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 <stdbool.h>
  36 #include <stdlib.h>
  37 #include <stdint.h>
  38 #include <limits.h>
  39 #include <assert.h>
  40
  41 struct string_to_uint_map;
  42
  43 #ifdef __cplusplus
  44 extern "C" {
  45 #endif
  46
  47 struct hash_table;
  48
  49 typedef unsigned (*hash_func_t)(const void *key);
  50 typedef 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  */
  63 extern 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  */
  73 extern 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  */
  81 extern 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  */
  95 extern 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  */
 112 extern 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  */
 129 extern 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  */
 135 extern 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  */
 148 extern 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  */
 172 unsigned
 173 hash_table_pointer_hash(const void *key);
 174
 175
 176 /**
 177  * Compare two pointers used as keys
 178  *
 179  * \sa hash_table_pointer_hash
 180  */
 181 int
 182 hash_table_pointer_compare(const void *key1, const void *key2);
 183
 184 void
 185 hash_table_call_foreach(struct hash_table *ht,
 186                         void (*callback)(const void *key,
 187                                          void *data,
 188                                          void *closure),
 189                         void *closure);
 190
 191 struct string_to_uint_map *
 192 string_to_uint_map_ctor();
 193
 194 void
 195 string_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  */
 208 struct string_to_uint_map {
 209 public:
 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
 275 private:
 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 */