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#include "structures/heap.h"
#include <stdlib.h>
#include <string.h>
#include "utils/memory.h"
Heap *heap_new(size_t el_size, int (*compare)(void *el1, void *el2), void (*el_cleanup)(void *el)) {
Heap *heap = safe_malloc(sizeof(Heap));
heap->data = safe_malloc(INIT_HEAP_CAPACITY * el_size);
heap->count = 0;
heap->el_size = el_size;
heap->capacity = INIT_HEAP_CAPACITY;
heap->compare = compare;
heap->el_cleanup = el_cleanup;
return heap;
}
// return index of parent in heap
size_t parent(size_t i) {
return (i - 1) / 2;
}
// return index of left child in heap
size_t left(size_t i) {
return 2 * i + 1;
}
// return index of right child in heap
size_t right(size_t i) {
return 2 * i + 2;
}
// swap two elements in heap
void swap(Heap *heap, size_t i1, size_t i2) {
char tmp[heap->el_size];
memcpy(tmp, heap->data + i1, heap->el_size);
memcpy(heap->data + i1, heap->data + i2, heap->el_size);
memcpy(heap->data + i2, tmp, heap->el_size);
}
// expand heap exponentially to fit el_count elements
void expand_heap(Heap *heap, size_t el_count) {
while (heap->capacity < el_count)
heap->capacity = (heap->capacity << 1) | 1;
heap->data = safe_realloc(heap->data, heap->capacity * heap->el_size);
}
void heap_insert(Heap *heap, void *element) {
// expand heap if capacity is too small
if (heap->count >= heap->capacity)
expand_heap(heap, heap->count + 1);
// insert into the last position
size_t i = heap->count++;
memcpy(heap->data + i, element, heap->count);
// heapify up
while (i > 0 && heap->compare(heap->data + i, heap->data + parent(i))) {
swap(heap, i, parent(i));
i = parent(i);
}
}
void *heap_top_get(Heap *heap) {
return heap->count <= 0 ? NULL : heap->data;
}
void heap_top_remove(Heap *heap) {
if (heap->count <= 0)
return;
if (heap->el_cleanup)
heap->el_cleanup(heap->data);
// move last element to root
memcpy(heap->data, heap->data + --heap->count, heap->el_size);
// heapify down
size_t i = 0;
int changed;
do {
size_t l = left(i);
size_t r = right(i);
size_t new_par = i;
if (l < heap->count && heap->compare(heap->data + l, heap->data + new_par))
new_par = l;
if (r < heap->count && heap->compare(heap->data + r, heap->data + new_par))
new_par = r;
if ((changed = new_par != i)) {
swap(heap, new_par, i);
i = new_par;
}
} while (changed);
}
void heap_free(Heap *heap) {
if (!heap)
return;
if (heap->el_cleanup) {
for (size_t i = 0; i < heap->count; i++)
heap->el_cleanup(heap->data + i);
}
free(heap->data);
free(heap);
}
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