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 #include "util/hash_table.h"
  41
  42 struct string_to_uint_map;
  43
  44 #ifdef __cplusplus
  45 extern "C" {
  46 #endif
  47
  48 typedef unsigned (*hash_func_t)(const void *key);
  49 typedef bool (*hash_compare_func_t)(const void *key1, const void *key2);
  50
  51 /**
  52  * Hash table constructor
  53  *
  54  * Creates a hash table with the specified number of buckets.  The supplied
  55  * \c hash and \c compare routines are used when adding elements to the table
  56  * and when searching for elements in the table.
  57  *
  58  * \param num_buckets  Number of buckets (bins) in the hash table.
  59  * \param hash         Function used to compute hash value of input keys.
  60  * \param compare      Function used to compare keys.
  61  */
  62 static inline struct hash_table *hash_table_ctor(UNUSED unsigned num_buckets,
  63     hash_func_t hash, hash_compare_func_t compare)
  64 {
  65    return _mesa_hash_table_create(NULL, hash, compare);
  66 }
  67
  68 /**
  69  * Release all memory associated with a hash table
  70  *
  71  * \warning
  72  * This function does not release memory occupied either by keys or data.
  73  */
  74 static inline void hash_table_dtor(struct hash_table *ht)
  75 {
  76    return _mesa_hash_table_destroy(ht, NULL);
  77 }
  78
  79 /**
  80  * Flush all entries from a hash table
  81  *
  82  * \param ht  Table to be cleared of its entries.
  83  */
  84 static inline void hash_table_clear(struct hash_table *ht)
  85 {
  86    return _mesa_hash_table_clear(ht, NULL);
  87 }
  88
  89 /**
  90  * Search a hash table for a specific element
  91  *
  92  * \param ht   Table to be searched
  93  * \param key  Key of the desired element
  94  *
  95  * \return
  96  * The \c data value supplied to \c hash_table_insert when the element with
  97  * the matching key was added.  If no matching key exists in the table,
  98  * \c NULL is returned.
  99  */
 100 static inline void *hash_table_find(struct hash_table *ht, const void *key)
 101 {
 102    struct hash_entry *entry = _mesa_hash_table_search(ht, key);
 103    if (!entry)
 104       return NULL;
 105    return entry->data;
 106 }
 107
 108 /**
 109  * Add an element to a hash table
 110  *
 111  * \warning
 112  * The value passed by \c key is kept in the hash table and is used by later
 113  * calls to \c hash_table_find.
 114  *
 115  * \sa hash_table_replace
 116  */
 117 static inline void hash_table_insert(struct hash_table *ht, void *data,
 118                                      const void *key)
 119 {
 120    _mesa_hash_table_insert(ht, key, data);
 121 }
 122
 123 /**
 124  * Add an element to a hash table with replacement
 125  *
 126  * \return
 127  * 1 if it did replace the value (in which case the old key is kept), 0 if it
 128  * did not replace the value (in which case the new key is kept).
 129  *
 130  * \warning
 131  * If \c key is already in the hash table, \c data will \b replace the most
 132  * recently inserted \c data (see the warning in \c hash_table_insert) for
 133  * that key.
 134  *
 135  * \sa hash_table_insert
 136  */
 137 static inline bool hash_table_replace(struct hash_table *ht, void *data,
 138                                       const void *key)
 139 {
 140    struct hash_entry *entry = _mesa_hash_table_search(ht, key);
 141    if (entry) {
 142       entry->data = data;
 143       return true;
 144    } else {
 145       _mesa_hash_table_insert(ht, key, data);
 146       return false;
 147    }
 148 }
 149
 150 /**
 151  * Remove a specific element from a hash table.
 152  */
 153 static inline void hash_table_remove(struct hash_table *ht, const void *key)
 154 {
 155    struct hash_entry *entry = _mesa_hash_table_search(ht, key);
 156
 157    if (entry)
 158       _mesa_hash_table_remove(ht, entry);
 159 }
 160
 161 /**
 162  * Compute hash value of a string
 163  *
 164  * Computes the hash value of a string using the DJB2 algorithm developed by
 165  * Professor Daniel J. Bernstein.  It was published on comp.lang.c once upon
 166  * a time.  I was unable to find the original posting in the archives.
 167  *
 168  * \param key  Pointer to a NUL terminated string to be hashed.
 169  *
 170  * \sa hash_table_string_compare
 171  */
 172 extern unsigned hash_table_string_hash(const void *key);
 173
 174
 175 /**
 176  * Compare two strings used as keys
 177  *
 178  * This is just a wrapper around \c strcmp.
 179  *
 180  * \sa hash_table_string_hash
 181  */
 182 bool hash_table_string_compare(const void *a, const void *b);
 183
 184 /**
 185  * Compute hash value of a pointer
 186  *
 187  * \param key  Pointer to be used as a hash key
 188  *
 189  * \note
 190  * The memory pointed to by \c key is \b never accessed.  The value of \c key
 191  * itself is used as the hash key
 192  *
 193  * \sa hash_table_pointer_compare
 194  */
 195 unsigned
 196 hash_table_pointer_hash(const void *key);
 197
 198
 199 /**
 200  * Compare two pointers used as keys
 201  *
 202  * \sa hash_table_pointer_hash
 203  */
 204 bool
 205 hash_table_pointer_compare(const void *key1, const void *key2);
 206
 207 static inline void
 208 hash_table_call_foreach(struct hash_table *ht,
 209                         void (*callback)(const void *key,
 210                                          void *data,
 211                                          void *closure),
 212                         void *closure)
 213 {
 214    struct hash_entry *entry;
 215
 216    hash_table_foreach(ht, entry)
 217       callback(entry->key, entry->data, closure);
 218 }
 219
 220 struct string_to_uint_map *
 221 string_to_uint_map_ctor();
 222
 223 void
 224 string_to_uint_map_dtor(struct string_to_uint_map *);
 225
 226
 227 #ifdef __cplusplus
 228 }
 229
 230 struct string_map_iterate_wrapper_closure {
 231    void (*callback)(const char *key, unsigned value, void *closure);
 232    void *closure;
 233 };
 234
 235 /**
 236  * Map from a string (name) to an unsigned integer value
 237  *
 238  * \note
 239  * Because of the way this class interacts with the \c hash_table
 240  * implementation, values of \c UINT_MAX cannot be stored in the map.
 241  */
 242 struct string_to_uint_map {
 243 public:
 244    string_to_uint_map()
 245    {
 246       this->ht = hash_table_ctor(0, hash_table_string_hash,
 247                                  hash_table_string_compare);
 248    }
 249
 250    ~string_to_uint_map()
 251    {
 252       hash_table_call_foreach(this->ht, delete_key, NULL);
 253       hash_table_dtor(this->ht);
 254    }
 255
 256    /**
 257     * Remove all mappings from this map.
 258     */
 259    void clear()
 260    {
 261       hash_table_call_foreach(this->ht, delete_key, NULL);
 262       hash_table_clear(this->ht);
 263    }
 264
 265    /**
 266     * Runs a passed callback for the hash
 267     */
 268    void iterate(void (*func)(const char *, unsigned, void *), void *closure)
 269    {
 270       struct string_map_iterate_wrapper_closure *wrapper;
 271
 272       wrapper = (struct string_map_iterate_wrapper_closure *)
 273          malloc(sizeof(struct string_map_iterate_wrapper_closure));
 274       if (wrapper == NULL)
 275          return;
 276
 277       wrapper->callback = func;
 278       wrapper->closure = closure;
 279
 280       hash_table_call_foreach(this->ht, subtract_one_wrapper, wrapper);
 281       free(wrapper);
 282    }
 283
 284    /**
 285     * Get the value associated with a particular key
 286     *
 287     * \return
 288     * If \c key is found in the map, \c true is returned.  Otherwise \c false
 289     * is returned.
 290     *
 291     * \note
 292     * If \c key is not found in the table, \c value is not modified.
 293     */
 294    bool get(unsigned &value, const char *key)
 295    {
 296       const intptr_t v =
 297          (intptr_t) hash_table_find(this->ht, (const void *) key);
 298
 299       if (v == 0)
 300          return false;
 301
 302       value = (unsigned)(v - 1);
 303       return true;
 304    }
 305
 306    void put(unsigned value, const char *key)
 307    {
 308       /* The low-level hash table structure returns NULL if key is not in the
 309        * hash table.  However, users of this map might want to store zero as a
 310        * valid value in the table.  Bias the value by +1 so that a
 311        * user-specified zero is stored as 1.  This enables ::get to tell the
 312        * difference between a user-specified zero (returned as 1 by
 313        * hash_table_find) and the key not in the table (returned as 0 by
 314        * hash_table_find).
 315        *
 316        * The net effect is that we can't store UINT_MAX in the table.  This is
 317        * because UINT_MAX+1 = 0.
 318        */
 319       assert(value != UINT_MAX);
 320       char *dup_key = strdup(key);
 321       bool result = hash_table_replace(this->ht,
 322                                        (void *) (intptr_t) (value + 1),
 323                                        dup_key);
 324       if (result)
 325          free(dup_key);
 326    }
 327
 328 private:
 329    static void delete_key(const void *key, void *data, void *closure)
 330    {
 331       (void) data;
 332       (void) closure;
 333
 334       free((char *)key);
 335    }
 336
 337    static void subtract_one_wrapper(const void *key, void *data, void *closure)
 338    {
 339       struct string_map_iterate_wrapper_closure *wrapper =
 340          (struct string_map_iterate_wrapper_closure *) closure;
 341       unsigned value = (intptr_t) data;
 342
 343       value -= 1;
 344
 345       wrapper->callback((const char *) key, value, wrapper->closure);
 346    }
 347
 348    struct hash_table *ht;
 349 };
 350
 351 #endif /* __cplusplus */
 352 #endif /* HASH_TABLE_H */