cc283d3c86
Now that xenocara has been made clean with respect to using kernel headers instead of those provided with libdrm, remove the copy of the headers included here. Since it is now very simple, move it over to using standard bsd makefiles instead of autoconf. ok matthieu@
429 lines
12 KiB
C
429 lines
12 KiB
C
/* xf86drmHash.c -- Small hash table support for integer -> integer mapping
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* Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
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*
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* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* Authors: Rickard E. (Rik) Faith <faith@valinux.com>
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*
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* DESCRIPTION
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*
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* This file contains a straightforward implementation of a fixed-sized
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* hash table using self-organizing linked lists [Knuth73, pp. 398-399] for
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* collision resolution. There are two potentially interesting things
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* about this implementation:
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*
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* 1) The table is power-of-two sized. Prime sized tables are more
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* traditional, but do not have a significant advantage over power-of-two
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* sized table, especially when double hashing is not used for collision
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* resolution.
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*
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* 2) The hash computation uses a table of random integers [Hanson97,
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* pp. 39-41].
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*
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* FUTURE ENHANCEMENTS
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*
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* With a table size of 512, the current implementation is sufficient for a
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* few hundred keys. Since this is well above the expected size of the
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* tables for which this implementation was designed, the implementation of
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* dynamic hash tables was postponed until the need arises. A common (and
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* naive) approach to dynamic hash table implementation simply creates a
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* new hash table when necessary, rehashes all the data into the new table,
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* and destroys the old table. The approach in [Larson88] is superior in
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* two ways: 1) only a portion of the table is expanded when needed,
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* distributing the expansion cost over several insertions, and 2) portions
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* of the table can be locked, enabling a scalable thread-safe
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* implementation.
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*
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* REFERENCES
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*
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* [Hanson97] David R. Hanson. C Interfaces and Implementations:
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* Techniques for Creating Reusable Software. Reading, Massachusetts:
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* Addison-Wesley, 1997.
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*
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* [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
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* Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
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*
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* [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
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* 1988, pp. 446-457.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#define HASH_MAIN 0
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#if !HASH_MAIN
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# include "xf86drm.h"
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#endif
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#define HASH_MAGIC 0xdeadbeef
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#define HASH_DEBUG 0
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#define HASH_SIZE 512 /* Good for about 100 entries */
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/* If you change this value, you probably
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have to change the HashHash hashing
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function! */
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#if HASH_MAIN
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#define HASH_ALLOC malloc
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#define HASH_FREE free
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#define HASH_RANDOM_DECL
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#define HASH_RANDOM_INIT(seed) srandom(seed)
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#define HASH_RANDOM random()
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#define HASH_RANDOM_DESTROY
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#else
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#define HASH_ALLOC drmMalloc
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#define HASH_FREE drmFree
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#define HASH_RANDOM_DECL void *state
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#define HASH_RANDOM_INIT(seed) state = drmRandomCreate(seed)
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#define HASH_RANDOM drmRandom(state)
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#define HASH_RANDOM_DESTROY drmRandomDestroy(state)
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#endif
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typedef struct HashBucket {
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unsigned long key;
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void *value;
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struct HashBucket *next;
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} HashBucket, *HashBucketPtr;
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typedef struct HashTable {
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unsigned long magic;
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unsigned long entries;
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unsigned long hits; /* At top of linked list */
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unsigned long partials; /* Not at top of linked list */
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unsigned long misses; /* Not in table */
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HashBucketPtr buckets[HASH_SIZE];
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int p0;
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HashBucketPtr p1;
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} HashTable, *HashTablePtr;
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#if HASH_MAIN
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extern void *drmHashCreate(void);
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extern int drmHashDestroy(void *t);
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extern int drmHashLookup(void *t, unsigned long key, unsigned long *value);
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extern int drmHashInsert(void *t, unsigned long key, unsigned long value);
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extern int drmHashDelete(void *t, unsigned long key);
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#endif
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static unsigned long HashHash(unsigned long key)
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{
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unsigned long hash = 0;
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unsigned long tmp = key;
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static int init = 0;
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static unsigned long scatter[256];
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int i;
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if (!init) {
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HASH_RANDOM_DECL;
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HASH_RANDOM_INIT(37);
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for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM;
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HASH_RANDOM_DESTROY;
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++init;
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}
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while (tmp) {
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hash = (hash << 1) + scatter[tmp & 0xff];
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tmp >>= 8;
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}
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hash %= HASH_SIZE;
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#if HASH_DEBUG
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printf( "Hash(%d) = %d\n", key, hash);
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#endif
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return hash;
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}
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void *drmHashCreate(void)
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{
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HashTablePtr table;
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int i;
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table = HASH_ALLOC(sizeof(*table));
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if (!table) return NULL;
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table->magic = HASH_MAGIC;
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table->entries = 0;
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table->hits = 0;
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table->partials = 0;
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table->misses = 0;
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for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
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return table;
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}
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int drmHashDestroy(void *t)
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{
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HashTablePtr table = (HashTablePtr)t;
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HashBucketPtr bucket;
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HashBucketPtr next;
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int i;
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if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
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for (i = 0; i < HASH_SIZE; i++) {
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for (bucket = table->buckets[i]; bucket;) {
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next = bucket->next;
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HASH_FREE(bucket);
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bucket = next;
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}
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}
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HASH_FREE(table);
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return 0;
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}
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/* Find the bucket and organize the list so that this bucket is at the
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top. */
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static HashBucketPtr HashFind(HashTablePtr table,
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unsigned long key, unsigned long *h)
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{
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unsigned long hash = HashHash(key);
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HashBucketPtr prev = NULL;
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HashBucketPtr bucket;
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if (h) *h = hash;
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for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
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if (bucket->key == key) {
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if (prev) {
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/* Organize */
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prev->next = bucket->next;
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bucket->next = table->buckets[hash];
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table->buckets[hash] = bucket;
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++table->partials;
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} else {
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++table->hits;
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}
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return bucket;
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}
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prev = bucket;
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}
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++table->misses;
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return NULL;
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}
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int drmHashLookup(void *t, unsigned long key, void **value)
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{
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HashTablePtr table = (HashTablePtr)t;
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HashBucketPtr bucket;
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if (!table || table->magic != HASH_MAGIC) return -1; /* Bad magic */
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bucket = HashFind(table, key, NULL);
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if (!bucket) return 1; /* Not found */
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*value = bucket->value;
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return 0; /* Found */
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}
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int drmHashInsert(void *t, unsigned long key, void *value)
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{
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HashTablePtr table = (HashTablePtr)t;
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HashBucketPtr bucket;
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unsigned long hash;
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if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
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if (HashFind(table, key, &hash)) return 1; /* Already in table */
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bucket = HASH_ALLOC(sizeof(*bucket));
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if (!bucket) return -1; /* Error */
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bucket->key = key;
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bucket->value = value;
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bucket->next = table->buckets[hash];
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table->buckets[hash] = bucket;
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#if HASH_DEBUG
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printf("Inserted %d at %d/%p\n", key, hash, bucket);
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#endif
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return 0; /* Added to table */
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}
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int drmHashDelete(void *t, unsigned long key)
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{
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HashTablePtr table = (HashTablePtr)t;
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unsigned long hash;
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HashBucketPtr bucket;
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if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
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bucket = HashFind(table, key, &hash);
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if (!bucket) return 1; /* Not found */
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table->buckets[hash] = bucket->next;
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HASH_FREE(bucket);
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return 0;
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}
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int drmHashNext(void *t, unsigned long *key, void **value)
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{
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HashTablePtr table = (HashTablePtr)t;
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while (table->p0 < HASH_SIZE) {
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if (table->p1) {
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*key = table->p1->key;
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*value = table->p1->value;
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table->p1 = table->p1->next;
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return 1;
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}
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table->p1 = table->buckets[table->p0];
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++table->p0;
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}
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return 0;
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}
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int drmHashFirst(void *t, unsigned long *key, void **value)
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{
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HashTablePtr table = (HashTablePtr)t;
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if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
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table->p0 = 0;
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table->p1 = table->buckets[0];
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return drmHashNext(table, key, value);
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}
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#if HASH_MAIN
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#define DIST_LIMIT 10
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static int dist[DIST_LIMIT];
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static void clear_dist(void) {
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int i;
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for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
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}
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static int count_entries(HashBucketPtr bucket)
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{
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int count = 0;
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for (; bucket; bucket = bucket->next) ++count;
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return count;
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}
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static void update_dist(int count)
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{
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if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
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else ++dist[count];
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}
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static void compute_dist(HashTablePtr table)
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{
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int i;
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HashBucketPtr bucket;
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printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
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table->entries, table->hits, table->partials, table->misses);
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clear_dist();
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for (i = 0; i < HASH_SIZE; i++) {
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bucket = table->buckets[i];
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update_dist(count_entries(bucket));
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}
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for (i = 0; i < DIST_LIMIT; i++) {
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if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]);
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else printf("other %10d\n", dist[i]);
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}
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}
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static void check_table(HashTablePtr table,
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unsigned long key, unsigned long value)
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{
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unsigned long retval = 0;
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int retcode = drmHashLookup(table, key, &retval);
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switch (retcode) {
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case -1:
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printf("Bad magic = 0x%08lx:"
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" key = %lu, expected = %lu, returned = %lu\n",
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table->magic, key, value, retval);
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break;
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case 1:
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printf("Not found: key = %lu, expected = %lu returned = %lu\n",
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key, value, retval);
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break;
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case 0:
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if (value != retval)
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printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
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key, value, retval);
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break;
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default:
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printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
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retcode, key, value, retval);
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break;
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}
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}
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int main(void)
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{
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HashTablePtr table;
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int i;
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printf("\n***** 256 consecutive integers ****\n");
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table = drmHashCreate();
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for (i = 0; i < 256; i++) drmHashInsert(table, i, i);
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for (i = 0; i < 256; i++) check_table(table, i, i);
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for (i = 256; i >= 0; i--) check_table(table, i, i);
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compute_dist(table);
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drmHashDestroy(table);
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printf("\n***** 1024 consecutive integers ****\n");
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table = drmHashCreate();
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for (i = 0; i < 1024; i++) drmHashInsert(table, i, i);
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for (i = 0; i < 1024; i++) check_table(table, i, i);
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for (i = 1024; i >= 0; i--) check_table(table, i, i);
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compute_dist(table);
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drmHashDestroy(table);
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printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
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table = drmHashCreate();
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for (i = 0; i < 1024; i++) drmHashInsert(table, i*4096, i);
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for (i = 0; i < 1024; i++) check_table(table, i*4096, i);
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for (i = 1024; i >= 0; i--) check_table(table, i*4096, i);
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compute_dist(table);
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drmHashDestroy(table);
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printf("\n***** 1024 random integers ****\n");
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table = drmHashCreate();
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srandom(0xbeefbeef);
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for (i = 0; i < 1024; i++) drmHashInsert(table, random(), i);
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srandom(0xbeefbeef);
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for (i = 0; i < 1024; i++) check_table(table, random(), i);
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srandom(0xbeefbeef);
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for (i = 0; i < 1024; i++) check_table(table, random(), i);
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compute_dist(table);
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drmHashDestroy(table);
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printf("\n***** 5000 random integers ****\n");
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table = drmHashCreate();
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srandom(0xbeefbeef);
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for (i = 0; i < 5000; i++) drmHashInsert(table, random(), i);
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srandom(0xbeefbeef);
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for (i = 0; i < 5000; i++) check_table(table, random(), i);
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srandom(0xbeefbeef);
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for (i = 0; i < 5000; i++) check_table(table, random(), i);
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compute_dist(table);
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drmHashDestroy(table);
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return 0;
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}
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#endif
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