1 /* glxhash.c -- Small hash table support for integer -> integer mapping
2 * Taken from libdrm.
3 *
4 * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
5 *
6 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
7 * All Rights Reserved.
8 *
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the "Software"),
11 * to deal in the Software without restriction, including without limitation
12 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 * and/or sell copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following conditions:
15 *
16 * The above copyright notice and this permission notice (including the next
17 * paragraph) shall be included in all copies or substantial portions of the
18 * Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
23 * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
24 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
25 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
26 * DEALINGS IN THE SOFTWARE.
27 *
28 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
29 *
30 * DESCRIPTION
31 *
32 * This file contains a straightforward implementation of a fixed-sized
33 * hash table using self-organizing linked lists [Knuth73, pp. 398-399] for
34 * collision resolution. There are two potentially interesting things
35 * about this implementation:
36 *
37 * 1) The table is power-of-two sized. Prime sized tables are more
38 * traditional, but do not have a significant advantage over power-of-two
39 * sized table, especially when double hashing is not used for collision
40 * resolution.
41 *
42 * 2) The hash computation uses a table of random integers [Hanson97,
43 * pp. 39-41].
44 *
45 * FUTURE ENHANCEMENTS
46 *
47 * With a table size of 512, the current implementation is sufficient for a
48 * few hundred keys. Since this is well above the expected size of the
49 * tables for which this implementation was designed, the implementation of
50 * dynamic hash tables was postponed until the need arises. A common (and
51 * naive) approach to dynamic hash table implementation simply creates a
52 * new hash table when necessary, rehashes all the data into the new table,
53 * and destroys the old table. The approach in [Larson88] is superior in
54 * two ways: 1) only a portion of the table is expanded when needed,
55 * distributing the expansion cost over several insertions, and 2) portions
56 * of the table can be locked, enabling a scalable thread-safe
57 * implementation.
58 *
59 * REFERENCES
60 *
61 * [Hanson97] David R. Hanson. C Interfaces and Implementations:
62 * Techniques for Creating Reusable Software. Reading, Massachusetts:
63 * Addison-Wesley, 1997.
64 *
65 * [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
66 * Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
67 *
68 * [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
69 * 1988, pp. 446-457.
70 *
71 */
72
73 #include "glxhash.h"
74 #include <X11/Xfuncproto.h>
75
76 #define HASH_MAIN 0
77
78 #include <stdio.h>
79 #include <stdlib.h>
80 #include <string.h>
81
82 #define HASH_MAGIC 0xdeadbeef
83 #define HASH_DEBUG 0
84 #define HASH_SIZE 512 /* Good for about 100 entries */
85 /* If you change this value, you probably
86 have to change the HashHash hashing
87 function! */
88
89 #define HASH_ALLOC malloc
90 #define HASH_FREE free
91 #ifndef HAVE_RANDOM_R
92 #define HASH_RANDOM_DECL char *ps, rs[256]
93 #define HASH_RANDOM_INIT(seed) ps = initstate(seed, rs, sizeof(rs))
94 #define HASH_RANDOM random()
95 #define HASH_RANDOM_DESTROY setstate(ps)
96 #else
97 #define HASH_RANDOM_DECL struct random_data rd; int32_t rv; char rs[256]
98 #define HASH_RANDOM_INIT(seed) \
99 do { \
100 (void) memset(&rd, 0, sizeof(rd)); \
101 (void) initstate_r(seed, rs, sizeof(rs), &rd); \
102 } while(0)
103 #define HASH_RANDOM ((void) random_r(&rd, &rv), rv)
104 #define HASH_RANDOM_DESTROY
105 #endif
106
107 typedef struct __glxHashBucket
108 {
109 unsigned long key;
110 void *value;
111 struct __glxHashBucket *next;
112 } __glxHashBucket, *__glxHashBucketPtr;
113
114 typedef struct __glxHashTable *__glxHashTablePtr;
115 struct __glxHashTable
116 {
117 unsigned long magic;
118 unsigned long hits; /* At top of linked list */
119 unsigned long partials; /* Not at top of linked list */
120 unsigned long misses; /* Not in table */
121 __glxHashBucketPtr buckets[HASH_SIZE];
122 int p0;
123 __glxHashBucketPtr p1;
124 };
125
126 static unsigned long
HashHash(unsigned long key)127 HashHash(unsigned long key)
128 {
129 unsigned long hash = 0;
130 unsigned long tmp = key;
131 static int init = 0;
132 static unsigned long scatter[256];
133 int i;
134
135 if (!init) {
136 HASH_RANDOM_DECL;
137 HASH_RANDOM_INIT(37);
138 for (i = 0; i < 256; i++)
139 scatter[i] = HASH_RANDOM;
140 HASH_RANDOM_DESTROY;
141 ++init;
142 }
143
144 while (tmp) {
145 hash = (hash << 1) + scatter[tmp & 0xff];
146 tmp >>= 8;
147 }
148
149 hash %= HASH_SIZE;
150 #if HASH_DEBUG
151 printf("Hash(%d) = %d\n", key, hash);
152 #endif
153 return hash;
154 }
155
156 _X_HIDDEN __glxHashTable *
__glxHashCreate(void)157 __glxHashCreate(void)
158 {
159 __glxHashTablePtr table;
160 int i;
161
162 table = HASH_ALLOC(sizeof(*table));
163 if (!table)
164 return NULL;
165 table->magic = HASH_MAGIC;
166 table->hits = 0;
167 table->partials = 0;
168 table->misses = 0;
169
170 for (i = 0; i < HASH_SIZE; i++)
171 table->buckets[i] = NULL;
172 return table;
173 }
174
175 _X_HIDDEN int
__glxHashDestroy(__glxHashTable * t)176 __glxHashDestroy(__glxHashTable * t)
177 {
178 __glxHashTablePtr table = (__glxHashTablePtr) t;
179 __glxHashBucketPtr bucket;
180 __glxHashBucketPtr next;
181 int i;
182
183 if (table->magic != HASH_MAGIC)
184 return -1; /* Bad magic */
185
186 for (i = 0; i < HASH_SIZE; i++) {
187 for (bucket = table->buckets[i]; bucket;) {
188 next = bucket->next;
189 HASH_FREE(bucket);
190 bucket = next;
191 }
192 }
193 HASH_FREE(table);
194 return 0;
195 }
196
197 /* Find the bucket and organize the list so that this bucket is at the
198 top. */
199
200 static __glxHashBucketPtr
HashFind(__glxHashTablePtr table,unsigned long key,unsigned long * h)201 HashFind(__glxHashTablePtr table, unsigned long key, unsigned long *h)
202 {
203 unsigned long hash = HashHash(key);
204 __glxHashBucketPtr prev = NULL;
205 __glxHashBucketPtr bucket;
206
207 if (h)
208 *h = hash;
209
210 for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
211 if (bucket->key == key) {
212 if (prev) {
213 /* Organize */
214 prev->next = bucket->next;
215 bucket->next = table->buckets[hash];
216 table->buckets[hash] = bucket;
217 ++table->partials;
218 }
219 else {
220 ++table->hits;
221 }
222 return bucket;
223 }
224 prev = bucket;
225 }
226 ++table->misses;
227 return NULL;
228 }
229
230 _X_HIDDEN int
__glxHashLookup(__glxHashTable * t,unsigned long key,void ** value)231 __glxHashLookup(__glxHashTable * t, unsigned long key, void **value)
232 {
233 __glxHashTablePtr table = (__glxHashTablePtr) t;
234 __glxHashBucketPtr bucket;
235
236 if (!table || table->magic != HASH_MAGIC)
237 return -1; /* Bad magic */
238
239 bucket = HashFind(table, key, NULL);
240 if (!bucket)
241 return 1; /* Not found */
242 *value = bucket->value;
243 return 0; /* Found */
244 }
245
246 _X_HIDDEN int
__glxHashInsert(__glxHashTable * t,unsigned long key,void * value)247 __glxHashInsert(__glxHashTable * t, unsigned long key, void *value)
248 {
249 __glxHashTablePtr table = (__glxHashTablePtr) t;
250 __glxHashBucketPtr bucket;
251 unsigned long hash;
252
253 if (table->magic != HASH_MAGIC)
254 return -1; /* Bad magic */
255
256 if (HashFind(table, key, &hash))
257 return 1; /* Already in table */
258
259 bucket = HASH_ALLOC(sizeof(*bucket));
260 if (!bucket)
261 return -1; /* Error */
262 bucket->key = key;
263 bucket->value = value;
264 bucket->next = table->buckets[hash];
265 table->buckets[hash] = bucket;
266 #if HASH_DEBUG
267 printf("Inserted %d at %d/%p\n", key, hash, bucket);
268 #endif
269 return 0; /* Added to table */
270 }
271
272 _X_HIDDEN int
__glxHashDelete(__glxHashTable * t,unsigned long key)273 __glxHashDelete(__glxHashTable * t, unsigned long key)
274 {
275 __glxHashTablePtr table = (__glxHashTablePtr) t;
276 unsigned long hash;
277 __glxHashBucketPtr bucket;
278
279 if (table->magic != HASH_MAGIC)
280 return -1; /* Bad magic */
281
282 bucket = HashFind(table, key, &hash);
283
284 if (!bucket)
285 return 1; /* Not found */
286
287 table->buckets[hash] = bucket->next;
288 HASH_FREE(bucket);
289 return 0;
290 }
291
292 _X_HIDDEN int
__glxHashNext(__glxHashTable * t,unsigned long * key,void ** value)293 __glxHashNext(__glxHashTable * t, unsigned long *key, void **value)
294 {
295 __glxHashTablePtr table = (__glxHashTablePtr) t;
296
297 while (table->p0 < HASH_SIZE) {
298 if (table->p1) {
299 *key = table->p1->key;
300 *value = table->p1->value;
301 table->p1 = table->p1->next;
302 return 1;
303 }
304 table->p1 = table->buckets[table->p0];
305 ++table->p0;
306 }
307 return 0;
308 }
309
310 _X_HIDDEN int
__glxHashFirst(__glxHashTable * t,unsigned long * key,void ** value)311 __glxHashFirst(__glxHashTable * t, unsigned long *key, void **value)
312 {
313 __glxHashTablePtr table = (__glxHashTablePtr) t;
314
315 if (table->magic != HASH_MAGIC)
316 return -1; /* Bad magic */
317
318 table->p0 = 0;
319 table->p1 = table->buckets[0];
320 return __glxHashNext(table, key, value);
321 }
322
323 #if HASH_MAIN
324 #define DIST_LIMIT 10
325 static int dist[DIST_LIMIT];
326
327 static void
clear_dist(void)328 clear_dist(void)
329 {
330 int i;
331
332 for (i = 0; i < DIST_LIMIT; i++)
333 dist[i] = 0;
334 }
335
336 static int
count_entries(__glxHashBucketPtr bucket)337 count_entries(__glxHashBucketPtr bucket)
338 {
339 int count = 0;
340
341 for (; bucket; bucket = bucket->next)
342 ++count;
343 return count;
344 }
345
346 static void
update_dist(int count)347 update_dist(int count)
348 {
349 if (count >= DIST_LIMIT)
350 ++dist[DIST_LIMIT - 1];
351 else
352 ++dist[count];
353 }
354
355 static void
compute_dist(__glxHashTablePtr table)356 compute_dist(__glxHashTablePtr table)
357 {
358 int i;
359 __glxHashBucketPtr bucket;
360
361 printf("Hits = %ld, partials = %ld, misses = %ld\n",
362 table->hits, table->partials, table->misses);
363 clear_dist();
364 for (i = 0; i < HASH_SIZE; i++) {
365 bucket = table->buckets[i];
366 update_dist(count_entries(bucket));
367 }
368 for (i = 0; i < DIST_LIMIT; i++) {
369 if (i != DIST_LIMIT - 1)
370 printf("%5d %10d\n", i, dist[i]);
371 else
372 printf("other %10d\n", dist[i]);
373 }
374 }
375
376 static void
check_table(__glxHashTablePtr table,unsigned long key,unsigned long value)377 check_table(__glxHashTablePtr table, unsigned long key, unsigned long value)
378 {
379 unsigned long retval = 0;
380 int retcode = __glxHashLookup(table, key, &retval);
381
382 switch (retcode) {
383 case -1:
384 printf("Bad magic = 0x%08lx:"
385 " key = %lu, expected = %lu, returned = %lu\n",
386 table->magic, key, value, retval);
387 break;
388 case 1:
389 printf("Not found: key = %lu, expected = %lu returned = %lu\n",
390 key, value, retval);
391 break;
392 case 0:
393 if (value != retval)
394 printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
395 key, value, retval);
396 break;
397 default:
398 printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
399 retcode, key, value, retval);
400 break;
401 }
402 }
403
404 int
main(void)405 main(void)
406 {
407 __glxHashTablePtr table;
408 int i;
409
410 printf("\n***** 256 consecutive integers ****\n");
411 table = __glxHashCreate();
412 for (i = 0; i < 256; i++)
413 __glxHashInsert(table, i, i);
414 for (i = 0; i < 256; i++)
415 check_table(table, i, i);
416 for (i = 256; i >= 0; i--)
417 check_table(table, i, i);
418 compute_dist(table);
419 __glxHashDestroy(table);
420
421 printf("\n***** 1024 consecutive integers ****\n");
422 table = __glxHashCreate();
423 for (i = 0; i < 1024; i++)
424 __glxHashInsert(table, i, i);
425 for (i = 0; i < 1024; i++)
426 check_table(table, i, i);
427 for (i = 1024; i >= 0; i--)
428 check_table(table, i, i);
429 compute_dist(table);
430 __glxHashDestroy(table);
431
432 printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
433 table = __glxHashCreate();
434 for (i = 0; i < 1024; i++)
435 __glxHashInsert(table, i * 4096, i);
436 for (i = 0; i < 1024; i++)
437 check_table(table, i * 4096, i);
438 for (i = 1024; i >= 0; i--)
439 check_table(table, i * 4096, i);
440 compute_dist(table);
441 __glxHashDestroy(table);
442
443 printf("\n***** 1024 random integers ****\n");
444 table = __glxHashCreate();
445 srandom(0xbeefbeef);
446 for (i = 0; i < 1024; i++)
447 __glxHashInsert(table, random(), i);
448 srandom(0xbeefbeef);
449 for (i = 0; i < 1024; i++)
450 check_table(table, random(), i);
451 srandom(0xbeefbeef);
452 for (i = 0; i < 1024; i++)
453 check_table(table, random(), i);
454 compute_dist(table);
455 __glxHashDestroy(table);
456
457 printf("\n***** 5000 random integers ****\n");
458 table = __glxHashCreate();
459 srandom(0xbeefbeef);
460 for (i = 0; i < 5000; i++)
461 __glxHashInsert(table, random(), i);
462 srandom(0xbeefbeef);
463 for (i = 0; i < 5000; i++)
464 check_table(table, random(), i);
465 srandom(0xbeefbeef);
466 for (i = 0; i < 5000; i++)
467 check_table(table, random(), i);
468 compute_dist(table);
469 __glxHashDestroy(table);
470
471 return 0;
472 }
473 #endif
474