snapraid/tommyds/tommyhashdyn.h
2023-07-01 12:07:26 +02:00

297 lines
10 KiB
C

/*
* Copyright (c) 2010, Andrea Mazzoleni. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/** \file
* Dynamic chained hashtable.
*
* This hashtable resizes dynamically. It starts with the minimal size of 16 buckets, it doubles
* the size then it reaches a load factor greater than 0.5 and it halves the size with a load
* factor lower than 0.125.
*
* All the elements are reallocated in a single resize operation done inside
* tommy_hashdyn_insert() or tommy_hashdyn_remove().
*
* Note that the resize operation takes approximately 100 [ms] with 1 million of elements,
* and 1 [second] with 10 millions. This could be a problem in real-time applications.
*
* The resize also fragment the heap, as it involves allocating a double-sized table, copy elements,
* and deallocating the older table. Leaving a big hole in the heap.
*
* The ::tommy_hashlin hashtable fixes both problems.
*
* To initialize the hashtable you have to call tommy_hashdyn_init().
*
* \code
* tommy_hashslin hashdyn;
*
* tommy_hashdyn_init(&hashdyn);
* \endcode
*
* To insert elements in the hashtable you have to call tommy_hashdyn_insert() for
* each element.
* In the insertion call you have to specify the address of the node, the
* address of the object, and the hash value of the key to use.
* The address of the object is used to initialize the tommy_node::data field
* of the node, and the hash to initialize the tommy_node::key field.
*
* \code
* struct object {
* int value;
* // other fields
* tommy_node node;
* };
*
* struct object* obj = malloc(sizeof(struct object)); // creates the object
*
* obj->value = ...; // initializes the object
*
* tommy_hashdyn_insert(&hashdyn, &obj->node, obj, tommy_inthash_u32(obj->value)); // inserts the object
* \endcode
*
* To find and element in the hashtable you have to call tommy_hashtable_search()
* providing a comparison function, its argument, and the hash of the key to search.
*
* \code
* int compare(const void* arg, const void* obj)
* {
* return *(const int*)arg != ((const struct object*)obj)->value;
* }
*
* int value_to_find = 1;
* struct object* obj = tommy_hashdyn_search(&hashdyn, compare, &value_to_find, tommy_inthash_u32(value_to_find));
* if (!obj) {
* // not found
* } else {
* // found
* }
* \endcode
*
* To iterate over all the elements in the hashtable with the same key, you have to
* use tommy_hashdyn_bucket() and follow the tommy_node::next pointer until NULL.
* You have also to check explicitly for the key, as the bucket may contains
* different keys.
*
* \code
* int value_to_find = 1;
* tommy_node* i = tommy_hashdyn_bucket(&hashdyn, tommy_inthash_u32(value_to_find));
* while (i) {
* struct object* obj = i->data; // gets the object pointer
*
* if (obj->value == value_to_find) {
* printf("%d\n", obj->value); // process the object
* }
*
* i = i->next; // goes to the next element
* }
* \endcode
*
* To remove an element from the hashtable you have to call tommy_hashdyn_remove()
* providing a comparison function, its argument, and the hash of the key to search
* and remove.
*
* \code
* struct object* obj = tommy_hashdyn_remove(&hashdyn, compare, &value_to_remove, tommy_inthash_u32(value_to_remove));
* if (obj) {
* free(obj); // frees the object allocated memory
* }
* \endcode
*
* To destroy the hashtable you have to remove all the elements, and deinitialize
* the hashtable calling tommy_hashdyn_done().
*
* \code
* tommy_hashdyn_done(&hashdyn);
* \endcode
*
* If you need to iterate over all the elements in the hashtable, you can use
* tommy_hashdyn_foreach() or tommy_hashdyn_foreach_arg().
* If you need a more precise control with a real iteration, you have to insert
* all the elements also in a ::tommy_list, and use the list to iterate.
* See the \ref multiindex example for more detail.
*/
#ifndef __TOMMYHASHDYN_H
#define __TOMMYHASHDYN_H
#include "tommyhash.h"
/******************************************************************************/
/* hashdyn */
/** \internal
* Initial and minimal size of the hashtable expressed as a power of 2.
* The initial size is 2^TOMMY_HASHDYN_BIT.
*/
#define TOMMY_HASHDYN_BIT 4
/**
* Hashtable node.
* This is the node that you have to include inside your objects.
*/
typedef tommy_node tommy_hashdyn_node;
/**
* Hashtable container type.
* \note Don't use internal fields directly, but access the container only using functions.
*/
typedef struct tommy_hashdyn_struct {
tommy_hashdyn_node** bucket; /**< Hash buckets. One list for each hash modulus. */
tommy_size_t bucket_max; /**< Number of buckets. */
tommy_size_t bucket_mask; /**< Bit mask to access the buckets. */
tommy_size_t count; /**< Number of elements. */
tommy_uint_t bucket_bit; /**< Bits used in the bit mask. */
} tommy_hashdyn;
/**
* Initializes the hashtable.
*/
void tommy_hashdyn_init(tommy_hashdyn* hashdyn);
/**
* Deinitializes the hashtable.
*
* You can call this function with elements still contained,
* but such elements are not going to be freed by this call.
*/
void tommy_hashdyn_done(tommy_hashdyn* hashdyn);
/**
* Inserts an element in the hashtable.
*/
void tommy_hashdyn_insert(tommy_hashdyn* hashdyn, tommy_hashdyn_node* node, void* data, tommy_hash_t hash);
/**
* Searches and removes an element from the hashtable.
* You have to provide a compare function and the hash of the element you want to remove.
* If the element is not found, 0 is returned.
* If more equal elements are present, the first one is removed.
* \param cmp Compare function called with cmp_arg as first argument and with the element to compare as a second one.
* The function should return 0 for equal elements, anything other for different elements.
* \param cmp_arg Compare argument passed as first argument of the compare function.
* \param hash Hash of the element to find and remove.
* \return The removed element, or 0 if not found.
*/
void* tommy_hashdyn_remove(tommy_hashdyn* hashdyn, tommy_search_func* cmp, const void* cmp_arg, tommy_hash_t hash);
/**
* Gets the bucket of the specified hash.
* The bucket is guaranteed to contain ALL the elements with the specified hash,
* but it can contain also others.
* You can access elements in the bucket following the ::next pointer until 0.
* \param hash Hash of the element to find.
* \return The head of the bucket, or 0 if empty.
*/
tommy_inline tommy_hashdyn_node* tommy_hashdyn_bucket(tommy_hashdyn* hashdyn, tommy_hash_t hash)
{
return hashdyn->bucket[hash & hashdyn->bucket_mask];
}
/**
* Searches an element in the hashtable.
* You have to provide a compare function and the hash of the element you want to find.
* If more equal elements are present, the first one is returned.
* \param cmp Compare function called with cmp_arg as first argument and with the element to compare as a second one.
* The function should return 0 for equal elements, anything other for different elements.
* \param cmp_arg Compare argument passed as first argument of the compare function.
* \param hash Hash of the element to find.
* \return The first element found, or 0 if none.
*/
tommy_inline void* tommy_hashdyn_search(tommy_hashdyn* hashdyn, tommy_search_func* cmp, const void* cmp_arg, tommy_hash_t hash)
{
tommy_hashdyn_node* i = tommy_hashdyn_bucket(hashdyn, hash);
while (i) {
/* we first check if the hash matches, as in the same bucket we may have multiples hash values */
if (i->index == hash && cmp(cmp_arg, i->data) == 0)
return i->data;
i = i->next;
}
return 0;
}
/**
* Removes an element from the hashtable.
* You must already have the address of the element to remove.
* \return The tommy_node::data field of the node removed.
*/
void* tommy_hashdyn_remove_existing(tommy_hashdyn* hashdyn, tommy_hashdyn_node* node);
/**
* Calls the specified function for each element in the hashtable.
*
* You cannot add or remove elements from the inside of the callback,
* but can use it to deallocate them.
*
* \code
* tommy_hashdyn hashdyn;
*
* // initializes the hashtable
* tommy_hashdyn_init(&hashdyn);
*
* ...
*
* // creates an object
* struct object* obj = malloc(sizeof(struct object));
*
* ...
*
* // insert it in the hashtable
* tommy_hashdyn_insert(&hashdyn, &obj->node, obj, tommy_inthash_u32(obj->value));
*
* ...
*
* // deallocates all the objects iterating the hashtable
* tommy_hashdyn_foreach(&hashdyn, free);
*
* // deallocates the hashtable
* tommy_hashdyn_done(&hashdyn);
* \endcode
*/
void tommy_hashdyn_foreach(tommy_hashdyn* hashdyn, tommy_foreach_func* func);
/**
* Calls the specified function with an argument for each element in the hashtable.
*/
void tommy_hashdyn_foreach_arg(tommy_hashdyn* hashdyn, tommy_foreach_arg_func* func, void* arg);
/**
* Gets the number of elements.
*/
tommy_inline tommy_size_t tommy_hashdyn_count(tommy_hashdyn* hashdyn)
{
return hashdyn->count;
}
/**
* Gets the size of allocated memory.
* It includes the size of the ::tommy_hashdyn_node of the stored elements.
*/
tommy_size_t tommy_hashdyn_memory_usage(tommy_hashdyn* hashdyn);
#endif