1 /* 2 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 3 * Copyright (c) 1997,1999 by Internet Software Consortium. 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 15 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 /*% 19 * Heap implementation of priority queues adapted from the following: 20 * 21 * _Introduction to Algorithms_, Cormen, Leiserson, and Rivest, 22 * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7. 23 * 24 * _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988, 25 * ISBN 0-201-06673-4, chapter 11. 26 */ 27 28 #include "port_before.h" 29 30 #include <stddef.h> 31 #include <stdlib.h> 32 #include <errno.h> 33 34 #include "port_after.h" 35 36 #include <isc/heap.h> 37 38 /*% 39 * Note: to make heap_parent and heap_left easy to compute, the first 40 * element of the heap array is not used; i.e. heap subscripts are 1-based, 41 * not 0-based. 42 */ 43 #define heap_parent(i) ((i) >> 1) 44 #define heap_left(i) ((i) << 1) 45 46 #define ARRAY_SIZE_INCREMENT 512 47 48 heap_context 49 heap_new(heap_higher_priority_func higher_priority, heap_index_func index, 50 int array_size_increment) { 51 heap_context ctx; 52 53 if (higher_priority == NULL) 54 return (NULL); 55 56 ctx = (heap_context)malloc(sizeof (struct heap_context)); 57 if (ctx == NULL) 58 return (NULL); 59 60 ctx->array_size = 0; 61 if (array_size_increment == 0) 62 ctx->array_size_increment = ARRAY_SIZE_INCREMENT; 63 else 64 ctx->array_size_increment = array_size_increment; 65 ctx->heap_size = 0; 66 ctx->heap = NULL; 67 ctx->higher_priority = higher_priority; 68 ctx->index = index; 69 return (ctx); 70 } 71 72 int 73 heap_free(heap_context ctx) { 74 if (ctx == NULL) { 75 errno = EINVAL; 76 return (-1); 77 } 78 79 if (ctx->heap != NULL) 80 free(ctx->heap); 81 free(ctx); 82 83 return (0); 84 } 85 86 static int 87 heap_resize(heap_context ctx) { 88 void **new_heap; 89 90 ctx->array_size += ctx->array_size_increment; 91 new_heap = (void **)realloc(ctx->heap, 92 (ctx->array_size) * (sizeof (void *))); 93 if (new_heap == NULL) { 94 errno = ENOMEM; 95 return (-1); 96 } 97 ctx->heap = new_heap; 98 return (0); 99 } 100 101 static void 102 float_up(heap_context ctx, int i, void *elt) { 103 int p; 104 105 for ( p = heap_parent(i); 106 i > 1 && ctx->higher_priority(elt, ctx->heap[p]); 107 i = p, p = heap_parent(i) ) { 108 ctx->heap[i] = ctx->heap[p]; 109 if (ctx->index != NULL) 110 (ctx->index)(ctx->heap[i], i); 111 } 112 ctx->heap[i] = elt; 113 if (ctx->index != NULL) 114 (ctx->index)(ctx->heap[i], i); 115 } 116 117 static void 118 sink_down(heap_context ctx, int i, void *elt) { 119 int j, size, half_size; 120 121 size = ctx->heap_size; 122 half_size = size / 2; 123 while (i <= half_size) { 124 /* find smallest of the (at most) two children */ 125 j = heap_left(i); 126 if (j < size && ctx->higher_priority(ctx->heap[j+1], 127 ctx->heap[j])) 128 j++; 129 if (ctx->higher_priority(elt, ctx->heap[j])) 130 break; 131 ctx->heap[i] = ctx->heap[j]; 132 if (ctx->index != NULL) 133 (ctx->index)(ctx->heap[i], i); 134 i = j; 135 } 136 ctx->heap[i] = elt; 137 if (ctx->index != NULL) 138 (ctx->index)(ctx->heap[i], i); 139 } 140 141 int 142 heap_insert(heap_context ctx, void *elt) { 143 int i; 144 145 if (ctx == NULL || elt == NULL) { 146 errno = EINVAL; 147 return (-1); 148 } 149 150 i = ++ctx->heap_size; 151 if (ctx->heap_size >= ctx->array_size && heap_resize(ctx) < 0) 152 return (-1); 153 154 float_up(ctx, i, elt); 155 156 return (0); 157 } 158 159 int 160 heap_delete(heap_context ctx, int i) { 161 void *elt; 162 int less; 163 164 if (ctx == NULL || i < 1 || i > ctx->heap_size) { 165 errno = EINVAL; 166 return (-1); 167 } 168 169 if (i == ctx->heap_size) { 170 ctx->heap_size--; 171 } else { 172 elt = ctx->heap[ctx->heap_size--]; 173 less = ctx->higher_priority(elt, ctx->heap[i]); 174 ctx->heap[i] = elt; 175 if (less) 176 float_up(ctx, i, ctx->heap[i]); 177 else 178 sink_down(ctx, i, ctx->heap[i]); 179 } 180 181 return (0); 182 } 183 184 int 185 heap_increased(heap_context ctx, int i) { 186 if (ctx == NULL || i < 1 || i > ctx->heap_size) { 187 errno = EINVAL; 188 return (-1); 189 } 190 191 float_up(ctx, i, ctx->heap[i]); 192 193 return (0); 194 } 195 196 int 197 heap_decreased(heap_context ctx, int i) { 198 if (ctx == NULL || i < 1 || i > ctx->heap_size) { 199 errno = EINVAL; 200 return (-1); 201 } 202 203 sink_down(ctx, i, ctx->heap[i]); 204 205 return (0); 206 } 207 208 void * 209 heap_element(heap_context ctx, int i) { 210 if (ctx == NULL || i < 1 || i > ctx->heap_size) { 211 errno = EINVAL; 212 return (NULL); 213 } 214 215 return (ctx->heap[i]); 216 } 217 218 int 219 heap_for_each(heap_context ctx, heap_for_each_func action, void *uap) { 220 int i; 221 222 if (ctx == NULL || action == NULL) { 223 errno = EINVAL; 224 return (-1); 225 } 226 227 for (i = 1; i <= ctx->heap_size; i++) 228 (action)(ctx->heap[i], uap); 229 return (0); 230 } 231 232 /*! \file */ 233