/* $NetBSD: heap.c,v 1.1.2.2 2024/02/24 13:07:20 martin Exp $ */ /* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * SPDX-License-Identifier: MPL-2.0 * * 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 https://mozilla.org/MPL/2.0/. * * See the COPYRIGHT file distributed with this work for additional * information regarding copyright ownership. */ /*! \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 memmove. */ #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; }; #ifdef ISC_HEAP_CHECK static void heap_check(isc_heap_t *heap) { unsigned int i; for (i = 1; i <= heap->last; i++) { INSIST(HEAPCONDITION(i)); } } #else /* ifdef ISC_HEAP_CHECK */ #define heap_check(x) (void)0 #endif /* ifdef ISC_HEAP_CHECK */ void isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare, isc_heapindex_t idx, 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)); heap->magic = HEAP_MAGIC; heap->size = 0; heap->mctx = NULL; isc_mem_attach(mctx, &heap->mctx); 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 = idx; *heapp = heap; } void isc_heap_destroy(isc_heap_t **heapp) { isc_heap_t *heap; REQUIRE(heapp != NULL); heap = *heapp; *heapp = NULL; REQUIRE(VALID_HEAP(heap)); if (heap->array != NULL) { isc_mem_put(heap->mctx, heap->array, heap->size * sizeof(void *)); } heap->magic = 0; isc_mem_putanddetach(&heap->mctx, heap, sizeof(*heap)); } static void resize(isc_heap_t *heap) { void **new_array; unsigned int 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 (heap->array != NULL) { memmove(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; } 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)); heap_check(heap); } 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)); heap_check(heap); } void isc_heap_insert(isc_heap_t *heap, void *elt) { unsigned int new_last; REQUIRE(VALID_HEAP(heap)); heap_check(heap); new_last = heap->last + 1; RUNTIME_CHECK(new_last > 0); /* overflow check */ if (new_last >= heap->size) { resize(heap); } heap->last = new_last; float_up(heap, new_last, elt); } void isc_heap_delete(isc_heap_t *heap, unsigned int idx) { void *elt; bool less; REQUIRE(VALID_HEAP(heap)); REQUIRE(idx >= 1 && idx <= heap->last); heap_check(heap); if (heap->index != NULL) { (heap->index)(heap->array[idx], 0); } if (idx == heap->last) { heap->array[heap->last] = NULL; heap->last--; heap_check(heap); } else { elt = heap->array[heap->last]; heap->array[heap->last] = NULL; heap->last--; less = heap->compare(elt, heap->array[idx]); heap->array[idx] = elt; if (less) { float_up(heap, idx, heap->array[idx]); } else { sink_down(heap, idx, heap->array[idx]); } } } void isc_heap_increased(isc_heap_t *heap, unsigned int idx) { REQUIRE(VALID_HEAP(heap)); REQUIRE(idx >= 1 && idx <= heap->last); float_up(heap, idx, heap->array[idx]); } void isc_heap_decreased(isc_heap_t *heap, unsigned int idx) { REQUIRE(VALID_HEAP(heap)); REQUIRE(idx >= 1 && idx <= heap->last); sink_down(heap, idx, heap->array[idx]); } void * isc_heap_element(isc_heap_t *heap, unsigned int idx) { REQUIRE(VALID_HEAP(heap)); REQUIRE(idx >= 1); heap_check(heap); if (idx <= heap->last) { return (heap->array[idx]); } 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); } }