4 * Copyright 2004, 2006 Develer S.r.l. (http://www.develer.com/)
5 * Copyright 2004 Giovanni Bajo
9 * \brief Portable hash table
11 * This file implements a portable hash table, with the following features:
13 * \li Open double-hashing. The maximum number of elements is fixed. The double hashing
14 * function improves recovery in case of collisions.
15 * \li Configurable size (which is clamped to a power of two)
16 * \li Visiting interface through iterator (returns the element in random order).
17 * \li The key is stored within the data and a hook is used to extract it. Optionally, it
18 * is possible to store a copy of the key within the hash table.
20 * Since the hashing is open, there is no way to remove elements from the table. Instead, a
21 * function is provided to clear the table completely.
23 * The data stored within the table must be a pointer. The NULL pointer is used as
24 * a marker for a free node, so it is invalid to store a NULL pointer in the table
25 * with \c ht_insert().
29 * \author Giovanni Bajo <rasky@develer.com>
34 *#* Revision 1.8 2006/07/19 12:56:27 bernie
35 *#* Convert to new Doxygen style.
37 *#* Revision 1.7 2006/06/01 12:27:39 marco
38 *#* Added utilities for protocols
42 #ifndef MWARE_HASHTABLE_H
43 #define MWARE_HASHTABLE_H
45 #include <cfg/compiler.h>
46 #include <cfg/macros.h>
47 #include <cfg/debug.h>
50 * Enable/disable support to declare special hash tables which maintain a copy of
51 * the key internally instead of relying on the hook to extract it from the data.
53 #define CONFIG_HT_OPTIONAL_INTERNAL_KEY 1
55 /// Maximum length of the internal key (use (2^n)-1 for slight speedup)
56 #define INTERNAL_KEY_MAX_LENGTH 15
59 * Hook to get the key from \a data, which is an element of the hash table. The
60 * key must be returned together with \a key_length (in words).
62 typedef const void *(*hook_get_key)(const void *data, uint8_t *key_length);
66 * Hash table description
68 * \note This structures MUST NOT be accessed directly. Its definition is
69 * provided in the header file only for optimization purposes (see the rationale
72 * \note If new elements must be added to this list, please double check
73 * \c DECLARE_HASHTABLE, which requires the existing elements to be at the top.
77 const void **mem; ///< Buckets of data
78 uint16_t max_elts_log2; ///< Log2 of the size of the table
80 bool key_internal : 1; ///< true if the key is copied internally
83 hook_get_key hook; ///< Hook to get the key
84 uint8_t *mem; ///< Pointer to the key memory
89 /// Iterator to walk the hash table
98 * Declare a hash table in the current scope
100 * \param name Variable name
101 * \param size Number of elements
102 * \param hook_gk Hook to be used to extract the key from the node
104 * \note The number of elements will be rounded down to the nearest
108 #define DECLARE_HASHTABLE(name, size, hook_gk) \
109 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
110 struct HashTable name = { name##_nodes, UINT32_LOG2(size), { false }, hook_gk }
112 /** Exactly like \c DECLARE_HASHTABLE, but the variable will be declared as static. */
113 #define DECLARE_HASHTABLE_STATIC(name, size, hook_gk) \
114 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
115 static struct HashTable name = { name##_nodes, UINT32_LOG2(size), { false }, { hook_gk } }
117 #if CONFIG_HT_OPTIONAL_INTERNAL_KEY
118 /** Declare a hash table with internal copies of the keys. This version does not
119 * require a hook, nor it requires the user to allocate static memory for the keys.
120 * It is mostly suggested for tables whose keys are computed on the fly and need
121 * to be stored somewhere.
123 #define DECLARE_HASHTABLE_INTERNALKEY(name, size) \
124 static uint8_t name##_keys[(1 << UINT32_LOG2(size)) * (INTERNAL_KEY_MAX_LENGTH + 1)]; \
125 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
126 struct HashTable name = { name##_nodes, UINT32_LOG2(size), { true }, name##_keys }
128 /** Exactly like \c DECLARE_HASHTABLE_INTERNALKEY, but the variable will be declared as static. */
129 #define DECLARE_HASHTABLE_INTERNALKEY_STATIC(name, size) \
130 static uint8_t name##_keys[(1 << UINT32_LOG2(size)) * (INTERNAL_KEY_MAX_LENGTH + 1)]; \
131 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
132 static struct HashTable name = { name##_nodes, UINT32_LOG2(size), { true }, name##_keys }
136 * Initialize (and clear) a hash table in a memory buffer.
138 * \param ht Hash table declared with \c DECLARE_HASHTABLE
140 * \note This function must be called before using the hash table. Optionally,
141 * it can be called later in the program to clear the hash table,
142 * removing all its elements.
144 void ht_init(struct HashTable* ht);
147 * Insert an element into the hash table
149 * \param ht Handle of the hash table
150 * \param data Data to be inserted into the table
151 * \return true if insertion was successful, false otherwise (table is full)
153 * \note The key for the element to insert is extract from the data with
154 * the hook. This means that this function cannot be called for hashtables
155 * with internal keys.
157 * \note If an element with the same key already exists in the table,
158 * it will be overwritten.
160 * \note It is not allowed to store NULL in the table. If you pass NULL as data,
161 * the function call will fail.
163 bool ht_insert(struct HashTable* ht, const void* data);
166 * Insert an element into the hash table
168 * \param ht Handle of the hash table
169 * \param key Key of the element
170 * \param key_length Length of the key in characters
171 * \param data Data to be inserted into the table
172 * \return true if insertion was successful, false otherwise (table is full)
174 * \note If this function is called for hash table with external keys,
175 * the key provided must be match the key that would be extracted with the
176 * hook, otherwise the function will fail.
178 * \note If an element with the same key already exists in the table,
179 * it will be overwritten.
181 * \note It is not allowed to store NULL in the table. If you pass NULL as data,
182 * the function call will fail.
184 bool ht_insert_with_key(struct HashTable* ht, const void* key, uint8_t key_length, const void* data);
187 * Find an element in the hash table
189 * \param ht Handle of the hash table
190 * \param key Key of the element
191 * \param key_length Length of the key in characters
192 * \return Data of the element, or NULL if no element was found for the given key.
194 const void* ht_find(struct HashTable* ht, const void* key, uint8_t key_length);
196 /** Similar to \c ht_insert_with_key() but \a key is an ASCIIZ string */
197 #define ht_insert_str(ht, key, data) ht_insert_with_key(ht, key, strlen(key), data)
199 /** Similar to \c ht_find() but \a key is an ASCIIZ string */
200 #define ht_find_str(ht, key) ht_find(ht, key, strlen(key))
202 /// Get an iterator to the begin of the hash table \a ht
203 INLINE HashIterator ht_iter_begin(struct HashTable* ht)
208 h.end = &ht->mem[1 << ht->max_elts_log2];
210 while (h.pos != h.end && !*h.pos)
217 * Get an iterator to the (exclusive) end of the hash table \a ht
219 * \note Like in STL, the end iterator is not a valid iterator (you
220 * cannot call \c ht_iter_get() on it), and it must be used only to
221 * detect if we reached the end of the iteration (through \c ht_iter_cmp()).
223 INLINE HashIterator ht_iter_end(struct HashTable* ht)
227 h.pos = h.end = &ht->mem[1 << ht->max_elts_log2];
232 /// Compare \a it1 and \a it2 for equality
233 INLINE bool ht_iter_cmp(HashIterator it1, HashIterator it2)
235 ASSERT(it1.end == it2.end);
236 return it1.pos == it2.pos;
239 /// Get the element within the hash table \a ht pointed by the iterator \a iter
240 INLINE const void* ht_iter_get(HashIterator iter)
241 { return *iter.pos; }
243 /** Return an iterator pointing to the element following \a h
245 * \note The order of the elements visited during the iteration is casual,
246 * and depends on the implementation.
249 INLINE HashIterator ht_iter_next(HashIterator h)
252 while (h.pos != h.end && !(*h.pos))
258 #endif /* MWARE_HASHTABLE_H */