summaryrefslogtreecommitdiffstats
path: root/runtime/hashtable.c
blob: 4673a502f04eb01110b503617ff023e711c98a48 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
/* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */
/* taken from http://www.cl.cam.ac.uk/~cwc22/hashtable/ */

#include "hashtable_private.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

/* this code has several warnings, but we ignore them because
 * this seems to work and we do not want to engage in that code body. If
 * we really run into troubles, it is better to change to libfastjson, which
 * we should do in the medium to long term anyhow...
 */
#ifdef __GNUC__
#pragma GCC diagnostic ignored "-Wredundant-decls"
#endif

/*
Credit for primes table: Aaron Krowne
http://br.endernet.org/~akrowne/
http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
*/
static const unsigned int primes[] = {
53, 97, 193, 389,
769, 1543, 3079, 6151,
12289, 24593, 49157, 98317,
196613, 393241, 786433, 1572869,
3145739, 6291469, 12582917, 25165843,
50331653, 100663319, 201326611, 402653189,
805306457, 1610612741
};
const unsigned int prime_table_length = sizeof(primes)/sizeof(primes[0]);

#define MAX_LOAD_FACTOR 65 /* to get real factor, divide by 100! */

/* compute max load. We use a constant factor of 0.65, but do
 * everything times 100, so that we do not need floats.
 */
static inline unsigned
getLoadLimit(unsigned size)
{
	return (unsigned int) ((unsigned long long) size * MAX_LOAD_FACTOR) / 100;
}

/*****************************************************************************/
struct hashtable *
create_hashtable(unsigned int minsize,
		unsigned int (*hashf) (void*),
		int (*eqf) (void*,void*), void (*dest)(void*))
{
	struct hashtable *h;
	unsigned int pindex, size = primes[0];
	/* Check requested hashtable isn't too large */
	if (minsize > (1u << 30)) return NULL;
	/* Enforce size as prime */
	for (pindex=0; pindex < prime_table_length; pindex++) {
		if (primes[pindex] > minsize) { size = primes[pindex]; break; }
	}
	h = (struct hashtable *)malloc(sizeof(struct hashtable));
	if (NULL == h) return NULL; /*oom*/
	h->table = (struct entry **)malloc(sizeof(struct entry*) * size);
	if (NULL == h->table) { free(h); return NULL; } /*oom*/
	memset(h->table, 0, size * sizeof(struct entry *));
	h->tablelength  = size;
	h->primeindex   = pindex;
	h->entrycount   = 0;
	h->hashfn       = hashf;
	h->eqfn         = eqf;
	h->dest         = dest;
	h->loadlimit    = getLoadLimit(size);
	return h;
}

/*****************************************************************************/
#if defined(__clang__)
#pragma GCC diagnostic ignored "-Wunknown-attributes"
#endif
unsigned int
#if defined(__clang__)
__attribute__((no_sanitize("unsigned-integer-overflow")))
#endif
hash(struct hashtable *h, void *k)
{
	/* Aim to protect against poor hash functions by adding logic here
	 * - logic taken from java 1.4 hashtable source */
	unsigned int i = h->hashfn(k);
	i += ~(i << 9);
	i ^=  ((i >> 14) | (i << 18)); /* >>> */
	i +=  (i << 4);
	i ^=  ((i >> 10) | (i << 22)); /* >>> */
	return i;
}

/*****************************************************************************/
static int
hashtable_expand(struct hashtable *h)
{
	/* Double the size of the table to accomodate more entries */
	struct entry **newtable;
	struct entry *e;
	struct entry **pE;
	unsigned int newsize, i, idx;
	/* Check we're not hitting max capacity */
	if (h->primeindex == (prime_table_length - 1)) return 0;
	newsize = primes[++(h->primeindex)];

	newtable = (struct entry **)malloc(sizeof(struct entry*) * newsize);
	if (NULL != newtable)
	{
		memset(newtable, 0, newsize * sizeof(struct entry *));
		/* This algorithm is not 'stable'. ie. it reverses the list
		 * when it transfers entries between the tables */
		for (i = 0; i < h->tablelength; i++) {
			while (NULL != (e = h->table[i])) {
				h->table[i] = e->next;
				idx = indexFor(newsize,e->h);
				e->next = newtable[idx];
				newtable[idx] = e;
			}
		}
		free(h->table);
		h->table = newtable;
	}
	/* Plan B: realloc instead */
	else
	{
		newtable = (struct entry **)
		realloc(h->table, newsize * sizeof(struct entry *));
		if (NULL == newtable) { (h->primeindex)--; return 0; }
		h->table = newtable;
		memset(newtable[h->tablelength], 0, newsize - h->tablelength);
		for (i = 0; i < h->tablelength; i++) {
			for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) {
				idx = indexFor(newsize,e->h);
				if (idx == i)
				{
					pE = &(e->next);
				}
				else
				{
					*pE = e->next;
					e->next = newtable[idx];
					newtable[idx] = e;
				}
			}
		}
	}
	h->tablelength = newsize;
	h->loadlimit   = getLoadLimit(newsize);
	return -1;
}

/*****************************************************************************/
unsigned int
hashtable_count(struct hashtable *h)
{
	return h->entrycount;
}

/*****************************************************************************/
int
hashtable_insert(struct hashtable *h, void *k, void *v)
{
	/* This method allows duplicate keys - but they shouldn't be used */
	unsigned int idx;
	struct entry *e;
	if (++(h->entrycount) > h->loadlimit)
	{
		/* Ignore the return value. If expand fails, we should
		 * still try cramming just this value into the existing table
		 * -- we may not have memory for a larger table, but one more
		 * element may be ok. Next time we insert, we'll try expanding again.*/
		hashtable_expand(h);
	}
	e = (struct entry *)malloc(sizeof(struct entry));
	if (NULL == e) { --(h->entrycount); return 0; } /*oom*/
	e->h = hash(h,k);
	idx = indexFor(h->tablelength,e->h);
	e->k = k;
	e->v = v;
	e->next = h->table[idx];
	h->table[idx] = e;
	return -1;
}

/*****************************************************************************/
void * /* returns value associated with key */
hashtable_search(struct hashtable *h, void *k)
{
	struct entry *e;
	unsigned int hashvalue, idx;
	hashvalue = hash(h,k);
	idx = indexFor(h->tablelength,hashvalue);
	e = h->table[idx];
	while (NULL != e)
	{
		/* Check hash value to short circuit heavier comparison */
		if ((hashvalue == e->h) && (h->eqfn(k, e->k))) return e->v;
			e = e->next;
	}
	return NULL;
}

/*****************************************************************************/
void * /* returns value associated with key */
hashtable_remove(struct hashtable *h, void *k)
{
	/* TODO: consider compacting the table when the load factor drops enough,
	 *       or provide a 'compact' method. */

	struct entry *e;
	struct entry **pE;
	void *v;
	unsigned int hashvalue, idx;

	hashvalue = hash(h,k);
	idx = indexFor(h->tablelength,hash(h,k));
	pE = &(h->table[idx]);
	e = *pE;
	while (NULL != e)
	{
		/* Check hash value to short circuit heavier comparison */
		if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
		{
			*pE = e->next;
			h->entrycount--;
			v = e->v;
			freekey(e->k);
			free(e);
			return v;
		}
		pE = &(e->next);
		e = e->next;
	}
	return NULL;
}

/*****************************************************************************/
/* destroy */
void
hashtable_destroy(struct hashtable *h, int free_values)
{
	unsigned int i;
	struct entry *e, *f;
	struct entry **table = h->table;
	if (free_values)
	{
		for (i = 0; i < h->tablelength; i++)
		{
			e = table[i];
			while (NULL != e)
			{
				f = e;
				e = e->next;
				freekey(f->k);
				if(h->dest == NULL)
					free(f->v);
				else
					h->dest(f->v);
				free(f);
			}
		}
	}
	else
	{
		for (i = 0; i < h->tablelength; i++)
		{
			e = table[i];
			while (NULL != e)
			{ f = e; e = e->next; freekey(f->k); free(f); }
		}
	}
	free(h->table);
	free(h);
}

/* some generic hash functions */

/* one provided by Aaaron Wiebe based on perl's hashing algorithm
 * (so probably pretty generic). Not for excessively large strings!
 */
#if defined(__clang__)
#pragma GCC diagnostic ignored "-Wunknown-attributes"
#endif
unsigned __attribute__((nonnull(1))) int
#if defined(__clang__)
__attribute__((no_sanitize("unsigned-integer-overflow")))
#endif
hash_from_string(void *k)
{
	char *rkey = (char*) k;
	unsigned hashval = 1;

	while (*rkey)
		hashval = hashval * 33 + *rkey++;

	return hashval;
}


int
key_equals_string(void *key1, void *key2)
{
	/* we must return true IF the keys are equal! */
	return !strcmp(key1, key2);
}


/*
 * Copyright (c) 2002, Christopher Clark
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of the original author; nor the names of any contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/