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Diffstat (limited to 'lib/bind/isc/heap.c')
| -rw-r--r-- | lib/bind/isc/heap.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/lib/bind/isc/heap.c b/lib/bind/isc/heap.c new file mode 100644 index 0000000..bea7678 --- /dev/null +++ b/lib/bind/isc/heap.c @@ -0,0 +1,236 @@ +/* + * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") + * Copyright (c) 1997,1999 by 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. + */ + +/*% + * Heap implementation of priority queues adapted from the following: + * + * _Introduction to Algorithms_, Cormen, Leiserson, and Rivest, + * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7. + * + * _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988, + * ISBN 0-201-06673-4, chapter 11. + */ + +#if !defined(LINT) && !defined(CODECENTER) +static const char rcsid[] = "$Id: heap.c,v 1.2.18.2 2006/03/10 00:20:08 marka Exp $"; +#endif /* not lint */ + +#include "port_before.h" + +#include <stddef.h> +#include <stdlib.h> +#include <errno.h> + +#include "port_after.h" + +#include <isc/heap.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. + */ +#define heap_parent(i) ((i) >> 1) +#define heap_left(i) ((i) << 1) + +#define ARRAY_SIZE_INCREMENT 512 + +heap_context +heap_new(heap_higher_priority_func higher_priority, heap_index_func index, + int array_size_increment) { + heap_context ctx; + + if (higher_priority == NULL) + return (NULL); + + ctx = (heap_context)malloc(sizeof (struct heap_context)); + if (ctx == NULL) + return (NULL); + + ctx->array_size = 0; + if (array_size_increment == 0) + ctx->array_size_increment = ARRAY_SIZE_INCREMENT; + else + ctx->array_size_increment = array_size_increment; + ctx->heap_size = 0; + ctx->heap = NULL; + ctx->higher_priority = higher_priority; + ctx->index = index; + return (ctx); +} + +int +heap_free(heap_context ctx) { + if (ctx == NULL) { + errno = EINVAL; + return (-1); + } + + if (ctx->heap != NULL) + free(ctx->heap); + free(ctx); + + return (0); +} + +static int +heap_resize(heap_context ctx) { + void **new_heap; + + ctx->array_size += ctx->array_size_increment; + new_heap = (void **)realloc(ctx->heap, + (ctx->array_size) * (sizeof (void *))); + if (new_heap == NULL) { + errno = ENOMEM; + return (-1); + } + ctx->heap = new_heap; + return (0); +} + +static void +float_up(heap_context ctx, int i, void *elt) { + int p; + + for ( p = heap_parent(i); + i > 1 && ctx->higher_priority(elt, ctx->heap[p]); + i = p, p = heap_parent(i) ) { + ctx->heap[i] = ctx->heap[p]; + if (ctx->index != NULL) + (ctx->index)(ctx->heap[i], i); + } + ctx->heap[i] = elt; + if (ctx->index != NULL) + (ctx->index)(ctx->heap[i], i); +} + +static void +sink_down(heap_context ctx, int i, void *elt) { + int j, size, half_size; + + size = ctx->heap_size; + half_size = size / 2; + while (i <= half_size) { + /* find smallest of the (at most) two children */ + j = heap_left(i); + if (j < size && ctx->higher_priority(ctx->heap[j+1], + ctx->heap[j])) + j++; + if (ctx->higher_priority(elt, ctx->heap[j])) + break; + ctx->heap[i] = ctx->heap[j]; + if (ctx->index != NULL) + (ctx->index)(ctx->heap[i], i); + i = j; + } + ctx->heap[i] = elt; + if (ctx->index != NULL) + (ctx->index)(ctx->heap[i], i); +} + +int +heap_insert(heap_context ctx, void *elt) { + int i; + + if (ctx == NULL || elt == NULL) { + errno = EINVAL; + return (-1); + } + + i = ++ctx->heap_size; + if (ctx->heap_size >= ctx->array_size && heap_resize(ctx) < 0) + return (-1); + + float_up(ctx, i, elt); + + return (0); +} + +int +heap_delete(heap_context ctx, int i) { + void *elt; + int less; + + if (ctx == NULL || i < 1 || i > ctx->heap_size) { + errno = EINVAL; + return (-1); + } + + if (i == ctx->heap_size) { + ctx->heap_size--; + } else { + elt = ctx->heap[ctx->heap_size--]; + less = ctx->higher_priority(elt, ctx->heap[i]); + ctx->heap[i] = elt; + if (less) + float_up(ctx, i, ctx->heap[i]); + else + sink_down(ctx, i, ctx->heap[i]); + } + + return (0); +} + +int +heap_increased(heap_context ctx, int i) { + if (ctx == NULL || i < 1 || i > ctx->heap_size) { + errno = EINVAL; + return (-1); + } + + float_up(ctx, i, ctx->heap[i]); + + return (0); +} + +int +heap_decreased(heap_context ctx, int i) { + if (ctx == NULL || i < 1 || i > ctx->heap_size) { + errno = EINVAL; + return (-1); + } + + sink_down(ctx, i, ctx->heap[i]); + + return (0); +} + +void * +heap_element(heap_context ctx, int i) { + if (ctx == NULL || i < 1 || i > ctx->heap_size) { + errno = EINVAL; + return (NULL); + } + + return (ctx->heap[i]); +} + +int +heap_for_each(heap_context ctx, heap_for_each_func action, void *uap) { + int i; + + if (ctx == NULL || action == NULL) { + errno = EINVAL; + return (-1); + } + + for (i = 1; i <= ctx->heap_size; i++) + (action)(ctx->heap[i], uap); + return (0); +} + +/*! \file */ |
