2 * Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
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
10 #include <openssl/crypto.h>
11 #include <openssl/err.h>
13 #include "internal/priority_queue.h"
14 #include "internal/safe_math.h"
16 OSSL_SAFE_MATH_UNSIGNED(size_t, size_t)
19 * Fundamental operations:
20 * Binary Heap Fibonacci Heap
21 * Get smallest O(1) O(1)
22 * Delete any O(log n) O(log n) average but worst O(n)
23 * Insert O(log n) O(1)
26 * Merge two structures O(log n) O(1)
27 * Decrease key O(log n) O(1)
28 * Increase key O(log n) ?
30 * The Fibonacci heap is quite a bit more complicated to implement and has
31 * larger overhead in practice. We favour the binary heap here. A multi-way
32 * (ternary or quaternary) heap might elicit a performance advantage via better
33 * cache access patterns.
37 void *data; /* User supplied data pointer */
38 size_t index; /* Constant index in elements[] */
42 size_t posn; /* Current index in heap[] or link in free list */
44 int used; /* Debug flag indicating that this is in use */
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 */
59 * The initial and maximum number of elements in the heap.
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));
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)
74 # define ASSERT_USED(pq, idx)
75 # define ASSERT_ELEM_USED(pq, elem)
79 * Calculate the array growth based on the target size.
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...).
86 * We use an expansion factor of 8 / 5 = 1.6
88 static ossl_inline size_t compute_pqueue_growth(size_t target, size_t current)
92 while (current < target) {
93 if (current >= max_nodes)
96 current = safe_muldiv_size_t(current, 8, 5, &err);
99 if (current >= max_nodes)
105 static ossl_inline void pqueue_swap_elem(OSSL_PQUEUE *pq, size_t i, size_t j)
107 struct pq_heap_st *h = pq->heap, t_h;
108 struct pq_elem_st *e = pq->elements;
117 e[h[i].index].posn = i;
118 e[h[j].index].posn = j;
121 static ossl_inline void pqueue_move_elem(OSSL_PQUEUE *pq, size_t from, size_t to)
123 struct pq_heap_st *h = pq->heap;
124 struct pq_elem_st *e = pq->elements;
126 ASSERT_USED(pq, from);
129 e[h[to].index].posn = to;
133 * Force the specified element to the front of the heap. This breaks
134 * the heap partial ordering pre-condition.
136 static ossl_inline void pqueue_force_bottom(OSSL_PQUEUE *pq, size_t n)
140 const size_t p = (n - 1) / 2;
143 pqueue_swap_elem(pq, n, p);
149 * Move an element down to its correct position to restore the partial
150 * order pre-condition.
152 static ossl_inline void pqueue_move_down(OSSL_PQUEUE *pq, size_t n)
154 struct pq_heap_st *h = pq->heap;
158 const size_t p = (n - 1) / 2;
161 if (pq->compare(h[n].data, h[p].data) >= 0)
163 pqueue_swap_elem(pq, n, p);
169 * Move an element up to its correct position to restore the partial
170 * order pre-condition.
172 static ossl_inline void pqueue_move_up(OSSL_PQUEUE *pq, size_t n)
174 struct pq_heap_st *h = pq->heap;
175 size_t p = n * 2 + 1;
178 if (pq->htop > p + 1) {
180 ASSERT_USED(pq, p + 1);
181 if (pq->compare(h[p].data, h[p + 1].data) > 0)
184 while (pq->htop > p && pq->compare(h[p].data, h[n].data) < 0) {
186 pqueue_swap_elem(pq, n, p);
189 if (pq->htop > p + 1) {
190 ASSERT_USED(pq, p + 1);
191 if (pq->compare(h[p].data, h[p + 1].data) > 0)
197 int ossl_pqueue_push(OSSL_PQUEUE *pq, void *data, size_t *elem)
201 if (!ossl_pqueue_reserve(pq, 1))
206 pq->freelist = pq->elements[m].posn;
208 pq->heap[n].data = data;
209 pq->heap[n].index = m;
211 pq->elements[m].posn = n;
213 pq->elements[m].used = 1;
215 pqueue_move_down(pq, n);
221 void *ossl_pqueue_peek(const OSSL_PQUEUE *pq)
225 return pq->heap->data;
230 void *ossl_pqueue_pop(OSSL_PQUEUE *pq)
235 if (pq == NULL || pq->htop == 0)
239 res = pq->heap->data;
240 elem = pq->heap->index;
242 if (--pq->htop != 0) {
243 pqueue_move_elem(pq, pq->htop, 0);
244 pqueue_move_up(pq, 0);
247 pq->elements[elem].posn = pq->freelist;
250 pq->elements[elem].used = 0;
255 void *ossl_pqueue_remove(OSSL_PQUEUE *pq, size_t elem)
259 if (pq == NULL || elem >= pq->hmax || pq->htop == 0)
262 ASSERT_ELEM_USED(pq, elem);
263 n = pq->elements[elem].posn;
267 if (n == pq->htop - 1)
268 return pq->heap[--pq->htop].data;
270 pqueue_force_bottom(pq, n);
271 return ossl_pqueue_pop(pq);
274 static void pqueue_add_freelist(OSSL_PQUEUE *pq, size_t from)
276 struct pq_elem_st *e = pq->elements;
280 for (i = from; i < pq->hmax; i++)
283 e[from].posn = pq->freelist;
284 for (i = from + 1; i < pq->hmax; i++)
286 pq->freelist = pq->hmax - 1;
289 int ossl_pqueue_reserve(OSSL_PQUEUE *pq, size_t n)
291 size_t new_max, cur_max;
292 struct pq_heap_st *h;
293 struct pq_elem_st *e;
298 if (pq->htop + n < cur_max)
301 new_max = compute_pqueue_growth(n + cur_max, cur_max);
303 ERR_raise(ERR_LIB_SSL, ERR_R_INTERNAL_ERROR);
307 h = OPENSSL_realloc(pq->heap, new_max * sizeof(*pq->heap));
312 e = OPENSSL_realloc(pq->elements, new_max * sizeof(*pq->elements));
318 pqueue_add_freelist(pq, cur_max);
322 OSSL_PQUEUE *ossl_pqueue_new(int (*compare)(const void *, const void *))
329 pq = OPENSSL_malloc(sizeof(*pq));
332 pq->compare = compare;
333 pq->hmax = min_nodes;
336 pq->heap = OPENSSL_malloc(sizeof(*pq->heap) * min_nodes);
337 pq->elements = OPENSSL_malloc(sizeof(*pq->elements) * min_nodes);
338 if (pq->heap == NULL || pq->elements == NULL) {
339 ossl_pqueue_free(pq);
342 pqueue_add_freelist(pq, 0);
346 void ossl_pqueue_free(OSSL_PQUEUE *pq)
349 OPENSSL_free(pq->heap);
350 OPENSSL_free(pq->elements);
355 void ossl_pqueue_pop_free(OSSL_PQUEUE *pq, void (*freefunc)(void *))
360 for (i = 0; i < pq->htop; i++)
361 (*freefunc)(pq->heap[i].data);
362 ossl_pqueue_free(pq);
366 size_t ossl_pqueue_num(const OSSL_PQUEUE *pq)
368 return pq != NULL ? pq->htop : 0;