src/glx/x11/glxhash.c

   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
  81 #define HASH_MAGIC 0xdeadbeef
  82 #define HASH_DEBUG 0
  83 #define HASH_SIZE  512          /* Good for about 100 entries */
  84                                 /* If you change this value, you probably
  85                                    have to change the HashHash hashing
  86                                    function! */
  87
  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
  95 typedef struct __glxHashBucket
  96 {
  97    unsigned long key;
  98    void *value;
  99    struct __glxHashBucket *next;
 100 } __glxHashBucket, *__glxHashBucketPtr;
 101
 102 typedef struct __glxHashTable *__glxHashTablePtr;
 103 struct __glxHashTable
 104 {
 105    unsigned long magic;
 106    unsigned long hits;          /* At top of linked list */
 107    unsigned long partials;      /* Not at top of linked list */
 108    unsigned long misses;        /* Not in table */
 109    __glxHashBucketPtr buckets[HASH_SIZE];
 110    int p0;
 111    __glxHashBucketPtr p1;
 112 };
 113
 114 static unsigned long
 115 HashHash(unsigned long key)
 116 {
 117    unsigned long hash = 0;
 118    unsigned long tmp = key;
 119    static int init = 0;
 120    static unsigned long scatter[256];
 121    int i;
 122
 123    if (!init) {
 124       HASH_RANDOM_DECL;
 125       HASH_RANDOM_INIT(37);
 126       for (i = 0; i < 256; i++)
 127          scatter[i] = HASH_RANDOM;
 128       HASH_RANDOM_DESTROY;
 129       ++init;
 130    }
 131
 132    while (tmp) {
 133       hash = (hash << 1) + scatter[tmp & 0xff];
 134       tmp >>= 8;
 135    }
 136
 137    hash %= HASH_SIZE;
 138 #if HASH_DEBUG
 139    printf("Hash(%d) = %d\n", key, hash);
 140 #endif
 141    return hash;
 142 }
 143
 144 _X_HIDDEN __glxHashTable *
 145 __glxHashCreate(void)
 146 {
 147    __glxHashTablePtr table;
 148    int i;
 149
 150    table = HASH_ALLOC(sizeof(*table));
 151    if (!table)
 152       return NULL;
 153    table->magic = HASH_MAGIC;
 154    table->hits = 0;
 155    table->partials = 0;
 156    table->misses = 0;
 157
 158    for (i = 0; i < HASH_SIZE; i++)
 159       table->buckets[i] = NULL;
 160    return table;
 161 }
 162
 163 _X_HIDDEN int
 164 __glxHashDestroy(__glxHashTable * t)
 165 {
 166    __glxHashTablePtr table = (__glxHashTablePtr) t;
 167    __glxHashBucketPtr bucket;
 168    __glxHashBucketPtr next;
 169    int i;
 170
 171    if (table->magic != HASH_MAGIC)
 172       return -1;                /* Bad magic */
 173
 174    for (i = 0; i < HASH_SIZE; i++) {
 175       for (bucket = table->buckets[i]; bucket;) {
 176          next = bucket->next;
 177          HASH_FREE(bucket);
 178          bucket = next;
 179       }
 180    }
 181    HASH_FREE(table);
 182    return 0;
 183 }
 184
 185 /* Find the bucket and organize the list so that this bucket is at the
 186    top. */
 187
 188 static __glxHashBucketPtr
 189 HashFind(__glxHashTablePtr table, unsigned long key, unsigned long *h)
 190 {
 191    unsigned long hash = HashHash(key);
 192    __glxHashBucketPtr prev = NULL;
 193    __glxHashBucketPtr bucket;
 194
 195    if (h)
 196       *h = hash;
 197
 198    for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
 199       if (bucket->key == key) {
 200          if (prev) {
 201             /* Organize */
 202             prev->next = bucket->next;
 203             bucket->next = table->buckets[hash];
 204             table->buckets[hash] = bucket;
 205             ++table->partials;
 206          }
 207          else {
 208             ++table->hits;
 209          }
 210          return bucket;
 211       }
 212       prev = bucket;
 213    }
 214    ++table->misses;
 215    return NULL;
 216 }
 217
 218 _X_HIDDEN int
 219 __glxHashLookup(__glxHashTable * t, unsigned long key, void **value)
 220 {
 221    __glxHashTablePtr table = (__glxHashTablePtr) t;
 222    __glxHashBucketPtr bucket;
 223
 224    if (!table || table->magic != HASH_MAGIC)
 225       return -1;                /* Bad magic */
 226
 227    bucket = HashFind(table, key, NULL);
 228    if (!bucket)
 229       return 1;                 /* Not found */
 230    *value = bucket->value;
 231    return 0;                    /* Found */
 232 }
 233
 234 _X_HIDDEN int
 235 __glxHashInsert(__glxHashTable * t, unsigned long key, void *value)
 236 {
 237    __glxHashTablePtr table = (__glxHashTablePtr) t;
 238    __glxHashBucketPtr bucket;
 239    unsigned long hash;
 240
 241    if (table->magic != HASH_MAGIC)
 242       return -1;                /* Bad magic */
 243
 244    if (HashFind(table, key, &hash))
 245       return 1;                 /* Already in table */
 246
 247    bucket = HASH_ALLOC(sizeof(*bucket));
 248    if (!bucket)
 249       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
 260 _X_HIDDEN int
 261 __glxHashDelete(__glxHashTable * t, unsigned long key)
 262 {
 263    __glxHashTablePtr table = (__glxHashTablePtr) t;
 264    unsigned long hash;
 265    __glxHashBucketPtr bucket;
 266
 267    if (table->magic != HASH_MAGIC)
 268       return -1;                /* Bad magic */
 269
 270    bucket = HashFind(table, key, &hash);
 271
 272    if (!bucket)
 273       return 1;                 /* Not found */
 274
 275    table->buckets[hash] = bucket->next;
 276    HASH_FREE(bucket);
 277    return 0;
 278 }
 279
 280 _X_HIDDEN int
 281 __glxHashNext(__glxHashTable * t, unsigned long *key, void **value)
 282 {
 283    __glxHashTablePtr table = (__glxHashTablePtr) t;
 284
 285    while (table->p0 < HASH_SIZE) {
 286       if (table->p1) {
 287          *key = table->p1->key;
 288          *value = table->p1->value;
 289          table->p1 = table->p1->next;
 290          return 1;
 291       }
 292       table->p1 = table->buckets[table->p0];
 293       ++table->p0;
 294    }
 295    return 0;
 296 }
 297
 298 _X_HIDDEN int
 299 __glxHashFirst(__glxHashTable * t, unsigned long *key, void **value)
 300 {
 301    __glxHashTablePtr table = (__glxHashTablePtr) t;
 302
 303    if (table->magic != HASH_MAGIC)
 304       return -1;                /* Bad magic */
 305
 306    table->p0 = 0;
 307    table->p1 = table->buckets[0];
 308    return __glxHashNext(table, key, value);
 309 }
 310
 311 #if HASH_MAIN
 312 #define DIST_LIMIT 10
 313 static int dist[DIST_LIMIT];
 314
 315 static void
 316 clear_dist(void)
 317 {
 318    int i;
 319
 320    for (i = 0; i < DIST_LIMIT; i++)
 321       dist[i] = 0;
 322 }
 323
 324 static int
 325 count_entries(__glxHashBucketPtr bucket)
 326 {
 327    int count = 0;
 328
 329    for (; bucket; bucket = bucket->next)
 330       ++count;
 331    return count;
 332 }
 333
 334 static void
 335 update_dist(int count)
 336 {
 337    if (count >= DIST_LIMIT)
 338       ++dist[DIST_LIMIT - 1];
 339    else
 340       ++dist[count];
 341 }
 342
 343 static void
 344 compute_dist(__glxHashTablePtr table)
 345 {
 346    int i;
 347    __glxHashBucketPtr bucket;
 348
 349    printf("Hits = %ld, partials = %ld, misses = %ld\n",
 350           table->hits, table->partials, table->misses);
 351    clear_dist();
 352    for (i = 0; i < HASH_SIZE; i++) {
 353       bucket = table->buckets[i];
 354       update_dist(count_entries(bucket));
 355    }
 356    for (i = 0; i < DIST_LIMIT; i++) {
 357       if (i != DIST_LIMIT - 1)
 358          printf("%5d %10d\n", i, dist[i]);
 359       else
 360          printf("other %10d\n", dist[i]);
 361    }
 362 }
 363
 364 static void
 365 check_table(__glxHashTablePtr table, unsigned long key, unsigned long value)
 366 {
 367    unsigned long retval = 0;
 368    int retcode = __glxHashLookup(table, key, &retval);
 369
 370    switch (retcode) {
 371    case -1:
 372       printf("Bad magic = 0x%08lx:"
 373              " key = %lu, expected = %lu, returned = %lu\n",
 374              table->magic, key, value, retval);
 375       break;
 376    case 1:
 377       printf("Not found: key = %lu, expected = %lu returned = %lu\n",
 378              key, value, retval);
 379       break;
 380    case 0:
 381       if (value != retval)
 382          printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
 383                 key, value, retval);
 384       break;
 385    default:
 386       printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
 387              retcode, key, value, retval);
 388       break;
 389    }
 390 }
 391
 392 int
 393 main(void)
 394 {
 395    __glxHashTablePtr table;
 396    int i;
 397
 398    printf("\n***** 256 consecutive integers ****\n");
 399    table = __glxHashCreate();
 400    for (i = 0; i < 256; i++)
 401       __glxHashInsert(table, i, i);
 402    for (i = 0; i < 256; i++)
 403       check_table(table, i, i);
 404    for (i = 256; i >= 0; i--)
 405       check_table(table, i, i);
 406    compute_dist(table);
 407    __glxHashDestroy(table);
 408
 409    printf("\n***** 1024 consecutive integers ****\n");
 410    table = __glxHashCreate();
 411    for (i = 0; i < 1024; i++)
 412       __glxHashInsert(table, i, i);
 413    for (i = 0; i < 1024; i++)
 414       check_table(table, i, i);
 415    for (i = 1024; i >= 0; i--)
 416       check_table(table, i, i);
 417    compute_dist(table);
 418    __glxHashDestroy(table);
 419
 420    printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
 421    table = __glxHashCreate();
 422    for (i = 0; i < 1024; i++)
 423       __glxHashInsert(table, i * 4096, i);
 424    for (i = 0; i < 1024; i++)
 425       check_table(table, i * 4096, i);
 426    for (i = 1024; i >= 0; i--)
 427       check_table(table, i * 4096, i);
 428    compute_dist(table);
 429    __glxHashDestroy(table);
 430
 431    printf("\n***** 1024 random integers ****\n");
 432    table = __glxHashCreate();
 433    srandom(0xbeefbeef);
 434    for (i = 0; i < 1024; i++)
 435       __glxHashInsert(table, random(), i);
 436    srandom(0xbeefbeef);
 437    for (i = 0; i < 1024; i++)
 438       check_table(table, random(), i);
 439    srandom(0xbeefbeef);
 440    for (i = 0; i < 1024; i++)
 441       check_table(table, random(), i);
 442    compute_dist(table);
 443    __glxHashDestroy(table);
 444
 445    printf("\n***** 5000 random integers ****\n");
 446    table = __glxHashCreate();
 447    srandom(0xbeefbeef);
 448    for (i = 0; i < 5000; i++)
 449       __glxHashInsert(table, random(), i);
 450    srandom(0xbeefbeef);
 451    for (i = 0; i < 5000; i++)
 452       check_table(table, random(), i);
 453    srandom(0xbeefbeef);
 454    for (i = 0; i < 5000; i++)
 455       check_table(table, random(), i);
 456    compute_dist(table);
 457    __glxHashDestroy(table);
 458
 459    return 0;
 460 }
 461 #endif