1 /* 2 * Copyright © 2008 Intel Corporation 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining a 5 * copy of this software and associated documentation files (the "Software"), 6 * to deal in the Software without restriction, including without limitation 7 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 8 * and/or sell copies of the Software, and to permit persons to whom the 9 * Software is furnished to do so, subject to the following conditions: 10 * 11 * The above copyright notice and this permission notice (including the next 12 * paragraph) shall be included in all copies or substantial portions of the 13 * Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 21 * DEALINGS IN THE SOFTWARE. 22 */ 23 24 /** 25 * \file hash_table.h 26 * \brief Implementation of a generic, opaque hash table data type. 27 * 28 * \author Ian Romanick <ian.d.romanick@intel.com> 29 */ 30 31 #ifndef HASH_TABLE_H 32 #define HASH_TABLE_H 33 34 #include <string.h> 35 #include <stdbool.h> 36 #include <stdlib.h> 37 #include <stdint.h> 38 #include <limits.h> 39 #include <assert.h> 40 41 struct string_to_uint_map; 42 43 #ifdef __cplusplus 44 extern "C" { 45 #endif 46 47 struct hash_table; 48 49 typedef unsigned (*hash_func_t)(const void *key); 50 typedef int (*hash_compare_func_t)(const void *key1, const void *key2); 51 52 /** 53 * Hash table constructor 54 * 55 * Creates a hash table with the specified number of buckets. The supplied 56 * \c hash and \c compare routines are used when adding elements to the table 57 * and when searching for elements in the table. 58 * 59 * \param num_buckets Number of buckets (bins) in the hash table. 60 * \param hash Function used to compute hash value of input keys. 61 * \param compare Function used to compare keys. 62 */ 63 extern struct hash_table *hash_table_ctor(unsigned num_buckets, 64 hash_func_t hash, hash_compare_func_t compare); 65 66 67 /** 68 * Release all memory associated with a hash table 69 * 70 * \warning 71 * This function cannot release memory occupied either by keys or data. 72 */ 73 extern void hash_table_dtor(struct hash_table *ht); 74 75 76 /** 77 * Flush all entries from a hash table 78 * 79 * \param ht Table to be cleared of its entries. 80 */ 81 extern void hash_table_clear(struct hash_table *ht); 82 83 84 /** 85 * Search a hash table for a specific element 86 * 87 * \param ht Table to be searched 88 * \param key Key of the desired element 89 * 90 * \return 91 * The \c data value supplied to \c hash_table_insert when the element with 92 * the matching key was added. If no matching key exists in the table, 93 * \c NULL is returned. 94 */ 95 extern void *hash_table_find(struct hash_table *ht, const void *key); 96 97 98 /** 99 * Add an element to a hash table 100 * 101 * \warning 102 * If \c key is already in the hash table, it will be added again. Future 103 * calls to \c hash_table_find and \c hash_table_remove will return or remove, 104 * repsectively, the most recently added instance of \c key. 105 * 106 * \warning 107 * The value passed by \c key is kept in the hash table and is used by later 108 * calls to \c hash_table_find. 109 * 110 * \sa hash_table_replace 111 */ 112 extern void hash_table_insert(struct hash_table *ht, void *data, 113 const void *key); 114 115 /** 116 * Add an element to a hash table with replacement 117 * 118 * \return 119 * 1 if it did replace the the value (in which case the old key is kept), 0 if 120 * it did not replace the value (in which case the new key is kept). 121 * 122 * \warning 123 * If \c key is already in the hash table, \c data will \b replace the most 124 * recently inserted \c data (see the warning in \c hash_table_insert) for 125 * that key. 126 * 127 * \sa hash_table_insert 128 */ 129 extern bool hash_table_replace(struct hash_table *ht, void *data, 130 const void *key); 131 132 /** 133 * Remove a specific element from a hash table. 134 */ 135 extern void hash_table_remove(struct hash_table *ht, const void *key); 136 137 /** 138 * Compute hash value of a string 139 * 140 * Computes the hash value of a string using the DJB2 algorithm developed by 141 * Professor Daniel J. Bernstein. It was published on comp.lang.c once upon 142 * a time. I was unable to find the original posting in the archives. 143 * 144 * \param key Pointer to a NUL terminated string to be hashed. 145 * 146 * \sa hash_table_string_compare 147 */ 148 extern unsigned hash_table_string_hash(const void *key); 149 150 151 /** 152 * Compare two strings used as keys 153 * 154 * This is just a macro wrapper around \c strcmp. 155 * 156 * \sa hash_table_string_hash 157 */ 158 #define hash_table_string_compare ((hash_compare_func_t) strcmp) 159 160 161 /** 162 * Compute hash value of a pointer 163 * 164 * \param key Pointer to be used as a hash key 165 * 166 * \note 167 * The memory pointed to by \c key is \b never accessed. The value of \c key 168 * itself is used as the hash key 169 * 170 * \sa hash_table_pointer_compare 171 */ 172 unsigned 173 hash_table_pointer_hash(const void *key); 174 175 176 /** 177 * Compare two pointers used as keys 178 * 179 * \sa hash_table_pointer_hash 180 */ 181 int 182 hash_table_pointer_compare(const void *key1, const void *key2); 183 184 void 185 hash_table_call_foreach(struct hash_table *ht, 186 void (*callback)(const void *key, 187 void *data, 188 void *closure), 189 void *closure); 190 191 struct string_to_uint_map * 192 string_to_uint_map_ctor(); 193 194 void 195 string_to_uint_map_dtor(struct string_to_uint_map *); 196 197 198 #ifdef __cplusplus 199 } 200 201 /** 202 * Map from a string (name) to an unsigned integer value 203 * 204 * \note 205 * Because of the way this class interacts with the \c hash_table 206 * implementation, values of \c UINT_MAX cannot be stored in the map. 207 */ 208 struct string_to_uint_map { 209 public: string_to_uint_mapstring_to_uint_map210 string_to_uint_map() 211 { 212 this->ht = hash_table_ctor(0, hash_table_string_hash, 213 hash_table_string_compare); 214 } 215 ~string_to_uint_mapstring_to_uint_map216 ~string_to_uint_map() 217 { 218 hash_table_call_foreach(this->ht, delete_key, NULL); 219 hash_table_dtor(this->ht); 220 } 221 222 /** 223 * Remove all mappings from this map. 224 */ clearstring_to_uint_map225 void clear() 226 { 227 hash_table_call_foreach(this->ht, delete_key, NULL); 228 hash_table_clear(this->ht); 229 } 230 231 /** 232 * Get the value associated with a particular key 233 * 234 * \return 235 * If \c key is found in the map, \c true is returned. Otherwise \c false 236 * is returned. 237 * 238 * \note 239 * If \c key is not found in the table, \c value is not modified. 240 */ getstring_to_uint_map241 bool get(unsigned &value, const char *key) 242 { 243 const intptr_t v = 244 (intptr_t) hash_table_find(this->ht, (const void *) key); 245 246 if (v == 0) 247 return false; 248 249 value = (unsigned)(v - 1); 250 return true; 251 } 252 putstring_to_uint_map253 void put(unsigned value, const char *key) 254 { 255 /* The low-level hash table structure returns NULL if key is not in the 256 * hash table. However, users of this map might want to store zero as a 257 * valid value in the table. Bias the value by +1 so that a 258 * user-specified zero is stored as 1. This enables ::get to tell the 259 * difference between a user-specified zero (returned as 1 by 260 * hash_table_find) and the key not in the table (returned as 0 by 261 * hash_table_find). 262 * 263 * The net effect is that we can't store UINT_MAX in the table. This is 264 * because UINT_MAX+1 = 0. 265 */ 266 assert(value != UINT_MAX); 267 char *dup_key = strdup(key); 268 bool result = hash_table_replace(this->ht, 269 (void *) (intptr_t) (value + 1), 270 dup_key); 271 if (result) 272 free(dup_key); 273 } 274 275 private: delete_keystring_to_uint_map276 static void delete_key(const void *key, void *data, void *closure) 277 { 278 (void) data; 279 (void) closure; 280 281 free((char *)key); 282 } 283 284 struct hash_table *ht; 285 }; 286 287 #endif /* __cplusplus */ 288 #endif /* HASH_TABLE_H */ 289