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
189
190
191
192
193
194
195
196
197
198
199
200
|
/***
This file is part of systemd.
Copyright 2012 Kay Sievers <kay@vrfy.org>
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "alloc-util.h"
#include "strbuf.h"
/*
* Strbuf stores given strings in a single continuous allocated memory
* area. Identical strings are de-duplicated and return the same offset
* as the first string stored. If the tail of a string already exists
* in the buffer, the tail is returned.
*
* A trie (http://en.wikipedia.org/wiki/Trie) is used to maintain the
* information about the stored strings.
*
* Example of udev rules:
* $ ./udevadm test .
* ...
* read rules file: /usr/lib/udev/rules.d/99-systemd.rules
* rules contain 196608 bytes tokens (16384 * 12 bytes), 39742 bytes strings
* 23939 strings (207859 bytes), 20404 de-duplicated (171653 bytes), 3536 trie nodes used
* ...
*/
struct strbuf *strbuf_new(void) {
struct strbuf *str;
str = new0(struct strbuf, 1);
if (!str)
return NULL;
str->buf = new0(char, 1);
if (!str->buf)
goto err;
str->len = 1;
str->root = new0(struct strbuf_node, 1);
if (!str->root)
goto err;
str->nodes_count = 1;
return str;
err:
free(str->buf);
free(str->root);
free(str);
return NULL;
}
static void strbuf_node_cleanup(struct strbuf_node *node) {
size_t i;
for (i = 0; i < node->children_count; i++)
strbuf_node_cleanup(node->children[i].child);
free(node->children);
free(node);
}
/* clean up trie data, leave only the string buffer */
void strbuf_complete(struct strbuf *str) {
if (!str)
return;
if (str->root)
strbuf_node_cleanup(str->root);
str->root = NULL;
}
/* clean up everything */
void strbuf_cleanup(struct strbuf *str) {
if (!str)
return;
if (str->root)
strbuf_node_cleanup(str->root);
free(str->buf);
free(str);
}
static int strbuf_children_cmp(const struct strbuf_child_entry *n1,
const struct strbuf_child_entry *n2) {
return n1->c - n2->c;
}
static void bubbleinsert(struct strbuf_node *node,
uint8_t c,
struct strbuf_node *node_child) {
struct strbuf_child_entry new = {
.c = c,
.child = node_child,
};
int left = 0, right = node->children_count;
while (right > left) {
int middle = (right + left) / 2 ;
if (strbuf_children_cmp(&node->children[middle], &new) <= 0)
left = middle + 1;
else
right = middle;
}
memmove(node->children + left + 1, node->children + left,
sizeof(struct strbuf_child_entry) * (node->children_count - left));
node->children[left] = new;
node->children_count ++;
}
/* add string, return the index/offset into the buffer */
ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len) {
uint8_t c;
struct strbuf_node *node;
size_t depth;
char *buf_new;
struct strbuf_child_entry *child;
struct strbuf_node *node_child;
ssize_t off;
if (!str->root)
return -EINVAL;
/* search string; start from last character to find possibly matching tails */
if (len == 0)
return 0;
str->in_count++;
str->in_len += len;
node = str->root;
c = s[len-1];
for (depth = 0; depth <= len; depth++) {
struct strbuf_child_entry search;
/* match against current node */
off = node->value_off + node->value_len - len;
if (depth == len || (node->value_len >= len && memcmp(str->buf + off, s, len) == 0)) {
str->dedup_len += len;
str->dedup_count++;
return off;
}
/* lookup child node */
c = s[len - 1 - depth];
search.c = c;
child = bsearch(&search, node->children, node->children_count,
sizeof(struct strbuf_child_entry),
(__compar_fn_t) strbuf_children_cmp);
if (!child)
break;
node = child->child;
}
/* add new string */
buf_new = realloc(str->buf, str->len + len+1);
if (!buf_new)
return -ENOMEM;
str->buf = buf_new;
off = str->len;
memcpy(str->buf + off, s, len);
str->len += len;
str->buf[str->len++] = '\0';
/* new node */
node_child = new0(struct strbuf_node, 1);
if (!node_child)
return -ENOMEM;
node_child->value_off = off;
node_child->value_len = len;
/* extend array, add new entry, sort for bisection */
child = realloc(node->children, (node->children_count + 1) * sizeof(struct strbuf_child_entry));
if (!child) {
free(node_child);
return -ENOMEM;
}
str->nodes_count++;
node->children = child;
bubbleinsert(node, c, node_child);
return off;
}
|
