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hashtable.h


// $Id: hashtable.h,v 1.1 2004/10/27 16:58:58 we7u Exp $


/* Copyright (C) 2002 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */

#ifndef __HASHTABLE_CWC22_H__
#define __HASHTABLE_CWC22_H__

struct hashtable;

/* Example of use:
 *
 *      struct hashtable  *h;
 *      struct some_key   *k;
 *      struct some_value *v;
 *
 *      static unsigned int         hash_from_key_fn( void *k );
 *      static int                  keys_equal_fn ( void *key1, void *key2 );
 *
 *      h = create_hashtable(16, hash_from_key_fn, keys_equal_fn);
 *      k = (struct some_key *)     malloc(sizeof(struct some_key));
 *      v = (struct some_value *)   malloc(sizeof(struct some_value));
 *
 *      (initialise k and v to suitable values)
 * 
 *      if (! hashtable_insert(h,k,v) )
 *      {     exit(-1);               }
 *
 *      if (NULL == (found = hashtable_search(h,k) ))
 *      {    printf("not found!");                  }
 *
 *      if (NULL == (found = hashtable_remove(h,k) ))
 *      {    printf("Not found\n");                 }
 *
 */

/* Macros may be used to define type-safe(r) hashtable access functions, with
 * methods specialized to take known key and value types as parameters.
 * 
 * Example:
 *
 * Insert this at the start of your file:
 *
 * DEFINE_HASHTABLE_INSERT(insert_some, struct some_key, struct some_value);
 * DEFINE_HASHTABLE_SEARCH(search_some, struct some_key, struct some_value);
 * DEFINE_HASHTABLE_REMOVE(remove_some, struct some_key, struct some_value);
 *
 * This defines the functions 'insert_some', 'search_some' and 'remove_some'.
 * These operate just like hashtable_insert etc., with the same parameters,
 * but their function signatures have 'struct some_key *' rather than
 * 'void *', and hence can generate compile time errors if your program is
 * supplying incorrect data as a key (and similarly for value).
 *
 * Note that the hash and key equality functions passed to create_hashtable
 * still take 'void *' parameters instead of 'some key *'. This shouldn't be
 * a difficult issue as they're only defined and passed once, and the other
 * functions will ensure that only valid keys are supplied to them.
 *
 * The cost for this checking is increased code size and runtime overhead
 * - if performance is important, it may be worth switching back to the
 * unsafe methods once your program has been debugged with the safe methods.
 * This just requires switching to some simple alternative defines - eg:
 * #define insert_some hashtable_insert
 *
 */

/*****************************************************************************
 * create_hashtable
   
 * @name                    create_hashtable
 * @param   minsize         minimum initial size of hashtable
 * @param   hashfunction    function for hashing keys
 * @param   key_eq_fn       function for determining key equality
 * @return                  newly created hashtable or NULL on failure
 */

struct hashtable *
create_hashtable(unsigned int minsize,
                 unsigned int (*hashfunction) (void*),
                 int (*key_eq_fn) (void*,void*));

/*****************************************************************************
 * hashtable_insert
   
 * @name        hashtable_insert
 * @param   h   the hashtable to insert into
 * @param   k   the key - hashtable claims ownership and will free on removal
 * @param   v   the value - does not claim ownership
 * @return      non-zero for successful insertion
 *
 * This function will cause the table to expand if the insertion would take
 * the ratio of entries to table size over the maximum load factor.
 *
 * This function does not check for repeated insertions with a duplicate key.
 * The value returned when using a duplicate key is undefined -- when
 * the hashtable changes size, the order of retrieval of duplicate key
 * entries is reversed.
 * If in doubt, remove before insert.
 */

int 
hashtable_insert(struct hashtable *h, void *k, void *v);

#define DEFINE_HASHTABLE_INSERT(fnname, keytype, valuetype) \
int fnname (struct hashtable *h, keytype *k, valuetype *v) \
{ \
    return hashtable_insert(h,k,v); \
}

/*****************************************************************************
 * hashtable_search
   
 * @name        hashtable_search
 * @param   h   the hashtable to search
 * @param   k   the key to search for  - does not claim ownership
 * @return      the value associated with the key, or NULL if none found
 */

void *
hashtable_search(struct hashtable *h, void *k);

#define DEFINE_HASHTABLE_SEARCH(fnname, keytype, valuetype) \
valuetype * fnname (struct hashtable *h, keytype *k) \
{ \
    return (valuetype *) (hashtable_search(h,k)); \
}

/*****************************************************************************
 * hashtable_remove
   
 * @name        hashtable_remove
 * @param   h   the hashtable to remove the item from
 * @param   k   the key to search for  - does not claim ownership
 * @return      the value associated with the key, or NULL if none found
 */

void * /* returns value */
hashtable_remove(struct hashtable *h, void *k);

#define DEFINE_HASHTABLE_REMOVE(fnname, keytype, valuetype) \
valuetype * fnname (struct hashtable *h, keytype *k) \
{ \
    return (valuetype *) (hashtable_remove(h,k)); \
}


/*****************************************************************************
 * hashtable_count
   
 * @name        hashtable_count
 * @param   h   the hashtable
 * @return      the number of items stored in the hashtable
 */
unsigned int
hashtable_count(struct hashtable *h);


/*****************************************************************************
 * hashtable_destroy
   
 * @name        hashtable_destroy
 * @param   h   the hashtable
 * @param       free_values     whether to call 'free' on the remaining values
 */

void
hashtable_destroy(struct hashtable *h, int free_values);

#endif /* __HASHTABLE_CWC22_H__ */

/*
 * Copyright (C) 2002 Christopher Clark <firstname.lastname@cl.cam.ac.uk>
 *
 * 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 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
 * THE AUTHORS 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.
 * */



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