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 <stdlib.h>
  36 #include <stdint.h>
  37 #include <limits.h>
  38 #include <assert.h>
  39
  40 struct string_to_uint_map;
  41
  42 #ifdef __cplusplus
  43 extern "C" {
  44 #endif
  45
  46 struct hash_table;
  47
  48 typedef unsigned (*hash_func_t)(const void *key);
  49 typedef int (*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 extern struct hash_table *hash_table_ctor(unsigned num_buckets,
  63     hash_func_t hash, hash_compare_func_t compare);
  64
  65
  66 /**
  67  * Release all memory associated with a hash table
  68  *
  69  * \warning
  70  * This function cannot release memory occupied either by keys or data.
  71  */
  72 extern void hash_table_dtor(struct hash_table *ht);
  73
  74
  75 /**
  76  * Flush all entries from a hash table
  77  *
  78  * \param ht  Table to be cleared of its entries.
  79  */
  80 extern void hash_table_clear(struct hash_table *ht);
  81
  82
  83 /**
  84  * Search a hash table for a specific element
  85  *
  86  * \param ht   Table to be searched
  87  * \param key  Key of the desired element
  88  *
  89  * \return
  90  * The \c data value supplied to \c hash_table_insert when the element with
  91  * the matching key was added.  If no matching key exists in the table,
  92  * \c NULL is returned.
  93  */
  94 extern void *hash_table_find(struct hash_table *ht, const void *key);
  95
  96
  97 /**
  98  * Add an element to a hash table
  99  *
 100  * \warning
 101  * If \c key is already in the hash table, it will be added again.  Future
 102  * calls to \c hash_table_find and \c hash_table_remove will return or remove,
 103  * repsectively, the most recently added instance of \c key.
 104  *
 105  * \warning
 106  * The value passed by \c key is kept in the hash table and is used by later
 107  * calls to \c hash_table_find.
 108  *
 109  * \sa hash_table_replace
 110  */
 111 extern void hash_table_insert(struct hash_table *ht, void *data,
 112     const void *key);
 113
 114 /**
 115  * Add an element to a hash table with replacement
 116  *
 117  * \warning
 118  * If \c key is already in the hash table, \c data will \b replace the most
 119  * recently inserted \c data (see the warning in \c hash_table_insert) for
 120  * that key.
 121  *
 122  * \sa hash_table_insert
 123  */
 124 extern void hash_table_replace(struct hash_table *ht, void *data,
 125     const void *key);
 126
 127 /**
 128  * Remove a specific element from a hash table.
 129  */
 130 extern void hash_table_remove(struct hash_table *ht, const void *key);
 131
 132 /**
 133  * Compute hash value of a string
 134  *
 135  * Computes the hash value of a string using the DJB2 algorithm developed by
 136  * Professor Daniel J. Bernstein.  It was published on comp.lang.c once upon
 137  * a time.  I was unable to find the original posting in the archives.
 138  *
 139  * \param key  Pointer to a NUL terminated string to be hashed.
 140  *
 141  * \sa hash_table_string_compare
 142  */
 143 extern unsigned hash_table_string_hash(const void *key);
 144
 145
 146 /**
 147  * Compare two strings used as keys
 148  *
 149  * This is just a macro wrapper around \c strcmp.
 150  *
 151  * \sa hash_table_string_hash
 152  */
 153 #define hash_table_string_compare ((hash_compare_func_t) strcmp)
 154
 155
 156 /**
 157  * Compute hash value of a pointer
 158  *
 159  * \param key  Pointer to be used as a hash key
 160  *
 161  * \note
 162  * The memory pointed to by \c key is \b never accessed.  The value of \c key
 163  * itself is used as the hash key
 164  *
 165  * \sa hash_table_pointer_compare
 166  */
 167 unsigned
 168 hash_table_pointer_hash(const void *key);
 169
 170
 171 /**
 172  * Compare two pointers used as keys
 173  *
 174  * \sa hash_table_pointer_hash
 175  */
 176 int
 177 hash_table_pointer_compare(const void *key1, const void *key2);
 178
 179 void
 180 hash_table_call_foreach(struct hash_table *ht,
 181                         void (*callback)(const void *key,
 182                                          void *data,
 183                                          void *closure),
 184                         void *closure);
 185
 186 struct string_to_uint_map *
 187 string_to_uint_map_ctor();
 188
 189 void
 190 string_to_uint_map_dtor(struct string_to_uint_map *);
 191
 192
 193 #ifdef __cplusplus
 194 }
 195
 196 /**
 197  * Map from a string (name) to an unsigned integer value
 198  *
 199  * \note
 200  * Because of the way this class interacts with the \c hash_table
 201  * implementation, values of \c UINT_MAX cannot be stored in the map.
 202  */
 203 struct string_to_uint_map {
 204 public:
 205    string_to_uint_map()
 206    {
 207       this->ht = hash_table_ctor(0, hash_table_string_hash,
 208                                  hash_table_string_compare);
 209    }
 210
 211    ~string_to_uint_map()
 212    {
 213       hash_table_call_foreach(this->ht, delete_key, NULL);
 214       hash_table_dtor(this->ht);
 215    }
 216
 217    /**
 218     * Remove all mappings from this map.
 219     */
 220    void clear()
 221    {
 222       hash_table_clear(this->ht);
 223    }
 224
 225    /**
 226     * Get the value associated with a particular key
 227     *
 228     * \return
 229     * If \c key is found in the map, \c true is returned.  Otherwise \c false
 230     * is returned.
 231     *
 232     * \note
 233     * If \c key is not found in the table, \c value is not modified.
 234     */
 235    bool get(unsigned &value, const char *key)
 236    {
 237       const intptr_t v =
 238          (intptr_t) hash_table_find(this->ht, (const void *) key);
 239
 240       if (v == 0)
 241          return false;
 242
 243       value = (unsigned)(v - 1);
 244       return true;
 245    }
 246
 247    void put(unsigned value, const char *key)
 248    {
 249       /* The low-level hash table structure returns NULL if key is not in the
 250        * hash table.  However, users of this map might want to store zero as a
 251        * valid value in the table.  Bias the value by +1 so that a
 252        * user-specified zero is stored as 1.  This enables ::get to tell the
 253        * difference between a user-specified zero (returned as 1 by
 254        * hash_table_find) and the key not in the table (returned as 0 by
 255        * hash_table_find).
 256        *
 257        * The net effect is that we can't store UINT_MAX in the table.  This is
 258        * because UINT_MAX+1 = 0.
 259        */
 260       assert(value != UINT_MAX);
 261       hash_table_replace(this->ht,
 262                          (void *) (intptr_t) (value + 1),
 263                          strdup(key));
 264    }
 265
 266 private:
 267    static void delete_key(const void *key, void *data, void *closure)
 268    {
 269       (void) data;
 270       (void) closure;
 271
 272       free((char *)key);
 273    }
 274
 275    struct hash_table *ht;
 276 };
 277
 278 #endif /* __cplusplus */
 279 #endif /* HASH_TABLE_H */