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26 * \brief Implementation of a generic, opaque hash table data type.
28 * \author Ian Romanick <ian.d.romanick@intel.com>
40 struct string_to_uint_map;
48 typedef unsigned (*hash_func_t)(const void *key);
49 typedef int (*hash_compare_func_t)(const void *key1, const void *key2);
52 * Hash table constructor
54 * Creates a hash table with the specified number of buckets. The supplied
55 * \c hash and \c compare routines are used when adding elements to the table
56 * and when searching for elements in the table.
58 * \param num_buckets Number of buckets (bins) in the hash table.
59 * \param hash Function used to compute hash value of input keys.
60 * \param compare Function used to compare keys.
62 extern struct hash_table *hash_table_ctor(unsigned num_buckets,
63 hash_func_t hash, hash_compare_func_t compare);
67 * Release all memory associated with a hash table
70 * This function cannot release memory occupied either by keys or data.
72 extern void hash_table_dtor(struct hash_table *ht);
76 * Flush all entries from a hash table
78 * \param ht Table to be cleared of its entries.
80 extern void hash_table_clear(struct hash_table *ht);
84 * Search a hash table for a specific element
86 * \param ht Table to be searched
87 * \param key Key of the desired element
90 * The \c data value supplied to \c hash_table_insert when the element with
91 * the matching key was added. If no matching key exists in the table,
92 * \c NULL is returned.
94 extern void *hash_table_find(struct hash_table *ht, const void *key);
98 * Add an element to a hash table
101 * If \c key is already in the hash table, it will be added again. Future
102 * calls to \c hash_table_find and \c hash_table_remove will return or remove,
103 * repsectively, the most recently added instance of \c key.
106 * The value passed by \c key is kept in the hash table and is used by later
107 * calls to \c hash_table_find.
109 * \sa hash_table_replace
111 extern void hash_table_insert(struct hash_table *ht, void *data,
115 * Add an element to a hash table with replacement
118 * If \c key is already in the hash table, \c data will \b replace the most
119 * recently inserted \c data (see the warning in \c hash_table_insert) for
122 * \sa hash_table_insert
124 extern void hash_table_replace(struct hash_table *ht, void *data,
128 * Remove a specific element from a hash table.
130 extern void hash_table_remove(struct hash_table *ht, const void *key);
133 * Compute hash value of a string
135 * Computes the hash value of a string using the DJB2 algorithm developed by
136 * Professor Daniel J. Bernstein. It was published on comp.lang.c once upon
137 * a time. I was unable to find the original posting in the archives.
139 * \param key Pointer to a NUL terminated string to be hashed.
141 * \sa hash_table_string_compare
143 extern unsigned hash_table_string_hash(const void *key);
147 * Compare two strings used as keys
149 * This is just a macro wrapper around \c strcmp.
151 * \sa hash_table_string_hash
153 #define hash_table_string_compare ((hash_compare_func_t) strcmp)
157 * Compute hash value of a pointer
159 * \param key Pointer to be used as a hash key
162 * The memory pointed to by \c key is \b never accessed. The value of \c key
163 * itself is used as the hash key
165 * \sa hash_table_pointer_compare
168 hash_table_pointer_hash(const void *key);
172 * Compare two pointers used as keys
174 * \sa hash_table_pointer_hash
177 hash_table_pointer_compare(const void *key1, const void *key2);
180 hash_table_call_foreach(struct hash_table *ht,
181 void (*callback)(const void *key,
186 struct string_to_uint_map *
187 string_to_uint_map_ctor();
190 string_to_uint_map_dtor(struct string_to_uint_map *);
197 * Map from a string (name) to an unsigned integer value
200 * Because of the way this class interacts with the \c hash_table
201 * implementation, values of \c UINT_MAX cannot be stored in the map.
203 struct string_to_uint_map {
207 this->ht = hash_table_ctor(0, hash_table_string_hash,
208 hash_table_string_compare);
211 ~string_to_uint_map()
213 hash_table_call_foreach(this->ht, delete_key, NULL);
214 hash_table_dtor(this->ht);
218 * Remove all mappings from this map.
222 hash_table_clear(this->ht);
226 * Get the value associated with a particular key
229 * If \c key is found in the map, \c true is returned. Otherwise \c false
233 * If \c key is not found in the table, \c value is not modified.
235 bool get(unsigned &value, const char *key)
238 (intptr_t) hash_table_find(this->ht, (const void *) key);
243 value = (unsigned)(v - 1);
247 void put(unsigned value, const char *key)
249 /* The low-level hash table structure returns NULL if key is not in the
250 * hash table. However, users of this map might want to store zero as a
251 * valid value in the table. Bias the value by +1 so that a
252 * user-specified zero is stored as 1. This enables ::get to tell the
253 * difference between a user-specified zero (returned as 1 by
254 * hash_table_find) and the key not in the table (returned as 0 by
257 * The net effect is that we can't store UINT_MAX in the table. This is
258 * because UINT_MAX+1 = 0.
260 assert(value != UINT_MAX);
261 hash_table_replace(this->ht,
262 (void *) (intptr_t) (value + 1),
267 static void delete_key(const void *key, void *data, void *closure)
275 struct hash_table *ht;
278 #endif /* __cplusplus */
279 #endif /* HASH_TABLE_H */