src/mesa/program/hash_table.h

   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 <stdint.h>
  36 #include <limits.h>
  37 #include <assert.h>
  38
  39 struct hash_table;
  40 struct string_to_uint_map;
  41
  42 typedef unsigned (*hash_func_t)(const void *key);
  43 typedef int (*hash_compare_func_t)(const void *key1, const void *key2);
  44
  45 #ifdef __cplusplus
  46 extern "C" {
  47 #endif
  48
  49 /**
  50  * Hash table constructor
  51  *
  52  * Creates a hash table with the specified number of buckets.  The supplied
  53  * \c hash and \c compare routines are used when adding elements to the table
  54  * and when searching for elements in the table.
  55  *
  56  * \param num_buckets  Number of buckets (bins) in the hash table.
  57  * \param hash         Function used to compute hash value of input keys.
  58  * \param compare      Function used to compare keys.
  59  */
  60 extern struct hash_table *hash_table_ctor(unsigned num_buckets,
  61     hash_func_t hash, hash_compare_func_t compare);
  62
  63
  64 /**
  65  * Release all memory associated with a hash table
  66  *
  67  * \warning
  68  * This function cannot release memory occupied either by keys or data.
  69  */
  70 extern void hash_table_dtor(struct hash_table *ht);
  71
  72
  73 /**
  74  * Flush all entries from a hash table
  75  *
  76  * \param ht  Table to be cleared of its entries.
  77  */
  78 extern void hash_table_clear(struct hash_table *ht);
  79
  80
  81 /**
  82  * Search a hash table for a specific element
  83  *
  84  * \param ht   Table to be searched
  85  * \param key  Key of the desired element
  86  *
  87  * \return
  88  * The \c data value supplied to \c hash_table_insert when the element with
  89  * the matching key was added.  If no matching key exists in the table,
  90  * \c NULL is returned.
  91  */
  92 extern void *hash_table_find(struct hash_table *ht, const void *key);
  93
  94
  95 /**
  96  * Add an element to a hash table
  97  *
  98  * \warning
  99  * If \c key is already in the hash table, it will be added again.  Future
 100  * calls to \c hash_table_find and \c hash_table_remove will return or remove,
 101  * repsectively, the most recently added instance of \c key.
 102  *
 103  * \sa hash_table_replace
 104  */
 105 extern void hash_table_insert(struct hash_table *ht, void *data,
 106     const void *key);
 107
 108 /**
 109  * Add an element to a hash table with replacement
 110  *
 111  * \warning
 112  * If \c key is already in the hash table, \c data will \b replace the most
 113  * recently inserted \c data (see the warning in \c hash_table_insert) for
 114  * that key.
 115  *
 116  * \sa hash_table_insert
 117  */
 118 extern void hash_table_replace(struct hash_table *ht, void *data,
 119     const void *key);
 120
 121 /**
 122  * Remove a specific element from a hash table.
 123  */
 124 extern void hash_table_remove(struct hash_table *ht, const void *key);
 125
 126 /**
 127  * Compute hash value of a string
 128  *
 129  * Computes the hash value of a string using the DJB2 algorithm developed by
 130  * Professor Daniel J. Bernstein.  It was published on comp.lang.c once upon
 131  * a time.  I was unable to find the original posting in the archives.
 132  *
 133  * \param key  Pointer to a NUL terminated string to be hashed.
 134  *
 135  * \sa hash_table_string_compare
 136  */
 137 extern unsigned hash_table_string_hash(const void *key);
 138
 139
 140 /**
 141  * Compare two strings used as keys
 142  *
 143  * This is just a macro wrapper around \c strcmp.
 144  *
 145  * \sa hash_table_string_hash
 146  */
 147 #define hash_table_string_compare ((hash_compare_func_t) strcmp)
 148
 149
 150 /**
 151  * Compute hash value of a pointer
 152  *
 153  * \param key  Pointer to be used as a hash key
 154  *
 155  * \note
 156  * The memory pointed to by \c key is \b never accessed.  The value of \c key
 157  * itself is used as the hash key
 158  *
 159  * \sa hash_table_pointer_compare
 160  */
 161 unsigned
 162 hash_table_pointer_hash(const void *key);
 163
 164
 165 /**
 166  * Compare two pointers used as keys
 167  *
 168  * \sa hash_table_pointer_hash
 169  */
 170 int
 171 hash_table_pointer_compare(const void *key1, const void *key2);
 172
 173 void
 174 hash_table_call_foreach(struct hash_table *ht,
 175                         void (*callback)(const void *key,
 176                                          void *data,
 177                                          void *closure),
 178                         void *closure);
 179
 180 struct string_to_uint_map *
 181 string_to_uint_map_ctor();
 182
 183 void
 184 string_to_uint_map_dtor(struct string_to_uint_map *);
 185
 186
 187 #ifdef __cplusplus
 188 }
 189
 190 /**
 191  * Map from a string (name) to an unsigned integer value
 192  *
 193  * \note
 194  * Because of the way this class interacts with the \c hash_table
 195  * implementation, values of \c UINT_MAX cannot be stored in the map.
 196  */
 197 struct string_to_uint_map {
 198 public:
 199    string_to_uint_map()
 200    {
 201       this->ht = hash_table_ctor(0, hash_table_string_hash,
 202                                  hash_table_string_compare);
 203    }
 204
 205    ~string_to_uint_map()
 206    {
 207       hash_table_dtor(this->ht);
 208    }
 209
 210    /**
 211     * Get the value associated with a particular key
 212     *
 213     * \return
 214     * If \c key is found in the map, \c true is returned.  Otherwise \c false
 215     * is returned.
 216     *
 217     * \note
 218     * If \c key is not found in the table, \c value is not modified.
 219     */
 220    bool get(unsigned &value, const char *key)
 221    {
 222       const intptr_t v =
 223          (intptr_t) hash_table_find(this->ht, (const void *) key);
 224
 225       if (v == 0)
 226          return false;
 227
 228       value = (unsigned)(v - 1);
 229       return true;
 230    }
 231
 232    void put(unsigned value, const char *key)
 233    {
 234       /* The low-level hash table structure returns NULL if key is not in the
 235        * hash table.  However, users of this map might want to store zero as a
 236        * valid value in the table.  Bias the value by +1 so that a
 237        * user-specified zero is stored as 1.  This enables ::get to tell the
 238        * difference between a user-specified zero (returned as 1 by
 239        * hash_table_find) and the key not in the table (returned as 0 by
 240        * hash_table_find).
 241        *
 242        * The net effect is that we can't store UINT_MAX in the table.  This is
 243        * because UINT_MAX+1 = 0.
 244        */
 245       assert(value != UINT_MAX);
 246       hash_table_replace(ht, (void *) (intptr_t) (value + 1), key);
 247    }
 248
 249 private:
 250    struct hash_table *ht;
 251 };
 252
 253 #endif /* __cplusplus */
 254 #endif /* HASH_TABLE_H */