sys/external/bsd/drm/dist/libdrm/xf86drmHash.c

   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
 104 typedef struct HashBucket {
 105     unsigned long     key;
 106     void              *value;
 107     struct HashBucket *next;
 108 } HashBucket, *HashBucketPtr;
 109
 110 typedef 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
 122 extern void *drmHashCreate(void);
 123 extern int  drmHashDestroy(void *t);
 124 extern int  drmHashLookup(void *t, unsigned long key, unsigned long *value);
 125 extern int  drmHashInsert(void *t, unsigned long key, unsigned long value);
 126 extern int  drmHashDelete(void *t, unsigned long key);
 127 #endif
 128
 129 static 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
 157 void *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
 174 int 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
 197 static 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
 225 int 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
 238 int 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
 260 int 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
 277 int 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
 294 int 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
 307 static int dist[DIST_LIMIT];
 308
 309 static void clear_dist(void) {
 310     int i;
 311
 312     for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
 313 }
 314
 315 static int count_entries(HashBucketPtr bucket)
 316 {
 317     int count = 0;
 318
 319     for (; bucket; bucket = bucket->next) ++count;
 320     return count;
 321 }
 322
 323 static void update_dist(int count)
 324 {
 325     if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
 326     else                     ++dist[count];
 327 }
 328
 329 static 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
 347 static 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
 375 int 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