4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 * GNU General Public License for more details.
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17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
29 * Copyright 2004, 2006, 2008 Develer S.r.l. (http://www.develer.com/)
30 * Copyright 2004 Giovanni Bajo
33 * \brief Portable hash table
35 * This file implements a portable hash table, with the following features:
37 * \li Open double-hashing. The maximum number of elements is fixed. The double hashing
38 * function improves recovery in case of collisions.
39 * \li Configurable size (which is clamped to a power of two)
40 * \li Visiting interface through iterator (returns the element in random order).
41 * \li The key is stored within the data and a hook is used to extract it. Optionally, it
42 * is possible to store a copy of the key within the hash table.
44 * Since the hashing is open, there is no way to remove elements from the table. Instead, a
45 * function is provided to clear the table completely.
47 * The data stored within the table must be a pointer. The NULL pointer is used as
48 * a marker for a free node, so it is invalid to store a NULL pointer in the table
49 * with \c ht_insert().
52 * \author Giovanni Bajo <rasky@develer.com>
55 #ifndef STRUCT_HASHTABLE_H
56 #define STRUCT_HASHTABLE_H
58 #include <cfg/compiler.h>
59 #include <cfg/macros.h>
60 #include <cfg/debug.h>
63 * Enable/disable support to declare special hash tables which maintain a copy of
64 * the key internally instead of relying on the hook to extract it from the data.
66 #define CONFIG_HT_OPTIONAL_INTERNAL_KEY 1
68 /// Maximum length of the internal key (use (2^n)-1 for slight speedup)
69 #define INTERNAL_KEY_MAX_LENGTH 15
72 * Hook to get the key from \a data, which is an element of the hash table. The
73 * key must be returned together with \a key_length (in words).
75 typedef const void *(*hook_get_key)(const void *data, uint8_t *key_length);
79 * Hash table description
81 * \note This structures MUST NOT be accessed directly. Its definition is
82 * provided in the header file only for optimization purposes (see the rationale
85 * \note If new elements must be added to this list, please double check
86 * \c DECLARE_HASHTABLE, which requires the existing elements to be at the top.
90 const void **mem; ///< Buckets of data
91 uint16_t max_elts_log2; ///< Log2 of the size of the table
93 bool key_internal : 1; ///< true if the key is copied internally
96 hook_get_key hook; ///< Hook to get the key
97 uint8_t *mem; ///< Pointer to the key memory
102 /// Iterator to walk the hash table
111 * Declare a hash table in the current scope
113 * \param name Variable name
114 * \param size Number of elements
115 * \param hook_gk Hook to be used to extract the key from the node
117 * \note The number of elements will be rounded down to the nearest
121 #define DECLARE_HASHTABLE(name, size, hook_gk) \
122 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
123 struct HashTable name = { name##_nodes, UINT32_LOG2(size), { false }, hook_gk }
125 /** Exactly like \c DECLARE_HASHTABLE, but the variable will be declared as static. */
126 #define DECLARE_HASHTABLE_STATIC(name, size, hook_gk) \
127 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
128 static struct HashTable name = { name##_nodes, UINT32_LOG2(size), { false }, { hook_gk } }
130 #if CONFIG_HT_OPTIONAL_INTERNAL_KEY
131 /** Declare a hash table with internal copies of the keys. This version does not
132 * require a hook, nor it requires the user to allocate static memory for the keys.
133 * It is mostly suggested for tables whose keys are computed on the fly and need
134 * to be stored somewhere.
136 #define DECLARE_HASHTABLE_INTERNALKEY(name, size) \
137 static uint8_t name##_keys[(1 << UINT32_LOG2(size)) * (INTERNAL_KEY_MAX_LENGTH + 1)]; \
138 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
139 struct HashTable name = { name##_nodes, UINT32_LOG2(size), { true }, name##_keys }
141 /** Exactly like \c DECLARE_HASHTABLE_INTERNALKEY, but the variable will be declared as static. */
142 #define DECLARE_HASHTABLE_INTERNALKEY_STATIC(name, size) \
143 static uint8_t name##_keys[(1 << UINT32_LOG2(size)) * (INTERNAL_KEY_MAX_LENGTH + 1)]; \
144 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
145 static struct HashTable name = { name##_nodes, UINT32_LOG2(size), { true }, name##_keys }
149 * Initialize (and clear) a hash table in a memory buffer.
151 * \param ht Hash table declared with \c DECLARE_HASHTABLE
153 * \note This function must be called before using the hash table. Optionally,
154 * it can be called later in the program to clear the hash table,
155 * removing all its elements.
157 void ht_init(struct HashTable* ht);
160 * Insert an element into the hash table
162 * \param ht Handle of the hash table
163 * \param data Data to be inserted into the table
164 * \return true if insertion was successful, false otherwise (table is full)
166 * \note The key for the element to insert is extract from the data with
167 * the hook. This means that this function cannot be called for hashtables
168 * with internal keys.
170 * \note If an element with the same key already exists in the table,
171 * it will be overwritten.
173 * \note It is not allowed to store NULL in the table. If you pass NULL as data,
174 * the function call will fail.
176 bool ht_insert(struct HashTable* ht, const void* data);
179 * Insert an element into the hash table
181 * \param ht Handle of the hash table
182 * \param key Key of the element
183 * \param key_length Length of the key in characters
184 * \param data Data to be inserted into the table
185 * \return true if insertion was successful, false otherwise (table is full)
187 * \note If this function is called for hash table with external keys,
188 * the key provided must be match the key that would be extracted with the
189 * hook, otherwise the function will fail.
191 * \note If an element with the same key already exists in the table,
192 * it will be overwritten.
194 * \note It is not allowed to store NULL in the table. If you pass NULL as data,
195 * the function call will fail.
197 bool ht_insert_with_key(struct HashTable* ht, const void* key, uint8_t key_length, const void* data);
200 * Find an element in the hash table
202 * \param ht Handle of the hash table
203 * \param key Key of the element
204 * \param key_length Length of the key in characters
205 * \return Data of the element, or NULL if no element was found for the given key.
207 const void* ht_find(struct HashTable* ht, const void* key, uint8_t key_length);
209 /** Similar to \c ht_insert_with_key() but \a key is an ASCIIZ string */
210 #define ht_insert_str(ht, key, data) ht_insert_with_key(ht, key, strlen(key), data)
212 /** Similar to \c ht_find() but \a key is an ASCIIZ string */
213 #define ht_find_str(ht, key) ht_find(ht, key, strlen(key))
215 /// Get an iterator to the begin of the hash table \a ht
216 INLINE HashIterator ht_iter_begin(struct HashTable* ht)
221 h.end = &ht->mem[1 << ht->max_elts_log2];
223 while (h.pos != h.end && !*h.pos)
230 * Get an iterator to the (exclusive) end of the hash table \a ht
232 * \note Like in STL, the end iterator is not a valid iterator (you
233 * cannot call \c ht_iter_get() on it), and it must be used only to
234 * detect if we reached the end of the iteration (through \c ht_iter_cmp()).
236 INLINE HashIterator ht_iter_end(struct HashTable* ht)
240 h.pos = h.end = &ht->mem[1 << ht->max_elts_log2];
245 /// Compare \a it1 and \a it2 for equality
246 INLINE bool ht_iter_cmp(HashIterator it1, HashIterator it2)
248 ASSERT(it1.end == it2.end);
249 return it1.pos == it2.pos;
252 /// Get the element within the hash table \a ht pointed by the iterator \a iter
253 INLINE const void* ht_iter_get(HashIterator iter)
254 { return *iter.pos; }
256 /** Return an iterator pointing to the element following \a h
258 * \note The order of the elements visited during the iteration is casual,
259 * and depends on the implementation.
262 INLINE HashIterator ht_iter_next(HashIterator h)
265 while (h.pos != h.end && !(*h.pos))
271 #endif /* STRUCT_HASHTABLE_H */