summaryrefslogtreecommitdiff
path: root/src/glx/glxhash.c
blob: b76ec32345940c3020e0f5045d223f171e17e048 (plain)
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
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
/* glxhash.c -- Small hash table support for integer -> integer mapping
 * Taken from libdrm.
 *
 * 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 "glxhash.h"
#include <X11/Xfuncproto.h>

#define HASH_MAIN 0

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define HASH_MAGIC 0xdeadbeef
#define HASH_DEBUG 0
#define HASH_SIZE  512          /* Good for about 100 entries */
                                /* If you change this value, you probably
                                   have to change the HashHash hashing
                                   function! */

#define HASH_ALLOC malloc
#define HASH_FREE  free
#ifndef __GLIBC__
#define HASH_RANDOM_DECL	char *ps, rs[256]
#define HASH_RANDOM_INIT(seed)	ps = initstate(seed, rs, sizeof(rs))
#define HASH_RANDOM		random()
#define HASH_RANDOM_DESTROY	setstate(ps)
#else
#define HASH_RANDOM_DECL	struct random_data rd; int32_t rv; char rs[256]
#define HASH_RANDOM_INIT(seed)					\
   do {								\
      (void) memset(&rd, 0, sizeof(rd));			\
      (void) initstate_r(seed, rs, sizeof(rs), &rd);		\
   } while(0)
#define HASH_RANDOM             ((void) random_r(&rd, &rv), rv)
#define HASH_RANDOM_DESTROY
#endif

typedef struct __glxHashBucket
{
   unsigned long key;
   void *value;
   struct __glxHashBucket *next;
} __glxHashBucket, *__glxHashBucketPtr;

typedef struct __glxHashTable *__glxHashTablePtr;
struct __glxHashTable
{
   unsigned long magic;
   unsigned long hits;          /* At top of linked list */
   unsigned long partials;      /* Not at top of linked list */
   unsigned long misses;        /* Not in table */
   __glxHashBucketPtr buckets[HASH_SIZE];
   int p0;
   __glxHashBucketPtr p1;
};

static unsigned long
HashHash(unsigned long key)
{
   unsigned long hash = 0;
   unsigned long tmp = key;
   static int init = 0;
   static unsigned long scatter[256];
   int i;

   if (!init) {
      HASH_RANDOM_DECL;
      HASH_RANDOM_INIT(37);
      for (i = 0; i < 256; i++)
         scatter[i] = HASH_RANDOM;
      HASH_RANDOM_DESTROY;
      ++init;
   }

   while (tmp) {
      hash = (hash << 1) + scatter[tmp & 0xff];
      tmp >>= 8;
   }

   hash %= HASH_SIZE;
#if HASH_DEBUG
   printf("Hash(%d) = %d\n", key, hash);
#endif
   return hash;
}

_X_HIDDEN __glxHashTable *
__glxHashCreate(void)
{
   __glxHashTablePtr table;
   int i;

   table = HASH_ALLOC(sizeof(*table));
   if (!table)
      return NULL;
   table->magic = HASH_MAGIC;
   table->hits = 0;
   table->partials = 0;
   table->misses = 0;

   for (i = 0; i < HASH_SIZE; i++)
      table->buckets[i] = NULL;
   return table;
}

_X_HIDDEN int
__glxHashDestroy(__glxHashTable * t)
{
   __glxHashTablePtr table = (__glxHashTablePtr) t;
   __glxHashBucketPtr bucket;
   __glxHashBucketPtr next;
   int i;

   if (table->magic != HASH_MAGIC)
      return -1;                /* Bad magic */

   for (i = 0; i < HASH_SIZE; i++) {
      for (bucket = table->buckets[i]; bucket;) {
         next = bucket->next;
         HASH_FREE(bucket);
         bucket = next;
      }
   }
   HASH_FREE(table);
   return 0;
}

/* Find the bucket and organize the list so that this bucket is at the
   top. */

static __glxHashBucketPtr
HashFind(__glxHashTablePtr table, unsigned long key, unsigned long *h)
{
   unsigned long hash = HashHash(key);
   __glxHashBucketPtr prev = NULL;
   __glxHashBucketPtr bucket;

   if (h)
      *h = hash;

   for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
      if (bucket->key == key) {
         if (prev) {
            /* Organize */
            prev->next = bucket->next;
            bucket->next = table->buckets[hash];
            table->buckets[hash] = bucket;
            ++table->partials;
         }
         else {
            ++table->hits;
         }
         return bucket;
      }
      prev = bucket;
   }
   ++table->misses;
   return NULL;
}

_X_HIDDEN int
__glxHashLookup(__glxHashTable * t, unsigned long key, void **value)
{
   __glxHashTablePtr table = (__glxHashTablePtr) t;
   __glxHashBucketPtr bucket;

   if (!table || table->magic != HASH_MAGIC)
      return -1;                /* Bad magic */

   bucket = HashFind(table, key, NULL);
   if (!bucket)
      return 1;                 /* Not found */
   *value = bucket->value;
   return 0;                    /* Found */
}

_X_HIDDEN int
__glxHashInsert(__glxHashTable * t, unsigned long key, void *value)
{
   __glxHashTablePtr table = (__glxHashTablePtr) t;
   __glxHashBucketPtr bucket;
   unsigned long hash;

   if (table->magic != HASH_MAGIC)
      return -1;                /* Bad magic */

   if (HashFind(table, key, &hash))
      return 1;                 /* Already in table */

   bucket = HASH_ALLOC(sizeof(*bucket));
   if (!bucket)
      return -1;                /* Error */
   bucket->key = key;
   bucket->value = value;
   bucket->next = table->buckets[hash];
   table->buckets[hash] = bucket;
#if HASH_DEBUG
   printf("Inserted %d at %d/%p\n", key, hash, bucket);
#endif
   return 0;                    /* Added to table */
}

_X_HIDDEN int
__glxHashDelete(__glxHashTable * t, unsigned long key)
{
   __glxHashTablePtr table = (__glxHashTablePtr) t;
   unsigned long hash;
   __glxHashBucketPtr bucket;

   if (table->magic != HASH_MAGIC)
      return -1;                /* Bad magic */

   bucket = HashFind(table, key, &hash);

   if (!bucket)
      return 1;                 /* Not found */

   table->buckets[hash] = bucket->next;
   HASH_FREE(bucket);
   return 0;
}

_X_HIDDEN int
__glxHashNext(__glxHashTable * t, unsigned long *key, void **value)
{
   __glxHashTablePtr table = (__glxHashTablePtr) t;

   while (table->p0 < HASH_SIZE) {
      if (table->p1) {
         *key = table->p1->key;
         *value = table->p1->value;
         table->p1 = table->p1->next;
         return 1;
      }
      table->p1 = table->buckets[table->p0];
      ++table->p0;
   }
   return 0;
}

_X_HIDDEN int
__glxHashFirst(__glxHashTable * t, unsigned long *key, void **value)
{
   __glxHashTablePtr table = (__glxHashTablePtr) t;

   if (table->magic != HASH_MAGIC)
      return -1;                /* Bad magic */

   table->p0 = 0;
   table->p1 = table->buckets[0];
   return __glxHashNext(table, key, value);
}

#if HASH_MAIN
#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(__glxHashBucketPtr 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(__glxHashTablePtr table)
{
   int i;
   __glxHashBucketPtr bucket;

   printf("Hits = %ld, partials = %ld, misses = %ld\n",
          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 void
check_table(__glxHashTablePtr table, unsigned long key, unsigned long value)
{
   unsigned long retval = 0;
   int retcode = __glxHashLookup(table, key, &retval);

   switch (retcode) {
   case -1:
      printf("Bad magic = 0x%08lx:"
             " key = %lu, expected = %lu, returned = %lu\n",
             table->magic, key, value, retval);
      break;
   case 1:
      printf("Not found: key = %lu, expected = %lu returned = %lu\n",
             key, value, retval);
      break;
   case 0:
      if (value != retval)
         printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
                key, value, retval);
      break;
   default:
      printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
             retcode, key, value, retval);
      break;
   }
}

int
main(void)
{
   __glxHashTablePtr table;
   int i;

   printf("\n***** 256 consecutive integers ****\n");
   table = __glxHashCreate();
   for (i = 0; i < 256; i++)
      __glxHashInsert(table, i, i);
   for (i = 0; i < 256; i++)
      check_table(table, i, i);
   for (i = 256; i >= 0; i--)
      check_table(table, i, i);
   compute_dist(table);
   __glxHashDestroy(table);

   printf("\n***** 1024 consecutive integers ****\n");
   table = __glxHashCreate();
   for (i = 0; i < 1024; i++)
      __glxHashInsert(table, i, i);
   for (i = 0; i < 1024; i++)
      check_table(table, i, i);
   for (i = 1024; i >= 0; i--)
      check_table(table, i, i);
   compute_dist(table);
   __glxHashDestroy(table);

   printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
   table = __glxHashCreate();
   for (i = 0; i < 1024; i++)
      __glxHashInsert(table, i * 4096, i);
   for (i = 0; i < 1024; i++)
      check_table(table, i * 4096, i);
   for (i = 1024; i >= 0; i--)
      check_table(table, i * 4096, i);
   compute_dist(table);
   __glxHashDestroy(table);

   printf("\n***** 1024 random integers ****\n");
   table = __glxHashCreate();
   srandom(0xbeefbeef);
   for (i = 0; i < 1024; i++)
      __glxHashInsert(table, random(), i);
   srandom(0xbeefbeef);
   for (i = 0; i < 1024; i++)
      check_table(table, random(), i);
   srandom(0xbeefbeef);
   for (i = 0; i < 1024; i++)
      check_table(table, random(), i);
   compute_dist(table);
   __glxHashDestroy(table);

   printf("\n***** 5000 random integers ****\n");
   table = __glxHashCreate();
   srandom(0xbeefbeef);
   for (i = 0; i < 5000; i++)
      __glxHashInsert(table, random(), i);
   srandom(0xbeefbeef);
   for (i = 0; i < 5000; i++)
      check_table(table, random(), i);
   srandom(0xbeefbeef);
   for (i = 0; i < 5000; i++)
      check_table(table, random(), i);
   compute_dist(table);
   __glxHashDestroy(table);

   return 0;
}
#endif