/*      $NetBSD: heap.c,v 1.1.1.2 2012/09/09 16:08:00 christos Exp $    */

/*
* 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 1.4 2006/03/09 23:57:56 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 */

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