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authorKristian Høgsberg2009-11-17 10:14:54 -0600
committerKristian Høgsberg2009-11-17 10:15:06 -0600
commit4f57abfe66091281c9f59c14e6ea27b524b55d5b (patch)
treef00d1022cf208b381b93aa5c96858164e6a3f602 /xf86drmHash.c
parent9dd3613073aa2491cef440725fdfa0cf1e8f1a42 (diff)
downloadexternal-libdrm-4f57abfe66091281c9f59c14e6ea27b524b55d5b.tar.gz
external-libdrm-4f57abfe66091281c9f59c14e6ea27b524b55d5b.tar.xz
external-libdrm-4f57abfe66091281c9f59c14e6ea27b524b55d5b.zip
Move libdrm/ up one level
Diffstat (limited to 'xf86drmHash.c')
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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#define HASH_MAIN 0
75
76#if !HASH_MAIN
77# include "xf86drm.h"
78#endif
79
80#define HASH_MAGIC 0xdeadbeef
81#define HASH_DEBUG 0
82#define HASH_SIZE 512 /* Good for about 100 entries */
83 /* If you change this value, you probably
84 have to change the HashHash hashing
85 function! */
86
87#if HASH_MAIN
88#define HASH_ALLOC malloc
89#define HASH_FREE free
90#define HASH_RANDOM_DECL
91#define HASH_RANDOM_INIT(seed) srandom(seed)
92#define HASH_RANDOM random()
93#define HASH_RANDOM_DESTROY
94#else
95#define HASH_ALLOC drmMalloc
96#define HASH_FREE drmFree
97#define HASH_RANDOM_DECL void *state
98#define HASH_RANDOM_INIT(seed) state = drmRandomCreate(seed)
99#define HASH_RANDOM drmRandom(state)
100#define HASH_RANDOM_DESTROY drmRandomDestroy(state)
101
102#endif
103
104typedef struct HashBucket {
105 unsigned long key;
106 void *value;
107 struct HashBucket *next;
108} HashBucket, *HashBucketPtr;
109
110typedef struct HashTable {
111 unsigned long magic;
112 unsigned long entries;
113 unsigned long hits; /* At top of linked list */
114 unsigned long partials; /* Not at top of linked list */
115 unsigned long misses; /* Not in table */
116 HashBucketPtr buckets[HASH_SIZE];
117 int p0;
118 HashBucketPtr p1;
119} HashTable, *HashTablePtr;
120
121#if HASH_MAIN
122extern void *drmHashCreate(void);
123extern int drmHashDestroy(void *t);
124extern int drmHashLookup(void *t, unsigned long key, unsigned long *value);
125extern int drmHashInsert(void *t, unsigned long key, unsigned long value);
126extern int drmHashDelete(void *t, unsigned long key);
127#endif
128
129static unsigned long HashHash(unsigned long key)
130{
131 unsigned long hash = 0;
132 unsigned long tmp = key;
133 static int init = 0;
134 static unsigned long scatter[256];
135 int i;
136
137 if (!init) {
138 HASH_RANDOM_DECL;
139 HASH_RANDOM_INIT(37);
140 for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM;
141 HASH_RANDOM_DESTROY;
142 ++init;
143 }
144
145 while (tmp) {
146 hash = (hash << 1) + scatter[tmp & 0xff];
147 tmp >>= 8;
148 }
149
150 hash %= HASH_SIZE;
151#if HASH_DEBUG
152 printf( "Hash(%d) = %d\n", key, hash);
153#endif
154 return hash;
155}
156
157void *drmHashCreate(void)
158{
159 HashTablePtr table;
160 int i;
161
162 table = HASH_ALLOC(sizeof(*table));
163 if (!table) return NULL;
164 table->magic = HASH_MAGIC;
165 table->entries = 0;
166 table->hits = 0;
167 table->partials = 0;
168 table->misses = 0;
169
170 for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
171 return table;
172}
173
174int drmHashDestroy(void *t)
175{
176 HashTablePtr table = (HashTablePtr)t;
177 HashBucketPtr bucket;
178 HashBucketPtr next;
179 int i;
180
181 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
182
183 for (i = 0; i < HASH_SIZE; i++) {
184 for (bucket = table->buckets[i]; bucket;) {
185 next = bucket->next;
186 HASH_FREE(bucket);
187 bucket = next;
188 }
189 }
190 HASH_FREE(table);
191 return 0;
192}
193
194/* Find the bucket and organize the list so that this bucket is at the
195 top. */
196
197static HashBucketPtr HashFind(HashTablePtr table,
198 unsigned long key, unsigned long *h)
199{
200 unsigned long hash = HashHash(key);
201 HashBucketPtr prev = NULL;
202 HashBucketPtr bucket;
203
204 if (h) *h = hash;
205
206 for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
207 if (bucket->key == key) {
208 if (prev) {
209 /* Organize */
210 prev->next = bucket->next;
211 bucket->next = table->buckets[hash];
212 table->buckets[hash] = bucket;
213 ++table->partials;
214 } else {
215 ++table->hits;
216 }
217 return bucket;
218 }
219 prev = bucket;
220 }
221 ++table->misses;
222 return NULL;
223}
224
225int drmHashLookup(void *t, unsigned long key, void **value)
226{
227 HashTablePtr table = (HashTablePtr)t;
228 HashBucketPtr bucket;
229
230 if (!table || table->magic != HASH_MAGIC) return -1; /* Bad magic */
231
232 bucket = HashFind(table, key, NULL);
233 if (!bucket) return 1; /* Not found */
234 *value = bucket->value;
235 return 0; /* Found */
236}
237
238int drmHashInsert(void *t, unsigned long key, void *value)
239{
240 HashTablePtr table = (HashTablePtr)t;
241 HashBucketPtr bucket;
242 unsigned long hash;
243
244 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
245
246 if (HashFind(table, key, &hash)) return 1; /* Already in table */
247
248 bucket = HASH_ALLOC(sizeof(*bucket));
249 if (!bucket) return -1; /* Error */
250 bucket->key = key;
251 bucket->value = value;
252 bucket->next = table->buckets[hash];
253 table->buckets[hash] = bucket;
254#if HASH_DEBUG
255 printf("Inserted %d at %d/%p\n", key, hash, bucket);
256#endif
257 return 0; /* Added to table */
258}
259
260int drmHashDelete(void *t, unsigned long key)
261{
262 HashTablePtr table = (HashTablePtr)t;
263 unsigned long hash;
264 HashBucketPtr bucket;
265
266 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
267
268 bucket = HashFind(table, key, &hash);
269
270 if (!bucket) return 1; /* Not found */
271
272 table->buckets[hash] = bucket->next;
273 HASH_FREE(bucket);
274 return 0;
275}
276
277int drmHashNext(void *t, unsigned long *key, void **value)
278{
279 HashTablePtr table = (HashTablePtr)t;
280
281 while (table->p0 < HASH_SIZE) {
282 if (table->p1) {
283 *key = table->p1->key;
284 *value = table->p1->value;
285 table->p1 = table->p1->next;
286 return 1;
287 }
288 table->p1 = table->buckets[table->p0];
289 ++table->p0;
290 }
291 return 0;
292}
293
294int drmHashFirst(void *t, unsigned long *key, void **value)
295{
296 HashTablePtr table = (HashTablePtr)t;
297
298 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
299
300 table->p0 = 0;
301 table->p1 = table->buckets[0];
302 return drmHashNext(table, key, value);
303}
304
305#if HASH_MAIN
306#define DIST_LIMIT 10
307static int dist[DIST_LIMIT];
308
309static void clear_dist(void) {
310 int i;
311
312 for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
313}
314
315static int count_entries(HashBucketPtr bucket)
316{
317 int count = 0;
318
319 for (; bucket; bucket = bucket->next) ++count;
320 return count;
321}
322
323static void update_dist(int count)
324{
325 if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
326 else ++dist[count];
327}
328
329static void compute_dist(HashTablePtr table)
330{
331 int i;
332 HashBucketPtr bucket;
333
334 printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
335 table->entries, table->hits, table->partials, table->misses);
336 clear_dist();
337 for (i = 0; i < HASH_SIZE; i++) {
338 bucket = table->buckets[i];
339 update_dist(count_entries(bucket));
340 }
341 for (i = 0; i < DIST_LIMIT; i++) {
342 if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]);
343 else printf("other %10d\n", dist[i]);
344 }
345}
346
347static void check_table(HashTablePtr table,
348 unsigned long key, unsigned long value)
349{
350 unsigned long retval = 0;
351 int retcode = drmHashLookup(table, key, &retval);
352
353 switch (retcode) {
354 case -1:
355 printf("Bad magic = 0x%08lx:"
356 " key = %lu, expected = %lu, returned = %lu\n",
357 table->magic, key, value, retval);
358 break;
359 case 1:
360 printf("Not found: key = %lu, expected = %lu returned = %lu\n",
361 key, value, retval);
362 break;
363 case 0:
364 if (value != retval)
365 printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
366 key, value, retval);
367 break;
368 default:
369 printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
370 retcode, key, value, retval);
371 break;
372 }
373}
374
375int main(void)
376{
377 HashTablePtr table;
378 int i;
379
380 printf("\n***** 256 consecutive integers ****\n");
381 table = drmHashCreate();
382 for (i = 0; i < 256; i++) drmHashInsert(table, i, i);
383 for (i = 0; i < 256; i++) check_table(table, i, i);
384 for (i = 256; i >= 0; i--) check_table(table, i, i);
385 compute_dist(table);
386 drmHashDestroy(table);
387
388 printf("\n***** 1024 consecutive integers ****\n");
389 table = drmHashCreate();
390 for (i = 0; i < 1024; i++) drmHashInsert(table, i, i);
391 for (i = 0; i < 1024; i++) check_table(table, i, i);
392 for (i = 1024; i >= 0; i--) check_table(table, i, i);
393 compute_dist(table);
394 drmHashDestroy(table);
395
396 printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
397 table = drmHashCreate();
398 for (i = 0; i < 1024; i++) drmHashInsert(table, i*4096, i);
399 for (i = 0; i < 1024; i++) check_table(table, i*4096, i);
400 for (i = 1024; i >= 0; i--) check_table(table, i*4096, i);
401 compute_dist(table);
402 drmHashDestroy(table);
403
404 printf("\n***** 1024 random integers ****\n");
405 table = drmHashCreate();
406 srandom(0xbeefbeef);
407 for (i = 0; i < 1024; i++) drmHashInsert(table, random(), i);
408 srandom(0xbeefbeef);
409 for (i = 0; i < 1024; i++) check_table(table, random(), i);
410 srandom(0xbeefbeef);
411 for (i = 0; i < 1024; i++) check_table(table, random(), i);
412 compute_dist(table);
413 drmHashDestroy(table);
414
415 printf("\n***** 5000 random integers ****\n");
416 table = drmHashCreate();
417 srandom(0xbeefbeef);
418 for (i = 0; i < 5000; i++) drmHashInsert(table, random(), i);
419 srandom(0xbeefbeef);
420 for (i = 0; i < 5000; i++) check_table(table, random(), i);
421 srandom(0xbeefbeef);
422 for (i = 0; i < 5000; i++) check_table(table, random(), i);
423 compute_dist(table);
424 drmHashDestroy(table);
425
426 return 0;
427}
428#endif