1 /* $OpenBSD: min_heap.h,v 1.3 2014/10/29 22:47:29 bluhm 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 { 36 struct event** p; 37 unsigned n, a; 38 } min_heap_t; 39 40 static inline void min_heap_ctor(min_heap_t* s); 41 static inline void min_heap_dtor(min_heap_t* s); 42 static inline void min_heap_elem_init(struct event* e); 43 static inline int min_heap_elem_greater(struct event *a, struct event *b); 44 static inline int min_heap_empty(min_heap_t* s); 45 static inline unsigned min_heap_size(min_heap_t* s); 46 static inline struct event* min_heap_top(min_heap_t* s); 47 static inline int min_heap_reserve(min_heap_t* s, unsigned n); 48 static inline int min_heap_push(min_heap_t* s, struct event* e); 49 static inline struct event* min_heap_pop(min_heap_t* s); 50 static inline int min_heap_erase(min_heap_t* s, struct event* e); 51 static inline void min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e); 52 static inline void min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e); 53 54 int min_heap_elem_greater(struct event *a, struct event *b) 55 { 56 return timercmp(&a->ev_timeout, &b->ev_timeout, >); 57 } 58 59 void min_heap_ctor(min_heap_t* s) { s->p = 0; s->n = 0; s->a = 0; } 60 void min_heap_dtor(min_heap_t* s) { if(s->p) free(s->p); } 61 void min_heap_elem_init(struct event* e) { e->min_heap_idx = -1; } 62 int min_heap_empty(min_heap_t* s) { return 0u == s->n; } 63 unsigned min_heap_size(min_heap_t* s) { return s->n; } 64 struct event* min_heap_top(min_heap_t* s) { return s->n ? *s->p : 0; } 65 66 int min_heap_push(min_heap_t* s, struct event* e) 67 { 68 if(min_heap_reserve(s, s->n + 1)) 69 return -1; 70 min_heap_shift_up_(s, s->n++, e); 71 return 0; 72 } 73 74 struct event* min_heap_pop(min_heap_t* s) 75 { 76 if(s->n) 77 { 78 struct event* e = *s->p; 79 min_heap_shift_down_(s, 0u, s->p[--s->n]); 80 e->min_heap_idx = -1; 81 return e; 82 } 83 return 0; 84 } 85 86 int min_heap_erase(min_heap_t* s, struct event* e) 87 { 88 if(((unsigned int)-1) != e->min_heap_idx) 89 { 90 struct event *last = s->p[--s->n]; 91 unsigned parent = (e->min_heap_idx - 1) / 2; 92 /* we replace e with the last element in the heap. We might need to 93 shift it upward if it is less than its parent, or downward if it is 94 greater than one or both its children. Since the children are known 95 to be less than the parent, it can't need to shift both up and 96 down. */ 97 if (e->min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], last)) 98 min_heap_shift_up_(s, e->min_heap_idx, last); 99 else 100 min_heap_shift_down_(s, e->min_heap_idx, last); 101 e->min_heap_idx = -1; 102 return 0; 103 } 104 return -1; 105 } 106 107 int min_heap_reserve(min_heap_t* s, unsigned n) 108 { 109 if(s->a < n) 110 { 111 struct event** p; 112 unsigned a = s->a ? s->a * 2 : 8; 113 if(a < n) 114 a = n; 115 if(!(p = (struct event**)realloc(s->p, a * sizeof *p))) 116 return -1; 117 s->p = p; 118 s->a = a; 119 } 120 return 0; 121 } 122 123 void min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e) 124 { 125 unsigned parent = (hole_index - 1) / 2; 126 while(hole_index && min_heap_elem_greater(s->p[parent], e)) 127 { 128 (s->p[hole_index] = s->p[parent])->min_heap_idx = hole_index; 129 hole_index = parent; 130 parent = (hole_index - 1) / 2; 131 } 132 (s->p[hole_index] = e)->min_heap_idx = hole_index; 133 } 134 135 void min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e) 136 { 137 unsigned min_child = 2 * (hole_index + 1); 138 while(min_child <= s->n) 139 { 140 min_child -= min_child == s->n || min_heap_elem_greater(s->p[min_child], s->p[min_child - 1]); 141 if(!(min_heap_elem_greater(e, s->p[min_child]))) 142 break; 143 (s->p[hole_index] = s->p[min_child])->min_heap_idx = hole_index; 144 hole_index = min_child; 145 min_child = 2 * (hole_index + 1); 146 } 147 min_heap_shift_up_(s, hole_index, e); 148 } 149 150 #endif /* _MIN_HEAP_H_ */ 151