266 lines
6.5 KiB
C
266 lines
6.5 KiB
C
/*
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* Copyright (C) 2004-2007, 2010-2012 Internet Systems Consortium, Inc. ("ISC")
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* Copyright (C) 1997-2001 Internet Software Consortium.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*/
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/* $Id$ */
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/*! \file
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* Heap implementation of priority queues adapted from the following:
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*
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* \li "Introduction to Algorithms," Cormen, Leiserson, and Rivest,
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* MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
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*
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* \li "Algorithms," Second Edition, Sedgewick, Addison-Wesley, 1988,
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* ISBN 0-201-06673-4, chapter 11.
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*/
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#include <config.h>
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#include <isc/heap.h>
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#include <isc/magic.h>
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#include <isc/mem.h>
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#include <isc/string.h> /* Required for memcpy. */
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#include <isc/util.h>
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/*@{*/
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/*%
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* Note: to make heap_parent and heap_left easy to compute, the first
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* element of the heap array is not used; i.e. heap subscripts are 1-based,
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* not 0-based. The parent is index/2, and the left-child is index*2.
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* The right child is index*2+1.
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*/
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#define heap_parent(i) ((i) >> 1)
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#define heap_left(i) ((i) << 1)
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/*@}*/
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#define SIZE_INCREMENT 1024
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#define HEAP_MAGIC ISC_MAGIC('H', 'E', 'A', 'P')
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#define VALID_HEAP(h) ISC_MAGIC_VALID(h, HEAP_MAGIC)
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/*%
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* When the heap is in a consistent state, the following invariant
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* holds true: for every element i > 1, heap_parent(i) has a priority
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* higher than or equal to that of i.
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*/
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#define HEAPCONDITION(i) ((i) == 1 || \
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! heap->compare(heap->array[(i)], \
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heap->array[heap_parent(i)]))
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/*% ISC heap structure. */
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struct isc_heap {
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unsigned int magic;
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isc_mem_t * mctx;
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unsigned int size;
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unsigned int size_increment;
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unsigned int last;
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void **array;
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isc_heapcompare_t compare;
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isc_heapindex_t index;
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};
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isc_result_t
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isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare,
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isc_heapindex_t index, unsigned int size_increment,
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isc_heap_t **heapp)
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{
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isc_heap_t *heap;
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REQUIRE(heapp != NULL && *heapp == NULL);
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REQUIRE(compare != NULL);
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heap = isc_mem_get(mctx, sizeof(*heap));
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if (heap == NULL)
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return (ISC_R_NOMEMORY);
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heap->magic = HEAP_MAGIC;
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heap->size = 0;
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heap->mctx = NULL;
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isc_mem_attach(mctx, &heap->mctx);
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if (size_increment == 0)
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heap->size_increment = SIZE_INCREMENT;
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else
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heap->size_increment = size_increment;
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heap->last = 0;
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heap->array = NULL;
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heap->compare = compare;
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heap->index = index;
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*heapp = heap;
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return (ISC_R_SUCCESS);
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}
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void
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isc_heap_destroy(isc_heap_t **heapp) {
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isc_heap_t *heap;
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REQUIRE(heapp != NULL);
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heap = *heapp;
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REQUIRE(VALID_HEAP(heap));
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if (heap->array != NULL)
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isc_mem_put(heap->mctx, heap->array,
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heap->size * sizeof(void *));
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heap->magic = 0;
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isc_mem_putanddetach(&heap->mctx, heap, sizeof(*heap));
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*heapp = NULL;
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}
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static isc_boolean_t
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resize(isc_heap_t *heap) {
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void **new_array;
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size_t new_size;
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REQUIRE(VALID_HEAP(heap));
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new_size = heap->size + heap->size_increment;
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new_array = isc_mem_get(heap->mctx, new_size * sizeof(void *));
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if (new_array == NULL)
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return (ISC_FALSE);
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if (heap->array != NULL) {
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memcpy(new_array, heap->array, heap->size * sizeof(void *));
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isc_mem_put(heap->mctx, heap->array,
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heap->size * sizeof(void *));
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}
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heap->size = new_size;
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heap->array = new_array;
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return (ISC_TRUE);
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}
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static void
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float_up(isc_heap_t *heap, unsigned int i, void *elt) {
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unsigned int p;
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for (p = heap_parent(i) ;
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i > 1 && heap->compare(elt, heap->array[p]) ;
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i = p, p = heap_parent(i)) {
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heap->array[i] = heap->array[p];
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if (heap->index != NULL)
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(heap->index)(heap->array[i], i);
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}
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heap->array[i] = elt;
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if (heap->index != NULL)
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(heap->index)(heap->array[i], i);
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INSIST(HEAPCONDITION(i));
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}
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static void
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sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
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unsigned int j, size, half_size;
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size = heap->last;
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half_size = size / 2;
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while (i <= half_size) {
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/* Find the smallest of the (at most) two children. */
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j = heap_left(i);
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if (j < size && heap->compare(heap->array[j+1],
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heap->array[j]))
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j++;
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if (heap->compare(elt, heap->array[j]))
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break;
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heap->array[i] = heap->array[j];
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if (heap->index != NULL)
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(heap->index)(heap->array[i], i);
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i = j;
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}
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heap->array[i] = elt;
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if (heap->index != NULL)
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(heap->index)(heap->array[i], i);
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INSIST(HEAPCONDITION(i));
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}
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isc_result_t
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isc_heap_insert(isc_heap_t *heap, void *elt) {
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unsigned int new_last;
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REQUIRE(VALID_HEAP(heap));
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new_last = heap->last + 1;
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RUNTIME_CHECK(new_last > 0); /* overflow check */
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if (new_last >= heap->size && !resize(heap))
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return (ISC_R_NOMEMORY);
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heap->last = new_last;
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float_up(heap, new_last, elt);
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return (ISC_R_SUCCESS);
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}
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void
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isc_heap_delete(isc_heap_t *heap, unsigned int index) {
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void *elt;
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isc_boolean_t less;
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REQUIRE(VALID_HEAP(heap));
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REQUIRE(index >= 1 && index <= heap->last);
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if (index == heap->last) {
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heap->array[heap->last] = NULL;
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heap->last--;
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} else {
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elt = heap->array[heap->last];
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heap->array[heap->last] = NULL;
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heap->last--;
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less = heap->compare(elt, heap->array[index]);
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heap->array[index] = elt;
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if (less)
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float_up(heap, index, heap->array[index]);
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else
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sink_down(heap, index, heap->array[index]);
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}
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}
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void
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isc_heap_increased(isc_heap_t *heap, unsigned int index) {
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REQUIRE(VALID_HEAP(heap));
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REQUIRE(index >= 1 && index <= heap->last);
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float_up(heap, index, heap->array[index]);
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}
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void
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isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
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REQUIRE(VALID_HEAP(heap));
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REQUIRE(index >= 1 && index <= heap->last);
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sink_down(heap, index, heap->array[index]);
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}
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void *
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isc_heap_element(isc_heap_t *heap, unsigned int index) {
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REQUIRE(VALID_HEAP(heap));
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REQUIRE(index >= 1);
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if (index <= heap->last)
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return (heap->array[index]);
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return (NULL);
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}
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void
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isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
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unsigned int i;
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REQUIRE(VALID_HEAP(heap));
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REQUIRE(action != NULL);
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for (i = 1 ; i <= heap->last ; i++)
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(action)(heap->array[i], uap);
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}
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