src/glx/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 #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
 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 *
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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