1/* Hash tables for Objective C method dispatch.
2   Copyright (C) 1993, 1995, 1996 Free Software Foundation, Inc.
3
4This file is part of GNU CC.
5
6GNU CC is free software; you can redistribute it and/or modify
7it under the terms of the GNU General Public License as published by
8the Free Software Foundation; either version 2, or (at your option)
9any later version.
10
11GNU CC is distributed in the hope that it will be useful,
12but WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14GNU General Public License for more details.
15
16You should have received a copy of the GNU General Public License
17along with GNU CC; see the file COPYING.  If not, write to
18the Free Software Foundation, 59 Temple Place - Suite 330,
19Boston, MA 02111-1307, 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 <objc/objc.h>
33
34/*
35 * This data structure is used to hold items
36 *  stored in a hash table.  Each node holds
37 *  a key/value pair.
38 *
39 * Items in the cache are really of type void *.
40 */
41typedef struct cache_node
42{
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
48				   value. */
49  void *value;			/* Value stored for the key. */
50} *node_ptr;
51
52
53/*
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
56 * to the key type.
57 *
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.
61 */
62typedef unsigned int (*hash_func_type)(void *, const void *);
63
64/*
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
68 * second.
69 */
70
71typedef int (*compare_func_type)(const void *, const void *);
72
73
74/*
75 * This data structure is the cache.
76 *
77 * It must be passed to all of the hashing routines
78 *   (except for new).
79 */
80typedef struct cache
81{
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
85    when to resize it.  */
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.  */
91
92  /* Variables used to implement indexing through the hash table.  */
93
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;
101} *cache_ptr;
102
103
104/* Two important hash tables.  */
105extern cache_ptr module_hash_table, class_hash_table;
106
107/* Allocate and initialize a hash table.  */
108
109cache_ptr hash_new (unsigned int size,
110		    hash_func_type hash_func,
111		    compare_func_type compare_func);
112
113/* Deallocate all of the hash nodes and the cache itself.  */
114
115void hash_delete (cache_ptr cache);
116
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.
119
120   assert if the key is already in the hash.  */
121
122void hash_add (cache_ptr *cachep, const void *key, void *value);
123
124/* Remove the key/value pair from the hash table.
125   assert if the key isn't in the table.  */
126
127void hash_remove (cache_ptr cache, const void *key);
128
129/* Used to index through the hash table.  Start with NULL
130   to get the first entry.
131
132   Successive calls pass the value returned previously.
133   ** Don't modify the hash during this operation ***
134
135   Cache nodes are returned such that key or value can
136   be extracted.  */
137
138node_ptr hash_next (cache_ptr cache, node_ptr node);
139
140/* Used to return a value from a hash table using a given key.  */
141
142void *hash_value_for_key (cache_ptr cache, const void *key);
143
144/* Used to determine if the given key exists in the hash table */
145
146BOOL hash_is_key_in_hash (cache_ptr cache, const void *key);
147
148/************************************************
149
150        Useful hashing functions.
151
152        Declared inline for your pleasure.
153
154************************************************/
155
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.)  */
159
160static inline unsigned int
161hash_ptr (cache_ptr cache, const void *key)
162{
163  return ((size_t)key / sizeof (void *)) & cache->mask;
164}
165
166
167/* Calculate a hash code by iterating over a NULL
168   terminate string.  */
169static inline unsigned int
170hash_string (cache_ptr cache, const void *key)
171{
172  unsigned int ret = 0;
173  unsigned int ctr = 0;
174
175
176  while (*(char*)key) {
177    ret ^= *(char*)key++ << ctr;
178    ctr = (ctr + 1) % sizeof (void *);
179  }
180
181  return ret & cache->mask;
182}
183
184
185/* Compare two pointers for equality.  */
186static inline int
187compare_ptrs (const void *k1, const void *k2)
188{
189  return !(k1 - k2);
190}
191
192
193/* Compare two strings.  */
194static inline int
195compare_strings (const void *k1, const void *k2)
196{
197  if (k1 == k2)
198    return 1;
199  else if (k1 == 0 || k2 == 0)
200    return 0;
201  else
202    return !strcmp (k1, k2);
203}
204
205
206#endif /* not __hash_INCLUDE_GNU */
207