libobjc/objc-private/hash.h

   1 /* Hash tables for Objective C method dispatch.
   2    Copyright (C) 1993-2018 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 Under Section 7 of GPL version 3, you are granted additional
  17 permissions described in the GCC Runtime Library Exception, version
  18 3.1, as published by the Free Software Foundation.
  19
  20 You should have received a copy of the GNU General Public License and
  21 a copy of the GCC Runtime Library Exception along with this program;
  22 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 <http://www.gnu.org/licenses/>.  */
  24
  25 /* You need to include this file after including objc.h  */
  26
  27 #ifndef __hash_INCLUDE_GNU
  28 #define __hash_INCLUDE_GNU
  29
  30 #include <stddef.h>
  31 #include <string.h>
  32
  33 /*
  34  * This data structure is used to hold items
  35  *  stored in a hash table.  Each node holds
  36  *  a key/value pair.
  37  *
  38  * Items in the cache are really of type void *.
  39  */
  40 typedef struct cache_node
  41 {
  42   struct cache_node *next;      /* Pointer to next entry on the list.
  43                                    NULL indicates end of list. */
  44   const void *key;              /* Key used to locate the value.  Used
  45                                    to locate value when more than one
  46                                    key computes the same hash
  47                                    value. */
  48   void *value;                  /* Value stored for the key. */
  49 } *node_ptr;
  50
  51
  52 /*
  53  * This data type is the function that computes a hash code given a key.
  54  * Therefore, the key can be a pointer to anything and the function specific
  55  * to the key type.
  56  *
  57  * Unfortunately there is a mutual data structure reference problem with this
  58  * typedef.  Therefore, to remove compiler warnings the functions passed to
  59  * objc_hash_new will have to be casted to this type.
  60  */
  61 typedef unsigned int (*hash_func_type) (void *, const void *);
  62
  63 /*
  64  * This data type is the function that compares two hash keys and returns an
  65  * integer greater than, equal to, or less than 0, according as the first
  66  * parameter is lexicographically greater than, equal to, or less than the
  67  * second.
  68  */
  69
  70 typedef int (*compare_func_type) (const void *, const void *);
  71
  72
  73 /*
  74  * This data structure is the cache.
  75  *
  76  * It must be passed to all of the hashing routines
  77  *   (except for new).
  78  */
  79 typedef struct cache
  80 {
  81   /* Variables used to implement the hash itself.  */
  82   node_ptr *node_table; /* Pointer to an array of hash nodes.  */
  83   /* Variables used to track the size of the hash table so to determine
  84     when to resize it.  */
  85   unsigned int size; /* Number of buckets allocated for the hash table
  86                         (number of array entries allocated for
  87                         "node_table").  Must be a power of two.  */
  88   unsigned int used; /* Current number of entries in the hash table.  */
  89   unsigned int mask; /* Precomputed mask.  */
  90
  91   /* Variables used to implement indexing through the hash table.  */
  92
  93   unsigned int last_bucket; /* Tracks which entry in the array where
  94                                the last value was returned.  */
  95   /* Function used to compute a hash code given a key.
  96      This function is specified when the hash table is created.  */
  97   hash_func_type    hash_func;
  98   /* Function used to compare two hash keys to see if they are equal.  */
  99   compare_func_type compare_func;
 100 } *cache_ptr;
 101
 102
 103 /* Allocate and initialize a hash table.  */
 104
 105 cache_ptr objc_hash_new (unsigned int size,
 106                          hash_func_type hash_func,
 107                          compare_func_type compare_func);
 108
 109 /* Deallocate all of the hash nodes and the cache itself.  */
 110
 111 void objc_hash_delete (cache_ptr cache);
 112
 113 /* Add the key/value pair to the hash table.  If the
 114    hash table reaches a level of fullness then it will be resized.
 115
 116    assert if the key is already in the hash.  */
 117
 118 void objc_hash_add (cache_ptr *cachep, const void *key, void *value);
 119
 120 /* Remove the key/value pair from the hash table.
 121    assert if the key isn't in the table.  */
 122
 123 void objc_hash_remove (cache_ptr cache, const void *key);
 124
 125 /* Used to index through the hash table.  Start with NULL
 126    to get the first entry.
 127
 128    Successive calls pass the value returned previously.
 129    ** Don't modify the hash during this operation ***
 130
 131    Cache nodes are returned such that key or value can
 132    be extracted.  */
 133
 134 node_ptr objc_hash_next (cache_ptr cache, node_ptr node);
 135
 136 /* Used to return a value from a hash table using a given key.  */
 137
 138 void *objc_hash_value_for_key (cache_ptr cache, const void *key);
 139
 140 /* Used to determine if the given key exists in the hash table */
 141
 142 BOOL objc_hash_is_key_in_hash (cache_ptr cache, const void *key);
 143
 144 /************************************************
 145
 146         Useful hashing functions.
 147
 148         Declared inline for your pleasure.
 149
 150 ************************************************/
 151
 152 /* Calculate a hash code by performing some
 153    manipulation of the key pointer.  (Use the lowest bits
 154    except for those likely to be 0 due to alignment.)  */
 155
 156 static inline unsigned int
 157 objc_hash_ptr (cache_ptr cache, const void *key)
 158 {
 159   return ((size_t)key / sizeof (void *)) & cache->mask;
 160 }
 161
 162
 163 /* Calculate a hash code by iterating over a NULL
 164    terminate string.  */
 165 static inline unsigned int
 166 objc_hash_string (cache_ptr cache, const void *key)
 167 {
 168   unsigned int ret = 0;
 169   unsigned int ctr = 0;
 170   const char *ckey = (const char *) key;
 171
 172   while (*ckey) {
 173     ret ^= *ckey++ << ctr;
 174     ctr = (ctr + 1) % sizeof (void *);
 175   }
 176
 177   return ret & cache->mask;
 178 }
 179
 180
 181 /* Compare two pointers for equality.  */
 182 static inline int
 183 objc_compare_ptrs (const void *k1, const void *k2)
 184 {
 185   return (k1 == k2);
 186 }
 187
 188
 189 /* Compare two strings.  */
 190 static inline int
 191 objc_compare_strings (const void *k1, const void *k2)
 192 {
 193   if (k1 == k2)
 194     return 1;
 195   else if (k1 == 0 || k2 == 0)
 196     return 0;
 197   else
 198     return ! strcmp ((const char *) k1, (const char *) k2);
 199 }
 200
 201 #endif /* not __hash_INCLUDE_GNU */