/* $NetBSD: heap.c,v 1.5 2007/01/27 21:24:11 christos Exp $ */ /* * 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 #include #include #include #include /* Required for memcpy. */ #include /*@{*/ /*% * 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); }