	343	register NODE **np;
	344	register int i;
	345
	346	(void)printf("%s\n", n->n_name);
	347	for (np = n->n_arcs, i = n->n_narcs; --i >= 0; np++)
	348	--(*np)->n_refcnt;
	349	n->n_narcs = 0;
	350	*n->n_prevp = n->n_next;
	351	if (n->n_next)
	352	n->n_next->n_prevp = n->n_prevp;
	353	}
	354
439c584a	355	/* look for a path from node from to node to. */
15637ed4 RG	356	find_cycle(from, to, longest_len, depth)
	357	NODE from, to;
	358	int depth, longest_len;
	359	{
	360	register NODE **np;
	361	register int i, len;
	362
	363	/*
	364	* avoid infinite loops and ignore portions of the graph known
	365	* to be acyclic
	366	*/
	367	if (from->n_flags & (NF_MARK\|NF_ACYCLIC))
	368	return(0);
	369	from->n_flags = NF_MARK;
	370
	371	for (np = from->n_arcs, i = from->n_narcs; --i >= 0; np++) {
	372	cycle_buf[depth] = *np;
	373	if (*np == to) {
	374	if (depth + 1 > longest_len) {
	375	longest_len = depth + 1;
	376	(void)memcpy((char *)longest_cycle,
	377	(char *)cycle_buf,
	378	longest_len * sizeof(NODE *));
	379	}
	380	} else {
	381	len = find_cycle(*np, to, longest_len, depth + 1);
439c584a	382	if (len > longest_len) {
15637ed4	383	longest_len = len;
439c584a JH	384	break;
439c584a JH	385	}
15637ed4 RG	386	}
15637ed4 RG	387	}
15637ed4 RG	388	return(longest_len);
	389	}
	390
	391	void
	392	no_memory()
	393	{
	394	(void)fprintf(stderr, "tsort: %s.\n", strerror(ENOMEM));
	395	exit(1);
	396	}