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