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-/*
- * Copyright (C) 2004-2006 Internet Systems Consortium, Inc. ("ISC")
- * Copyright (C) 1997-2001 Internet Software Consortium.
- *
- * Permission to use, copy, modify, and distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
- * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
- * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
- * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
- * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
- * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
- * PERFORMANCE OF THIS SOFTWARE.
- */
-
-/* $Id: heap.c,v 1.30.18.3 2006/04/17 18:27:33 explorer Exp $ */
-
-/*! \file
- * Heap implementation of priority queues adapted from the following:
- *
- * \li "Introduction to Algorithms," Cormen, Leiserson, and Rivest,
- * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
- *
- * \li "Algorithms," Second Edition, Sedgewick, Addison-Wesley, 1988,
- * ISBN 0-201-06673-4, chapter 11.
- */
-
-#include <config.h>
-
-#include <isc/heap.h>
-#include <isc/magic.h>
-#include <isc/mem.h>
-#include <isc/string.h> /* Required for memcpy. */
-#include <isc/util.h>
-
-/*@{*/
-/*%
- * Note: to make heap_parent and heap_left easy to compute, the first
- * element of the heap array is not used; i.e. heap subscripts are 1-based,
- * not 0-based. The parent is index/2, and the left-child is index*2.
- * The right child is index*2+1.
- */
-#define heap_parent(i) ((i) >> 1)
-#define heap_left(i) ((i) << 1)
-/*@}*/
-
-#define SIZE_INCREMENT 1024
-
-#define HEAP_MAGIC ISC_MAGIC('H', 'E', 'A', 'P')
-#define VALID_HEAP(h) ISC_MAGIC_VALID(h, HEAP_MAGIC)
-
-/*%
- * When the heap is in a consistent state, the following invariant
- * holds true: for every element i > 1, heap_parent(i) has a priority
- * higher than or equal to that of i.
- */
-#define HEAPCONDITION(i) ((i) == 1 || \
- ! heap->compare(heap->array[(i)], \
- heap->array[heap_parent(i)]))
-
-/*% ISC heap structure. */
-struct isc_heap {
- unsigned int magic;
- isc_mem_t * mctx;
- unsigned int size;
- unsigned int size_increment;
- unsigned int last;
- void **array;
- isc_heapcompare_t compare;
- isc_heapindex_t index;
-};
-
-isc_result_t
-isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare,
- isc_heapindex_t index, unsigned int size_increment,
- isc_heap_t **heapp)
-{
- isc_heap_t *heap;
-
- REQUIRE(heapp != NULL && *heapp == NULL);
- REQUIRE(compare != NULL);
-
- heap = isc_mem_get(mctx, sizeof(*heap));
- if (heap == NULL)
- return (ISC_R_NOMEMORY);
- heap->magic = HEAP_MAGIC;
- heap->mctx = mctx;
- heap->size = 0;
- if (size_increment == 0)
- heap->size_increment = SIZE_INCREMENT;
- else
- heap->size_increment = size_increment;
- heap->last = 0;
- heap->array = NULL;
- heap->compare = compare;
- heap->index = index;
-
- *heapp = heap;
-
- return (ISC_R_SUCCESS);
-}
-
-void
-isc_heap_destroy(isc_heap_t **heapp) {
- isc_heap_t *heap;
-
- REQUIRE(heapp != NULL);
- heap = *heapp;
- REQUIRE(VALID_HEAP(heap));
-
- if (heap->array != NULL)
- isc_mem_put(heap->mctx, heap->array,
- heap->size * sizeof(void *));
- heap->magic = 0;
- isc_mem_put(heap->mctx, heap, sizeof(*heap));
-
- *heapp = NULL;
-}
-
-static isc_boolean_t
-resize(isc_heap_t *heap) {
- void **new_array;
- size_t new_size;
-
- REQUIRE(VALID_HEAP(heap));
-
- new_size = heap->size + heap->size_increment;
- new_array = isc_mem_get(heap->mctx, new_size * sizeof(void *));
- if (new_array == NULL)
- return (ISC_FALSE);
- if (heap->array != NULL) {
- memcpy(new_array, heap->array, heap->size * sizeof(void *));
- isc_mem_put(heap->mctx, heap->array,
- heap->size * sizeof(void *));
- }
- heap->size = new_size;
- heap->array = new_array;
-
- return (ISC_TRUE);
-}
-
-static void
-float_up(isc_heap_t *heap, unsigned int i, void *elt) {
- unsigned int p;
-
- for (p = heap_parent(i) ;
- i > 1 && heap->compare(elt, heap->array[p]) ;
- i = p, p = heap_parent(i)) {
- heap->array[i] = heap->array[p];
- if (heap->index != NULL)
- (heap->index)(heap->array[i], i);
- }
- heap->array[i] = elt;
- if (heap->index != NULL)
- (heap->index)(heap->array[i], i);
-
- INSIST(HEAPCONDITION(i));
-}
-
-static void
-sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
- unsigned int j, size, half_size;
- size = heap->last;
- half_size = size / 2;
- while (i <= half_size) {
- /* Find the smallest of the (at most) two children. */
- j = heap_left(i);
- if (j < size && heap->compare(heap->array[j+1],
- heap->array[j]))
- j++;
- if (heap->compare(elt, heap->array[j]))
- break;
- heap->array[i] = heap->array[j];
- if (heap->index != NULL)
- (heap->index)(heap->array[i], i);
- i = j;
- }
- heap->array[i] = elt;
- if (heap->index != NULL)
- (heap->index)(heap->array[i], i);
-
- INSIST(HEAPCONDITION(i));
-}
-
-isc_result_t
-isc_heap_insert(isc_heap_t *heap, void *elt) {
- unsigned int i;
-
- REQUIRE(VALID_HEAP(heap));
-
- i = ++heap->last;
- if (heap->last >= heap->size && !resize(heap))
- return (ISC_R_NOMEMORY);
-
- float_up(heap, i, elt);
-
- return (ISC_R_SUCCESS);
-}
-
-void
-isc_heap_delete(isc_heap_t *heap, unsigned int index) {
- void *elt;
- isc_boolean_t less;
-
- REQUIRE(VALID_HEAP(heap));
- REQUIRE(index >= 1 && index <= heap->last);
-
- if (index == heap->last) {
- heap->last--;
- } else {
- elt = heap->array[heap->last--];
- less = heap->compare(elt, heap->array[index]);
- heap->array[index] = elt;
- if (less)
- float_up(heap, index, heap->array[index]);
- else
- sink_down(heap, index, heap->array[index]);
- }
-}
-
-void
-isc_heap_increased(isc_heap_t *heap, unsigned int index) {
- REQUIRE(VALID_HEAP(heap));
- REQUIRE(index >= 1 && index <= heap->last);
-
- float_up(heap, index, heap->array[index]);
-}
-
-void
-isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
- REQUIRE(VALID_HEAP(heap));
- REQUIRE(index >= 1 && index <= heap->last);
-
- sink_down(heap, index, heap->array[index]);
-}
-
-void *
-isc_heap_element(isc_heap_t *heap, unsigned int index) {
- REQUIRE(VALID_HEAP(heap));
- REQUIRE(index >= 1 && index <= heap->last);
-
- return (heap->array[index]);
-}
-
-void
-isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
- unsigned int i;
-
- REQUIRE(VALID_HEAP(heap));
- REQUIRE(action != NULL);
-
- for (i = 1 ; i <= heap->last ; i++)
- (action)(heap->array[i], uap);
-}
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