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/*
* Binary Heap.
*
* Copyright (c) 2009 Marko Kreen, Skype Technologies OÜ
*
* Permission to use, copy, modify, and/or 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
*/
#include <usual/heap.h>
struct Heap {
void **data;
unsigned allocated;
unsigned used;
heap_is_better_f is_better;
heap_save_pos_f save_pos;
CxMem *cx;
};
/*
* Low-level operations.
*/
static unsigned get_parent(unsigned i)
{
return (i - 1) / 2;
}
static unsigned get_child(unsigned i, unsigned child_nr)
{
return 2*i + 1 + child_nr;
}
static bool is_better(struct Heap *h, unsigned i1, unsigned i2)
{
return h->is_better(h->data[i1], h->data[i2]);
}
static void set(struct Heap *h, unsigned i, void *ptr)
{
h->data[i] = ptr;
if (h->save_pos)
h->save_pos(ptr, i);
}
static void swap(struct Heap *h, unsigned i1, unsigned i2)
{
void *tmp = h->data[i1];
set(h, i1, h->data[i2]);
set(h, i2, tmp);
}
static void bubble_up(struct Heap *h, unsigned i)
{
unsigned p;
while (i > 0) {
p = get_parent(i);
if (!is_better(h, i, p))
break;
swap(h, i, p);
i = p;
}
}
static void bubble_down(struct Heap *h, unsigned i)
{
unsigned c = get_child(i, 0);
while (c < h->used) {
if (c + 1 < h->used) {
if (is_better(h, c + 1, c))
c = c + 1;
}
if (!is_better(h, c, i))
break;
swap(h, i, c);
i = c;
c = get_child(i, 0);
}
}
static void rebalance(struct Heap *h, unsigned pos)
{
if (pos == 0) {
bubble_down(h, pos);
} else if (pos == h->used - 1) {
bubble_up(h, pos);
} else if (is_better(h, pos, get_parent(pos))) {
bubble_up(h, pos);
} else {
bubble_down(h, pos);
}
}
/*
* Actual API.
*/
struct Heap *heap_create(heap_is_better_f is_better_cb, heap_save_pos_f save_pos_cb, CxMem *cx)
{
struct Heap *h;
h = cx_alloc0(cx, sizeof(*h));
if (!h)
return NULL;
h->save_pos = save_pos_cb;
h->is_better = is_better_cb;
h->cx = cx;
return h;
}
void heap_destroy(struct Heap *h)
{
if (h) {
cx_free(h->cx, h->data);
cx_free(h->cx, h);
}
}
bool heap_reserve(struct Heap *h, unsigned extra)
{
void *tmp;
unsigned newalloc;
if (h->used + extra < h->allocated)
return true;
newalloc = h->allocated * 2;
if (newalloc < 32)
newalloc = 32;
if (newalloc < h->used + extra)
newalloc = h->used + extra;
tmp = cx_realloc(h->cx, h->data, newalloc * sizeof(void *));
if (!tmp)
return false;
h->data = tmp;
h->allocated = newalloc;
return true;
}
void *heap_top(struct Heap *h)
{
return (h->used > 0) ? h->data[0] : NULL;
}
bool heap_push(struct Heap *h, void *ptr)
{
unsigned pos;
if (h->used >= h->allocated) {
if (!heap_reserve(h, 1))
return false;
}
pos = h->used++;
set(h, pos, ptr);
bubble_up(h, pos);
return true;
}
void *heap_remove(struct Heap *h, unsigned pos)
{
unsigned last;
void *obj;
if (pos >= h->used)
return NULL;
obj = h->data[pos];
last = --h->used;
if (pos < last) {
set(h, pos, h->data[last]);
rebalance(h, pos);
}
h->data[last] = NULL;
return obj;
}
void *heap_pop(struct Heap *h)
{
return heap_remove(h, 0);
}
unsigned heap_size(struct Heap *h)
{
return h->used;
}
void *heap_get_obj(struct Heap *h, unsigned pos)
{
if (pos < h->used)
return h->data[pos];
return NULL;
}
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