1/*
2 * Copyright © 2008 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24/**
25 * \file hash_table.h
26 * \brief Implementation of a generic, opaque hash table data type.
27 *
28 * \author Ian Romanick <ian.d.romanick@intel.com>
29 */
30
31#ifndef HASH_TABLE_H
32#define HASH_TABLE_H
33
34#include <string.h>
35#include <stdbool.h>
36#include <stdlib.h>
37#include <stdint.h>
38#include <limits.h>
39#include <assert.h>
40
41struct string_to_uint_map;
42
43#ifdef __cplusplus
44extern "C" {
45#endif
46
47struct hash_table;
48
49typedef unsigned (*hash_func_t)(const void *key);
50typedef int (*hash_compare_func_t)(const void *key1, const void *key2);
51
52/**
53 * Hash table constructor
54 *
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.
58 *
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.
62 */
63extern struct hash_table *hash_table_ctor(unsigned num_buckets,
64    hash_func_t hash, hash_compare_func_t compare);
65
66
67/**
68 * Release all memory associated with a hash table
69 *
70 * \warning
71 * This function cannot release memory occupied either by keys or data.
72 */
73extern void hash_table_dtor(struct hash_table *ht);
74
75
76/**
77 * Flush all entries from a hash table
78 *
79 * \param ht  Table to be cleared of its entries.
80 */
81extern void hash_table_clear(struct hash_table *ht);
82
83
84/**
85 * Search a hash table for a specific element
86 *
87 * \param ht   Table to be searched
88 * \param key  Key of the desired element
89 *
90 * \return
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.
94 */
95extern void *hash_table_find(struct hash_table *ht, const void *key);
96
97
98/**
99 * Add an element to a hash table
100 *
101 * \warning
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.
105 *
106 * \warning
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.
109 *
110 * \sa hash_table_replace
111 */
112extern void hash_table_insert(struct hash_table *ht, void *data,
113    const void *key);
114
115/**
116 * Add an element to a hash table with replacement
117 *
118 * \return
119 * 1 if it did replace the the value (in which case the old key is kept), 0 if
120 * it did not replace the value (in which case the new key is kept).
121 *
122 * \warning
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
125 * that key.
126 *
127 * \sa hash_table_insert
128 */
129extern bool hash_table_replace(struct hash_table *ht, void *data,
130    const void *key);
131
132/**
133 * Remove a specific element from a hash table.
134 */
135extern void hash_table_remove(struct hash_table *ht, const void *key);
136
137/**
138 * Compute hash value of a string
139 *
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.
143 *
144 * \param key  Pointer to a NUL terminated string to be hashed.
145 *
146 * \sa hash_table_string_compare
147 */
148extern unsigned hash_table_string_hash(const void *key);
149
150
151/**
152 * Compare two strings used as keys
153 *
154 * This is just a macro wrapper around \c strcmp.
155 *
156 * \sa hash_table_string_hash
157 */
158#define hash_table_string_compare ((hash_compare_func_t) strcmp)
159
160
161/**
162 * Compute hash value of a pointer
163 *
164 * \param key  Pointer to be used as a hash key
165 *
166 * \note
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
169 *
170 * \sa hash_table_pointer_compare
171 */
172unsigned
173hash_table_pointer_hash(const void *key);
174
175
176/**
177 * Compare two pointers used as keys
178 *
179 * \sa hash_table_pointer_hash
180 */
181int
182hash_table_pointer_compare(const void *key1, const void *key2);
183
184void
185hash_table_call_foreach(struct hash_table *ht,
186			void (*callback)(const void *key,
187					 void *data,
188					 void *closure),
189			void *closure);
190
191struct string_to_uint_map *
192string_to_uint_map_ctor();
193
194void
195string_to_uint_map_dtor(struct string_to_uint_map *);
196
197
198#ifdef __cplusplus
199}
200
201/**
202 * Map from a string (name) to an unsigned integer value
203 *
204 * \note
205 * Because of the way this class interacts with the \c hash_table
206 * implementation, values of \c UINT_MAX cannot be stored in the map.
207 */
208struct string_to_uint_map {
209public:
210   string_to_uint_map()
211   {
212      this->ht = hash_table_ctor(0, hash_table_string_hash,
213				 hash_table_string_compare);
214   }
215
216   ~string_to_uint_map()
217   {
218      hash_table_call_foreach(this->ht, delete_key, NULL);
219      hash_table_dtor(this->ht);
220   }
221
222   /**
223    * Remove all mappings from this map.
224    */
225   void clear()
226   {
227      hash_table_call_foreach(this->ht, delete_key, NULL);
228      hash_table_clear(this->ht);
229   }
230
231   /**
232    * Get the value associated with a particular key
233    *
234    * \return
235    * If \c key is found in the map, \c true is returned.  Otherwise \c false
236    * is returned.
237    *
238    * \note
239    * If \c key is not found in the table, \c value is not modified.
240    */
241   bool get(unsigned &value, const char *key)
242   {
243      const intptr_t v =
244	 (intptr_t) hash_table_find(this->ht, (const void *) key);
245
246      if (v == 0)
247	 return false;
248
249      value = (unsigned)(v - 1);
250      return true;
251   }
252
253   void put(unsigned value, const char *key)
254   {
255      /* The low-level hash table structure returns NULL if key is not in the
256       * hash table.  However, users of this map might want to store zero as a
257       * valid value in the table.  Bias the value by +1 so that a
258       * user-specified zero is stored as 1.  This enables ::get to tell the
259       * difference between a user-specified zero (returned as 1 by
260       * hash_table_find) and the key not in the table (returned as 0 by
261       * hash_table_find).
262       *
263       * The net effect is that we can't store UINT_MAX in the table.  This is
264       * because UINT_MAX+1 = 0.
265       */
266      assert(value != UINT_MAX);
267      char *dup_key = strdup(key);
268      bool result = hash_table_replace(this->ht,
269				       (void *) (intptr_t) (value + 1),
270				       dup_key);
271      if (result)
272	 free(dup_key);
273   }
274
275private:
276   static void delete_key(const void *key, void *data, void *closure)
277   {
278      (void) data;
279      (void) closure;
280
281      free((char *)key);
282   }
283
284   struct hash_table *ht;
285};
286
287#endif /* __cplusplus */
288#endif /* HASH_TABLE_H */
289