From 3f13df4d019cfcbef3f9909e3b993896d3c934e6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 28 Apr 2024 11:22:22 +0200 Subject: Adding upstream version 2.4.114. Signed-off-by: Daniel Baumann --- xf86drmHash.c | 242 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 242 insertions(+) create mode 100644 xf86drmHash.c (limited to 'xf86drmHash.c') diff --git a/xf86drmHash.c b/xf86drmHash.c new file mode 100644 index 0000000..2cf2b80 --- /dev/null +++ b/xf86drmHash.c @@ -0,0 +1,242 @@ +/* xf86drmHash.c -- Small hash table support for integer -> integer mapping + * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com + * + * 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 + * + * 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 +#include + +#include "libdrm_macros.h" +#include "xf86drm.h" +#include "xf86drmHash.h" + +#define HASH_MAGIC 0xdeadbeef + +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) { + void *state; + state = drmRandomCreate(37); + for (i = 0; i < 256; i++) scatter[i] = drmRandom(state); + drmRandomDestroy(state); + ++init; + } + + while (tmp) { + hash = (hash << 1) + scatter[tmp & 0xff]; + tmp >>= 8; + } + + hash %= HASH_SIZE; + return hash; +} + +drm_public void *drmHashCreate(void) +{ + HashTablePtr table; + + table = drmMalloc(sizeof(*table)); + if (!table) return NULL; + table->magic = HASH_MAGIC; + + return table; +} + +drm_public int drmHashDestroy(void *t) +{ + HashTablePtr table = (HashTablePtr)t; + HashBucketPtr bucket; + HashBucketPtr 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; + drmFree(bucket); + bucket = next; + } + } + drmFree(table); + return 0; +} + +/* Find the bucket and organize the list so that this bucket is at the + top. */ + +static HashBucketPtr HashFind(HashTablePtr table, + unsigned long key, unsigned long *h) +{ + unsigned long hash = HashHash(key); + HashBucketPtr prev = NULL; + HashBucketPtr 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; +} + +drm_public int drmHashLookup(void *t, unsigned long key, void **value) +{ + HashTablePtr table = (HashTablePtr)t; + HashBucketPtr 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 */ +} + +drm_public int drmHashInsert(void *t, unsigned long key, void *value) +{ + HashTablePtr table = (HashTablePtr)t; + HashBucketPtr bucket; + unsigned long hash; + + if (table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + if (HashFind(table, key, &hash)) return 1; /* Already in table */ + + bucket = drmMalloc(sizeof(*bucket)); + if (!bucket) return -1; /* Error */ + bucket->key = key; + bucket->value = value; + bucket->next = table->buckets[hash]; + table->buckets[hash] = bucket; + return 0; /* Added to table */ +} + +drm_public int drmHashDelete(void *t, unsigned long key) +{ + HashTablePtr table = (HashTablePtr)t; + unsigned long hash; + HashBucketPtr 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; + drmFree(bucket); + return 0; +} + +drm_public int drmHashNext(void *t, unsigned long *key, void **value) +{ + HashTablePtr table = (HashTablePtr)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; +} + +drm_public int drmHashFirst(void *t, unsigned long *key, void **value) +{ + HashTablePtr table = (HashTablePtr)t; + + if (table->magic != HASH_MAGIC) return -1; /* Bad magic */ + + table->p0 = 0; + table->p1 = table->buckets[0]; + return drmHashNext(table, key, value); +} -- cgit v1.2.3