1 /* xf86drmHash.c -- Small hash table support for integer -> integer mapping
2 * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
3 *
4 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
5 * All Rights Reserved.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a
8 * copy of this software and associated documentation files (the "Software"),
9 * to deal in the Software without restriction, including without limitation
10 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
11 * and/or sell copies of the Software, and to permit persons to whom the
12 * Software is furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice (including the next
15 * paragraph) shall be included in all copies or substantial portions of the
16 * Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
21 * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
22 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
23 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
24 * DEALINGS IN THE SOFTWARE.
25 *
26 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
27 *
28 * DESCRIPTION
29 *
30 * This file contains a straightforward implementation of a fixed-sized
31 * hash table using self-organizing linked lists [Knuth73, pp. 398-399] for
32 * collision resolution. There are two potentially interesting things
33 * about this implementation:
34 *
35 * 1) The table is power-of-two sized. Prime sized tables are more
36 * traditional, but do not have a significant advantage over power-of-two
37 * sized table, especially when double hashing is not used for collision
38 * resolution.
39 *
40 * 2) The hash computation uses a table of random integers [Hanson97,
41 * pp. 39-41].
42 *
43 * FUTURE ENHANCEMENTS
44 *
45 * With a table size of 512, the current implementation is sufficient for a
46 * few hundred keys. Since this is well above the expected size of the
47 * tables for which this implementation was designed, the implementation of
48 * dynamic hash tables was postponed until the need arises. A common (and
49 * naive) approach to dynamic hash table implementation simply creates a
50 * new hash table when necessary, rehashes all the data into the new table,
51 * and destroys the old table. The approach in [Larson88] is superior in
52 * two ways: 1) only a portion of the table is expanded when needed,
53 * distributing the expansion cost over several insertions, and 2) portions
54 * of the table can be locked, enabling a scalable thread-safe
55 * implementation.
56 *
57 * REFERENCES
58 *
59 * [Hanson97] David R. Hanson. C Interfaces and Implementations:
60 * Techniques for Creating Reusable Software. Reading, Massachusetts:
61 * Addison-Wesley, 1997.
62 *
63 * [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
64 * Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
65 *
66 * [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
67 * 1988, pp. 446-457.
68 *
69 */
70
71 #include <stdio.h>
72 #include <stdlib.h>
73
74 #include "xf86drm.h"
75 #include "xf86drmHash.h"
76
77 #define DIST_LIMIT 10
78 static int dist[DIST_LIMIT];
79
clear_dist(void)80 static void clear_dist(void) {
81 int i;
82
83 for (i = 0; i < DIST_LIMIT; i++)
84 dist[i] = 0;
85 }
86
count_entries(HashBucketPtr bucket)87 static int count_entries(HashBucketPtr bucket)
88 {
89 int count = 0;
90
91 for (; bucket; bucket = bucket->next)
92 ++count;
93 return count;
94 }
95
update_dist(int count)96 static void update_dist(int count)
97 {
98 if (count >= DIST_LIMIT)
99 ++dist[DIST_LIMIT-1];
100 else
101 ++dist[count];
102 }
103
compute_dist(HashTablePtr table)104 static void compute_dist(HashTablePtr table)
105 {
106 int i;
107 HashBucketPtr bucket;
108
109 printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
110 table->entries, table->hits, table->partials, table->misses);
111 clear_dist();
112 for (i = 0; i < HASH_SIZE; i++) {
113 bucket = table->buckets[i];
114 update_dist(count_entries(bucket));
115 }
116 for (i = 0; i < DIST_LIMIT; i++) {
117 if (i != DIST_LIMIT-1)
118 printf("%5d %10d\n", i, dist[i]);
119 else
120 printf("other %10d\n", dist[i]);
121 }
122 }
123
check_table(HashTablePtr table,unsigned long key,void * value)124 static int check_table(HashTablePtr table,
125 unsigned long key, void * value)
126 {
127 void *retval;
128 int retcode = drmHashLookup(table, key, &retval);
129
130 switch (retcode) {
131 case -1:
132 printf("Bad magic = 0x%08lx:"
133 " key = %lu, expected = %p, returned = %p\n",
134 table->magic, key, value, retval);
135 break;
136 case 1:
137 printf("Not found: key = %lu, expected = %p, returned = %p\n",
138 key, value, retval);
139 break;
140 case 0:
141 if (value != retval) {
142 printf("Bad value: key = %lu, expected = %p, returned = %p\n",
143 key, value, retval);
144 retcode = -1;
145 }
146 break;
147 default:
148 printf("Bad retcode = %d: key = %lu, expected = %p, returned = %p\n",
149 retcode, key, value, retval);
150 break;
151 }
152 return retcode;
153 }
154
main(void)155 int main(void)
156 {
157 HashTablePtr table;
158 unsigned long i;
159 int ret = 0;
160
161 printf("\n***** 256 consecutive integers ****\n");
162 table = drmHashCreate();
163 for (i = 0; i < 256; i++)
164 drmHashInsert(table, i, (void *)(i << 16 | i));
165 for (i = 0; i < 256; i++)
166 ret |= check_table(table, i, (void *)(i << 16 | i));
167 compute_dist(table);
168 drmHashDestroy(table);
169
170 printf("\n***** 1024 consecutive integers ****\n");
171 table = drmHashCreate();
172 for (i = 0; i < 1024; i++)
173 drmHashInsert(table, i, (void *)(i << 16 | i));
174 for (i = 0; i < 1024; i++)
175 ret |= check_table(table, i, (void *)(i << 16 | i));
176 compute_dist(table);
177 drmHashDestroy(table);
178
179 printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
180 table = drmHashCreate();
181 for (i = 0; i < 1024; i++)
182 drmHashInsert(table, i*4096, (void *)(i << 16 | i));
183 for (i = 0; i < 1024; i++)
184 ret |= check_table(table, i*4096, (void *)(i << 16 | i));
185 compute_dist(table);
186 drmHashDestroy(table);
187
188 printf("\n***** 1024 random integers ****\n");
189 table = drmHashCreate();
190 srandom(0xbeefbeef);
191 for (i = 0; i < 1024; i++)
192 drmHashInsert(table, random(), (void *)(i << 16 | i));
193 srandom(0xbeefbeef);
194 for (i = 0; i < 1024; i++)
195 ret |= check_table(table, random(), (void *)(i << 16 | i));
196 srandom(0xbeefbeef);
197 for (i = 0; i < 1024; i++)
198 ret |= check_table(table, random(), (void *)(i << 16 | i));
199 compute_dist(table);
200 drmHashDestroy(table);
201
202 printf("\n***** 5000 random integers ****\n");
203 table = drmHashCreate();
204 srandom(0xbeefbeef);
205 for (i = 0; i < 5000; i++)
206 drmHashInsert(table, random(), (void *)(i << 16 | i));
207 srandom(0xbeefbeef);
208 for (i = 0; i < 5000; i++)
209 ret |= check_table(table, random(), (void *)(i << 16 | i));
210 srandom(0xbeefbeef);
211 for (i = 0; i < 5000; i++)
212 ret |= check_table(table, random(), (void *)(i << 16 | i));
213 compute_dist(table);
214 drmHashDestroy(table);
215
216 return ret;
217 }
218