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26 * \brief Implementation of a generic, opaque hash table data type.
28 * \author Ian Romanick <ian.d.romanick@intel.com>
41 struct string_to_uint_map
;
49 typedef unsigned (*hash_func_t
)(const void *key
);
50 typedef int (*hash_compare_func_t
)(const void *key1
, const void *key2
);
53 * Hash table constructor
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.
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.
63 extern struct hash_table
*hash_table_ctor(unsigned num_buckets
,
64 hash_func_t hash
, hash_compare_func_t compare
);
68 * Release all memory associated with a hash table
71 * This function cannot release memory occupied either by keys or data.
73 extern void hash_table_dtor(struct hash_table
*ht
);
77 * Flush all entries from a hash table
79 * \param ht Table to be cleared of its entries.
81 extern void hash_table_clear(struct hash_table
*ht
);
85 * Search a hash table for a specific element
87 * \param ht Table to be searched
88 * \param key Key of the desired element
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.
95 extern void *hash_table_find(struct hash_table
*ht
, const void *key
);
99 * Add an element to a hash table
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.
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.
110 * \sa hash_table_replace
112 extern void hash_table_insert(struct hash_table
*ht
, void *data
,
116 * Add an element to a hash table with replacement
119 * 1 if it did replace the value (in which case the old key is kept), 0 if it
120 * did not replace the value (in which case the new key is kept).
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
127 * \sa hash_table_insert
129 extern bool hash_table_replace(struct hash_table
*ht
, void *data
,
133 * Remove a specific element from a hash table.
135 extern void hash_table_remove(struct hash_table
*ht
, const void *key
);
138 * Compute hash value of a string
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.
144 * \param key Pointer to a NUL terminated string to be hashed.
146 * \sa hash_table_string_compare
148 extern unsigned hash_table_string_hash(const void *key
);
152 * Compare two strings used as keys
154 * This is just a macro wrapper around \c strcmp.
156 * \sa hash_table_string_hash
158 #define hash_table_string_compare ((hash_compare_func_t) strcmp)
162 * Compute hash value of a pointer
164 * \param key Pointer to be used as a hash key
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
170 * \sa hash_table_pointer_compare
173 hash_table_pointer_hash(const void *key
);
177 * Compare two pointers used as keys
179 * \sa hash_table_pointer_hash
182 hash_table_pointer_compare(const void *key1
, const void *key2
);
185 hash_table_call_foreach(struct hash_table
*ht
,
186 void (*callback
)(const void *key
,
191 struct string_to_uint_map
*
192 string_to_uint_map_ctor();
195 string_to_uint_map_dtor(struct string_to_uint_map
*);
201 struct string_map_iterate_wrapper_closure
{
202 void (*callback
)(const char *key
, unsigned value
, void *closure
);
207 * Map from a string (name) to an unsigned integer value
210 * Because of the way this class interacts with the \c hash_table
211 * implementation, values of \c UINT_MAX cannot be stored in the map.
213 struct string_to_uint_map
{
217 this->ht
= hash_table_ctor(0, hash_table_string_hash
,
218 hash_table_string_compare
);
221 ~string_to_uint_map()
223 hash_table_call_foreach(this->ht
, delete_key
, NULL
);
224 hash_table_dtor(this->ht
);
228 * Remove all mappings from this map.
232 hash_table_call_foreach(this->ht
, delete_key
, NULL
);
233 hash_table_clear(this->ht
);
237 * Runs a passed callback for the hash
239 void iterate(void (*func
)(const char *, unsigned, void *), void *closure
)
241 struct string_map_iterate_wrapper_closure
*wrapper
;
243 wrapper
= (struct string_map_iterate_wrapper_closure
*)
244 malloc(sizeof(struct string_map_iterate_wrapper_closure
));
248 wrapper
->callback
= func
;
249 wrapper
->closure
= closure
;
251 hash_table_call_foreach(this->ht
, subtract_one_wrapper
, wrapper
);
256 * Get the value associated with a particular key
259 * If \c key is found in the map, \c true is returned. Otherwise \c false
263 * If \c key is not found in the table, \c value is not modified.
265 bool get(unsigned &value
, const char *key
)
268 (intptr_t) hash_table_find(this->ht
, (const void *) key
);
273 value
= (unsigned)(v
- 1);
277 void put(unsigned value
, const char *key
)
279 /* The low-level hash table structure returns NULL if key is not in the
280 * hash table. However, users of this map might want to store zero as a
281 * valid value in the table. Bias the value by +1 so that a
282 * user-specified zero is stored as 1. This enables ::get to tell the
283 * difference between a user-specified zero (returned as 1 by
284 * hash_table_find) and the key not in the table (returned as 0 by
287 * The net effect is that we can't store UINT_MAX in the table. This is
288 * because UINT_MAX+1 = 0.
290 assert(value
!= UINT_MAX
);
291 char *dup_key
= strdup(key
);
292 bool result
= hash_table_replace(this->ht
,
293 (void *) (intptr_t) (value
+ 1),
300 static void delete_key(const void *key
, void *data
, void *closure
)
308 static void subtract_one_wrapper(const void *key
, void *data
, void *closure
)
310 struct string_map_iterate_wrapper_closure
*wrapper
=
311 (struct string_map_iterate_wrapper_closure
*) closure
;
312 unsigned value
= (intptr_t) data
;
316 wrapper
->callback((const char *) key
, value
, wrapper
->closure
);
319 struct hash_table
*ht
;
322 #endif /* __cplusplus */
323 #endif /* HASH_TABLE_H */