about summary refs log tree commit diff
path: root/locale/programs/simple-hash.c
blob: 5d8a93cda96d37f7c67ea72f670518a3b9963b0d (plain) (blame)
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
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
/* Implement simple hashing table with string based keys.
   Copyright (C) 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
   Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, October 1994.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

#if HAVE_OBSTACK
# include <obstack.h>
#else
# include "obstack.h"
#endif

#ifdef HAVE_VALUES_H
# include <values.h>
#endif

#include "simple-hash.h"

#define obstack_chunk_alloc malloc
#define obstack_chunk_free free

#ifndef BITSPERBYTE
# define BITSPERBYTE 8
#endif

#ifndef	LONGBITS
# define LONGBITS (sizeof (long) * BITSPERBYTE)
#endif

#ifndef bcopy
# define bcopy(s, d, n)	memcpy ((d), (s), (n))
#endif

void *xmalloc __P ((size_t __n));

typedef struct hash_entry
{
  unsigned long used;
  const void *key;
  size_t keylen;
  void *data;
  struct hash_entry *next;
}
hash_entry;

/* Prototypes for local functions.  */
static void insert_entry_2 __P ((hash_table *htab, const void *key,
				 size_t keylen, unsigned long hval,
				 size_t idx, void *data));
static size_t lookup __P ((hash_table *htab, const void *key, size_t keylen,
			   unsigned long int hval));
static size_t lookup_2 __P ((hash_table *htab, const void *key,
			     size_t keylen, unsigned long int hval));
static unsigned long compute_hashval __P ((const void *key, size_t keylen));
static int is_prime __P ((unsigned long int candidate));


int
init_hash (htab, init_size)
     hash_table *htab;
     unsigned long int init_size;
{
  /* We need the size to be a prime.  */
  init_size = next_prime (init_size);

  /* Initialize the data structure.  */
  htab->size = init_size;
  htab->filled = 0;
  htab->first = NULL;
  htab->table = (void *) xmalloc ((init_size + 1) * sizeof (hash_entry));
  if (htab->table == NULL)
    return -1;

  memset (htab->table, '\0', (init_size + 1) * sizeof (hash_entry));
  obstack_init (&htab->mem_pool);

  return 0;
}


int
delete_hash (htab)
     hash_table *htab;
{
  free (htab->table);
  obstack_free (&htab->mem_pool, NULL);
  return 0;
}


int
insert_entry (htab, key, keylen, data)
     hash_table *htab;
     const void *key;
     size_t keylen;
     void *data;
{
  unsigned long int hval = compute_hashval (key, keylen);
  hash_entry *table = (hash_entry *) htab->table;
  size_t idx = lookup (htab, key, keylen, hval);

  if (table[idx].used)
    /* We don't want to overwrite the old value.  */
    return -1;
  else
    {
      /* An empty bucket has been found.  */
      insert_entry_2 (htab, obstack_copy (&htab->mem_pool, key, keylen),
		      keylen, hval, idx, data);
      return 0;
    }
}

static void
insert_entry_2 (htab, key, keylen, hval, idx, data)
     hash_table *htab;
     const void *key;
     size_t keylen;
     unsigned long int hval;
     size_t idx;
     void *data;
{
  hash_entry *table = (hash_entry *) htab->table;

  table[idx].used = hval;
  table[idx].key = key;
  table[idx].keylen = keylen;
  table[idx].data = data;

      /* List the new value in the list.  */
  if ((hash_entry *) htab->first == NULL)
    {
      table[idx].next = &table[idx];
      *(hash_entry **) &htab->first = &table[idx];
    }
  else
    {
      table[idx].next = ((hash_entry *) htab->first)->next;
      ((hash_entry *) htab->first)->next = &table[idx];
      *(hash_entry **) &htab->first = &table[idx];
    }

  ++htab->filled;
  if (100 * htab->filled > 90 * htab->size)
    {
      /* Table is filled more than 90%.  Resize the table.  */
      unsigned long int old_size = htab->size;

      htab->size = next_prime (htab->size * 2);
      htab->filled = 0;
      htab->first = NULL;
      htab->table = (void *) xmalloc ((1 + htab->size)
				      * sizeof (hash_entry));
      memset (htab->table, '\0', (1 + htab->size) * sizeof (hash_entry));

      for (idx = 1; idx <= old_size; ++idx)
	if (table[idx].used)
	  insert_entry_2 (htab, table[idx].key, table[idx].keylen,
			  table[idx].used,
			  lookup_2 (htab, table[idx].key, table[idx].keylen,
				    table[idx].used),
			  table[idx].data);

      free (table);
    }
}


int
find_entry (htab, key, keylen, result)
     hash_table *htab;
     const void *key;
     size_t keylen;
     void **result;
{
  hash_entry *table = (hash_entry *) htab->table;
  size_t idx = lookup (htab, key, keylen, compute_hashval (key, keylen));

  if (table[idx].used == 0)
    return -1;

  *result = table[idx].data;
  return 0;
}


int
set_entry (htab, key, keylen, newval)
     hash_table *htab;
     const void *key;
     size_t keylen;
     void *newval;
{
  hash_entry *table = (hash_entry *) htab->table;
  size_t idx = lookup (htab, key, keylen, compute_hashval (key, keylen));

  if (table[idx].used == 0)
    return -1;

  table[idx].data = newval;
  return 0;
}


int
iterate_table (htab, ptr, key, keylen, data)
     hash_table *htab;
     void **ptr;
     const void **key;
     size_t *keylen;
     void **data;
{
  if (*ptr == NULL)
    {
      if (htab->first == NULL)
	return -1;
      *ptr = (void *) ((hash_entry *) htab->first)->next;
    }
  else
    {
      if (*ptr == htab->first)
	return -1;
      *ptr = (void *) (((hash_entry *) *ptr)->next);
    }

  *key = ((hash_entry *) *ptr)->key;
  *keylen = ((hash_entry *) *ptr)->keylen;
  *data = ((hash_entry *) *ptr)->data;
  return 0;
}


static size_t
lookup (htab, key, keylen, hval)
     hash_table *htab;
     const void *key;
     size_t keylen;
     unsigned long hval;
{
  unsigned long hash;
  size_t idx;
  hash_entry *table = (hash_entry *) htab->table;

  /* First hash function: simply take the modul but prevent zero.  */
  hash = 1 + hval % htab->size;

  idx = hash;

  if (table[idx].used)
    {
      if (table[idx].used == hval && table[idx].keylen == keylen
	  && memcmp (key, table[idx].key, keylen) == 0)
	return idx;

      /* Second hash function as suggested in [Knuth].  */
      hash = 1 + hval % (htab->size - 2);

      do
	{
	  if (idx <= hash)
	    idx = htab->size + idx - hash;
	  else
	    idx -= hash;

	  /* If entry is found use it.  */
	  if (table[idx].used == hval && table[idx].keylen == keylen
	      && memcmp (key, table[idx].key, keylen) == 0)
	    return idx;
	}
      while (table[idx].used);
    }
  return idx;
}


/* References:
   [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
   [Knuth]	      The Art of Computer Programming, part3 (6.4) */

static size_t
lookup_2 (htab, key, keylen, hval)
     hash_table *htab;
     const void *key;
     size_t keylen;
     unsigned long int hval;
{
  unsigned long int hash;
  size_t idx;
  hash_entry *table = (hash_entry *) htab->table;

  /* First hash function: simply take the modul but prevent zero.  */
  hash = 1 + hval % htab->size;

  idx = hash;

  if (table[idx].used)
    {
      if (table[idx].used == hval && table[idx].keylen == keylen
	  && memcmp (table[idx].key, key, keylen) == 0)
	return idx;

      /* Second hash function as suggested in [Knuth].  */
      hash = 1 + hval % (htab->size - 2);

      do
	{
	  if (idx <= hash)
	    idx = htab->size + idx - hash;
	  else
	    idx -= hash;

	  /* If entry is found use it.  */
	  if (table[idx].used == hval && table[idx].keylen == keylen
	      && memcmp (table[idx].key, key, keylen) == 0)
	    return idx;
	}
      while (table[idx].used);
    }
  return idx;
}


static unsigned long
compute_hashval (key, keylen)
     const void *key;
     size_t keylen;
{
  size_t cnt;
  unsigned long int hval, g;

  /* Compute the hash value for the given string.  The algorithm
     is taken from [Aho,Sethi,Ullman].  */
  cnt = 0;
  hval = keylen;
  while (cnt < keylen)
    {
      hval <<= 4;
      hval += (unsigned long int) *(((char *) key) + cnt++);
      g = hval & ((unsigned long) 0xf << (LONGBITS - 4));
      if (g != 0)
	{
	  hval ^= g >> (LONGBITS - 8);
	  hval ^= g;
	}
    }
  return hval != 0 ? hval : ~((unsigned long) 0);
}


unsigned long
next_prime (seed)
     unsigned long int seed;
{
  /* Make it definitely odd.  */
  seed |= 1;

  while (!is_prime (seed))
    seed += 2;

  return seed;
}


static int
is_prime (candidate)
     unsigned long int candidate;
{
  /* No even number and none less than 10 will be passed here.  */
  unsigned long int divn = 3;
  unsigned long int sq = divn * divn;

  while (sq < candidate && candidate % divn != 0)
    {
      ++divn;
      sq += 4 * divn;
      ++divn;
    }

  return candidate % divn != 0;
}