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Diffstat (limited to 'mkfs.ubifs/hashtable/hashtable.h')
| -rw-r--r-- | mkfs.ubifs/hashtable/hashtable.h | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/mkfs.ubifs/hashtable/hashtable.h b/mkfs.ubifs/hashtable/hashtable.h new file mode 100644 index 0000000..b90781a --- /dev/null +++ b/mkfs.ubifs/hashtable/hashtable.h @@ -0,0 +1,199 @@ +/* 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 + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * 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. + * + * * Neither the name of the original author; nor the names of any contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * + * 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. +*/ |