src/mesa/drivers/dri/dri_client/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  * $XFree86: xc/programs/Xserver/hw/xfree86/os-support/linux/drm/xf86drmHash.c,v 1.4 2001/03/21 18:08:54 dawes Exp $
  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 #define HASH_MAIN 0
  74
  75 #if HASH_MAIN
  76 # include <stdio.h>
  77 # include <stdlib.h>
  78 #else
  79 # include "xf86drm.h"
  80 # ifdef XFree86LOADER
  81 #  include "xf86.h"
  82 #  include "xf86_ansic.h"
  83 # else
  84 #  include <stdio.h>
  85 #  include <stdlib.h>
  86 # endif
  87 #endif
  88
  89 #define HASH_MAGIC 0xdeadbeef
  90 #define HASH_DEBUG 0
  91 #define HASH_SIZE  512          /* Good for about 100 entries */
  92                                 /* If you change this value, you probably
  93                                    have to change the HashHash hashing
  94                                    function! */
  95
  96 #if HASH_MAIN
  97 #define HASH_ALLOC malloc
  98 #define HASH_FREE  free
  99 #define HASH_RANDOM_DECL
 100 #define HASH_RANDOM_INIT(seed)  srandom(seed)
 101 #define HASH_RANDOM             random()
 102 #else
 103 #define HASH_ALLOC drmMalloc
 104 #define HASH_FREE  drmFree
 105 #define HASH_RANDOM_DECL        void *state
 106 #define HASH_RANDOM_INIT(seed)  state = drmRandomCreate(seed)
 107 #define HASH_RANDOM             drmRandom(state)
 108
 109 #endif
 110
 111 typedef struct HashBucket {
 112     unsigned long     key;
 113     void              *value;
 114     struct HashBucket *next;
 115 } HashBucket, *HashBucketPtr;
 116
 117 typedef struct HashTable {
 118     unsigned long    magic;
 119     unsigned long    entries;
 120     unsigned long    hits;      /* At top of linked list */
 121     unsigned long    partials;  /* Not at top of linked list */
 122     unsigned long    misses;    /* Not in table */
 123     HashBucketPtr    buckets[HASH_SIZE];
 124     int              p0;
 125     HashBucketPtr    p1;
 126 } HashTable, *HashTablePtr;
 127
 128 #if HASH_MAIN
 129 extern void *drmHashCreate(void);
 130 extern int  drmHashDestroy(void *t);
 131 extern int  drmHashLookup(void *t, unsigned long key, unsigned long *value);
 132 extern int  drmHashInsert(void *t, unsigned long key, unsigned long value);
 133 extern int  drmHashDelete(void *t, unsigned long key);
 134 #endif
 135
 136 static unsigned long HashHash(unsigned long key)
 137 {
 138     unsigned long        hash = 0;
 139     unsigned long        tmp  = key;
 140     static int           init = 0;
 141     static unsigned long scatter[256];
 142     int                  i;
 143
 144     if (!init) {
 145         HASH_RANDOM_DECL;
 146         HASH_RANDOM_INIT(37);
 147         for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM;
 148         ++init;
 149     }
 150
 151     while (tmp) {
 152         hash = (hash << 1) + scatter[tmp & 0xff];
 153         tmp >>= 8;
 154     }
 155
 156     hash %= HASH_SIZE;
 157 #if HASH_DEBUG
 158     printf( "Hash(%d) = %d\n", key, hash);
 159 #endif
 160     return hash;
 161 }
 162
 163 void *drmHashCreate(void)
 164 {
 165     HashTablePtr table;
 166     int          i;
 167
 168     table           = HASH_ALLOC(sizeof(*table));
 169     if (!table) return NULL;
 170     table->magic    = HASH_MAGIC;
 171     table->entries  = 0;
 172     table->hits     = 0;
 173     table->partials = 0;
 174     table->misses   = 0;
 175
 176     for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
 177     return table;
 178 }
 179
 180 int drmHashDestroy(void *t)
 181 {
 182     HashTablePtr  table = (HashTablePtr)t;
 183     HashBucketPtr bucket;
 184     HashBucketPtr next;
 185     int           i;
 186
 187     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 188
 189     for (i = 0; i < HASH_SIZE; i++) {
 190         for (bucket = table->buckets[i]; bucket;) {
 191             next = bucket->next;
 192             HASH_FREE(bucket);
 193             bucket = next;
 194         }
 195     }
 196     HASH_FREE(table);
 197     return 0;
 198 }
 199
 200 /* Find the bucket and organize the list so that this bucket is at the
 201    top. */
 202
 203 static HashBucketPtr HashFind(HashTablePtr table,
 204                               unsigned long key, unsigned long *h)
 205 {
 206     unsigned long hash = HashHash(key);
 207     HashBucketPtr prev = NULL;
 208     HashBucketPtr bucket;
 209
 210     if (h) *h = hash;
 211
 212     for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
 213         if (bucket->key == key) {
 214             if (prev) {
 215                                 /* Organize */
 216                 prev->next           = bucket->next;
 217                 bucket->next         = table->buckets[hash];
 218                 table->buckets[hash] = bucket;
 219                 ++table->partials;
 220             } else {
 221                 ++table->hits;
 222             }
 223             return bucket;
 224         }
 225         prev = bucket;
 226     }
 227     ++table->misses;
 228     return NULL;
 229 }
 230
 231 int drmHashLookup(void *t, unsigned long key, void **value)
 232 {
 233     HashTablePtr  table = (HashTablePtr)t;
 234     HashBucketPtr bucket;
 235
 236     if (!table || table->magic != HASH_MAGIC) return -1; /* Bad magic */
 237
 238     bucket = HashFind(table, key, NULL);
 239     if (!bucket) return 1;      /* Not found */
 240     *value = bucket->value;
 241     return 0;                   /* Found */
 242 }
 243
 244 int drmHashInsert(void *t, unsigned long key, void *value)
 245 {
 246     HashTablePtr  table = (HashTablePtr)t;
 247     HashBucketPtr bucket;
 248     unsigned long hash;
 249
 250     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 251
 252     if (HashFind(table, key, &hash)) return 1; /* Already in table */
 253
 254     bucket               = HASH_ALLOC(sizeof(*bucket));
 255     if (!bucket) return -1;     /* Error */
 256     bucket->key          = key;
 257     bucket->value        = value;
 258     bucket->next         = table->buckets[hash];
 259     table->buckets[hash] = bucket;
 260 #if HASH_DEBUG
 261     printf("Inserted %d at %d/%p\n", key, hash, bucket);
 262 #endif
 263     return 0;                   /* Added to table */
 264 }
 265
 266 int drmHashDelete(void *t, unsigned long key)
 267 {
 268     HashTablePtr  table = (HashTablePtr)t;
 269     unsigned long hash;
 270     HashBucketPtr bucket;
 271
 272     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 273
 274     bucket = HashFind(table, key, &hash);
 275
 276     if (!bucket) return 1;      /* Not found */
 277
 278     table->buckets[hash] = bucket->next;
 279     HASH_FREE(bucket);
 280     return 0;
 281 }
 282
 283 int drmHashNext(void *t, unsigned long *key, void **value)
 284 {
 285     HashTablePtr  table = (HashTablePtr)t;
 286
 287     for (; table->p0 < HASH_SIZE;
 288          ++table->p0, table->p1 = table->buckets[table->p0]) {
 289         if (table->p1) {
 290             *key       = table->p1->key;
 291             *value     = table->p1->value;
 292             table->p1  = table->p1->next;
 293             return 1;
 294         }
 295     }
 296     return 0;
 297 }
 298
 299 int drmHashFirst(void *t, unsigned long *key, void **value)
 300 {
 301     HashTablePtr  table = (HashTablePtr)t;
 302
 303     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 304
 305     table->p0 = 0;
 306     table->p1 = table->buckets[0];
 307     return drmHashNext(table, key, value);
 308 }
 309
 310 #if HASH_MAIN
 311 #define DIST_LIMIT 10
 312 static int dist[DIST_LIMIT];
 313
 314 static void clear_dist(void) {
 315     int i;
 316
 317     for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
 318 }
 319
 320 static int count_entries(HashBucketPtr bucket)
 321 {
 322     int count = 0;
 323
 324     for (; bucket; bucket = bucket->next) ++count;
 325     return count;
 326 }
 327
 328 static void update_dist(int count)
 329 {
 330     if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
 331     else                     ++dist[count];
 332 }
 333
 334 static void compute_dist(HashTablePtr table)
 335 {
 336     int           i;
 337     HashBucketPtr bucket;
 338
 339     printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
 340            table->entries, table->hits, table->partials, table->misses);
 341     clear_dist();
 342     for (i = 0; i < HASH_SIZE; i++) {
 343         bucket = table->buckets[i];
 344         update_dist(count_entries(bucket));
 345     }
 346     for (i = 0; i < DIST_LIMIT; i++) {
 347         if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]);
 348         else                   printf("other %10d\n", dist[i]);
 349     }
 350 }
 351
 352 static void check_table(HashTablePtr table,
 353                         unsigned long key, unsigned long value)
 354 {
 355     unsigned long retval  = 0;
 356     int           retcode = drmHashLookup(table, key, &retval);
 357
 358     switch (retcode) {
 359     case -1:
 360         printf("Bad magic = 0x%08lx:"
 361                " key = %lu, expected = %lu, returned = %lu\n",
 362                table->magic, key, value, retval);
 363         break;
 364     case 1:
 365         printf("Not found: key = %lu, expected = %lu returned = %lu\n",
 366                key, value, retval);
 367         break;
 368     case 0:
 369         if (value != retval)
 370             printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
 371                    key, value, retval);
 372         break;
 373     default:
 374         printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
 375                retcode, key, value, retval);
 376         break;
 377     }
 378 }
 379
 380 int main(void)
 381 {
 382     HashTablePtr table;
 383     int          i;
 384
 385     printf("\n***** 256 consecutive integers ****\n");
 386     table = drmHashCreate();
 387     for (i = 0; i < 256; i++) drmHashInsert(table, i, i);
 388     for (i = 0; i < 256; i++) check_table(table, i, i);
 389     for (i = 256; i >= 0; i--) check_table(table, i, i);
 390     compute_dist(table);
 391     drmHashDestroy(table);
 392
 393     printf("\n***** 1024 consecutive integers ****\n");
 394     table = drmHashCreate();
 395     for (i = 0; i < 1024; i++) drmHashInsert(table, i, i);
 396     for (i = 0; i < 1024; i++) check_table(table, i, i);
 397     for (i = 1024; i >= 0; i--) check_table(table, i, i);
 398     compute_dist(table);
 399     drmHashDestroy(table);
 400
 401     printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
 402     table = drmHashCreate();
 403     for (i = 0; i < 1024; i++) drmHashInsert(table, i*4096, i);
 404     for (i = 0; i < 1024; i++) check_table(table, i*4096, i);
 405     for (i = 1024; i >= 0; i--) check_table(table, i*4096, i);
 406     compute_dist(table);
 407     drmHashDestroy(table);
 408
 409     printf("\n***** 1024 random integers ****\n");
 410     table = drmHashCreate();
 411     srandom(0xbeefbeef);
 412     for (i = 0; i < 1024; i++) drmHashInsert(table, random(), i);
 413     srandom(0xbeefbeef);
 414     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 415     srandom(0xbeefbeef);
 416     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 417     compute_dist(table);
 418     drmHashDestroy(table);
 419
 420     printf("\n***** 5000 random integers ****\n");
 421     table = drmHashCreate();
 422     srandom(0xbeefbeef);
 423     for (i = 0; i < 5000; i++) drmHashInsert(table, random(), i);
 424     srandom(0xbeefbeef);
 425     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 426     srandom(0xbeefbeef);
 427     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 428     compute_dist(table);
 429     drmHashDestroy(table);
 430
 431     return 0;
 432 }
 433 #endif