1 /* Hash tables for Objective C method dispatch.
2 Copyright (C) 1993, 1995, 1996, 2004, 2009 Free Software Foundation, Inc.
4 This file is part of GCC.
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)
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.
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.
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/>. */
27 #ifndef __hash_INCLUDE_GNU
28 #define __hash_INCLUDE_GNU
36 #endif /* __cplusplus */
39 * This data structure is used to hold items
40 * stored in a hash table. Each node holds
43 * Items in the cache are really of type void *.
45 typedef struct cache_node
47 struct cache_node *next; /* Pointer to next entry on the list.
48 NULL indicates end of list. */
49 const void *key; /* Key used to locate the value. Used
50 to locate value when more than one
51 key computes the same hash
53 void *value; /* Value stored for the key. */
58 * This data type is the function that computes a hash code given a key.
59 * Therefore, the key can be a pointer to anything and the function specific
62 * Unfortunately there is a mutual data structure reference problem with this
63 * typedef. Therefore, to remove compiler warnings the functions passed to
64 * objc_hash_new will have to be casted to this type.
66 typedef unsigned int (*hash_func_type) (void *, const void *);
69 * This data type is the function that compares two hash keys and returns an
70 * integer greater than, equal to, or less than 0, according as the first
71 * parameter is lexicographically greater than, equal to, or less than the
75 typedef int (*compare_func_type) (const void *, const void *);
79 * This data structure is the cache.
81 * It must be passed to all of the hashing routines
86 /* Variables used to implement the hash itself. */
87 node_ptr *node_table; /* Pointer to an array of hash nodes. */
88 /* Variables used to track the size of the hash table so to determine
90 unsigned int size; /* Number of buckets allocated for the hash table
91 (number of array entries allocated for
92 "node_table"). Must be a power of two. */
93 unsigned int used; /* Current number of entries in the hash table. */
94 unsigned int mask; /* Precomputed mask. */
96 /* Variables used to implement indexing through the hash table. */
98 unsigned int last_bucket; /* Tracks which entry in the array where
99 the last value was returned. */
100 /* Function used to compute a hash code given a key.
101 This function is specified when the hash table is created. */
102 hash_func_type hash_func;
103 /* Function used to compare two hash keys to see if they are equal. */
104 compare_func_type compare_func;
108 /* Two important hash tables. */
109 extern cache_ptr module_hash_table, class_hash_table;
111 /* Allocate and initialize a hash table. */
113 cache_ptr objc_hash_new (unsigned int size,
114 hash_func_type hash_func,
115 compare_func_type compare_func);
117 /* Deallocate all of the hash nodes and the cache itself. */
119 void objc_hash_delete (cache_ptr cache);
121 /* Add the key/value pair to the hash table. If the
122 hash table reaches a level of fullness then it will be resized.
124 assert if the key is already in the hash. */
126 void objc_hash_add (cache_ptr *cachep, const void *key, void *value);
128 /* Remove the key/value pair from the hash table.
129 assert if the key isn't in the table. */
131 void objc_hash_remove (cache_ptr cache, const void *key);
133 /* Used to index through the hash table. Start with NULL
134 to get the first entry.
136 Successive calls pass the value returned previously.
137 ** Don't modify the hash during this operation ***
139 Cache nodes are returned such that key or value can
142 node_ptr objc_hash_next (cache_ptr cache, node_ptr node);
144 /* Used to return a value from a hash table using a given key. */
146 void *objc_hash_value_for_key (cache_ptr cache, const void *key);
148 /* Used to determine if the given key exists in the hash table */
150 BOOL objc_hash_is_key_in_hash (cache_ptr cache, const void *key);
152 /************************************************
154 Useful hashing functions.
156 Declared inline for your pleasure.
158 ************************************************/
160 /* Calculate a hash code by performing some
161 manipulation of the key pointer. (Use the lowest bits
162 except for those likely to be 0 due to alignment.) */
164 static inline unsigned int
165 objc_hash_ptr (cache_ptr cache, const void *key)
167 return ((size_t)key / sizeof (void *)) & cache->mask;
171 /* Calculate a hash code by iterating over a NULL
173 static inline unsigned int
174 objc_hash_string (cache_ptr cache, const void *key)
176 unsigned int ret = 0;
177 unsigned int ctr = 0;
178 const char *ckey = (const char *) key;
181 ret ^= *ckey++ << ctr;
182 ctr = (ctr + 1) % sizeof (void *);
185 return ret & cache->mask;
189 /* Compare two pointers for equality. */
191 objc_compare_ptrs (const void *k1, const void *k2)
197 /* Compare two strings. */
199 objc_compare_strings (const void *k1, const void *k2)
203 else if (k1 == 0 || k2 == 0)
206 return ! strcmp ((const char *) k1, (const char *) k2);
212 #endif /* __cplusplus */
215 #endif /* not __hash_INCLUDE_GNU */