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-rw-r--r--source3/lib/hash.c320
1 files changed, 320 insertions, 0 deletions
diff --git a/source3/lib/hash.c b/source3/lib/hash.c
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+/*
+ Unix SMB/Netbios implementation.
+ Version 2.0
+
+ Copyright (C) Ying Chen 2000.
+ Copyright (C) Jeremy Allison 2000.
+ - added some defensive programming.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+ * NB. We may end up replacing this functionality in a future 2.x
+ * release to reduce the number of hashing/lookup methods we support. JRA.
+ */
+
+#include "includes.h"
+
+extern int DEBUGLEVEL;
+
+#define NUM_PRIMES 11
+
+static BOOL enlarge_hash_table(hash_table *table);
+static int primes[NUM_PRIMES] =
+ {17, 37, 67, 131, 257, 521, 1031, 2053, 4099, 8209, 16411};
+
+/****************************************************************************
+ * This function initializes the hash table.
+ * This hash function hashes on string keys.
+ * This number of hash buckets is always rounded up to a power of
+ * 2 first, then to a prime number that is large than the power of two.
+ * Input:
+ * table -- the hash table pointer.
+ * num_buckets -- the number of buckets to be allocated. This
+ * hash function can dynamically increase its size when the
+ * the hash table size becomes small. There is a MAX hash table
+ * size defined in hash.h.
+ * compare_func -- the function pointer to a comparison function
+ * used by the hash key comparison.
+ ****************************************************************************
+ */
+
+BOOL hash_table_init(hash_table *table, int num_buckets, compare_function compare_func)
+{
+ int i;
+ ubi_dlList *bucket;
+
+ table->num_elements = 0;
+ table->size = 2;
+ table->comp_func = compare_func;
+ while (table->size < num_buckets)
+ table->size <<= 1;
+ for (i = 0; i < NUM_PRIMES; i++) {
+ if (primes[i] > table->size) {
+ table->size = primes[i];
+ break;
+ }
+ }
+
+ DEBUG(5, ("Hash size = %d.\n", table->size));
+
+ if(!(table->buckets = (ubi_dlList *) malloc(sizeof(ubi_dlList) * table->size))) {
+ DEBUG(0,("hash_table_init: malloc fail !\n"));
+ return False;
+ }
+ ubi_dlInitList(&(table->lru_chain));
+ for (i=0, bucket = table->buckets; i < table->size; i++, bucket++)
+ ubi_dlInitList(bucket);
+
+ return True;
+}
+
+/*
+ **************************************************************
+ * Compute a hash value based on a string key value.
+ * Make the string key into an array of int's if possible.
+ * For the last few chars that cannot be int'ed, use char instead.
+ * The function returns the bucket index number for the hashed
+ * key.
+ **************************************************************
+ */
+
+int string_hash(int hash_size, const char *key)
+{
+ int j=0;
+ while (*key)
+ j = j*10 + *key++;
+ return(((j>=0)?j:(-j)) % hash_size);
+}
+
+/* *************************************************************************
+ * Search the hash table for the entry in the hash chain.
+ * The function returns the pointer to the
+ * element found in the chain or NULL if none is found.
+ * If the element is found, the element is also moved to
+ * the head of the LRU list.
+ *
+ * Input:
+ * table -- The hash table where the element is stored in.
+ * hash_chain -- The pointer to the bucket that stores the
+ * element to be found.
+ * key -- The hash key to be found.
+ ***************************************************************************
+ */
+
+static hash_element *hash_chain_find(hash_table *table, ubi_dlList *hash_chain, char *key)
+{
+ hash_element *hash_elem;
+ ubi_dlNodePtr lru_item;
+ int i = 0;
+
+ for (hash_elem = (hash_element *)(ubi_dlFirst(hash_chain)); i < hash_chain->count;
+ i++, hash_elem = (hash_element *)(ubi_dlNext(hash_elem))) {
+ if ((table->comp_func)(hash_elem->key, key) == 0) {
+ /* Move to the head of the lru List. */
+ lru_item = ubi_dlRemove(&(table->lru_chain), &(hash_elem->lru_link.lru_link));
+ ubi_dlAddHead(&(table->lru_chain), lru_item);
+ return(hash_elem);
+ }
+ }
+ return ((hash_element *) NULL);
+}
+
+/* ***************************************************************************
+ *
+ * Lookup a hash table for an element with key.
+ * The function returns a pointer to the hash element.
+ * If no element is found, the function returns NULL.
+ *
+ * Input:
+ * table -- The hash table to be searched on.
+ * key -- The key to be found.
+ *****************************************************************************
+ */
+
+hash_element *hash_lookup(hash_table *table, char *key)
+{
+ return (hash_chain_find(table, &(table->buckets[string_hash(table->size, key)]), key));
+}
+
+/* ***************************************************************
+ *
+ * This function first checks if an element with key "key"
+ * exists in the hash table. If so, the function moves the
+ * element to the front of the LRU list. Otherwise, a new
+ * hash element corresponding to "value" and "key" is allocated
+ * and inserted into the hash table. The new elements are
+ * always inserted in the LRU order to the LRU list as well.
+ *
+ * Input:
+ * table -- The hash table to be inserted in.
+ * value -- The content of the element to be inserted.
+ * key -- The key of the new element to be inserted.
+ *
+ ****************************************************************
+ */
+
+hash_element *hash_insert(hash_table *table, char *value, char *key)
+{
+ hash_element *hash_elem;
+ ubi_dlNodePtr lru_item;
+ ubi_dlList *bucket;
+
+ /*
+ * If the hash table size has not reached the MAX_HASH_TABLE_SIZE,
+ * the hash table may be enlarged if the current hash table is full.
+ * If the hash table size has reached the MAX_HASH_TABLE_SIZE,
+ * use LRU to remove the oldest element from the hash table.
+ */
+
+ if ((table->num_elements >= table->size) &&
+ (table->num_elements < MAX_HASH_TABLE_SIZE)) {
+ if(!enlarge_hash_table(table))
+ return (hash_element *)NULL;
+ table->num_elements += 1;
+ } else if (table->num_elements >= MAX_HASH_TABLE_SIZE) {
+ /* Do an LRU replacement. */
+ lru_item = ubi_dlLast(&(table->lru_chain));
+ hash_elem = (hash_element *)(((lru_node *)lru_item)->hash_elem);
+ bucket = hash_elem->bucket;
+ ubi_dlRemThis(&(table->lru_chain), &(hash_elem->lru_link.lru_link));
+ ubi_dlRemThis(bucket, (ubi_dlNodePtr)hash_elem);
+ free((char*)(hash_elem->value));
+ free(hash_elem);
+ } else {
+ table->num_elements += 1;
+ }
+
+ bucket = &(table->buckets[string_hash(table->size, key)]);
+
+ /* Since we only have 1-byte for the key string, we need to
+ * allocate extra space in the hash_element to store the entire key
+ * string.
+ */
+
+ if(!(hash_elem = (hash_element *) malloc(sizeof(hash_element) + strlen(key)))) {
+ DEBUG(0,("hash_insert: malloc fail !\n"));
+ return (hash_element *)NULL;
+ }
+
+ safe_strcpy((char *) hash_elem->key, key, strlen(key)+1);
+
+ hash_elem->value = (char *)value;
+ hash_elem->bucket = bucket;
+ /* Insert in front of the lru list and the bucket list. */
+ ubi_dlAddHead(bucket, hash_elem);
+ hash_elem->lru_link.hash_elem = hash_elem;
+ ubi_dlAddHead(&(table->lru_chain), &(hash_elem->lru_link.lru_link));
+
+ return(hash_elem);
+}
+
+/* **************************************************************************
+ *
+ * Remove a hash element from the hash table. The hash element is
+ * removed from both the LRU list and the hash bucket chain.
+ *
+ * Input:
+ * table -- the hash table to be manipulated on.
+ * hash_elem -- the element to be removed.
+ **************************************************************************
+ */
+
+void hash_remove(hash_table *table, hash_element *hash_elem)
+{
+ if (hash_elem) {
+ ubi_dlRemove(&(table->lru_chain), &(hash_elem->lru_link.lru_link));
+ ubi_dlRemove(hash_elem->bucket, (ubi_dlNodePtr) hash_elem);
+ if(hash_elem->value)
+ free((char *)(hash_elem->value));
+ if(hash_elem)
+ free((char *) hash_elem);
+ table->num_elements--;
+ }
+}
+
+/* ******************************************************************
+ * Increase the hash table size if it is too small.
+ * The hash table size is increased by the HASH_TABLE_INCREMENT
+ * ratio.
+ * Input:
+ * table -- the hash table to be enlarged.
+ ******************************************************************
+ */
+
+static BOOL enlarge_hash_table(hash_table *table)
+{
+ hash_element *hash_elem;
+ int size, hash_value;
+ ubi_dlList *buckets;
+ ubi_dlList *old_bucket;
+ ubi_dlList *bucket;
+ ubi_dlList lru_chain;
+
+ buckets = table->buckets;
+ lru_chain = table->lru_chain;
+ size = table->size;
+
+ /* Reinitialize the hash table. */
+ if(!hash_table_init(table, table->size * HASH_TABLE_INCREMENT, table->comp_func))
+ return False;
+
+ for (old_bucket = buckets; size > 0; size--, old_bucket++) {
+ while (old_bucket->count != 0) {
+ hash_elem = (hash_element *) ubi_dlRemHead(old_bucket);
+ ubi_dlRemove(&lru_chain, &(hash_elem->lru_link.lru_link));
+ hash_value = string_hash(table->size, (char *) hash_elem->key);
+ bucket = &(table->buckets[hash_value]);
+ ubi_dlAddHead(bucket, hash_elem);
+ ubi_dlAddHead(&(table->lru_chain), &(hash_elem->lru_link.lru_link));
+ hash_elem->bucket = bucket;
+ hash_elem->lru_link.hash_elem = hash_elem;
+ table->num_elements++;
+ }
+ }
+ if(buckets)
+ free((char *) buckets);
+
+ return True;
+}
+
+/* **********************************************************************
+ *
+ * Remove everything from a hash table and free up the memory it
+ * occupies.
+ * Input:
+ * table -- the hash table to be cleared.
+ *
+ *************************************************************************
+ */
+
+void hash_clear(hash_table *table)
+{
+ int i;
+ ubi_dlList *bucket = table->buckets;
+ hash_element *hash_elem;
+ for (i = 0; i < table->size; bucket++, i++) {
+ while (bucket->count != 0) {
+ hash_elem = (hash_element *) ubi_dlRemHead(bucket);
+ if(hash_elem->value)
+ free((char *)(hash_elem->value));
+ if(hash_elem)
+ free((char *)hash_elem);
+ }
+ }
+ if(table->buckets)
+ free((char *) table->buckets);
+}
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