1 /* Hash tables for Objective C internal structures
2 Copyright (C) 1993-2022 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/>. */
25 #include "objc-private/common.h"
26 #include <assert.h> /* For assert. */
28 #include "objc/runtime.h" /* For objc_calloc. */
29 #include "objc-private/hash.h"
31 /* These two macros determine when a hash table is full and
32 by how much it should be expanded respectively.
34 These equations are percentages. */
35 #define FULLNESS(cache) \
36 ((((cache)->size * 75) / 100) <= (cache)->used)
37 #define EXPANSION(cache) \
41 objc_hash_new (unsigned int size
, hash_func_type hash_func
,
42 compare_func_type compare_func
)
46 /* Pass me a value greater than 0 and a power of 2. */
48 assert (! (size
& (size
- 1)));
50 /* Allocate the cache structure. calloc insures its initialization
51 for default values. */
52 cache
= (cache_ptr
) objc_calloc (1, sizeof (struct cache
));
55 /* Allocate the array of buckets for the cache. calloc initializes
56 all of the pointers to NULL. */
58 = (node_ptr
*) objc_calloc (size
, sizeof (node_ptr
));
59 assert (cache
->node_table
);
63 /* This should work for all processor architectures (?). */
64 cache
->mask
= (size
- 1);
66 /* Store the hashing function so that codes can be computed. */
67 cache
->hash_func
= hash_func
;
69 /* Store the function that compares hash keys to determine if they
71 cache
->compare_func
= compare_func
;
78 objc_hash_delete (cache_ptr cache
)
84 /* Purge all key/value pairs from the table. */
85 /* Step through the nodes one by one and remove every node WITHOUT
86 using objc_hash_next. this makes objc_hash_delete much more
88 for (i
= 0; i
< cache
->size
; i
++)
90 if ((node
= cache
->node_table
[i
]))
92 /* An entry in the hash table has been found. Now step
93 through the nodes next in the list and free them. */
94 while ((next_node
= node
->next
))
96 objc_hash_remove (cache
,node
->key
);
99 objc_hash_remove (cache
,node
->key
);
103 /* Release the array of nodes and the cache itself. */
104 objc_free(cache
->node_table
);
110 objc_hash_add (cache_ptr
*cachep
, const void *key
, void *value
)
112 size_t indx
= (*(*cachep
)->hash_func
) (*cachep
, key
);
113 node_ptr node
= (node_ptr
) objc_calloc (1, sizeof (struct cache_node
));
117 /* Initialize the new node. */
120 node
->next
= (*cachep
)->node_table
[indx
];
122 /* Debugging. Check the list for another key. */
125 node_ptr node1
= (*cachep
)->node_table
[indx
];
128 assert (node1
->key
!= key
);
134 /* Install the node as the first element on the list. */
135 (*cachep
)->node_table
[indx
] = node
;
137 /* Bump the number of entries in the cache. */
140 /* Check the hash table's fullness. We're going to expand if it is
141 above the fullness level. */
142 if (FULLNESS (*cachep
))
144 /* The hash table has reached its fullness level. Time to
147 I'm using a slow method here but is built on other primitive
148 functions thereby increasing its correctness. */
149 node_ptr node1
= NULL
;
150 cache_ptr
new = objc_hash_new (EXPANSION (*cachep
),
151 (*cachep
)->hash_func
,
152 (*cachep
)->compare_func
);
154 DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n",
155 (int) *cachep
, (*cachep
)->size
, new->size
);
157 /* Copy the nodes from the first hash table to the new one. */
158 while ((node1
= objc_hash_next (*cachep
, node1
)))
159 objc_hash_add (&new, node1
->key
, node1
->value
);
161 /* Trash the old cache. */
162 objc_hash_delete (*cachep
);
164 /* Return a pointer to the new hash table. */
170 objc_hash_remove (cache_ptr cache
, const void *key
)
172 size_t indx
= (*cache
->hash_func
) (cache
, key
);
173 node_ptr node
= cache
->node_table
[indx
];
175 /* We assume there is an entry in the table. Error if it is
179 /* Special case. First element is the key/value pair to be
181 if ((*cache
->compare_func
) (node
->key
, key
))
183 cache
->node_table
[indx
] = node
->next
;
188 /* Otherwise, find the hash entry. */
189 node_ptr prev
= node
;
193 if ((*cache
->compare_func
) (node
->key
, key
))
195 prev
->next
= node
->next
, removed
= YES
;
199 prev
= node
, node
= node
->next
;
201 while (!removed
&& node
);
205 /* Decrement the number of entries in the hash table. */
211 objc_hash_next (cache_ptr cache
, node_ptr node
)
213 /* If the scan is being started then reset the last node visitied
214 pointer and bucket index. */
216 cache
->last_bucket
= 0;
218 /* If there is a node visited last then check for another entry in
219 the same bucket. Otherwise step to the next bucket. */
224 /* There is a node which follows the last node returned.
225 Step to that node and retun it. */
229 ++cache
->last_bucket
;
232 /* If the list isn't exhausted then search the buckets for other
234 if (cache
->last_bucket
< cache
->size
)
236 /* Scan the remainder of the buckets looking for an entry at
237 the head of the list. Return the first item found. */
238 while (cache
->last_bucket
< cache
->size
)
239 if (cache
->node_table
[cache
->last_bucket
])
240 return cache
->node_table
[cache
->last_bucket
];
242 ++cache
->last_bucket
;
244 /* No further nodes were found in the hash table. */
252 /* Given KEY, return corresponding value for it in CACHE. Return NULL
253 if the KEY is not recorded. */
255 objc_hash_value_for_key (cache_ptr cache
, const void *key
)
257 node_ptr node
= cache
->node_table
[(*cache
->hash_func
) (cache
, key
)];
263 if ((*cache
->compare_func
) (node
->key
, key
))
265 retval
= node
->value
;
271 while (! retval
&& node
);
276 /* Given KEY, return YES if it exists in the CACHE. Return NO if it
279 objc_hash_is_key_in_hash (cache_ptr cache
, const void *key
)
281 node_ptr node
= cache
->node_table
[(*cache
->hash_func
) (cache
, key
)];
286 if ((*cache
->compare_func
)(node
->key
, key
))