1 /* $OpenBSD: min_heap.h,v 1.6 2019/04/29 17:11:52 tobias Exp $ */ 2 3 /* 4 * Copyright (c) 2006 Maxim Yegorushkin <maxim.yegorushkin@gmail.com> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 #ifndef _MIN_HEAP_H_ 30 #define _MIN_HEAP_H_ 31 32 #include "event.h" 33 34 typedef struct min_heap { 35 struct event **p; 36 size_t n, a; 37 } min_heap_t; 38 39 static inline void min_heap_ctor(min_heap_t * s); 40 static inline void min_heap_dtor(min_heap_t * s); 41 static inline void min_heap_elem_init(struct event * e); 42 static inline int min_heap_elem_greater(struct event * a, struct event * b); 43 static inline int min_heap_empty(min_heap_t * s); 44 static inline size_t min_heap_size(min_heap_t * s); 45 static inline struct event *min_heap_top(min_heap_t * s); 46 static inline int min_heap_reserve(min_heap_t * s, size_t n); 47 static inline int min_heap_push(min_heap_t * s, struct event * e); 48 static inline struct event *min_heap_pop(min_heap_t * s); 49 static inline int min_heap_erase(min_heap_t * s, struct event * e); 50 static inline void min_heap_shift_up_(min_heap_t * s, size_t hole_index, struct event * e); 51 static inline void min_heap_shift_down_(min_heap_t * s, size_t hole_index, struct event * e); 52 53 int 54 min_heap_elem_greater(struct event * a, struct event * b) 55 { 56 return timercmp(&a->ev_timeout, &b->ev_timeout, >); 57 } 58 59 void 60 min_heap_ctor(min_heap_t * s) 61 { 62 s->p = 0; 63 s->n = 0; 64 s->a = 0; 65 } 66 void min_heap_dtor(min_heap_t * s) { 67 if (s->p) 68 free(s->p); 69 } 70 void 71 min_heap_elem_init(struct event * e) 72 { 73 e->min_heap_idx = SIZE_MAX; 74 } 75 int 76 min_heap_empty(min_heap_t * s) 77 { 78 return 0 == s->n; 79 } 80 size_t 81 min_heap_size(min_heap_t * s) 82 { 83 return s->n; 84 } 85 struct event * 86 min_heap_top(min_heap_t * s) 87 { 88 return s->n ? *s->p : 0; 89 } 90 91 int 92 min_heap_push(min_heap_t * s, struct event * e) 93 { 94 if (min_heap_reserve(s, s->n + 1)) 95 return -1; 96 min_heap_shift_up_(s, s->n++, e); 97 return 0; 98 } 99 100 struct event * 101 min_heap_pop(min_heap_t * s) 102 { 103 if (s->n) { 104 struct event *e = *s->p; 105 min_heap_shift_down_(s, 0, s->p[--s->n]); 106 e->min_heap_idx = SIZE_MAX; 107 return e; 108 } 109 return 0; 110 } 111 112 int 113 min_heap_erase(min_heap_t * s, struct event * e) 114 { 115 if (e->min_heap_idx != SIZE_MAX) { 116 struct event *last = s->p[--s->n]; 117 size_t parent = (e->min_heap_idx - 1) / 2; 118 /* 119 * we replace e with the last element in the heap. We might 120 * need to shift it upward if it is less than its parent, or 121 * downward if it is greater than one or both its children. 122 * Since the children are known to be less than the parent, 123 * it can't need to shift both up and down. 124 */ 125 if (e->min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], last)) 126 min_heap_shift_up_(s, e->min_heap_idx, last); 127 else 128 min_heap_shift_down_(s, e->min_heap_idx, last); 129 e->min_heap_idx = SIZE_MAX; 130 return 0; 131 } 132 return -1; 133 } 134 135 int 136 min_heap_reserve(min_heap_t * s, size_t n) 137 { 138 if (s->a < n) { 139 struct event **p; 140 size_t a = s->a ? s->a * 2 : 8; 141 if (a < n) 142 a = n; 143 if (!(p = recallocarray(s->p, s->a, a, sizeof *p))) 144 return -1; 145 s->p = p; 146 s->a = a; 147 } 148 return 0; 149 } 150 151 void 152 min_heap_shift_up_(min_heap_t * s, size_t hole_index, struct event * e) 153 { 154 size_t parent = (hole_index - 1) / 2; 155 while (hole_index && min_heap_elem_greater(s->p[parent], e)) { 156 s->p[hole_index] = s->p[parent]; 157 s->p[hole_index]->min_heap_idx = hole_index; 158 hole_index = parent; 159 parent = (hole_index - 1) / 2; 160 } 161 e->min_heap_idx = hole_index; 162 s->p[hole_index] = e; 163 } 164 165 void 166 min_heap_shift_down_(min_heap_t * s, size_t hole_index, struct event * e) 167 { 168 size_t min_child = 2 * (hole_index + 1); 169 while (min_child <= s->n) { 170 if (min_child == s->n || 171 min_heap_elem_greater(s->p[min_child], s->p[min_child - 1])) 172 min_child -= 1; 173 if (!(min_heap_elem_greater(e, s->p[min_child]))) 174 break; 175 s->p[hole_index] = s->p[min_child]; 176 s->p[hole_index]->min_heap_idx = hole_index; 177 hole_index = min_child; 178 min_child = 2 * (hole_index + 1); 179 } 180 min_heap_shift_up_(s, hole_index, e); 181 } 182 #endif /* _MIN_HEAP_H_ */ 183