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
78static int dist[DIST_LIMIT];
79
80static void clear_dist(void) {
81    int i;
82
83    for (i = 0; i < DIST_LIMIT; i++)
84        dist[i] = 0;
85}
86
87static int count_entries(HashBucketPtr bucket)
88{
89    int count = 0;
90
91    for (; bucket; bucket = bucket->next)
92        ++count;
93    return count;
94}
95
96static void update_dist(int count)
97{
98    if (count >= DIST_LIMIT)
99        ++dist[DIST_LIMIT-1];
100    else
101        ++dist[count];
102}
103
104static 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
124static 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
155int 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