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663996b3 MS |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2012 Kay Sievers <kay@vrfy.org> | |
5 | ||
6 | systemd is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | systemd is distributed in the hope that it will be useful, but | |
12 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public License | |
17 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
18 | ***/ | |
19 | ||
4c89c718 | 20 | #include <errno.h> |
663996b3 MS |
21 | #include <stdlib.h> |
22 | #include <string.h> | |
23 | ||
db2df898 | 24 | #include "alloc-util.h" |
663996b3 MS |
25 | #include "strbuf.h" |
26 | ||
27 | /* | |
28 | * Strbuf stores given strings in a single continuous allocated memory | |
29 | * area. Identical strings are de-duplicated and return the same offset | |
30 | * as the first string stored. If the tail of a string already exists | |
31 | * in the buffer, the tail is returned. | |
32 | * | |
33 | * A trie (http://en.wikipedia.org/wiki/Trie) is used to maintain the | |
34 | * information about the stored strings. | |
35 | * | |
36 | * Example of udev rules: | |
37 | * $ ./udevadm test . | |
38 | * ... | |
39 | * read rules file: /usr/lib/udev/rules.d/99-systemd.rules | |
40 | * rules contain 196608 bytes tokens (16384 * 12 bytes), 39742 bytes strings | |
41 | * 23939 strings (207859 bytes), 20404 de-duplicated (171653 bytes), 3536 trie nodes used | |
42 | * ... | |
43 | */ | |
44 | ||
45 | struct strbuf *strbuf_new(void) { | |
46 | struct strbuf *str; | |
47 | ||
48 | str = new0(struct strbuf, 1); | |
49 | if (!str) | |
50 | return NULL; | |
51 | ||
52 | str->buf = new0(char, 1); | |
53 | if (!str->buf) | |
54 | goto err; | |
55 | str->len = 1; | |
56 | ||
57 | str->root = new0(struct strbuf_node, 1); | |
58 | if (!str->root) | |
59 | goto err; | |
60 | str->nodes_count = 1; | |
61 | return str; | |
62 | err: | |
63 | free(str->buf); | |
64 | free(str->root); | |
65 | free(str); | |
66 | return NULL; | |
67 | } | |
68 | ||
69 | static void strbuf_node_cleanup(struct strbuf_node *node) { | |
70 | size_t i; | |
71 | ||
72 | for (i = 0; i < node->children_count; i++) | |
73 | strbuf_node_cleanup(node->children[i].child); | |
74 | free(node->children); | |
75 | free(node); | |
76 | } | |
77 | ||
78 | /* clean up trie data, leave only the string buffer */ | |
79 | void strbuf_complete(struct strbuf *str) { | |
80 | if (!str) | |
81 | return; | |
82 | if (str->root) | |
83 | strbuf_node_cleanup(str->root); | |
84 | str->root = NULL; | |
85 | } | |
86 | ||
87 | /* clean up everything */ | |
88 | void strbuf_cleanup(struct strbuf *str) { | |
89 | if (!str) | |
90 | return; | |
91 | if (str->root) | |
92 | strbuf_node_cleanup(str->root); | |
93 | free(str->buf); | |
94 | free(str); | |
95 | } | |
96 | ||
97 | static int strbuf_children_cmp(const struct strbuf_child_entry *n1, | |
98 | const struct strbuf_child_entry *n2) { | |
99 | return n1->c - n2->c; | |
100 | } | |
101 | ||
102 | static void bubbleinsert(struct strbuf_node *node, | |
103 | uint8_t c, | |
104 | struct strbuf_node *node_child) { | |
105 | ||
106 | struct strbuf_child_entry new = { | |
107 | .c = c, | |
108 | .child = node_child, | |
109 | }; | |
110 | int left = 0, right = node->children_count; | |
111 | ||
112 | while (right > left) { | |
113 | int middle = (right + left) / 2 ; | |
114 | if (strbuf_children_cmp(&node->children[middle], &new) <= 0) | |
115 | left = middle + 1; | |
116 | else | |
117 | right = middle; | |
118 | } | |
119 | ||
120 | memmove(node->children + left + 1, node->children + left, | |
121 | sizeof(struct strbuf_child_entry) * (node->children_count - left)); | |
122 | node->children[left] = new; | |
123 | ||
124 | node->children_count ++; | |
125 | } | |
126 | ||
127 | /* add string, return the index/offset into the buffer */ | |
128 | ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len) { | |
129 | uint8_t c; | |
130 | struct strbuf_node *node; | |
131 | size_t depth; | |
132 | char *buf_new; | |
133 | struct strbuf_child_entry *child; | |
134 | struct strbuf_node *node_child; | |
135 | ssize_t off; | |
136 | ||
137 | if (!str->root) | |
138 | return -EINVAL; | |
139 | ||
140 | /* search string; start from last character to find possibly matching tails */ | |
141 | if (len == 0) | |
142 | return 0; | |
143 | str->in_count++; | |
144 | str->in_len += len; | |
145 | ||
146 | node = str->root; | |
147 | c = s[len-1]; | |
148 | for (depth = 0; depth <= len; depth++) { | |
149 | struct strbuf_child_entry search; | |
150 | ||
151 | /* match against current node */ | |
152 | off = node->value_off + node->value_len - len; | |
153 | if (depth == len || (node->value_len >= len && memcmp(str->buf + off, s, len) == 0)) { | |
154 | str->dedup_len += len; | |
155 | str->dedup_count++; | |
156 | return off; | |
157 | } | |
158 | ||
159 | /* lookup child node */ | |
160 | c = s[len - 1 - depth]; | |
161 | search.c = c; | |
162 | child = bsearch(&search, node->children, node->children_count, | |
163 | sizeof(struct strbuf_child_entry), | |
164 | (__compar_fn_t) strbuf_children_cmp); | |
165 | if (!child) | |
166 | break; | |
167 | node = child->child; | |
168 | } | |
169 | ||
170 | /* add new string */ | |
171 | buf_new = realloc(str->buf, str->len + len+1); | |
172 | if (!buf_new) | |
173 | return -ENOMEM; | |
174 | str->buf = buf_new; | |
175 | off = str->len; | |
176 | memcpy(str->buf + off, s, len); | |
177 | str->len += len; | |
178 | str->buf[str->len++] = '\0'; | |
179 | ||
180 | /* new node */ | |
181 | node_child = new0(struct strbuf_node, 1); | |
182 | if (!node_child) | |
183 | return -ENOMEM; | |
184 | node_child->value_off = off; | |
185 | node_child->value_len = len; | |
186 | ||
187 | /* extend array, add new entry, sort for bisection */ | |
188 | child = realloc(node->children, (node->children_count + 1) * sizeof(struct strbuf_child_entry)); | |
189 | if (!child) { | |
190 | free(node_child); | |
191 | return -ENOMEM; | |
192 | } | |
193 | ||
194 | str->nodes_count++; | |
195 | ||
196 | node->children = child; | |
197 | bubbleinsert(node, c, node_child); | |
198 | ||
199 | return off; | |
200 | } |