Annotation of embedaddon/dhcp/common/heap.c, revision 1.1
1.1 ! misho 1: /*
! 2: * Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
! 3: * Copyright (C) 1997-2001 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 WITH
! 10: * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
! 11: * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
! 12: * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
! 13: * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
! 14: * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
! 15: * PERFORMANCE OF THIS SOFTWARE.
! 16: */
! 17:
! 18: /* $Id: heap.c,v 1.2 2007-05-08 23:05:20 dhankins Exp $ */
! 19:
! 20: /*
! 21: * This heap implementation is taken from the BIND 9 code. It has been
! 22: * modified to use the DHCP memory management rather than BIND memory
! 23: * contexts.
! 24: */
! 25:
! 26: /*! \file
! 27: * Heap implementation of priority queues adapted from the following:
! 28: *
! 29: * \li "Introduction to Algorithms," Cormen, Leiserson, and Rivest,
! 30: * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
! 31: *
! 32: * \li "Algorithms," Second Edition, Sedgewick, Addison-Wesley, 1988,
! 33: * ISBN 0-201-06673-4, chapter 11.
! 34: */
! 35:
! 36: #include "dhcpd.h"
! 37: #include "omapip/omapip.h"
! 38: #include "heap.h"
! 39:
! 40: #include <assert.h>
! 41: #define REQUIRE assert
! 42: #define INSIST assert
! 43:
! 44: /*@{*/
! 45: /*%
! 46: * Note: to make heap_parent and heap_left easy to compute, the first
! 47: * element of the heap array is not used; i.e. heap subscripts are 1-based,
! 48: * not 0-based. The parent is index/2, and the left-child is index*2.
! 49: * The right child is index*2+1.
! 50: */
! 51: #define heap_parent(i) ((i) >> 1)
! 52: #define heap_left(i) ((i) << 1)
! 53: /*@}*/
! 54:
! 55: #define SIZE_INCREMENT 1024
! 56:
! 57: /*%
! 58: * When the heap is in a consistent state, the following invariant
! 59: * holds true: for every element i > 1, heap_parent(i) has a priority
! 60: * higher than or equal to that of i.
! 61: */
! 62: #define HEAPCONDITION(i) ((i) == 1 || \
! 63: ! heap->compare(heap->array[(i)], \
! 64: heap->array[heap_parent(i)]))
! 65:
! 66: /*% ISC heap structure. */
! 67: struct isc_heap {
! 68: unsigned int size;
! 69: unsigned int size_increment;
! 70: unsigned int last;
! 71: void **array;
! 72: isc_heapcompare_t compare;
! 73: isc_heapindex_t index;
! 74: };
! 75:
! 76: isc_result_t
! 77: isc_heap_create(isc_heapcompare_t compare,
! 78: isc_heapindex_t index, unsigned int size_increment,
! 79: isc_heap_t **heapp)
! 80: {
! 81: isc_heap_t *heap;
! 82:
! 83: REQUIRE(heapp != NULL && *heapp == NULL);
! 84: REQUIRE(compare != NULL);
! 85:
! 86: heap = dmalloc(sizeof(*heap), MDL);
! 87: if (heap == NULL)
! 88: return (ISC_R_NOMEMORY);
! 89: heap->size = 0;
! 90: if (size_increment == 0)
! 91: heap->size_increment = SIZE_INCREMENT;
! 92: else
! 93: heap->size_increment = size_increment;
! 94: heap->last = 0;
! 95: heap->array = NULL;
! 96: heap->compare = compare;
! 97: heap->index = index;
! 98:
! 99: *heapp = heap;
! 100:
! 101: return (ISC_R_SUCCESS);
! 102: }
! 103:
! 104: void
! 105: isc_heap_destroy(isc_heap_t **heapp) {
! 106: isc_heap_t *heap;
! 107:
! 108: REQUIRE(heapp != NULL);
! 109: heap = *heapp;
! 110:
! 111: if (heap->array != NULL)
! 112: dfree(heap->array, MDL);
! 113: dfree(heap, MDL);
! 114:
! 115: *heapp = NULL;
! 116: }
! 117:
! 118: static isc_boolean_t
! 119: resize(isc_heap_t *heap) {
! 120: void **new_array;
! 121: size_t new_size;
! 122:
! 123: new_size = heap->size + heap->size_increment;
! 124: new_array = dmalloc(new_size * sizeof(void *), MDL);
! 125: if (new_array == NULL)
! 126: return (ISC_FALSE);
! 127: if (heap->array != NULL) {
! 128: memcpy(new_array, heap->array, heap->size * sizeof(void *));
! 129: dfree(heap->array, MDL);
! 130: }
! 131: heap->size = new_size;
! 132: heap->array = new_array;
! 133:
! 134: return (ISC_TRUE);
! 135: }
! 136:
! 137: static void
! 138: float_up(isc_heap_t *heap, unsigned int i, void *elt) {
! 139: unsigned int p;
! 140:
! 141: for (p = heap_parent(i) ;
! 142: i > 1 && heap->compare(elt, heap->array[p]) ;
! 143: i = p, p = heap_parent(i)) {
! 144: heap->array[i] = heap->array[p];
! 145: if (heap->index != NULL)
! 146: (heap->index)(heap->array[i], i);
! 147: }
! 148: heap->array[i] = elt;
! 149: if (heap->index != NULL)
! 150: (heap->index)(heap->array[i], i);
! 151:
! 152: INSIST(HEAPCONDITION(i));
! 153: }
! 154:
! 155: static void
! 156: sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
! 157: unsigned int j, size, half_size;
! 158: size = heap->last;
! 159: half_size = size / 2;
! 160: while (i <= half_size) {
! 161: /* Find the smallest of the (at most) two children. */
! 162: j = heap_left(i);
! 163: if (j < size && heap->compare(heap->array[j+1],
! 164: heap->array[j]))
! 165: j++;
! 166: if (heap->compare(elt, heap->array[j]))
! 167: break;
! 168: heap->array[i] = heap->array[j];
! 169: if (heap->index != NULL)
! 170: (heap->index)(heap->array[i], i);
! 171: i = j;
! 172: }
! 173: heap->array[i] = elt;
! 174: if (heap->index != NULL)
! 175: (heap->index)(heap->array[i], i);
! 176:
! 177: INSIST(HEAPCONDITION(i));
! 178: }
! 179:
! 180: isc_result_t
! 181: isc_heap_insert(isc_heap_t *heap, void *elt) {
! 182: unsigned int i;
! 183:
! 184: i = ++heap->last;
! 185: if (heap->last >= heap->size && !resize(heap))
! 186: return (ISC_R_NOMEMORY);
! 187:
! 188: float_up(heap, i, elt);
! 189:
! 190: return (ISC_R_SUCCESS);
! 191: }
! 192:
! 193: void
! 194: isc_heap_delete(isc_heap_t *heap, unsigned int index) {
! 195: void *elt;
! 196: isc_boolean_t less;
! 197:
! 198: REQUIRE(index >= 1 && index <= heap->last);
! 199:
! 200: if (index == heap->last) {
! 201: heap->last--;
! 202: } else {
! 203: elt = heap->array[heap->last--];
! 204: less = heap->compare(elt, heap->array[index]);
! 205: heap->array[index] = elt;
! 206: if (less)
! 207: float_up(heap, index, heap->array[index]);
! 208: else
! 209: sink_down(heap, index, heap->array[index]);
! 210: }
! 211: }
! 212:
! 213: void
! 214: isc_heap_increased(isc_heap_t *heap, unsigned int index) {
! 215: REQUIRE(index >= 1 && index <= heap->last);
! 216:
! 217: float_up(heap, index, heap->array[index]);
! 218: }
! 219:
! 220: void
! 221: isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
! 222: REQUIRE(index >= 1 && index <= heap->last);
! 223:
! 224: sink_down(heap, index, heap->array[index]);
! 225: }
! 226:
! 227: void *
! 228: isc_heap_element(isc_heap_t *heap, unsigned int index) {
! 229: REQUIRE(index >= 1 && index <= heap->last);
! 230:
! 231: return (heap->array[index]);
! 232: }
! 233:
! 234: void
! 235: isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
! 236: unsigned int i;
! 237:
! 238: REQUIRE(action != NULL);
! 239:
! 240: for (i = 1 ; i <= heap->last ; i++)
! 241: (action)(heap->array[i], uap);
! 242: }
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>
![[BACK]](/icons/cvsweb/back.gif){kind=icon}
Return to heap.c CVS log ![[TXT]](/icons/cvsweb/text.gif){kind=icon}
![[DIR]](/icons/cvsweb/dir.gif){kind=icon}
Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / dhcp / common