heap.c revision 7bae6a079bb304bf69ffb83a5ac4cfaec9967ffc
/*
* Copyright (c) 1997, 1998 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
* CONSORTIUM 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 char rcsid[] = "$Id: heap.c,v 1.1 1998/10/15 23:42:56 halley Exp $";
#endif /* not lint */
#include <stdlib.h>
#include <isc/assertions.h>
#include <isc/boolean.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
#define HEAP_MAGIC 0x48454150U /* HEAP. */
#define VALID_CONTEXT(ctx) ((ctx) != NULL && \
(ctx)->magic == HEAP_MAGIC)
struct heap_context {
unsigned int magic;
mem_context_t mctx;
unsigned int array_size;
unsigned int array_size_increment;
unsigned int heap_size;
void **heap;
heap_higher_priority_func higher_priority;
heap_index_func index;
};
isc_result
heap_create(mem_context_t mctx, heap_higher_priority_func higher_priority,
heap_index_func index, unsigned int array_size_increment,
heap_context_t *ctxp)
{
heap_context_t ctx;
REQUIRE(ctxp != NULL && *ctxp == NULL);
REQUIRE(higher_priority != NULL);
ctx = mem_get(mctx, sizeof *ctx);
if (ctx == NULL)
return (ISC_R_NOMEMORY);
ctx->magic = HEAP_MAGIC;
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;
*ctxp = ctx;
return (ISC_R_SUCCESS);
}
void
heap_destroy(heap_context_t *ctxp) {
heap_context_t ctx;
REQUIRE(ctxp != NULL);
ctx = *ctxp;
REQUIRE(VALID_CONTEXT(ctx));
if (ctx->heap != NULL)
mem_put(ctx->mctx, ctx->heap,
ctx->array_size * sizeof (void *));
ctx->magic = 0;
mem_put(ctx->mctx, ctx, sizeof *ctx);
*ctxp = NULL;
}
static boolean_t
heap_resize(heap_context_t ctx) {
void **new_heap;
size_t new_size;
REQUIRE(VALID_CONTEXT(ctx));
new_size = ctx->array_size + ctx->array_size_increment;
new_heap = mem_get(ctx->mctx, new_size * sizeof (void *));
if (new_heap == NULL)
return (FALSE);
memcpy(new_heap, ctx->heap, ctx->array_size);
mem_put(ctx->mctx, ctx->heap,
ctx->array_size * sizeof (void *));
ctx->array_size = new_size;
ctx->heap = new_heap;
return (TRUE);
}
static void
float_up(heap_context_t ctx, unsigned int i, void *elt) {
unsigned 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_t ctx, unsigned int i, void *elt) {
unsigned 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);
}
isc_result
heap_insert(heap_context_t ctx, void *elt) {
unsigned int i;
REQUIRE(VALID_CONTEXT(ctx));
i = ++ctx->heap_size;
if (ctx->heap_size >= ctx->array_size && !heap_resize(ctx))
return (ISC_R_NOMEMORY);
float_up(ctx, i, elt);
return (ISC_R_SUCCESS);
}
void
heap_delete(heap_context_t ctx, unsigned int i) {
void *elt;
REQUIRE(VALID_CONTEXT(ctx));
REQUIRE(i >= 1 && i <= ctx->heap_size);
elt = ctx->heap[ctx->heap_size];
if (--ctx->heap_size > 0)
sink_down(ctx, i, elt);
}
void
heap_increased(heap_context_t ctx, unsigned int i) {
REQUIRE(VALID_CONTEXT(ctx));
REQUIRE(i >= 1 && i <= ctx->heap_size);
float_up(ctx, i, ctx->heap[i]);
}
void
heap_decreased(heap_context_t ctx, unsigned int i) {
REQUIRE(VALID_CONTEXT(ctx));
REQUIRE(i >= 1 && i <= ctx->heap_size);
sink_down(ctx, i, ctx->heap[i]);
}
void *
heap_element(heap_context_t ctx, unsigned int i) {
REQUIRE(VALID_CONTEXT(ctx));
REQUIRE(i >= 1 && i <= ctx->heap_size);
return (ctx->heap[i]);
}
void
heap_for_each(heap_context_t ctx, heap_for_each_func action, void *uap) {
unsigned int i;
REQUIRE(VALID_CONTEXT(ctx));
REQUIRE(action != NULL);
for (i = 1; i <= ctx->heap_size; i++)
(action)(ctx->heap[i], uap);
}