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Diffstat (limited to 'src/glx/x11/glxhash.c')
-rw-r--r-- | src/glx/x11/glxhash.c | 411 |
1 files changed, 411 insertions, 0 deletions
diff --git a/src/glx/x11/glxhash.c b/src/glx/x11/glxhash.c new file mode 100644 index 00000000000..1b284c5f451 --- /dev/null +++ b/src/glx/x11/glxhash.c @@ -0,0 +1,411 @@ +/* glxhash.c -- Small hash table support for integer -> integer mapping + * Taken from libdrm. + * + * Created: Sun Apr 18 09:35:45 1999 by [email protected] + * + * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. + * All Rights Reserved. + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER + * DEALINGS IN THE SOFTWARE. + * + * Authors: Rickard E. (Rik) Faith <[email protected]> + * + * DESCRIPTION + * + * This file contains a straightforward implementation of a fixed-sized + * hash table using self-organizing linked lists [Knuth73, pp. 398-399] for + * collision resolution. There are two potentially interesting things + * about this implementation: + * + * 1) The table is power-of-two sized. Prime sized tables are more + * traditional, but do not have a significant advantage over power-of-two + * sized table, especially when double hashing is not used for collision + * resolution. + * + * 2) The hash computation uses a table of random integers [Hanson97, + * pp. 39-41]. + * + * FUTURE ENHANCEMENTS + * + * With a table size of 512, the current implementation is sufficient for a + * few hundred keys. Since this is well above the expected size of the + * tables for which this implementation was designed, the implementation of + * dynamic hash tables was postponed until the need arises. A common (and + * naive) approach to dynamic hash table implementation simply creates a + * new hash table when necessary, rehashes all the data into the new table, + * and destroys the old table. The approach in [Larson88] is superior in + * two ways: 1) only a portion of the table is expanded when needed, + * distributing the expansion cost over several insertions, and 2) portions + * of the table can be locked, enabling a scalable thread-safe + * implementation. + * + * REFERENCES + * + * [Hanson97] David R. Hanson. C Interfaces and Implementations: + * Techniques for Creating Reusable Software. Reading, Massachusetts: + * Addison-Wesley, 1997. + * + * [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3: + * Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973. + * + * [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April + * 1988, pp. 446-457. + * + */ + +#include "glxhash.h" + +#define HASH_MAIN 0 + +#include <stdio.h> +#include <stdlib.h> + +#define HASH_MAGIC 0xdeadbeef +#define HASH_DEBUG 0 +#define HASH_SIZE 512 /* Good for about 100 entries */ + /* If you change this value, you probably + have to change the HashHash hashing + function! */ + +#define HASH_ALLOC malloc +#define HASH_FREE free +#define HASH_RANDOM_DECL +#define HASH_RANDOM_INIT(seed) srandom(seed) +#define HASH_RANDOM random() +#define HASH_RANDOM_DESTROY + +typedef struct __glxHashBucket { + unsigned long key; + void *value; + struct __glxHashBucket *next; +} __glxHashBucket, *__glxHashBucketPtr; + +typedef struct __glxHashTable *__glxHashTablePtr; +struct __glxHashTable { + unsigned long magic; + unsigned long entries; + unsigned long hits; /* At top of linked list */ + unsigned long partials; /* Not at top of linked list */ + unsigned long misses; /* Not in table */ + __glxHashBucketPtr buckets[HASH_SIZE]; + int p0; + __glxHashBucketPtr p1; +}; + +static unsigned long HashHash(unsigned long key) +{ + unsigned long hash = 0; + unsigned long tmp = key; + static int init = 0; + static unsigned long scatter[256]; + int i; + + if (!init) { + HASH_RANDOM_DECL; + HASH_RANDOM_INIT(37); + for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM; + HASH_RANDOM_DESTROY; + ++init; + } + + while (tmp) { + hash = (hash << 1) + scatter[tmp & 0xff]; + tmp >>= 8; + } + + hash %= HASH_SIZE; +#if HASH_DEBUG + printf( "Hash(%d) = %d\n", key, hash); +#endif + return hash; +} + +__glxHashTable *__glxHashCreate(void) +{ + __glxHashTablePtr table; + int i; + + table = HASH_ALLOC(sizeof(*table)); + if (!table) return NULL; + table->magic = HASH_MAGIC; + table->entries = 0; + table->hits = 0; + table->partials = 0; + table->misses = 0; + + for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL; + return table; +} + +int __glxHashDestroy(__glxHashTable *t) +{ + __glxHashTablePtr table = (__glxHashTablePtr)t; + __glxHashBucketPtr bucket; + __glxHashBucketPtr next; + int i; + + if (table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + for (i = 0; i < HASH_SIZE; i++) { + for (bucket = table->buckets[i]; bucket;) { + next = bucket->next; + HASH_FREE(bucket); + bucket = next; + } + } + HASH_FREE(table); + return 0; +} + +/* Find the bucket and organize the list so that this bucket is at the + top. */ + +static __glxHashBucketPtr HashFind(__glxHashTablePtr table, + unsigned long key, unsigned long *h) +{ + unsigned long hash = HashHash(key); + __glxHashBucketPtr prev = NULL; + __glxHashBucketPtr bucket; + + if (h) *h = hash; + + for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) { + if (bucket->key == key) { + if (prev) { + /* Organize */ + prev->next = bucket->next; + bucket->next = table->buckets[hash]; + table->buckets[hash] = bucket; + ++table->partials; + } else { + ++table->hits; + } + return bucket; + } + prev = bucket; + } + ++table->misses; + return NULL; +} + +int __glxHashLookup(__glxHashTable *t, unsigned long key, void **value) +{ + __glxHashTablePtr table = (__glxHashTablePtr)t; + __glxHashBucketPtr bucket; + + if (!table || table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + bucket = HashFind(table, key, NULL); + if (!bucket) return 1; /* Not found */ + *value = bucket->value; + return 0; /* Found */ +} + +int __glxHashInsert(__glxHashTable *t, unsigned long key, void *value) +{ + __glxHashTablePtr table = (__glxHashTablePtr)t; + __glxHashBucketPtr bucket; + unsigned long hash; + + if (table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + if (HashFind(table, key, &hash)) return 1; /* Already in table */ + + bucket = HASH_ALLOC(sizeof(*bucket)); + if (!bucket) return -1; /* Error */ + bucket->key = key; + bucket->value = value; + bucket->next = table->buckets[hash]; + table->buckets[hash] = bucket; +#if HASH_DEBUG + printf("Inserted %d at %d/%p\n", key, hash, bucket); +#endif + return 0; /* Added to table */ +} + +int __glxHashDelete(__glxHashTable *t, unsigned long key) +{ + __glxHashTablePtr table = (__glxHashTablePtr)t; + unsigned long hash; + __glxHashBucketPtr bucket; + + if (table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + bucket = HashFind(table, key, &hash); + + if (!bucket) return 1; /* Not found */ + + table->buckets[hash] = bucket->next; + HASH_FREE(bucket); + return 0; +} + +int __glxHashNext(__glxHashTable *t, unsigned long *key, void **value) +{ + __glxHashTablePtr table = (__glxHashTablePtr)t; + + while (table->p0 < HASH_SIZE) { + if (table->p1) { + *key = table->p1->key; + *value = table->p1->value; + table->p1 = table->p1->next; + return 1; + } + table->p1 = table->buckets[table->p0]; + ++table->p0; + } + return 0; +} + +int __glxHashFirst(__glxHashTable *t, unsigned long *key, void **value) +{ + __glxHashTablePtr table = (__glxHashTablePtr)t; + + if (table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + table->p0 = 0; + table->p1 = table->buckets[0]; + return __glxHashNext(table, key, value); +} + +#if HASH_MAIN +#define DIST_LIMIT 10 +static int dist[DIST_LIMIT]; + +static void clear_dist(void) { + int i; + + for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0; +} + +static int count_entries(__glxHashBucketPtr bucket) +{ + int count = 0; + + for (; bucket; bucket = bucket->next) ++count; + return count; +} + +static void update_dist(int count) +{ + if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1]; + else ++dist[count]; +} + +static void compute_dist(__glxHashTablePtr table) +{ + int i; + __glxHashBucketPtr bucket; + + printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n", + table->entries, table->hits, table->partials, table->misses); + clear_dist(); + for (i = 0; i < HASH_SIZE; i++) { + bucket = table->buckets[i]; + update_dist(count_entries(bucket)); + } + for (i = 0; i < DIST_LIMIT; i++) { + if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]); + else printf("other %10d\n", dist[i]); + } +} + +static void check_table(__glxHashTablePtr table, + unsigned long key, unsigned long value) +{ + unsigned long retval = 0; + int retcode = __glxHashLookup(table, key, &retval); + + switch (retcode) { + case -1: + printf("Bad magic = 0x%08lx:" + " key = %lu, expected = %lu, returned = %lu\n", + table->magic, key, value, retval); + break; + case 1: + printf("Not found: key = %lu, expected = %lu returned = %lu\n", + key, value, retval); + break; + case 0: + if (value != retval) + printf("Bad value: key = %lu, expected = %lu, returned = %lu\n", + key, value, retval); + break; + default: + printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n", + retcode, key, value, retval); + break; + } +} + +int main(void) +{ + __glxHashTablePtr table; + int i; + + printf("\n***** 256 consecutive integers ****\n"); + table = __glxHashCreate(); + for (i = 0; i < 256; i++) __glxHashInsert(table, i, i); + for (i = 0; i < 256; i++) check_table(table, i, i); + for (i = 256; i >= 0; i--) check_table(table, i, i); + compute_dist(table); + __glxHashDestroy(table); + + printf("\n***** 1024 consecutive integers ****\n"); + table = __glxHashCreate(); + for (i = 0; i < 1024; i++) __glxHashInsert(table, i, i); + for (i = 0; i < 1024; i++) check_table(table, i, i); + for (i = 1024; i >= 0; i--) check_table(table, i, i); + compute_dist(table); + __glxHashDestroy(table); + + printf("\n***** 1024 consecutive page addresses (4k pages) ****\n"); + table = __glxHashCreate(); + for (i = 0; i < 1024; i++) __glxHashInsert(table, i*4096, i); + for (i = 0; i < 1024; i++) check_table(table, i*4096, i); + for (i = 1024; i >= 0; i--) check_table(table, i*4096, i); + compute_dist(table); + __glxHashDestroy(table); + + printf("\n***** 1024 random integers ****\n"); + table = __glxHashCreate(); + srandom(0xbeefbeef); + for (i = 0; i < 1024; i++) __glxHashInsert(table, random(), i); + srandom(0xbeefbeef); + for (i = 0; i < 1024; i++) check_table(table, random(), i); + srandom(0xbeefbeef); + for (i = 0; i < 1024; i++) check_table(table, random(), i); + compute_dist(table); + __glxHashDestroy(table); + + printf("\n***** 5000 random integers ****\n"); + table = __glxHashCreate(); + srandom(0xbeefbeef); + for (i = 0; i < 5000; i++) __glxHashInsert(table, random(), i); + srandom(0xbeefbeef); + for (i = 0; i < 5000; i++) check_table(table, random(), i); + srandom(0xbeefbeef); + for (i = 0; i < 5000; i++) check_table(table, random(), i); + compute_dist(table); + __glxHashDestroy(table); + + return 0; +} +#endif |