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lib: min_heap: Refactor heapify_up/down functions

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Remove using `swap()` which was using VLA and replace it
with `byteswp()`.
Reduce the scope of local variables in `heapify_up/down` to
the smallest necessary block.
Replace `while(true)` loop in `heapify_down()` with a bounded `for`
loop.

Signed-off-by: Sayooj K Karun <sayooj@aerlync.com>
This commit is contained in:
Sayooj K Karun
2025-06-11 15:19:09 +05:30
committed by Anas Nashif
parent cabf2c4d1d
commit 964a832702
1 changed files with 22 additions and 41 deletions
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63
lib/min_heap/min_heap.c
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@@ -10,27 +10,6 @@
LOG_MODULE_REGISTER(min_heap);
/**
* @brief Swap two elements in the heap.
*
* This function swaps the contents of two elements at the specified indices
* within the heap.
*
* @param heap Pointer to the min-heap.
* @param a Index of the first element.
* @param b Index of the second element.
*/
static void swap(struct min_heap *heap, size_t a, size_t b)
{
uint8_t tmp[heap->elem_size];
void *elem_a = min_heap_get_element(heap, a);
void *elem_b = min_heap_get_element(heap, b);
memcpy(tmp, elem_a, heap->elem_size);
memcpy(elem_a, elem_b, heap->elem_size);
memcpy(elem_b, tmp, heap->elem_size);
}
/**
* @brief Restore heap order by moving a node up the tree.
*
@@ -42,17 +21,15 @@ static void swap(struct min_heap *heap, size_t a, size_t b)
*/
static void heapify_up(struct min_heap *heap, size_t index)
{
size_t parent;
void *curr, *par;
while (index > 0) {
parent = (index - 1) / 2;
curr = min_heap_get_element(heap, index);
par = min_heap_get_element(heap, parent);
size_t parent = (index - 1) / 2;
void *curr = min_heap_get_element(heap, index);
void *par = min_heap_get_element(heap, parent);
if (heap->cmp(curr, par) >= 0) {
break;
}
swap(heap, index, parent);
byteswp(curr, par, heap->elem_size);
index = parent;
}
}
@@ -69,30 +46,34 @@ static void heapify_up(struct min_heap *heap, size_t index)
static void heapify_down(struct min_heap *heap, size_t index)
{
size_t left, right, smallest;
/* Terminate the loop naturally when the left child is out of bounds */
for (size_t left = 2 * index + 1; left < heap->size; left = 2 * index + 1) {
while (true) {
left = 2 * index + 1;
right = 2 * index + 2;
smallest = index;
size_t right = left + 1;
size_t smallest = index;
void *elem_index = min_heap_get_element(heap, index);
void *elem_left = min_heap_get_element(heap, left);
void *elem_smallest = elem_index;
if (left < heap->size &&
heap->cmp(min_heap_get_element(heap, left),
min_heap_get_element(heap, smallest)) < 0) {
if (heap->cmp(elem_left, elem_index) < 0) {
smallest = left;
elem_smallest = elem_left;
}
if (right < heap->size &&
heap->cmp(min_heap_get_element(heap, right),
min_heap_get_element(heap, smallest)) < 0) {
smallest = right;
if (right < heap->size) {
void *elem_right = min_heap_get_element(heap, right);
if (heap->cmp(elem_right, elem_smallest) < 0) {
smallest = right;
elem_smallest = elem_right;
}
}
if (smallest == index) {
break;
}
swap(heap, index, smallest);
byteswp(elem_index, elem_smallest, heap->elem_size);
index = smallest;
}
}