1 /* Hash tables for Objective C method dispatch.
2 Copyright (C) 1993, 1995, 1996, 2004 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 2, 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 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, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
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. */
28 #ifndef __hash_INCLUDE_GNU
29 #define __hash_INCLUDE_GNU
31 #include <objc/objc.h>
35 #endif /* __cplusplus */
41 * This data structure is used to hold items
42 * stored in a hash table. Each node holds
45 * Items in the cache are really of type void *.
47 typedef struct cache_node
49 struct cache_node *next; /* Pointer to next entry on the list.
50 NULL indicates end of list. */
51 const void *key; /* Key used to locate the value. Used
52 to locate value when more than one
53 key computes the same hash
55 void *value; /* Value stored for the key. */
60 * This data type is the function that computes a hash code given a key.
61 * Therefore, the key can be a pointer to anything and the function specific
64 * Unfortunately there is a mutual data structure reference problem with this
65 * typedef. Therefore, to remove compiler warnings the functions passed to
66 * hash_new will have to be casted to this type.
68 typedef unsigned int (*hash_func_type) (void *, const void *);
71 * This data type is the function that compares two hash keys and returns an
72 * integer greater than, equal to, or less than 0, according as the first
73 * parameter is lexicographically greater than, equal to, or less than the
77 typedef int (*compare_func_type) (const void *, const void *);
81 * This data structure is the cache.
83 * It must be passed to all of the hashing routines
88 /* Variables used to implement the hash itself. */
89 node_ptr *node_table; /* Pointer to an array of hash nodes. */
90 /* Variables used to track the size of the hash table so to determine
92 unsigned int size; /* Number of buckets allocated for the hash table
93 (number of array entries allocated for
94 "node_table"). Must be a power of two. */
95 unsigned int used; /* Current number of entries in the hash table. */
96 unsigned int mask; /* Precomputed mask. */
98 /* Variables used to implement indexing through the hash table. */
100 unsigned int last_bucket; /* Tracks which entry in the array where
101 the last value was returned. */
102 /* Function used to compute a hash code given a key.
103 This function is specified when the hash table is created. */
104 hash_func_type hash_func;
105 /* Function used to compare two hash keys to see if they are equal. */
106 compare_func_type compare_func;
110 /* Two important hash tables. */
111 extern cache_ptr module_hash_table, class_hash_table;
113 /* Allocate and initialize a hash table. */
115 cache_ptr hash_new (unsigned int size,
116 hash_func_type hash_func,
117 compare_func_type compare_func);
119 /* Deallocate all of the hash nodes and the cache itself. */
121 void hash_delete (cache_ptr cache);
123 /* Add the key/value pair to the hash table. If the
124 hash table reaches a level of fullness then it will be resized.
126 assert if the key is already in the hash. */
128 void hash_add (cache_ptr *cachep, const void *key, void *value);
130 /* Remove the key/value pair from the hash table.
131 assert if the key isn't in the table. */
133 void hash_remove (cache_ptr cache, const void *key);
135 /* Used to index through the hash table. Start with NULL
136 to get the first entry.
138 Successive calls pass the value returned previously.
139 ** Don't modify the hash during this operation ***
141 Cache nodes are returned such that key or value can
144 node_ptr hash_next (cache_ptr cache, node_ptr node);
146 /* Used to return a value from a hash table using a given key. */
148 void *hash_value_for_key (cache_ptr cache, const void *key);
150 /* Used to determine if the given key exists in the hash table */
152 BOOL hash_is_key_in_hash (cache_ptr cache, const void *key);
154 /************************************************
156 Useful hashing functions.
158 Declared inline for your pleasure.
160 ************************************************/
162 /* Calculate a hash code by performing some
163 manipulation of the key pointer. (Use the lowest bits
164 except for those likely to be 0 due to alignment.) */
166 static inline unsigned int
167 hash_ptr (cache_ptr cache, const void *key)
169 return ((size_t)key / sizeof (void *)) & cache->mask;
173 /* Calculate a hash code by iterating over a NULL
175 static inline unsigned int
176 hash_string (cache_ptr cache, const void *key)
178 unsigned int ret = 0;
179 unsigned int ctr = 0;
180 const char *ckey = (const char *) key;
183 ret ^= *ckey++ << ctr;
184 ctr = (ctr + 1) % sizeof (void *);
187 return ret & cache->mask;
191 /* Compare two pointers for equality. */
193 compare_ptrs (const void *k1, const void *k2)
199 /* Compare two strings. */
201 compare_strings (const void *k1, const void *k2)
205 else if (k1 == 0 || k2 == 0)
208 return ! strcmp ((const char *) k1, (const char *) k2);
213 #endif /* __cplusplus */
216 #endif /* not __hash_INCLUDE_GNU */