libobjc/objc/hash.h

   1 /* Hash tables for Objective C method dispatch.
   2    Copyright (C) 1993, 1995, 1996, 2004 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 2, 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 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  19 Boston, MA 02110-1301, USA.  */
  20
  21 /* As a special exception, if you link this library with files
  22    compiled with GCC to produce an executable, this does not cause
  23    the resulting executable to be covered by the GNU General Public License.
  24    This exception does not however invalidate any other reasons why
  25    the executable file might be covered by the GNU General Public License.  */
  26
  27
  28 #ifndef __hash_INCLUDE_GNU
  29 #define __hash_INCLUDE_GNU
  30
  31 #include <stddef.h>
  32 #include <string.h>
  33 #include "objc.h"
  34
  35 #ifdef __cplusplus
  36 extern "C" {
  37 #endif /* __cplusplus */
  38
  39 /*
  40  * This data structure is used to hold items
  41  *  stored in a hash table.  Each node holds
  42  *  a key/value pair.
  43  *
  44  * Items in the cache are really of type void *.
  45  */
  46 typedef struct cache_node
  47 {
  48   struct cache_node *next;      /* Pointer to next entry on the list.
  49                                    NULL indicates end of list. */
  50   const void *key;              /* Key used to locate the value.  Used
  51                                    to locate value when more than one
  52                                    key computes the same hash
  53                                    value. */
  54   void *value;                  /* Value stored for the key. */
  55 } *node_ptr;
  56
  57
  58 /*
  59  * This data type is the function that computes a hash code given a key.
  60  * Therefore, the key can be a pointer to anything and the function specific
  61  * to the key type.
  62  *
  63  * Unfortunately there is a mutual data structure reference problem with this
  64  * typedef.  Therefore, to remove compiler warnings the functions passed to
  65  * objc_hash_new will have to be casted to this type.
  66  */
  67 typedef unsigned int (*hash_func_type) (void *, const void *);
  68
  69 /*
  70  * This data type is the function that compares two hash keys and returns an
  71  * integer greater than, equal to, or less than 0, according as the first
  72  * parameter is lexicographically greater than, equal to, or less than the
  73  * second.
  74  */
  75
  76 typedef int (*compare_func_type) (const void *, const void *);
  77
  78
  79 /*
  80  * This data structure is the cache.
  81  *
  82  * It must be passed to all of the hashing routines
  83  *   (except for new).
  84  */
  85 typedef struct cache
  86 {
  87   /* Variables used to implement the hash itself.  */
  88   node_ptr *node_table; /* Pointer to an array of hash nodes.  */
  89   /* Variables used to track the size of the hash table so to determine
  90     when to resize it.  */
  91   unsigned int size; /* Number of buckets allocated for the hash table
  92                         (number of array entries allocated for
  93                         "node_table").  Must be a power of two.  */
  94   unsigned int used; /* Current number of entries in the hash table.  */
  95   unsigned int mask; /* Precomputed mask.  */
  96
  97   /* Variables used to implement indexing through the hash table.  */
  98
  99   unsigned int last_bucket; /* Tracks which entry in the array where
 100                                the last value was returned.  */
 101   /* Function used to compute a hash code given a key.
 102      This function is specified when the hash table is created.  */
 103   hash_func_type    hash_func;
 104   /* Function used to compare two hash keys to see if they are equal.  */
 105   compare_func_type compare_func;
 106 } *cache_ptr;
 107
 108
 109 /* Two important hash tables.  */
 110 extern cache_ptr module_hash_table, class_hash_table;
 111
 112 /* Allocate and initialize a hash table.  */
 113
 114 cache_ptr objc_hash_new (unsigned int size,
 115                          hash_func_type hash_func,
 116                          compare_func_type compare_func);
 117
 118 /* Deallocate all of the hash nodes and the cache itself.  */
 119
 120 void objc_hash_delete (cache_ptr cache);
 121
 122 /* Add the key/value pair to the hash table.  If the
 123    hash table reaches a level of fullness then it will be resized.
 124
 125    assert if the key is already in the hash.  */
 126
 127 void objc_hash_add (cache_ptr *cachep, const void *key, void *value);
 128
 129 /* Remove the key/value pair from the hash table.
 130    assert if the key isn't in the table.  */
 131
 132 void objc_hash_remove (cache_ptr cache, const void *key);
 133
 134 /* Used to index through the hash table.  Start with NULL
 135    to get the first entry.
 136
 137    Successive calls pass the value returned previously.
 138    ** Don't modify the hash during this operation ***
 139
 140    Cache nodes are returned such that key or value can
 141    be extracted.  */
 142
 143 node_ptr objc_hash_next (cache_ptr cache, node_ptr node);
 144
 145 /* Used to return a value from a hash table using a given key.  */
 146
 147 void *objc_hash_value_for_key (cache_ptr cache, const void *key);
 148
 149 /* Used to determine if the given key exists in the hash table */
 150
 151 BOOL objc_hash_is_key_in_hash (cache_ptr cache, const void *key);
 152
 153 /************************************************
 154
 155         Useful hashing functions.
 156
 157         Declared inline for your pleasure.
 158
 159 ************************************************/
 160
 161 /* Calculate a hash code by performing some
 162    manipulation of the key pointer.  (Use the lowest bits
 163    except for those likely to be 0 due to alignment.)  */
 164
 165 static inline unsigned int
 166 objc_hash_ptr (cache_ptr cache, const void *key)
 167 {
 168   return ((size_t)key / sizeof (void *)) & cache->mask;
 169 }
 170
 171
 172 /* Calculate a hash code by iterating over a NULL
 173    terminate string.  */
 174 static inline unsigned int
 175 objc_hash_string (cache_ptr cache, const void *key)
 176 {
 177   unsigned int ret = 0;
 178   unsigned int ctr = 0;
 179   const char *ckey = (const char *) key;
 180
 181   while (*ckey) {
 182     ret ^= *ckey++ << ctr;
 183     ctr = (ctr + 1) % sizeof (void *);
 184   }
 185
 186   return ret & cache->mask;
 187 }
 188
 189
 190 /* Compare two pointers for equality.  */
 191 static inline int
 192 objc_compare_ptrs (const void *k1, const void *k2)
 193 {
 194   return (k1 == k2);
 195 }
 196
 197
 198 /* Compare two strings.  */
 199 static inline int
 200 objc_compare_strings (const void *k1, const void *k2)
 201 {
 202   if (k1 == k2)
 203     return 1;
 204   else if (k1 == 0 || k2 == 0)
 205     return 0;
 206   else
 207     return ! strcmp ((const char *) k1, (const char *) k2);
 208 }
 209
 210
 211 #ifdef __cplusplus
 212 }
 213 #endif /* __cplusplus */
 214
 215
 216 #endif /* not __hash_INCLUDE_GNU */