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/*
* Copyright (c) 2012 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "heap.h"
#include <stdlib.h>
#include "util.h"
static void put_node(struct heap *, struct heap_node *, size_t i);
static void swap_nodes(struct heap *, size_t i, size_t j);
static bool float_up(struct heap *, size_t i);
static void float_down(struct heap *, size_t i);
static void float_up_or_down(struct heap *, size_t i);
/* Initializes 'heap' as an empty heap. */
void
heap_init(struct heap *heap)
{
heap->array = NULL;
heap->n = 0;
heap->allocated = 0;
}
/* Frees memory owned internally by 'heap'. The caller is responsible for
* freeing 'heap' itself, if necessary. */
void
heap_destroy(struct heap *heap)
{
if (heap) {
free(heap->array);
}
}
/* Removes all of the elements from 'heap', without freeing any allocated
* memory. */
void
heap_clear(struct heap *heap)
{
heap->n = 0;
}
/* Exchanges the contents of 'a' and 'b'. */
void
heap_swap(struct heap *a, struct heap *b)
{
struct heap tmp = *a;
*a = *b;
*b = tmp;
}
/* Inserts 'node' into 'heap' with the specified 'priority'.
*
* This takes time O(lg n). */
void
heap_insert(struct heap *heap, struct heap_node *node, uint64_t priority)
{
heap_raw_insert(heap, node, priority);
float_up(heap, node->idx);
}
/* Removes 'node' from 'heap'.
*
* This takes time O(lg n). */
void
heap_remove(struct heap *heap, struct heap_node *node)
{
size_t i = node->idx;
heap_raw_remove(heap, node);
if (i <= heap->n) {
float_up_or_down(heap, i);
}
}
/* Changes the priority of 'node' (which must be in 'heap') to 'priority'.
*
* This takes time O(lg n). */
void
heap_change(struct heap *heap, struct heap_node *node, uint64_t priority)
{
heap_raw_change(node, priority);
float_up_or_down(heap, node->idx);
}
/* Inserts 'node' into 'heap' with the specified 'priority', without
* maintaining the heap invariant.
*
* After this call, heap_max() will no longer necessarily return the maximum
* value in the heap, and HEAP_FOR_EACH will no longer necessarily iterate in
* heap level order, until the next call to heap_rebuild(heap).
*
* This takes time O(1). */
void
heap_raw_insert(struct heap *heap, struct heap_node *node, uint64_t priority)
{
if (heap->n >= heap->allocated) {
heap->allocated = heap->n == 0 ? 1 : 2 * heap->n;
heap->array = xrealloc(heap->array,
(heap->allocated + 1) * sizeof *heap->array);
}
put_node(heap, node, ++heap->n);
node->priority = priority;
}
/* Removes 'node' from 'heap', without maintaining the heap invariant.
*
* After this call, heap_max() will no longer necessarily return the maximum
* value in the heap, and HEAP_FOR_EACH will no longer necessarily iterate in
* heap level order, until the next call to heap_rebuild(heap).
*
* This takes time O(1). */
void
heap_raw_remove(struct heap *heap, struct heap_node *node)
{
size_t i = node->idx;
if (i < heap->n) {
put_node(heap, heap->array[heap->n], i);
}
heap->n--;
}
/* Rebuilds 'heap' to restore the heap invariant following a series of one or
* more calls to heap_raw_*() functions. (Otherwise this function need not be
* called.)
*
* This takes time O(n) in the current size of the heap. */
void
heap_rebuild(struct heap *heap)
{
size_t i;
for (i = heap->n / 2; i >= 1; i--) {
float_down(heap, i);
}
}
static void
put_node(struct heap *heap, struct heap_node *node, size_t i)
{
heap->array[i] = node;
node->idx = i;
}
static void
swap_nodes(struct heap *heap, size_t i, size_t j)
{
struct heap_node *old_i = heap->array[i];
struct heap_node *old_j = heap->array[j];
put_node(heap, old_j, i);
put_node(heap, old_i, j);
}
static bool
float_up(struct heap *heap, size_t i)
{
bool moved = false;
size_t parent;
for (; i > 1; i = parent) {
parent = heap_parent__(i);
if (heap->array[parent]->priority >= heap->array[i]->priority) {
break;
}
swap_nodes(heap, parent, i);
moved = true;
}
return moved;
}
static void
float_down(struct heap *heap, size_t i)
{
while (!heap_is_leaf__(heap, i)) {
size_t left = heap_left__(i);
size_t right = heap_right__(i);
size_t max = i;
if (heap->array[left]->priority > heap->array[max]->priority) {
max = left;
}
if (right <= heap->n
&& heap->array[right]->priority > heap->array[max]->priority) {
max = right;
}
if (max == i) {
break;
}
swap_nodes(heap, max, i);
i = max;
}
}
static void
float_up_or_down(struct heap *heap, size_t i)
{
if (!float_up(heap, i)) {
float_down(heap, i);
}
}
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