diff options
Diffstat (limited to 'lib/isc/heap.c')
| -rw-r--r-- | lib/isc/heap.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/lib/isc/heap.c b/lib/isc/heap.c new file mode 100644 index 0000000..91d78c0 --- /dev/null +++ b/lib/isc/heap.c @@ -0,0 +1,262 @@ +/* + * Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC") + * Copyright (C) 1997-2001 Internet Software Consortium. + * + * Permission to use, copy, modify, and/or 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 1.37 2007/10/19 17:15:53 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->array[heap->last] = NULL; + heap->last--; + } else { + elt = heap->array[heap->last]; + heap->array[heap->last] = NULL; + 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); + + if (index <= heap->last) + return (heap->array[index]); + return (NULL); +} + +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); +} |