1/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to.  The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 *    notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 *    notice, this list of conditions and the following disclaimer in the
29 *    documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 *    must display the following acknowledgement:
32 *    "This product includes cryptographic software written by
33 *     Eric Young (eay@cryptsoft.com)"
34 *    The word 'cryptographic' can be left out if the rouines from the library
35 *    being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 *    the apps directory (application code) you must include an acknowledgement:
38 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed.  i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57#include <openssl/lhash.h>
58
59#include <assert.h>
60#include <limits.h>
61#include <string.h>
62
63#include <openssl/mem.h>
64
65/* kMinNumBuckets is the minimum size of the buckets array in an |_LHASH|. */
66static const size_t kMinNumBuckets = 16;
67
68/* kMaxAverageChainLength contains the maximum, average chain length. When the
69 * average chain length exceeds this value, the hash table will be resized. */
70static const size_t kMaxAverageChainLength = 2;
71static const size_t kMinAverageChainLength = 1;
72
73_LHASH *lh_new(lhash_hash_func hash, lhash_cmp_func comp) {
74  _LHASH *ret;
75
76  ret = OPENSSL_malloc(sizeof(_LHASH));
77  if (ret == NULL) {
78    return NULL;
79  }
80  memset(ret, 0, sizeof(_LHASH));
81
82  ret->num_buckets = kMinNumBuckets;
83  ret->buckets = OPENSSL_malloc(sizeof(LHASH_ITEM *) * ret->num_buckets);
84  if (ret->buckets == NULL) {
85    OPENSSL_free(ret);
86    return NULL;
87  }
88  memset(ret->buckets, 0, sizeof(LHASH_ITEM *) * ret->num_buckets);
89
90  ret->comp = comp;
91  if (ret->comp == NULL) {
92    ret->comp = (lhash_cmp_func) strcmp;
93  }
94  ret->hash = hash;
95  if (ret->hash == NULL) {
96    ret->hash = (lhash_hash_func) lh_strhash;
97  }
98
99  return ret;
100}
101
102void lh_free(_LHASH *lh) {
103  size_t i;
104  LHASH_ITEM *n, *next;
105
106  if (lh == NULL) {
107    return;
108  }
109
110  for (i = 0; i < lh->num_buckets; i++) {
111    for (n = lh->buckets[i]; n != NULL; n = next) {
112      next = n->next;
113      OPENSSL_free(n);
114    }
115  }
116
117  OPENSSL_free(lh->buckets);
118  OPENSSL_free(lh);
119}
120
121size_t lh_num_items(const _LHASH *lh) { return lh->num_items; }
122
123/* get_next_ptr_and_hash returns a pointer to the pointer that points to the
124 * item equal to |data|. In other words, it searches for an item equal to |data|
125 * and, if it's at the start of a chain, then it returns a pointer to an
126 * element of |lh->buckets|, otherwise it returns a pointer to the |next|
127 * element of the previous item in the chain. If an element equal to |data| is
128 * not found, it returns a pointer that points to a NULL pointer. If |out_hash|
129 * is not NULL, then it also puts the hash value of |data| in |*out_hash|. */
130static LHASH_ITEM **get_next_ptr_and_hash(const _LHASH *lh, uint32_t *out_hash,
131                                          const void *data) {
132  const uint32_t hash = lh->hash(data);
133  LHASH_ITEM *cur, **ret;
134
135  if (out_hash != NULL) {
136    *out_hash = hash;
137  }
138
139  ret = &lh->buckets[hash % lh->num_buckets];
140  for (cur = *ret; cur != NULL; cur = *ret) {
141    if (lh->comp(cur->data, data) == 0) {
142      break;
143    }
144    ret = &cur->next;
145  }
146
147  return ret;
148}
149
150void *lh_retrieve(const _LHASH *lh, const void *data) {
151  LHASH_ITEM **next_ptr;
152
153  next_ptr = get_next_ptr_and_hash(lh, NULL, data);
154
155  if (*next_ptr == NULL) {
156    return NULL;
157  }
158
159  return (*next_ptr)->data;
160}
161
162/* lh_rebucket allocates a new array of |new_num_buckets| pointers and
163 * redistributes the existing items into it before making it |lh->buckets| and
164 * freeing the old array. */
165static void lh_rebucket(_LHASH *lh, const size_t new_num_buckets) {
166  LHASH_ITEM **new_buckets, *cur, *next;
167  size_t i, alloc_size;
168
169  alloc_size = sizeof(LHASH_ITEM *) * new_num_buckets;
170  if (alloc_size / sizeof(LHASH_ITEM*) != new_num_buckets) {
171    return;
172  }
173
174  new_buckets = OPENSSL_malloc(alloc_size);
175  if (new_buckets == NULL) {
176    return;
177  }
178  memset(new_buckets, 0, alloc_size);
179
180  for (i = 0; i < lh->num_buckets; i++) {
181    for (cur = lh->buckets[i]; cur != NULL; cur = next) {
182      const size_t new_bucket = cur->hash % new_num_buckets;
183      next = cur->next;
184      cur->next = new_buckets[new_bucket];
185      new_buckets[new_bucket] = cur;
186    }
187  }
188
189  OPENSSL_free(lh->buckets);
190
191  lh->num_buckets = new_num_buckets;
192  lh->buckets = new_buckets;
193}
194
195/* lh_maybe_resize resizes the |buckets| array if needed. */
196static void lh_maybe_resize(_LHASH *lh) {
197  size_t avg_chain_length;
198
199  if (lh->callback_depth > 0) {
200    /* Don't resize the hash if we are currently iterating over it. */
201    return;
202  }
203
204  assert(lh->num_buckets >= kMinNumBuckets);
205  avg_chain_length = lh->num_items / lh->num_buckets;
206
207  if (avg_chain_length > kMaxAverageChainLength) {
208    const size_t new_num_buckets = lh->num_buckets * 2;
209
210    if (new_num_buckets > lh->num_buckets) {
211      lh_rebucket(lh, new_num_buckets);
212    }
213  } else if (avg_chain_length < kMinAverageChainLength &&
214             lh->num_buckets > kMinNumBuckets) {
215    size_t new_num_buckets = lh->num_buckets / 2;
216
217    if (new_num_buckets < kMinNumBuckets) {
218      new_num_buckets = kMinNumBuckets;
219    }
220
221    lh_rebucket(lh, new_num_buckets);
222  }
223}
224
225int lh_insert(_LHASH *lh, void **old_data, void *data) {
226  uint32_t hash;
227  LHASH_ITEM **next_ptr, *item;
228
229  *old_data = NULL;
230  next_ptr = get_next_ptr_and_hash(lh, &hash, data);
231
232
233  if (*next_ptr != NULL) {
234    /* An element equal to |data| already exists in the hash table. It will be
235     * replaced. */
236    *old_data = (*next_ptr)->data;
237    (*next_ptr)->data = data;
238    return 1;
239  }
240
241  /* An element equal to |data| doesn't exist in the hash table yet. */
242  item = OPENSSL_malloc(sizeof(LHASH_ITEM));
243  if (item == NULL) {
244    return 0;
245  }
246
247  item->data = data;
248  item->hash = hash;
249  item->next = NULL;
250  *next_ptr = item;
251  lh->num_items++;
252  lh_maybe_resize(lh);
253
254  return 1;
255}
256
257void *lh_delete(_LHASH *lh, const void *data) {
258  LHASH_ITEM **next_ptr, *item, *ret;
259
260  next_ptr = get_next_ptr_and_hash(lh, NULL, data);
261
262  if (*next_ptr == NULL) {
263    /* No such element. */
264    return NULL;
265  }
266
267  item = *next_ptr;
268  *next_ptr = item->next;
269  ret = item->data;
270  OPENSSL_free(item);
271
272  lh->num_items--;
273  lh_maybe_resize(lh);
274
275  return ret;
276}
277
278static void lh_doall_internal(_LHASH *lh, void (*no_arg_func)(void *),
279                              void (*arg_func)(void *, void *), void *arg) {
280  size_t i;
281  LHASH_ITEM *cur, *next;
282
283  if (lh == NULL) {
284    return;
285  }
286
287  if (lh->callback_depth < UINT_MAX) {
288    /* |callback_depth| is a saturating counter. */
289    lh->callback_depth++;
290  }
291
292  for (i = 0; i < lh->num_buckets; i++) {
293    for (cur = lh->buckets[i]; cur != NULL; cur = next) {
294      next = cur->next;
295      if (arg_func) {
296        arg_func(cur->data, arg);
297      } else {
298        no_arg_func(cur->data);
299      }
300    }
301  }
302
303  if (lh->callback_depth < UINT_MAX) {
304    lh->callback_depth--;
305  }
306
307  /* The callback may have added or removed elements and the non-zero value of
308   * |callback_depth| will have suppressed any resizing. Thus any needed
309   * resizing is done here. */
310  lh_maybe_resize(lh);
311}
312
313void lh_doall(_LHASH *lh, void (*func)(void *)) {
314  lh_doall_internal(lh, func, NULL, NULL);
315}
316
317void lh_doall_arg(_LHASH *lh, void (*func)(void *, void *), void *arg) {
318  lh_doall_internal(lh, NULL, func, arg);
319}
320
321uint32_t lh_strhash(const char *c) {
322  /* The following hash seems to work very well on normal text strings
323   * no collisions on /usr/dict/words and it distributes on %2^n quite
324   * well, not as good as MD5, but still good. */
325  unsigned long ret = 0;
326  long n;
327  unsigned long v;
328  int r;
329
330  if ((c == NULL) || (*c == '\0')) {
331    return (ret);
332  }
333
334  n = 0x100;
335  while (*c) {
336    v = n | (*c);
337    n += 0x100;
338    r = (int)((v >> 2) ^ v) & 0x0f;
339    ret = (ret << r) | (ret >> (32 - r));
340    ret &= 0xFFFFFFFFL;
341    ret ^= v * v;
342    c++;
343  }
344
345  return ((ret >> 16) ^ ret);
346}
347