tildefriends/deps/libuv/src/heap-inl.h

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/* Copyright (c) 2013, Ben Noordhuis <info@bnoordhuis.nl>
*
* 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.
*/
#ifndef UV_SRC_HEAP_H_
#define UV_SRC_HEAP_H_
#include <stddef.h> /* NULL */
#if defined(__GNUC__)
# define HEAP_EXPORT(declaration) __attribute__((unused)) static declaration
#else
# define HEAP_EXPORT(declaration) static declaration
#endif
struct heap_node {
struct heap_node* left;
struct heap_node* right;
struct heap_node* parent;
};
/* A binary min heap. The usual properties hold: the root is the lowest
* element in the set, the height of the tree is at most log2(nodes) and
* it's always a complete binary tree.
*
* The heap function try hard to detect corrupted tree nodes at the cost
* of a minor reduction in performance. Compile with -DNDEBUG to disable.
*/
struct heap {
struct heap_node* min;
unsigned int nelts;
};
/* Return non-zero if a < b. */
typedef int (*heap_compare_fn)(const struct heap_node* a,
const struct heap_node* b);
/* Public functions. */
HEAP_EXPORT(void heap_init(struct heap* heap));
HEAP_EXPORT(struct heap_node* heap_min(const struct heap* heap));
HEAP_EXPORT(void heap_insert(struct heap* heap,
struct heap_node* newnode,
heap_compare_fn less_than));
HEAP_EXPORT(void heap_remove(struct heap* heap,
struct heap_node* node,
heap_compare_fn less_than));
HEAP_EXPORT(void heap_dequeue(struct heap* heap, heap_compare_fn less_than));
/* Implementation follows. */
HEAP_EXPORT(void heap_init(struct heap* heap)) {
heap->min = NULL;
heap->nelts = 0;
}
HEAP_EXPORT(struct heap_node* heap_min(const struct heap* heap)) {
return heap->min;
}
/* Swap parent with child. Child moves closer to the root, parent moves away. */
static void heap_node_swap(struct heap* heap,
struct heap_node* parent,
struct heap_node* child) {
struct heap_node* sibling;
struct heap_node t;
t = *parent;
*parent = *child;
*child = t;
parent->parent = child;
if (child->left == child) {
child->left = parent;
sibling = child->right;
} else {
child->right = parent;
sibling = child->left;
}
if (sibling != NULL)
sibling->parent = child;
if (parent->left != NULL)
parent->left->parent = parent;
if (parent->right != NULL)
parent->right->parent = parent;
if (child->parent == NULL)
heap->min = child;
else if (child->parent->left == parent)
child->parent->left = child;
else
child->parent->right = child;
}
HEAP_EXPORT(void heap_insert(struct heap* heap,
struct heap_node* newnode,
heap_compare_fn less_than)) {
struct heap_node** parent;
struct heap_node** child;
unsigned int path;
unsigned int n;
unsigned int k;
newnode->left = NULL;
newnode->right = NULL;
newnode->parent = NULL;
/* Calculate the path from the root to the insertion point. This is a min
* heap so we always insert at the left-most free node of the bottom row.
*/
path = 0;
for (k = 0, n = 1 + heap->nelts; n >= 2; k += 1, n /= 2)
path = (path << 1) | (n & 1);
/* Now traverse the heap using the path we calculated in the previous step. */
parent = child = &heap->min;
while (k > 0) {
parent = child;
if (path & 1)
child = &(*child)->right;
else
child = &(*child)->left;
path >>= 1;
k -= 1;
}
/* Insert the new node. */
newnode->parent = *parent;
*child = newnode;
heap->nelts += 1;
/* Walk up the tree and check at each node if the heap property holds.
* It's a min heap so parent < child must be true.
*/
while (newnode->parent != NULL && less_than(newnode, newnode->parent))
heap_node_swap(heap, newnode->parent, newnode);
}
HEAP_EXPORT(void heap_remove(struct heap* heap,
struct heap_node* node,
heap_compare_fn less_than)) {
struct heap_node* smallest;
struct heap_node** max;
struct heap_node* child;
unsigned int path;
unsigned int k;
unsigned int n;
if (heap->nelts == 0)
return;
/* Calculate the path from the min (the root) to the max, the left-most node
* of the bottom row.
*/
path = 0;
for (k = 0, n = heap->nelts; n >= 2; k += 1, n /= 2)
path = (path << 1) | (n & 1);
/* Now traverse the heap using the path we calculated in the previous step. */
max = &heap->min;
while (k > 0) {
if (path & 1)
max = &(*max)->right;
else
max = &(*max)->left;
path >>= 1;
k -= 1;
}
heap->nelts -= 1;
/* Unlink the max node. */
child = *max;
*max = NULL;
if (child == node) {
/* We're removing either the max or the last node in the tree. */
if (child == heap->min) {
heap->min = NULL;
}
return;
}
/* Replace the to be deleted node with the max node. */
child->left = node->left;
child->right = node->right;
child->parent = node->parent;
if (child->left != NULL) {
child->left->parent = child;
}
if (child->right != NULL) {
child->right->parent = child;
}
if (node->parent == NULL) {
heap->min = child;
} else if (node->parent->left == node) {
node->parent->left = child;
} else {
node->parent->right = child;
}
/* Walk down the subtree and check at each node if the heap property holds.
* It's a min heap so parent < child must be true. If the parent is bigger,
* swap it with the smallest child.
*/
for (;;) {
smallest = child;
if (child->left != NULL && less_than(child->left, smallest))
smallest = child->left;
if (child->right != NULL && less_than(child->right, smallest))
smallest = child->right;
if (smallest == child)
break;
heap_node_swap(heap, child, smallest);
}
/* Walk up the subtree and check that each parent is less than the node
* this is required, because `max` node is not guaranteed to be the
* actual maximum in tree
*/
while (child->parent != NULL && less_than(child, child->parent))
heap_node_swap(heap, child->parent, child);
}
HEAP_EXPORT(void heap_dequeue(struct heap* heap, heap_compare_fn less_than)) {
heap_remove(heap, heap->min, less_than);
}
#undef HEAP_EXPORT
#endif /* UV_SRC_HEAP_H_ */