00001 /* 00002 * Asterisk -- An open source telephony toolkit. 00003 * 00004 * Copyright (C) 2006, Digium, Inc. 00005 * 00006 * Steve Murphy <murf@digium.com> 00007 * 00008 * See http://www.asterisk.org for more information about 00009 * the Asterisk project. Please do not directly contact 00010 * any of the maintainers of this project for assistance; 00011 * the project provides a web site, mailing lists and IRC 00012 * channels for your use. 00013 * 00014 * This program is free software, distributed under the terms of 00015 * the GNU General Public License Version 2. See the LICENSE file 00016 * at the top of the source tree. 00017 */ 00018 #ifndef _ASTERISK_HASHTAB_H_ 00019 #define _ASTERISK_HASHTAB_H_ 00020 #define __USE_UNIX98 1 /* to get the MUTEX_RECURSIVE stuff */ 00021 00022 /*! \file 00023 * \brief Generic (perhaps overly so) hashtable implementation 00024 * \ref AstHash 00025 */ 00026 /*! \page AstHash Hash Table support in Asterisk 00027 00028 A hash table is a structure that allows for an exact-match search 00029 in O(1) (or close to that) time. 00030 00031 The method: given: a set of {key,val} pairs. (at a minimum). 00032 given: a hash function, which, given a key, 00033 will return an integer. Ideally, each key in the 00034 set will have its own unique associated hash value. 00035 This hash number will index into an array. "buckets" 00036 are what the elements of this array are called. To 00037 handle possible collisions in hash values, buckets can form a list. 00038 00039 The key for a value must be contained in the value, or we won't 00040 be able to find it in the bucket list. 00041 00042 This implementation is pretty generic, because: 00043 00044 1. The value and key are expected to be in a structure 00045 (along with other data, perhaps) and it's address is a "void *". 00046 2. The pointer to a compare function must be passed in at the 00047 time of creation, and is stored in the hashtable. 00048 3. The pointer to a resize function, which returns 1 if the 00049 hash table is to be grown. A default routine is provided 00050 if the pointer is NULL, and uses the java hashtable metric 00051 of a 75% load factor. 00052 4. The pointer to a "new size" function, which returns a preferable 00053 new size for the hash table bucket array. By default, a function 00054 is supplied which roughly doubles the size of the array, is provided. 00055 This size should ideally be a prime number. 00056 5. The hashing function pointer must also be supplied. This function 00057 must be written by the user to access the keys in the objects being 00058 stored. Some helper functions that use a simple "mult by prime, add 00059 the next char", sort of string hash, or a simple modulus of the hash 00060 table size for ints, is provided; the user can use these simple 00061 algorithms to generate a hash, or implement any other algorithms they 00062 wish. 00063 6. Recently updated the hash routines to use Doubly-linked lists for buckets, 00064 and added a doubly-linked list that threads thru every bucket in the table. 00065 The list of all buckets is on the HashTab struct. The Traversal was modified 00066 to go thru this list instead of searching the bucket array for buckets. 00067 This also should make it safe to remove a bucket during the traversal. 00068 Removal and destruction routines will work faster. 00069 */ 00070 00071 struct ast_hashtab_bucket 00072 { 00073 const void *object; /*!< whatever it is we are storing in this table */ 00074 struct ast_hashtab_bucket *next; /*!< a DLL of buckets in hash collision */ 00075 struct ast_hashtab_bucket *prev; /*!< a DLL of buckets in hash collision */ 00076 struct ast_hashtab_bucket *tnext; /*!< a DLL of all the hash buckets for traversal */ 00077 struct ast_hashtab_bucket *tprev; /*!< a DLL of all the hash buckets for traversal */ 00078 }; 00079 00080 struct ast_hashtab 00081 { 00082 struct ast_hashtab_bucket **array; 00083 struct ast_hashtab_bucket *tlist; /*!< the head of a DLList of all the hashbuckets in the table (for traversal). */ 00084 00085 int (*compare) (const void *a, const void *b); /*!< a ptr to func that returns int, and take two void* ptrs, compares them, 00086 rets -1 if a < b; rets 0 if a==b; rets 1 if a>b */ 00087 int (*newsize) (struct ast_hashtab *tab); /*!< a ptr to func that returns int, a new size for hash tab, based on curr_size */ 00088 int (*resize) (struct ast_hashtab *tab); /*!< a function to decide whether this hashtable should be resized now */ 00089 unsigned int (*hash) (const void *obj); /*!< a hash func ptr for this table. Given a raw ptr to an obj, 00090 it calcs a hash.*/ 00091 int hash_tab_size; /*!< the size of the bucket array */ 00092 int hash_tab_elements; /*!< the number of objects currently stored in the table */ 00093 int largest_bucket_size; /*!< a stat on the health of the table */ 00094 int resize_count; /*!< a count of the number of times this table has been 00095 resized */ 00096 int do_locking; /*!< if 1 use locks to guarantee safety of insertions/deletions */ 00097 /* this spot reserved for the proper lock storage */ 00098 ast_rwlock_t lock; /* is this as good as it sounds? */ 00099 }; 00100 00101 /*! \brief an iterator for traversing the buckets */ 00102 struct ast_hashtab_iter 00103 { 00104 struct ast_hashtab *tab; 00105 struct ast_hashtab_bucket *next; 00106 }; 00107 00108 00109 /* some standard, default routines for general use */ 00110 00111 /*! \brief For sizing the hash table, tells if num is prime or not */ 00112 int ast_is_prime(int num); 00113 00114 /*! 00115 * \brief assumes a and b are char * 00116 * \return 0 if they match 00117 */ 00118 int ast_hashtab_compare_strings(const void *a, const void *b); 00119 00120 /*! 00121 * \brief assumes a & b are strings 00122 * \return 0 if they match (strcasecmp) 00123 */ 00124 int ast_hashtab_compare_strings_nocase(const void *a, const void *b); 00125 00126 /*! 00127 * \brief assumes a & b are int * 00128 * \retval 0 if match 00129 * \retval 1 a > b 00130 * \retval -1 a < b 00131 */ 00132 int ast_hashtab_compare_ints(const void *a, const void *b); 00133 00134 /*! 00135 * \brief assumes a & b are short * 00136 * \retval 0 if match 00137 * \retval 1 a > b 00138 * \retval -1 a < b 00139 */ 00140 int ast_hashtab_compare_shorts(const void *a, const void *b); 00141 00142 /*! 00143 * \brief determine if resize should occur 00144 * \returns 1 if the table is 75% full or more 00145 */ 00146 int ast_hashtab_resize_java(struct ast_hashtab *tab); 00147 00148 /*! \brief no resizing; always return 0 */ 00149 int ast_hashtab_resize_tight(struct ast_hashtab *tab); 00150 00151 /*! \brief no resizing; always return 0 */ 00152 int ast_hashtab_resize_none(struct ast_hashtab *tab); 00153 00154 /*! \brief Create a prime number roughly 2x the current table size */ 00155 int ast_hashtab_newsize_java(struct ast_hashtab *tab); 00156 00157 /* not yet specified, probably will return 1.5x the current table size */ 00158 int ast_hashtab_newsize_tight(struct ast_hashtab *tab); 00159 00160 /*! \brief always return current size -- no resizing */ 00161 int ast_hashtab_newsize_none(struct ast_hashtab *tab); 00162 00163 /*! 00164 * \brief Hashes a string to a number 00165 * \param obj 00166 * \note A modulus is applied so it in the range 0 to mod-1 00167 */ 00168 unsigned int ast_hashtab_hash_string(const void *obj); 00169 00170 /*! \brief Upperases each char before using them for a hash */ 00171 unsigned int ast_hashtab_hash_string_nocase(const void *obj); 00172 00173 00174 unsigned int ast_hashtab_hash_string_sax(const void *obj); /* from Josh */ 00175 00176 00177 unsigned int ast_hashtab_hash_int(const int num); /* right now, both these funcs are just result = num%modulus; */ 00178 00179 00180 unsigned int ast_hashtab_hash_short(const short num); 00181 00182 00183 /*! 00184 * \brief Create the hashtable list 00185 * \param initial_buckets starting number of buckets 00186 * \param compare a func ptr to compare two elements in the hash -- cannot be null 00187 * \param resize a func ptr to decide if the table needs to be resized, a NULL ptr here will cause a default to be used 00188 * \param newsize a func ptr that returns a new size of the array. A NULL will cause a default to be used 00189 * \param hash a func ptr to do the hashing 00190 * \param do_locking use locks to guarantee safety of iterators/insertion/deletion -- real simpleminded right now 00191 */ 00192 struct ast_hashtab * ast_hashtab_create(int initial_buckets, 00193 int (*compare)(const void *a, const void *b), 00194 int (*resize)(struct ast_hashtab *), 00195 int (*newsize)(struct ast_hashtab *tab), 00196 unsigned int (*hash)(const void *obj), 00197 int do_locking ); 00198 00199 /*! 00200 * \brief This func will free the hash table and all its memory. 00201 * \note It doesn't touch the objects stored in it, unless you 00202 * specify a destroy func; it will call that func for each 00203 * object in the hashtab, remove all the objects, and then 00204 * free the hashtab itself. If no destroyfunc is specified 00205 * then the routine will assume you will free it yourself. 00206 * \param tab 00207 * \param objdestroyfunc 00208 */ 00209 void ast_hashtab_destroy( struct ast_hashtab *tab, void (*objdestroyfunc)(void *obj)); 00210 00211 00212 /*! 00213 * \brief Insert without checking 00214 * \param tab 00215 * \param obj 00216 * 00217 * Normally, you'd insert "safely" by checking to see if the element is 00218 * already there; in this case, you must already have checked. If an element 00219 * is already in the hashtable, that matches this one, most likely this one 00220 * will be found first. 00221 * \note will force a resize if the resize func returns 1 00222 * \retval 1 on success 00223 * \retval 0 if there's a problem 00224 */ 00225 int ast_hashtab_insert_immediate(struct ast_hashtab *tab, const void *obj); 00226 00227 /*! 00228 * \brief Insert without checking, hashing or locking 00229 * \param tab 00230 * \param obj 00231 * \param h hashed index value 00232 * 00233 * \note Will force a resize if the resize func returns 1 00234 * \retval 1 on success 00235 * \retval 0 if there's a problem 00236 */ 00237 int ast_hashtab_insert_immediate_bucket(struct ast_hashtab *tab, const void *obj, unsigned int h); 00238 00239 /*! 00240 * \brief Check and insert new object only if it is not there. 00241 * \note Will force a resize if the resize func returns 1 00242 * \retval 1 on success 00243 * \retval 0 if there's a problem, or it's already there. 00244 */ 00245 int ast_hashtab_insert_safe(struct ast_hashtab *tab, const void *obj); 00246 00247 /*! 00248 * \brief Lookup this object in the hash table. 00249 * \param tab 00250 * \param obj 00251 * \retval a ptr if found 00252 * \retval NULL if not found 00253 */ 00254 void * ast_hashtab_lookup(struct ast_hashtab *tab, const void *obj); 00255 00256 /*! 00257 * \brief Use this if have the hash val for the object 00258 * \note This and avoid the recalc of the hash (the modulus (table_size) is not applied) 00259 */ 00260 void * ast_hashtab_lookup_with_hash(struct ast_hashtab *tab, const void *obj, unsigned int hashval); 00261 00262 /*! 00263 * \brief Similar to ast_hashtab_lookup but sets h to the key hash value if the lookup fails. 00264 * \note This has the modulus applied, and will not be useful for long term storage if the table is resizable. 00265 */ 00266 void * ast_hashtab_lookup_bucket(struct ast_hashtab *tab, const void *obj, unsigned int *h); 00267 00268 /*! \brief Returns key stats for the table */ 00269 void ast_hashtab_get_stats( struct ast_hashtab *tab, int *biggest_bucket_size, int *resize_count, int *num_objects, int *num_buckets); 00270 00271 /*! \brief Returns the number of elements stored in the hashtab */ 00272 int ast_hashtab_size( struct ast_hashtab *tab); 00273 00274 /*! \brief Returns the size of the bucket array in the hashtab */ 00275 int ast_hashtab_capacity( struct ast_hashtab *tab); 00276 00277 /*! \brief Return a copy of the hash table */ 00278 struct ast_hashtab *ast_hashtab_dup(struct ast_hashtab *tab, void *(*obj_dup_func)(const void *obj)); 00279 00280 /*! \brief Gives an iterator to hastable */ 00281 struct ast_hashtab_iter *ast_hashtab_start_traversal(struct ast_hashtab *tab); 00282 00283 /*! \brief end the traversal, free the iterator, unlock if necc. */ 00284 void ast_hashtab_end_traversal(struct ast_hashtab_iter *it); 00285 00286 /*! \brief Gets the next object in the list, advances iter one step returns null on end of traversal */ 00287 void *ast_hashtab_next(struct ast_hashtab_iter *it); 00288 00289 /*! \brief Looks up the object, removes the corresponding bucket */ 00290 void *ast_hashtab_remove_object_via_lookup(struct ast_hashtab *tab, void *obj); 00291 00292 /*! \brief Hash the object and then compare ptrs in bucket list instead of 00293 calling the compare routine, will remove the bucket */ 00294 void *ast_hashtab_remove_this_object(struct ast_hashtab *tab, void *obj); 00295 00296 /* ------------------ */ 00297 /* for lock-enabled traversals with ability to remove an object during the traversal*/ 00298 /* ------------------ */ 00299 00300 /*! \brief Gives an iterator to hastable */ 00301 struct ast_hashtab_iter *ast_hashtab_start_write_traversal(struct ast_hashtab *tab); 00302 00303 /*! \brief Looks up the object, removes the corresponding bucket */ 00304 void *ast_hashtab_remove_object_via_lookup_nolock(struct ast_hashtab *tab, void *obj); 00305 00306 /*! \brief Hash the object and then compare ptrs in bucket list instead of 00307 calling the compare routine, will remove the bucket */ 00308 void *ast_hashtab_remove_this_object_nolock(struct ast_hashtab *tab, void *obj); 00309 00310 /* ------------------ */ 00311 /* ------------------ */ 00312 00313 /* user-controlled hashtab locking. Create a hashtab without locking, then call the 00314 following locking routines yourself to lock the table between threads. */ 00315 00316 /*! \brief Call this after you create the table to init the lock */ 00317 void ast_hashtab_initlock(struct ast_hashtab *tab); 00318 /*! \brief Request a write-lock on the table. */ 00319 void ast_hashtab_wrlock(struct ast_hashtab *tab); 00320 /*! \brief Request a read-lock on the table -- don't change anything! */ 00321 void ast_hashtab_rdlock(struct ast_hashtab *tab); 00322 /*! \brief release a read- or write- lock. */ 00323 void ast_hashtab_unlock(struct ast_hashtab *tab); 00324 /*! \brief Call this before you destroy the table. */ 00325 void ast_hashtab_destroylock(struct ast_hashtab *tab); 00326 00327 00328 #endif