1 /*
2 * Copyright 2022-2024 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10 #include <openssl/crypto.h>
11 #include <openssl/err.h>
12 #include <assert.h>
13 #include "internal/priority_queue.h"
14 #include "internal/safe_math.h"
15 #include "internal/numbers.h"
16
17 OSSL_SAFE_MATH_UNSIGNED(size_t, size_t)
18
19 /*
20 * Fundamental operations:
21 * Binary Heap Fibonacci Heap
22 * Get smallest O(1) O(1)
23 * Delete any O(log n) O(log n) average but worst O(n)
24 * Insert O(log n) O(1)
25 *
26 * Not supported:
27 * Merge two structures O(log n) O(1)
28 * Decrease key O(log n) O(1)
29 * Increase key O(log n) ?
30 *
31 * The Fibonacci heap is quite a bit more complicated to implement and has
32 * larger overhead in practice. We favour the binary heap here. A multi-way
33 * (ternary or quaternary) heap might elicit a performance advantage via better
34 * cache access patterns.
35 */
36
37 struct pq_heap_st {
38 void *data; /* User supplied data pointer */
39 size_t index; /* Constant index in elements[] */
40 };
41
42 struct pq_elem_st {
43 size_t posn; /* Current index in heap[] or link in free list */
44 #ifndef NDEBUG
45 int used; /* Debug flag indicating that this is in use */
46 #endif
47 };
48
49 struct ossl_pqueue_st {
50 struct pq_heap_st *heap;
51 struct pq_elem_st *elements;
52 int (*compare)(const void *, const void *);
53 size_t htop; /* Highest used heap element */
54 size_t hmax; /* Allocated heap & element space */
55 size_t freelist; /* Index into elements[], start of free element list */
56 };
57
58 /*
59 * The initial and maximum number of elements in the heap.
60 */
61 static const size_t min_nodes = 8;
62 static const size_t max_nodes =
63 SIZE_MAX / (sizeof(struct pq_heap_st) > sizeof(struct pq_elem_st)
64 ? sizeof(struct pq_heap_st) : sizeof(struct pq_elem_st));
65
66 #ifndef NDEBUG
67 /* Some basic sanity checking of the data structure */
68 # define ASSERT_USED(pq, idx) \
69 assert(pq->elements[pq->heap[idx].index].used); \
70 assert(pq->elements[pq->heap[idx].index].posn == idx)
71 # define ASSERT_ELEM_USED(pq, elem) \
72 assert(pq->elements[elem].used)
73 #else
74 # define ASSERT_USED(pq, idx)
75 # define ASSERT_ELEM_USED(pq, elem)
76 #endif
77
78 /*
79 * Calculate the array growth based on the target size.
80 *
81 * The growth factor is a rational number and is defined by a numerator
82 * and a denominator. According to Andrew Koenig in his paper "Why Are
83 * Vectors Efficient?" from JOOP 11(5) 1998, this factor should be less
84 * than the golden ratio (1.618...).
85 *
86 * We use an expansion factor of 8 / 5 = 1.6
87 */
compute_pqueue_growth(size_t target,size_t current)88 static ossl_inline size_t compute_pqueue_growth(size_t target, size_t current)
89 {
90 int err = 0;
91
92 while (current < target) {
93 if (current >= max_nodes)
94 return 0;
95
96 current = safe_muldiv_size_t(current, 8, 5, &err);
97 if (err)
98 return 0;
99 if (current >= max_nodes)
100 current = max_nodes;
101 }
102 return current;
103 }
104
pqueue_swap_elem(OSSL_PQUEUE * pq,size_t i,size_t j)105 static ossl_inline void pqueue_swap_elem(OSSL_PQUEUE *pq, size_t i, size_t j)
106 {
107 struct pq_heap_st *h = pq->heap, t_h;
108 struct pq_elem_st *e = pq->elements;
109
110 ASSERT_USED(pq, i);
111 ASSERT_USED(pq, j);
112
113 t_h = h[i];
114 h[i] = h[j];
115 h[j] = t_h;
116
117 e[h[i].index].posn = i;
118 e[h[j].index].posn = j;
119 }
120
pqueue_move_elem(OSSL_PQUEUE * pq,size_t from,size_t to)121 static ossl_inline void pqueue_move_elem(OSSL_PQUEUE *pq, size_t from, size_t to)
122 {
123 struct pq_heap_st *h = pq->heap;
124 struct pq_elem_st *e = pq->elements;
125
126 ASSERT_USED(pq, from);
127
128 h[to] = h[from];
129 e[h[to].index].posn = to;
130 }
131
132 /*
133 * Force the specified element to the front of the heap. This breaks
134 * the heap partial ordering pre-condition.
135 */
pqueue_force_bottom(OSSL_PQUEUE * pq,size_t n)136 static ossl_inline void pqueue_force_bottom(OSSL_PQUEUE *pq, size_t n)
137 {
138 ASSERT_USED(pq, n);
139 while (n > 0) {
140 const size_t p = (n - 1) / 2;
141
142 ASSERT_USED(pq, p);
143 pqueue_swap_elem(pq, n, p);
144 n = p;
145 }
146 }
147
148 /*
149 * Move an element down to its correct position to restore the partial
150 * order pre-condition.
151 */
pqueue_move_down(OSSL_PQUEUE * pq,size_t n)152 static ossl_inline void pqueue_move_down(OSSL_PQUEUE *pq, size_t n)
153 {
154 struct pq_heap_st *h = pq->heap;
155
156 ASSERT_USED(pq, n);
157 while (n > 0) {
158 const size_t p = (n - 1) / 2;
159
160 ASSERT_USED(pq, p);
161 if (pq->compare(h[n].data, h[p].data) >= 0)
162 break;
163 pqueue_swap_elem(pq, n, p);
164 n = p;
165 }
166 }
167
168 /*
169 * Move an element up to its correct position to restore the partial
170 * order pre-condition.
171 */
pqueue_move_up(OSSL_PQUEUE * pq,size_t n)172 static ossl_inline void pqueue_move_up(OSSL_PQUEUE *pq, size_t n)
173 {
174 struct pq_heap_st *h = pq->heap;
175 size_t p = n * 2 + 1;
176
177 ASSERT_USED(pq, n);
178 if (pq->htop > p + 1) {
179 ASSERT_USED(pq, p);
180 ASSERT_USED(pq, p + 1);
181 if (pq->compare(h[p].data, h[p + 1].data) > 0)
182 p++;
183 }
184 while (pq->htop > p && pq->compare(h[p].data, h[n].data) < 0) {
185 ASSERT_USED(pq, p);
186 pqueue_swap_elem(pq, n, p);
187 n = p;
188 p = n * 2 + 1;
189 if (pq->htop > p + 1) {
190 ASSERT_USED(pq, p + 1);
191 if (pq->compare(h[p].data, h[p + 1].data) > 0)
192 p++;
193 }
194 }
195 }
196
ossl_pqueue_push(OSSL_PQUEUE * pq,void * data,size_t * elem)197 int ossl_pqueue_push(OSSL_PQUEUE *pq, void *data, size_t *elem)
198 {
199 size_t n, m;
200
201 if (!ossl_pqueue_reserve(pq, 1))
202 return 0;
203
204 n = pq->htop++;
205 m = pq->freelist;
206 pq->freelist = pq->elements[m].posn;
207
208 pq->heap[n].data = data;
209 pq->heap[n].index = m;
210
211 pq->elements[m].posn = n;
212 #ifndef NDEBUG
213 pq->elements[m].used = 1;
214 #endif
215 pqueue_move_down(pq, n);
216 if (elem != NULL)
217 *elem = m;
218 return 1;
219 }
220
ossl_pqueue_peek(const OSSL_PQUEUE * pq)221 void *ossl_pqueue_peek(const OSSL_PQUEUE *pq)
222 {
223 if (pq->htop > 0) {
224 ASSERT_USED(pq, 0);
225 return pq->heap->data;
226 }
227 return NULL;
228 }
229
ossl_pqueue_pop(OSSL_PQUEUE * pq)230 void *ossl_pqueue_pop(OSSL_PQUEUE *pq)
231 {
232 void *res;
233 size_t elem;
234
235 if (pq == NULL || pq->htop == 0)
236 return NULL;
237
238 ASSERT_USED(pq, 0);
239 res = pq->heap->data;
240 elem = pq->heap->index;
241
242 if (--pq->htop != 0) {
243 pqueue_move_elem(pq, pq->htop, 0);
244 pqueue_move_up(pq, 0);
245 }
246
247 pq->elements[elem].posn = pq->freelist;
248 pq->freelist = elem;
249 #ifndef NDEBUG
250 pq->elements[elem].used = 0;
251 #endif
252 return res;
253 }
254
ossl_pqueue_remove(OSSL_PQUEUE * pq,size_t elem)255 void *ossl_pqueue_remove(OSSL_PQUEUE *pq, size_t elem)
256 {
257 size_t n;
258
259 if (pq == NULL || elem >= pq->hmax || pq->htop == 0)
260 return 0;
261
262 ASSERT_ELEM_USED(pq, elem);
263 n = pq->elements[elem].posn;
264
265 ASSERT_USED(pq, n);
266
267 if (n == pq->htop - 1) {
268 pq->elements[elem].posn = pq->freelist;
269 pq->freelist = elem;
270 #ifndef NDEBUG
271 pq->elements[elem].used = 0;
272 #endif
273 return pq->heap[--pq->htop].data;
274 }
275 if (n > 0)
276 pqueue_force_bottom(pq, n);
277 return ossl_pqueue_pop(pq);
278 }
279
pqueue_add_freelist(OSSL_PQUEUE * pq,size_t from)280 static void pqueue_add_freelist(OSSL_PQUEUE *pq, size_t from)
281 {
282 struct pq_elem_st *e = pq->elements;
283 size_t i;
284
285 #ifndef NDEBUG
286 for (i = from; i < pq->hmax; i++)
287 e[i].used = 0;
288 #endif
289 e[from].posn = pq->freelist;
290 for (i = from + 1; i < pq->hmax; i++)
291 e[i].posn = i - 1;
292 pq->freelist = pq->hmax - 1;
293 }
294
ossl_pqueue_reserve(OSSL_PQUEUE * pq,size_t n)295 int ossl_pqueue_reserve(OSSL_PQUEUE *pq, size_t n)
296 {
297 size_t new_max, cur_max;
298 struct pq_heap_st *h;
299 struct pq_elem_st *e;
300
301 if (pq == NULL)
302 return 0;
303 cur_max = pq->hmax;
304 if (pq->htop + n < cur_max)
305 return 1;
306
307 new_max = compute_pqueue_growth(n + cur_max, cur_max);
308 if (new_max == 0) {
309 ERR_raise(ERR_LIB_SSL, ERR_R_INTERNAL_ERROR);
310 return 0;
311 }
312
313 h = OPENSSL_realloc(pq->heap, new_max * sizeof(*pq->heap));
314 if (h == NULL)
315 return 0;
316 pq->heap = h;
317
318 e = OPENSSL_realloc(pq->elements, new_max * sizeof(*pq->elements));
319 if (e == NULL)
320 return 0;
321 pq->elements = e;
322
323 pq->hmax = new_max;
324 pqueue_add_freelist(pq, cur_max);
325 return 1;
326 }
327
ossl_pqueue_new(int (* compare)(const void *,const void *))328 OSSL_PQUEUE *ossl_pqueue_new(int (*compare)(const void *, const void *))
329 {
330 OSSL_PQUEUE *pq;
331
332 if (compare == NULL)
333 return NULL;
334
335 pq = OPENSSL_malloc(sizeof(*pq));
336 if (pq == NULL)
337 return NULL;
338 pq->compare = compare;
339 pq->hmax = min_nodes;
340 pq->htop = 0;
341 pq->freelist = 0;
342 pq->heap = OPENSSL_malloc(sizeof(*pq->heap) * min_nodes);
343 pq->elements = OPENSSL_malloc(sizeof(*pq->elements) * min_nodes);
344 if (pq->heap == NULL || pq->elements == NULL) {
345 ossl_pqueue_free(pq);
346 return NULL;
347 }
348 pqueue_add_freelist(pq, 0);
349 return pq;
350 }
351
ossl_pqueue_free(OSSL_PQUEUE * pq)352 void ossl_pqueue_free(OSSL_PQUEUE *pq)
353 {
354 if (pq != NULL) {
355 OPENSSL_free(pq->heap);
356 OPENSSL_free(pq->elements);
357 OPENSSL_free(pq);
358 }
359 }
360
ossl_pqueue_pop_free(OSSL_PQUEUE * pq,void (* freefunc)(void *))361 void ossl_pqueue_pop_free(OSSL_PQUEUE *pq, void (*freefunc)(void *))
362 {
363 size_t i;
364
365 if (pq != NULL) {
366 for (i = 0; i < pq->htop; i++)
367 (*freefunc)(pq->heap[i].data);
368 ossl_pqueue_free(pq);
369 }
370 }
371
ossl_pqueue_num(const OSSL_PQUEUE * pq)372 size_t ossl_pqueue_num(const OSSL_PQUEUE *pq)
373 {
374 return pq != NULL ? pq->htop : 0;
375 }
376
