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/* tsort - topological sort.
Copyright (C) 1998, 1999 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
/* Written by Mark Kettenis <kettenis@phys.uva.nl>. */
/* The topological sort is done according to Algorithm T (Topological
sort) in Donald E. Knuth, The Art of Computer Programming, Volume
1/Fundamental Algorithms, page 262. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdio.h>
#include <assert.h>
#include <getopt.h>
#include "system.h"
#include "long-options.h"
#include "error.h"
#include "readtokens.h"
/* The official name of this program (e.g., no `g' prefix). */
#define PROGRAM_NAME "tsort"
#define AUTHORS "Mark Kettenis"
/* Token delimiters when reading from a file. */
#define DELIM " \t\n"
char *xstrdup ();
/* Members of the list of successors. */
struct successor
{
struct item *suc;
struct successor *next;
};
/* Each string is held in core as the head of a list of successors. */
struct item
{
const char *str;
struct item *left, *right;
int balance;
int count;
struct item *qlink;
struct successor *top;
};
/* The name this program was run with. */
char *program_name;
/* Nonzero if any of the input files are the standard input. */
static int have_read_stdin;
/* The head of the sorted list. */
static struct item *head = NULL;
/* The tail of the list of `zeros', strings that have no predecessors. */
static struct item *zeros = NULL;
/* The number of strings to sort. */
static int n_strings = 0;
static struct option const long_options[] =
{
{ NULL, 0, NULL, 0}
};
void
usage (int status)
{
if (status != 0)
fprintf (stderr, _("Try `%s --help' for more information.\n"),
program_name);
else
{
printf (_("\
Usage: %s [OPTION] [FILE]\n\
Write totally ordered list consistent with the partial ordering in FILE.\n\
With no FILE, or when FILE is -, read standard input.\n\
\n\
--help display this help and exit\n\
--version output version information and exit\n"),
program_name);
puts (_("\nReport bugs to <textutils-bugs@gnu.org>."));
}
exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
}
/* Create a new item/node for STR. */
static struct item *
new_item (const char *str)
{
struct item *k = xmalloc (sizeof (struct item));
k->str = (str ? xstrdup (str): NULL);
k->left = k->right = NULL;
k->balance = 0;
/* T1. Initialize (COUNT[k] <- 0 and TOP[k] <- ^). */
k->count = 0;
k->qlink = NULL;
k->top = NULL;
return k;
}
/* Search binary tree rooted at *ROOT for STR. Allocate a new tree if
*ROOT is NULL. Insert a node/item for STR if not found. Return
the node/item found/created for STR.
This is done according to Algorithm A (Balanced tree search and
insertion) in Donald E. Knuth, The Art of Computer Programming,
Volume 3/Searching and Sorting, pages 455--457. */
static struct item *
search_item (struct item *root, const char *str)
{
struct item *p, *q, *r, *s, *t;
int a;
assert (root);
/* Make sure the tree is not empty, since that is what the algorithm
below expects. */
if (root->right == NULL)
return (root->right = new_item (str));
/* A1. Initialize. */
t = root;
s = p = root->right;
for (;;)
{
/* A2. Compare. */
a = strcmp (str, p->str);
if (a == 0)
return p;
/* A3 & A4. Move left & right. */
if (a < 0)
q = p->left;
else
q = p->right;
if (q == NULL)
{
/* A5. Insert. */
q = new_item (str);
/* A3 & A4. (continued). */
if (a < 0)
p->left = q;
else
p->right = q;
/* A6. Adjust balance factors. */
assert (!STREQ (str, s->str));
if (strcmp (str, s->str) < 0)
{
r = p = s->left;
a = -1;
}
else
{
r = p = s->right;
a = +1;
}
while (p != q)
{
assert (!STREQ (str, p->str));
if (strcmp (str, p->str) < 0)
{
p->balance = -1;
p = p->left;
}
else
{
p->balance = +1;
p = p->right;
}
}
/* A7. Balancing act. */
if (s->balance == 0 || s->balance == -a)
{
s->balance += a;
return q;
}
if (r->balance == a)
{
/* A8. Single Rotation. */
p = r;
if (a < 0)
{
s->left = r->right;
r->right = s;
}
else
{
s->right = r->left;
r->left = s;
}
s->balance = r->balance = 0;
}
else
{
/* A9. Double rotation. */
if (a < 0)
{
p = r->right;
r->right = p->left;
p->left = r;
s->left = p->right;
p->right = s;
}
else
{
p = r->left;
r->left = p->right;
p->right = r;
s->right = p->left;
p->left = s;
}
s->balance = 0;
r->balance = 0;
if (p->balance == a)
s->balance = -a;
else if (p->balance == -a)
r->balance = a;
p->balance = 0;
}
/* A10. Finishing touch. */
if (s == t->right)
t->right = p;
else
t->left = p;
return q;
}
/* A3 & A4. (continued). */
if (q->balance)
{
t = p;
s = q;
}
p = q;
}
/* NOTREACHED */
}
/* Record the fact that J precedes K. */
static void
record_relation (struct item *j, struct item *k)
{
struct successor *p;
if (!STREQ (j->str, k->str))
{
k->count++;
p = xmalloc (sizeof (struct successor));
p->suc = k;
p->next = j->top;
j->top = p;
}
}
static void
count_items (struct item *k)
{
n_strings++;
}
static void
scan_zeros (struct item *k)
{
if (k->count == 0)
{
if (head == NULL)
head = k;
else
zeros->qlink = k;
zeros = k;
}
}
/* If K is part of a loop, print the loop on standard error, and exit. */
static void
detect_loop (struct item *k)
{
if (k->count > 0)
{
while (k && k->count > 0)
{
k->count = 0;
fprintf (stderr, "%s: %s\n", program_name, k->str);
k = k->top->suc;
}
exit (EXIT_FAILURE);
}
}
/* Recurse (sub)tree rooted at ROOT, calling ACTION for each node. */
static void
recurse_tree (struct item *root, void (*action) (struct item *))
{
if (root->left == NULL && root->right == NULL)
(*action) (root);
else
{
if (root->left != NULL)
recurse_tree (root->left, action);
(*action) (root);
if (root->right != NULL)
recurse_tree (root->right, action);
}
}
/* Walk the tree specified by the head ROOT, calling ACTION for
each node. */
static void
walk_tree (struct item *root, void (*action) (struct item *))
{
if (root->right)
recurse_tree (root->right, action);
}
/* Do a topological sort on FILE. */
static void
tsort (const char *file)
{
struct item *root;
struct item *j = NULL;
struct item *k = NULL;
register FILE *fp;
token_buffer tokenbuffer;
/* Intialize the head of the tree will hold the strings we're sorting. */
root = new_item (NULL);
if (STREQ (file, "-"))
{
fp = stdin;
have_read_stdin = 1;
}
else
{
fp = fopen (file, "r");
if (fp == NULL)
error (EXIT_FAILURE, errno, "%s", file);
}
init_tokenbuffer (&tokenbuffer);
while (1)
{
long int len;
/* T2. Next Relation. */
len = readtoken (fp, DELIM, sizeof (DELIM) - 1, &tokenbuffer);
if (len < 0)
break;
assert (len != 0);
k = search_item (root, tokenbuffer.buffer);
if (j)
{
/* T3. Record the relation. */
record_relation (j, k);
k = NULL;
}
j = k;
}
/* T1. Initialize (N <- n). */
walk_tree (root, count_items);
/* T4. Scan for zeros. */
walk_tree (root, scan_zeros);
while (head)
{
struct successor *p = head->top;
/* T5. Output front of queue. */
printf ("%s\n", head->str);
n_strings--;
/* T6. Erase relations. */
while (p)
{
p->suc->count--;
if (p->suc->count == 0)
{
zeros->qlink = p->suc;
zeros = p->suc;
}
p = p->next;
}
/* T7. Remove from queue. */
head = head->qlink;
}
/* T8. End of process. */
assert (n_strings >= 0);
if (n_strings > 0)
{
error (0, 0, _("%s: input contains a loop:\n"),
(have_read_stdin ? "-" : file));
/* Print out loop. */
walk_tree (root, detect_loop);
/* Should not happen. */
error (EXIT_FAILURE, 0, _("could not find loop"));
}
}
int
main (int argc, char **argv)
{
int opt;
program_name = argv[0];
setlocale (LC_ALL, "");
bindtextdomain (PACKAGE, LOCALEDIR);
textdomain (PACKAGE);
parse_long_options (argc, argv, PROGRAM_NAME, GNU_PACKAGE, VERSION,
"Mark Kettenis", usage);
while ((opt = getopt_long (argc, argv, "", long_options, NULL)) != -1)
switch (opt)
{
case 0: /* long option */
break;
default:
usage (EXIT_FAILURE);
}
have_read_stdin = 0;
if (optind + 1 < argc)
{
error (0, 0, _("only one argument may be specified"));
usage (EXIT_FAILURE);
}
if (optind < argc)
tsort (argv[optind]);
else
tsort ("-");
if (fclose (stdout) == EOF)
error (EXIT_FAILURE, errno, _("write error"));
if (have_read_stdin && fclose (stdin) == EOF)
error (EXIT_FAILURE, errno, _("standard input"));
exit (EXIT_SUCCESS);
}
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