4 * This file is part of BeRTOS.
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21 * library without restriction. Specifically, if other files instantiate
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24 * file does not by itself cause the resulting executable to be covered by
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29 * Copyright 2004, 2006, 2008 Develer S.r.l. (http://www.develer.com/)
30 * Copyright 2004 Giovanni Bajo
33 * \author Giovanni Bajo <rasky@develer.com>
35 * \brief Portable hash table
37 * This file implements a portable hash table, with the following features:
39 * \li Open double-hashing. The maximum number of elements is fixed. The double hashing
40 * function improves recovery in case of collisions.
41 * \li Configurable size (which is clamped to a power of two)
42 * \li Visiting interface through iterator (returns the element in random order).
43 * \li The key is stored within the data and a hook is used to extract it. Optionally, it
44 * is possible to store a copy of the key within the hash table.
46 * Since the hashing is open, there is no way to remove elements from the table. Instead, a
47 * function is provided to clear the table completely.
49 * The data stored within the table must be a pointer. The NULL pointer is used as
50 * a marker for a free node, so it is invalid to store a NULL pointer in the table
51 * with \c ht_insert().
53 * $WIZ$ module_name = "hashtable"
54 * $WIZ$ module_configuration = "bertos/cfg/cfg_hashtable.h"
57 #ifndef STRUCT_HASHTABLE_H
58 #define STRUCT_HASHTABLE_H
60 #include "cfg/cfg_hashtable.h"
62 #include <cfg/compiler.h>
63 #include <cfg/macros.h>
64 #include <cfg/debug.h>
66 /// Maximum length of the internal key (use (2^n)-1 for slight speedup)
67 #define INTERNAL_KEY_MAX_LENGTH 15
70 * Hook to get the key from \a data, which is an element of the hash table. The
71 * key must be returned together with \a key_length (in words).
73 typedef const void *(*hook_get_key)(const void *data, uint8_t *key_length);
77 * Hash table description
79 * \note This structures MUST NOT be accessed directly. Its definition is
80 * provided in the header file only for optimization purposes (see the rationale
83 * \note If new elements must be added to this list, please double check
84 * \c DECLARE_HASHTABLE, which requires the existing elements to be at the top.
88 const void **mem; ///< Buckets of data
89 uint16_t max_elts_log2; ///< Log2 of the size of the table
91 bool key_internal : 1; ///< true if the key is copied internally
94 hook_get_key hook; ///< Hook to get the key
95 uint8_t *mem; ///< Pointer to the key memory
100 /// Iterator to walk the hash table
109 * Declare a hash table in the current scope
111 * \param name Variable name
112 * \param size Number of elements
113 * \param hook_gk Hook to be used to extract the key from the node
115 * \note The number of elements will be rounded down to the nearest
119 #define DECLARE_HASHTABLE(name, size, hook_gk) \
120 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
121 struct HashTable name = { name##_nodes, UINT32_LOG2(size), { false }, hook_gk }
123 /** Exactly like \c DECLARE_HASHTABLE, but the variable will be declared as static. */
124 #define DECLARE_HASHTABLE_STATIC(name, size, hook_gk) \
125 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
126 static struct HashTable name = { name##_nodes, UINT32_LOG2(size), { false }, { hook_gk } }
128 #if CONFIG_HT_OPTIONAL_INTERNAL_KEY
129 /** Declare a hash table with internal copies of the keys. This version does not
130 * require a hook, nor it requires the user to allocate static memory for the keys.
131 * It is mostly suggested for tables whose keys are computed on the fly and need
132 * to be stored somewhere.
134 #define DECLARE_HASHTABLE_INTERNALKEY(name, size) \
135 static uint8_t name##_keys[(1 << UINT32_LOG2(size)) * (INTERNAL_KEY_MAX_LENGTH + 1)]; \
136 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
137 struct HashTable name = { name##_nodes, UINT32_LOG2(size), { true }, name##_keys }
139 /** Exactly like \c DECLARE_HASHTABLE_INTERNALKEY, but the variable will be declared as static. */
140 #define DECLARE_HASHTABLE_INTERNALKEY_STATIC(name, size) \
141 static uint8_t name##_keys[(1 << UINT32_LOG2(size)) * (INTERNAL_KEY_MAX_LENGTH + 1)]; \
142 static const void* name##_nodes[1 << UINT32_LOG2(size)]; \
143 static struct HashTable name = { name##_nodes, UINT32_LOG2(size), { true }, name##_keys }
147 * Initialize (and clear) a hash table in a memory buffer.
149 * \param ht Hash table declared with \c DECLARE_HASHTABLE
151 * \note This function must be called before using the hash table. Optionally,
152 * it can be called later in the program to clear the hash table,
153 * removing all its elements.
155 void ht_init(struct HashTable* ht);
158 * Insert an element into the hash table
160 * \param ht Handle of the hash table
161 * \param data Data to be inserted into the table
162 * \return true if insertion was successful, false otherwise (table is full)
164 * \note The key for the element to insert is extract from the data with
165 * the hook. This means that this function cannot be called for hashtables
166 * with internal keys.
168 * \note If an element with the same key already exists in the table,
169 * it will be overwritten.
171 * \note It is not allowed to store NULL in the table. If you pass NULL as data,
172 * the function call will fail.
174 bool ht_insert(struct HashTable* ht, const void* data);
177 * Insert an element into the hash table
179 * \param ht Handle of the hash table
180 * \param key Key of the element
181 * \param key_length Length of the key in characters
182 * \param data Data to be inserted into the table
183 * \return true if insertion was successful, false otherwise (table is full)
185 * \note If this function is called for hash table with external keys,
186 * the key provided must be match the key that would be extracted with the
187 * hook, otherwise the function will fail.
189 * \note If an element with the same key already exists in the table,
190 * it will be overwritten.
192 * \note It is not allowed to store NULL in the table. If you pass NULL as data,
193 * the function call will fail.
195 bool ht_insert_with_key(struct HashTable* ht, const void* key, uint8_t key_length, const void* data);
198 * Find an element in the hash table
200 * \param ht Handle of the hash table
201 * \param key Key of the element
202 * \param key_length Length of the key in characters
203 * \return Data of the element, or NULL if no element was found for the given key.
205 const void* ht_find(struct HashTable* ht, const void* key, uint8_t key_length);
207 /** Similar to \c ht_insert_with_key() but \a key is an ASCIIZ string */
208 #define ht_insert_str(ht, key, data) ht_insert_with_key(ht, key, strlen(key), data)
210 /** Similar to \c ht_find() but \a key is an ASCIIZ string */
211 #define ht_find_str(ht, key) ht_find(ht, key, strlen(key))
213 /// Get an iterator to the begin of the hash table \a ht
214 INLINE HashIterator ht_iter_begin(struct HashTable* ht)
219 h.end = &ht->mem[1 << ht->max_elts_log2];
221 while (h.pos != h.end && !*h.pos)
228 * Get an iterator to the (exclusive) end of the hash table \a ht
230 * \note Like in STL, the end iterator is not a valid iterator (you
231 * cannot call \c ht_iter_get() on it), and it must be used only to
232 * detect if we reached the end of the iteration (through \c ht_iter_cmp()).
234 INLINE HashIterator ht_iter_end(struct HashTable* ht)
238 h.pos = h.end = &ht->mem[1 << ht->max_elts_log2];
243 /// Compare \a it1 and \a it2 for equality
244 INLINE bool ht_iter_cmp(HashIterator it1, HashIterator it2)
246 ASSERT(it1.end == it2.end);
247 return it1.pos == it2.pos;
250 /// Get the element within the hash table \a ht pointed by the iterator \a iter
251 INLINE const void* ht_iter_get(HashIterator iter)
252 { return *iter.pos; }
254 /** Return an iterator pointing to the element following \a h
256 * \note The order of the elements visited during the iteration is casual,
257 * and depends on the implementation.
260 INLINE HashIterator ht_iter_next(HashIterator h)
263 while (h.pos != h.end && !(*h.pos))
269 #endif /* STRUCT_HASHTABLE_H */