1 /* xf86drmHash.c -- Small hash table support for integer -> integer mapping
2 * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
4 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
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:
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
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.
26 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
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:
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
40 * 2) The hash computation uses a table of random integers [Hanson97,
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
59 * [Hanson97] David R. Hanson. C Interfaces and Implementations:
60 * Techniques for Creating Reusable Software. Reading, Massachusetts:
61 * Addison-Wesley, 1997.
63 * [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
64 * Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
66 * [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
75 #include "xf86drmHash.h"
78 static int dist[DIST_LIMIT];
80 static void clear_dist(void) {
83 for (i = 0; i < DIST_LIMIT; i++)
87 static int count_entries(HashBucketPtr bucket)
91 for (; bucket; bucket = bucket->next)
96 static void update_dist(int count)
98 if (count >= DIST_LIMIT)
104 static void compute_dist(HashTablePtr table)
107 HashBucketPtr bucket;
109 printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
110 table->entries, table->hits, table->partials, table->misses);
112 for (i = 0; i < HASH_SIZE; i++) {
113 bucket = table->buckets[i];
114 update_dist(count_entries(bucket));
116 for (i = 0; i < DIST_LIMIT; i++) {
117 if (i != DIST_LIMIT-1)
118 printf("%5d %10d\n", i, dist[i]);
120 printf("other %10d\n", dist[i]);
124 static int check_table(HashTablePtr table,
125 unsigned long key, void * value)
128 int retcode = drmHashLookup(table, key, &retval);
132 printf("Bad magic = 0x%08lx:"
133 " key = %lu, expected = %p, returned = %p\n",
134 table->magic, key, value, retval);
137 printf("Not found: key = %lu, expected = %p, returned = %p\n",
141 if (value != retval) {
142 printf("Bad value: key = %lu, expected = %p, returned = %p\n",
148 printf("Bad retcode = %d: key = %lu, expected = %p, returned = %p\n",
149 retcode, key, value, retval);
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));
168 drmHashDestroy(table);
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));
177 drmHashDestroy(table);
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));
186 drmHashDestroy(table);
188 printf("\n***** 1024 random integers ****\n");
189 table = drmHashCreate();
191 for (i = 0; i < 1024; i++)
192 drmHashInsert(table, random(), (void *)(i << 16 | i));
194 for (i = 0; i < 1024; i++)
195 ret |= check_table(table, random(), (void *)(i << 16 | i));
197 for (i = 0; i < 1024; i++)
198 ret |= check_table(table, random(), (void *)(i << 16 | i));
200 drmHashDestroy(table);
202 printf("\n***** 5000 random integers ****\n");
203 table = drmHashCreate();
205 for (i = 0; i < 5000; i++)
206 drmHashInsert(table, random(), (void *)(i << 16 | i));
208 for (i = 0; i < 5000; i++)
209 ret |= check_table(table, random(), (void *)(i << 16 | i));
211 for (i = 0; i < 5000; i++)
212 ret |= check_table(table, random(), (void *)(i << 16 | i));
214 drmHashDestroy(table);