1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
/* vi: set sw=4 ts=4: */
/*
* tsort implementation for busybox
*
* public domain -- David Leonard, 2022
*/
//config:config TSORT
//config: bool "tsort (2.6 kb)"
//config: default y
//config: help
//config: tsort performs a topological sort.
//applet:IF_TSORT(APPLET(tsort, BB_DIR_USR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_TSORT) += tsort.o
/* BB_AUDIT SUSv3 compliant */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/tsort.html */
//usage:#define tsort_trivial_usage
//usage: "[FILE]"
//usage:#define tsort_full_usage "\n\n"
//usage: "Topological sort"
//usage:#define tsort_example_usage
//usage: "$ echo -e \"a b\\nb c\" | tsort\n"
//usage: "a\n"
//usage: "b\n"
//usage: "c\n"
#include "libbb.h"
#include "common_bufsiz.h"
struct node {
unsigned in_count;
unsigned out_count;
struct node **out;
char name[1];
};
struct globals {
struct node **nodes;
unsigned nodes_len;
};
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { \
setup_common_bufsiz(); \
BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
G.nodes = NULL; \
G.nodes_len = 0; \
} while (0)
static struct node *
get_node(const char *name)
{
struct node *n;
unsigned a = 0;
unsigned b = G.nodes_len;
/* Binary search for name */
while (a != b) {
unsigned m = (a + b) / 2;
int cmp = strcmp(name, G.nodes[m]->name);
if (cmp == 0)
return G.nodes[m]; /* found */
if (cmp < 0) {
b = m;
} else {
a = m + 1;
}
}
/* Allocate new node */
n = xzalloc(sizeof(*n) + strlen(name));
//n->in_count = 0;
//n->out_count = 0;
//n->out = NULL;
strcpy(n->name, name);
/* Insert to maintain sort */
G.nodes = xrealloc(G.nodes, (G.nodes_len + 1) * sizeof(*G.nodes));
memmove(&G.nodes[a + 1], &G.nodes[a],
(G.nodes_len - a) * sizeof(*G.nodes));
G.nodes[a] = n;
G.nodes_len++;
return n;
}
static void
add_edge(struct node *a, struct node *b)
{
a->out = xrealloc_vector(a->out, 6, a->out_count);
a->out[a->out_count++] = b;
b->in_count++;
}
int tsort_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tsort_main(int argc UNUSED_PARAM, char **argv)
{
char *line;
size_t linesz;
ssize_t len;
struct node *a;
int cycles;
INIT_G();
if (argv[1]) {
if (argv[2])
bb_show_usage();
if (NOT_LONE_DASH(argv[1])) {
close(STDIN_FILENO); /* == 0 */
xopen(argv[1], O_RDONLY); /* fd will be 0 */
}
}
/* Read in words separated by <blank>s */
a = NULL;
line = NULL;
linesz = 0;
while ((len = getline(&line, &linesz, stdin)) != -1) {
char *s = line;
while (*(s = skip_whitespace(s)) != '\0') {
struct node *b;
char *word;
word = s;
s = skip_non_whitespace(s);
if (*s)
*s++ = '\0';
/* Create nodes and edges for each word pair */
b = get_node(word);
if (!a) {
a = b;
} else {
if (a != b)
add_edge(a, b);
a = NULL;
}
}
}
// Most other tools do not check for input read error (treat them as EOF)
// die_if_ferror(in, input_filename);
if (a)
bb_simple_error_msg_and_die("odd input");
free(line);
/*
* Kahn's algorithm:
* - find a node that has no incoming edges, print and remove it
* - repeat until the graph is empty
* - if any nodes are left, they form cycles.
*/
cycles = 0;
while (G.nodes_len) {
struct node *n;
unsigned i;
/* Search for first node with no incoming edges */
for (i = 0; i < G.nodes_len; i++) {
if (!G.nodes[i]->in_count)
break;
}
if (i == G.nodes_len) {
/* Must be a cycle; arbitraily break it at node 0 */
cycles++;
i = 0;
#ifndef TINY
bb_error_msg("cycle at %s", G.nodes[i]->name);
#endif
}
/* Remove the node (need no longer maintain sort) */
n = G.nodes[i];
G.nodes[i] = G.nodes[--G.nodes_len];
/* And remove its outgoing edges */
for (i = 0; i < n->out_count; i++)
n->out[i]->in_count--;
free(n->out);
puts(n->name);
free(n);
}
free(G.nodes);
fflush_stdout_and_exit(cycles ? 1 : 0);
}
|
