From 3b9b6d0b8e7f798023c9d109c490449d528fde80 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 17:59:48 +0200 Subject: Adding upstream version 1:9.18.19. Signed-off-by: Daniel Baumann --- lib/isc/heap.c | 280 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 280 insertions(+) create mode 100644 lib/isc/heap.c (limited to 'lib/isc/heap.c') diff --git a/lib/isc/heap.c b/lib/isc/heap.c new file mode 100644 index 0000000..7b0cc28 --- /dev/null +++ b/lib/isc/heap.c @@ -0,0 +1,280 @@ +/* + * 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); + } +} -- cgit v1.2.3