1 /* Hash tables for Objective C method dispatch.
2 Copyright (C) 1993, 1995, 1996 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC 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 GNU CC 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 GNU CC; 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
32 #include <objc/objc.h>
35 * This data structure is used to hold items
36 * stored in a hash table. Each node holds
39 * Items in the cache are really of type void *.
41 typedef struct cache_node
43 struct cache_node
*next
; /* Pointer to next entry on the list.
44 NULL indicates end of list. */
45 const void *key
; /* Key used to locate the value. Used
46 to locate value when more than one
47 key computes the same hash
49 void *value
; /* Value stored for the key. */
54 * This data type is the function that computes a hash code given a key.
55 * Therefore, the key can be a pointer to anything and the function specific
58 * Unfortunately there is a mutual data structure reference problem with this
59 * typedef. Therefore, to remove compiler warnings the functions passed to
60 * hash_new will have to be casted to this type.
62 typedef unsigned int (*hash_func_type
)(void *, const void *);
65 * This data type is the function that compares two hash keys and returns an
66 * integer greater than, equal to, or less than 0, according as the first
67 * parameter is lexicographically greater than, equal to, or less than the
71 typedef int (*compare_func_type
)(const void *, const void *);
75 * This data structure is the cache.
77 * It must be passed to all of the hashing routines
82 /* Variables used to implement the hash itself. */
83 node_ptr
*node_table
; /* Pointer to an array of hash nodes. */
84 /* Variables used to track the size of the hash table so to determine
86 unsigned int size
; /* Number of buckets allocated for the hash table
87 (number of array entries allocated for
88 "node_table"). Must be a power of two. */
89 unsigned int used
; /* Current number of entries in the hash table. */
90 unsigned int mask
; /* Precomputed mask. */
92 /* Variables used to implement indexing through the hash table. */
94 unsigned int last_bucket
; /* Tracks which entry in the array where
95 the last value was returned. */
96 /* Function used to compute a hash code given a key.
97 This function is specified when the hash table is created. */
98 hash_func_type hash_func
;
99 /* Function used to compare two hash keys to see if they are equal. */
100 compare_func_type compare_func
;
104 /* Two important hash tables. */
105 extern cache_ptr module_hash_table
, class_hash_table
;
107 /* Allocate and initialize a hash table. */
109 cache_ptr
hash_new (unsigned int size
,
110 hash_func_type hash_func
,
111 compare_func_type compare_func
);
113 /* Deallocate all of the hash nodes and the cache itself. */
115 void hash_delete (cache_ptr cache
);
117 /* Add the key/value pair to the hash table. If the
118 hash table reaches a level of fullness then it will be resized.
120 assert if the key is already in the hash. */
122 void hash_add (cache_ptr
*cachep
, const void *key
, void *value
);
124 /* Remove the key/value pair from the hash table.
125 assert if the key isn't in the table. */
127 void hash_remove (cache_ptr cache
, const void *key
);
129 /* Used to index through the hash table. Start with NULL
130 to get the first entry.
132 Successive calls pass the value returned previously.
133 ** Don't modify the hash during this operation ***
135 Cache nodes are returned such that key or value can
138 node_ptr
hash_next (cache_ptr cache
, node_ptr node
);
140 /* Used to return a value from a hash table using a given key. */
142 void *hash_value_for_key (cache_ptr cache
, const void *key
);
144 /* Used to determine if the given key exists in the hash table */
146 BOOL
hash_is_key_in_hash (cache_ptr cache
, const void *key
);
148 /************************************************
150 Useful hashing functions.
152 Declared inline for your pleasure.
154 ************************************************/
156 /* Calculate a hash code by performing some
157 manipulation of the key pointer. (Use the lowest bits
158 except for those likely to be 0 due to alignment.) */
160 static inline unsigned int
161 hash_ptr (cache_ptr cache
, const void *key
)
163 return ((size_t)key
/ sizeof (void *)) & cache
->mask
;
167 /* Calculate a hash code by iterating over a NULL
169 static inline unsigned int
170 hash_string (cache_ptr cache
, const void *key
)
172 unsigned int ret
= 0;
173 unsigned int ctr
= 0;
176 while (*(char*)key
) {
177 ret
^= *(char*)key
++ << ctr
;
178 ctr
= (ctr
+ 1) % sizeof (void *);
181 return ret
& cache
->mask
;
185 /* Compare two pointers for equality. */
187 compare_ptrs (const void *k1
, const void *k2
)
193 /* Compare two strings. */
195 compare_strings (const void *k1
, const void *k2
)
199 else if (k1
== 0 || k2
== 0)
202 return !strcmp (k1
, k2
);
206 #endif /* not __hash_INCLUDE_GNU */