1 /***********************************************************
2 * Copyright 1987, 1998 The Open Group
3 *
4 * Permission to use, copy, modify, distribute, and sell this software and its
5 * documentation for any purpose is hereby granted without fee, provided that
6 * the above copyright notice appear in all copies and that both that
7 * copyright notice and this permission notice appear in supporting
8 * documentation.
9 *
10 * The above copyright notice and this permission notice shall be included in
11 * all copies or substantial portions of the Software.
12 *
13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16 * OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
17 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
18 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
19 *
20 * Except as contained in this notice, the name of The Open Group shall not be
21 * used in advertising or otherwise to promote the sale, use or other dealings
22 * in this Software without prior written authorization from The Open Group.
23 *
24 *
25 * Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.
26 *
27 * All Rights Reserved
28 *
29 * Permission to use, copy, modify, and distribute this software and its
30 * documentation for any purpose and without fee is hereby granted,
31 * provided that the above copyright notice appear in all copies and that
32 * both that copyright notice and this permission notice appear in
33 * supporting documentation, and that the name of Digital not be
34 * used in advertising or publicity pertaining to distribution of the
35 * software without specific, written prior permission.
36 *
37 * DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
38 * ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
39 * DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
40 * ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
41 * WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
42 * ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
43 * SOFTWARE.
44 *
45 ******************************************************************/
46
47 /************************************************************
48 * Copyright 1994 by Silicon Graphics Computer Systems, Inc.
49 *
50 * Permission to use, copy, modify, and distribute this
51 * software and its documentation for any purpose and without
52 * fee is hereby granted, provided that the above copyright
53 * notice appear in all copies and that both that copyright
54 * notice and this permission notice appear in supporting
55 * documentation, and that the name of Silicon Graphics not be
56 * used in advertising or publicity pertaining to distribution
57 * of the software without specific prior written permission.
58 * Silicon Graphics makes no representation about the suitability
59 * of this software for any purpose. It is provided "as is"
60 * without any express or implied warranty.
61 *
62 * SILICON GRAPHICS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
63 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
64 * AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
65 * GRAPHICS BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
66 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
67 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
68 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH
69 * THE USE OR PERFORMANCE OF THIS SOFTWARE.
70 *
71 ********************************************************/
72
73 #include "config.h"
74
75 #include "utils.h"
76 #include "atom.h"
77
78 /* FNV-1a (http://www.isthe.com/chongo/tech/comp/fnv/). */
79 static inline uint32_t
hash_buf(const char * string,size_t len)80 hash_buf(const char *string, size_t len)
81 {
82 uint32_t hash = 2166136261u;
83 for (size_t i = 0; i < (len + 1) / 2; i++) {
84 hash ^= (uint8_t) string[i];
85 hash *= 0x01000193;
86 hash ^= (uint8_t) string[len - 1 - i];
87 hash *= 0x01000193;
88 }
89 return hash;
90 }
91
92 /*
93 * The atom table is a insert-only unbalanced binary search tree
94 * mapping strings to atoms.
95 *
96 * The tree nodes are kept contiguously in the `table` array.
97 *
98 * The atom value is the index of the tree node in the array.
99 *
100 * As an optimization, strings are not compared by value directly,
101 * s1 < s2
102 * instead, they are compared by fingerprint (hash) and the value
103 * is only used to resolve collisions:
104 * (fingerprint(s1), s1) < (fingerprint(s2), s2)
105 * Fingerprint are pre-calculated and saved in the tree nodes.
106 *
107 * Why is this not just a hash table? Who knows!
108 */
109 struct atom_node {
110 xkb_atom_t left, right;
111 uint32_t fingerprint;
112 char *string;
113 };
114
115 struct atom_table {
116 xkb_atom_t root;
117 darray(struct atom_node) table;
118 };
119
120 struct atom_table *
atom_table_new(void)121 atom_table_new(void)
122 {
123 struct atom_table *table = calloc(1, sizeof(*table));
124 if (!table)
125 return NULL;
126
127 darray_init(table->table);
128 /* The original throw-away root is here, at the illegal atom 0. */
129 darray_resize0(table->table, 1);
130
131 return table;
132 }
133
134 void
atom_table_free(struct atom_table * table)135 atom_table_free(struct atom_table *table)
136 {
137 if (!table)
138 return;
139
140 struct atom_node *node;
141 darray_foreach(node, table->table)
142 free(node->string);
143 darray_free(table->table);
144 free(table);
145 }
146
147 const char *
atom_text(struct atom_table * table,xkb_atom_t atom)148 atom_text(struct atom_table *table, xkb_atom_t atom)
149 {
150 assert(atom < darray_size(table->table));
151 return darray_item(table->table, atom).string;
152 }
153
154 xkb_atom_t
atom_intern(struct atom_table * table,const char * string,size_t len,bool add)155 atom_intern(struct atom_table *table, const char *string, size_t len, bool add)
156 {
157 uint32_t fingerprint = hash_buf(string, len);
158
159 xkb_atom_t *atomp = &table->root;
160 while (*atomp != XKB_ATOM_NONE) {
161 struct atom_node *node = &darray_item(table->table, *atomp);
162
163 if (fingerprint > node->fingerprint) {
164 atomp = &node->right;
165 }
166 else if (fingerprint < node->fingerprint) {
167 atomp = &node->left;
168 }
169 else {
170 /* Now start testing the strings. */
171 const int cmp = strncmp(string, node->string, len);
172 if (likely(cmp == 0 && node->string[len] == '\0')) {
173 return *atomp;
174 }
175 else if (cmp > 0) {
176 atomp = &node->right;
177 }
178 else {
179 atomp = &node->left;
180 }
181 }
182 }
183
184 if (!add)
185 return XKB_ATOM_NONE;
186
187 struct atom_node node;
188 node.string = strndup(string, len);
189 assert(node.string != NULL);
190 node.left = node.right = XKB_ATOM_NONE;
191 node.fingerprint = fingerprint;
192 xkb_atom_t atom = darray_size(table->table);
193 /* Do this before the append, as it may realloc and change the offsets. */
194 *atomp = atom;
195 darray_append(table->table, node);
196 return atom;
197 }
198