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/*
* Copyright (C) 2004-2017 Internet Systems Consortium, Inc. ("ISC")
* Copyright (C) 1997-2001 Internet Software Consortium.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* 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 1.2 2007/05/08 23:05:20 dhankins Exp $ */
/*
* This heap implementation is taken from the BIND 9 code. It has been
* modified to use the DHCP memory management rather than BIND memory
* contexts.
*/
/*! \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 "dhcpd.h"
#include "omapip/omapip.h"
#include "heap.h"
#include <assert.h>
#define REQUIRE assert
#define INSIST assert
/*@{*/
/*%
* 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
/*%
* 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 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_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 = dmalloc(sizeof(*heap), MDL);
if (heap == NULL)
return (ISC_R_NOMEMORY);
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;
if (heap->array != NULL)
dfree(heap->array, MDL);
dfree(heap, MDL);
*heapp = NULL;
}
static isc_boolean_t
resize(isc_heap_t *heap) {
void **new_array;
size_t new_size;
new_size = heap->size + heap->size_increment;
new_array = dmalloc(new_size * sizeof(void *), MDL);
if (new_array == NULL)
return (ISC_FALSE);
if (heap->array != NULL) {
memcpy(new_array, heap->array, heap->size * sizeof(void *));
dfree(heap->array, MDL);
}
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;
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(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(index >= 1 && index <= heap->last);
float_up(heap, index, heap->array[index]);
}
void
isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
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(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(action != NULL);
for (i = 1 ; i <= heap->last ; i++)
(action)(heap->array[i], uap);
}
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