```   1 /* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */
2
3 #include "hashtable.h"
4 #include "hashtable_private.h"
5 #include <stdlib.h>
6 #include <stdio.h>
7 #include <string.h>
8 #include <math.h>
9
10 /*
11 Credit for primes table: Aaron Krowne
12  http://br.endernet.org/~akrowne/
13  http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
14 */
15 static const unsigned int primes[] = {
16 53, 97, 193, 389,
17 769, 1543, 3079, 6151,
18 12289, 24593, 49157, 98317,
19 196613, 393241, 786433, 1572869,
20 3145739, 6291469, 12582917, 25165843,
21 50331653, 100663319, 201326611, 402653189,
22 805306457, 1610612741
23 };
24 const unsigned int prime_table_length = sizeof(primes)/sizeof(primes[0]);
25 const float max_load_factor = 0.65;
26
27 /*****************************************************************************/
28 struct hashtable *
29 create_hashtable(unsigned int minsize,
30                  unsigned int (*hashf) (void*),
31                  int (*eqf) (void*,void*))
32 {
33     struct hashtable *h;
34     unsigned int pindex, size = primes[0];
35     /* Check requested hashtable isn't too large */
36     if (minsize > (1u << 30)) return NULL;
37     /* Enforce size as prime */
38     for (pindex=0; pindex < prime_table_length; pindex++) {
39         if (primes[pindex] > minsize) { size = primes[pindex]; break; }
40     }
41     h = (struct hashtable *)malloc(sizeof(struct hashtable));
42     if (NULL == h) return NULL; /*oom*/
43     h->table = (struct entry **)malloc(sizeof(struct entry*) * size);
44     if (NULL == h->table) { free(h); return NULL; } /*oom*/
45     memset(h->table, 0, size * sizeof(struct entry *));
46     h->tablelength  = size;
47     h->primeindex   = pindex;
48     h->entrycount   = 0;
49     h->hashfn       = hashf;
50     h->eqfn         = eqf;
51     h->loadlimit    = (unsigned int) ceil(size * max_load_factor);
52     return h;
53 }
54
55 /*****************************************************************************/
56 unsigned int
57 hash(struct hashtable *h, void *k)
58 {
59     /* Aim to protect against poor hash functions by adding logic here
60      * - logic taken from java 1.4 hashtable source */
61     unsigned int i = h->hashfn(k);
62     i += ~(i << 9);
63     i ^=  ((i >> 14) | (i << 18)); /* >>> */
64     i +=  (i << 4);
65     i ^=  ((i >> 10) | (i << 22)); /* >>> */
66     return i;
67 }
68
69 /*****************************************************************************/
70 static int
71 hashtable_expand(struct hashtable *h)
72 {
73     /* Double the size of the table to accomodate more entries */
74     struct entry **newtable;
75     struct entry *e;
76     struct entry **pE;
77     unsigned int newsize, i, index;
78     /* Check we're not hitting max capacity */
79     if (h->primeindex == (prime_table_length - 1)) return 0;
80     newsize = primes[++(h->primeindex)];
81
82     newtable = (struct entry **)malloc(sizeof(struct entry*) * newsize);
83     if (NULL != newtable)
84     {
85         memset(newtable, 0, newsize * sizeof(struct entry *));
86         /* This algorithm is not 'stable'. ie. it reverses the list
87          * when it transfers entries between the tables */
88         for (i = 0; i < h->tablelength; i++) {
89             while (NULL != (e = h->table[i])) {
90                 h->table[i] = e->next;
91                 index = indexFor(newsize,e->h);
92                 e->next = newtable[index];
93                 newtable[index] = e;
94             }
95         }
96         free(h->table);
97         h->table = newtable;
98     }
99     /* Plan B: realloc instead */
100     else
101     {
102         newtable = (struct entry **)
103                    realloc(h->table, newsize * sizeof(struct entry *));
104         if (NULL == newtable) { (h->primeindex)--; return 0; }
105         h->table = newtable;
106         memset(newtable[h->tablelength], 0, newsize - h->tablelength);
107         for (i = 0; i < h->tablelength; i++) {
108             for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) {
109                 index = indexFor(newsize,e->h);
110                 if (index == i)
111                 {
112                     pE = &(e->next);
113                 }
114                 else
115                 {
116                     *pE = e->next;
117                     e->next = newtable[index];
118                     newtable[index] = e;
119                 }
120             }
121         }
122     }
123     h->tablelength = newsize;
124     h->loadlimit   = (unsigned int) ceil(newsize * max_load_factor);
125     return -1;
126 }
127
128 /*****************************************************************************/
129 unsigned int
130 hashtable_count(struct hashtable *h)
131 {
132     return h->entrycount;
133 }
134
135 /*****************************************************************************/
136 int
137 hashtable_insert(struct hashtable *h, void *k, void *v)
138 {
139     /* This method allows duplicate keys - but they shouldn't be used */
140     unsigned int index;
141     struct entry *e;
142     if (++(h->entrycount) > h->loadlimit)
143     {
144         /* Ignore the return value. If expand fails, we should
145          * still try cramming just this value into the existing table
146          * -- we may not have memory for a larger table, but one more
147          * element may be ok. Next time we insert, we'll try expanding again.*/
148         hashtable_expand(h);
149     }
150     e = (struct entry *)malloc(sizeof(struct entry));
151     if (NULL == e) { --(h->entrycount); return 0; } /*oom*/
152     e->h = hash(h,k);
153     index = indexFor(h->tablelength,e->h);
154     e->k = k;
155     e->v = v;
156     e->next = h->table[index];
157     h->table[index] = e;
158     return -1;
159 }
160
161 /*****************************************************************************/
162 void * /* returns value associated with key */
163 hashtable_search(struct hashtable *h, void *k)
164 {
165     struct entry *e;
166     unsigned int hashvalue, index;
167     hashvalue = hash(h,k);
168     index = indexFor(h->tablelength,hashvalue);
169     e = h->table[index];
170     while (NULL != e)
171     {
172         /* Check hash value to short circuit heavier comparison */
173         if ((hashvalue == e->h) && (h->eqfn(k, e->k))) return e->v;
174         e = e->next;
175     }
176     return NULL;
177 }
178
179 /*****************************************************************************/
180 void * /* returns value associated with key */
181 hashtable_remove(struct hashtable *h, void *k)
182 {
183     /* TODO: consider compacting the table when the load factor drops enough,
184      *       or provide a 'compact' method. */
185
186     struct entry *e;
187     struct entry **pE;
188     void *v;
189     unsigned int hashvalue, index;
190
191     hashvalue = hash(h,k);
192     index = indexFor(h->tablelength,hash(h,k));
193     pE = &(h->table[index]);
194     e = *pE;
195     while (NULL != e)
196     {
197         /* Check hash value to short circuit heavier comparison */
198         if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
199         {
200             *pE = e->next;
201             h->entrycount--;
202             v = e->v;
203             freekey(e->k);
204             free(e);
205             return v;
206         }
207         pE = &(e->next);
208         e = e->next;
209     }
210     return NULL;
211 }
212
213 /*****************************************************************************/
214 /* destroy */
215 void
216 hashtable_destroy(struct hashtable *h, int free_values)
217 {
218     unsigned int i;
219     struct entry *e, *f;
220     struct entry **table = h->table;
221     if (free_values)
222     {
223         for (i = 0; i < h->tablelength; i++)
224         {
225             e = table[i];
226             while (NULL != e)
227             { f = e; e = e->next; freekey(f->k); free(f->v); free(f); }
228         }
229     }
230     else
231     {
232         for (i = 0; i < h->tablelength; i++)
233         {
234             e = table[i];
235             while (NULL != e)
236             { f = e; e = e->next; freekey(f->k); free(f); }
237         }
238     }
239     free(h->table);
240     free(h);
241 }
242
243 /*
244  * Copyright (c) 2002, Christopher Clark
246  *
247  * Redistribution and use in source and binary forms, with or without
248  * modification, are permitted provided that the following conditions
249  * are met:
250  *
251  * * Redistributions of source code must retain the above copyright
252  * notice, this list of conditions and the following disclaimer.
253  *
254  * * Redistributions in binary form must reproduce the above copyright
255  * notice, this list of conditions and the following disclaimer in the
256  * documentation and/or other materials provided with the distribution.
257  *
258  * * Neither the name of the original author; nor the names of any contributors
259  * may be used to endorse or promote products derived from this software
260  * without specific prior written permission.
261  *
262  *
263  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
264  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
265  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
266  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER
267  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
268  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
269  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
270  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
271  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
272  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
273  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
274 */
```