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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/** \file
* \ingroup bli
*
* A min-heap / priority queue ADT.
*
* Simplified version of the heap that only supports insertion and removal from top.
*
* See BLI_heap.c for a more full featured heap implementation.
*/
#include <stdlib.h>
#include <string.h>
#include "MEM_guardedalloc.h"
#include "BLI_heap_simple.h"
#include "BLI_strict_flags.h"
#include "BLI_utildefines.h"
#define HEAP_PARENT(i) (((i)-1) >> 1)
/* -------------------------------------------------------------------- */
/** \name HeapSimple Internal Structs
* \{ */
typedef struct HeapSimpleNode {
float value;
void *ptr;
} HeapSimpleNode;
struct HeapSimple {
uint size;
uint bufsize;
HeapSimpleNode *tree;
};
/** \} */
/* -------------------------------------------------------------------- */
/** \name HeapSimple Internal Functions
* \{ */
static void heapsimple_down(HeapSimple *heap, uint start_i, const HeapSimpleNode *init)
{
#if 1
/* The compiler isn't smart enough to realize that all computations
* using index here can be modified to work with byte offset. */
uint8_t *const tree_buf = (uint8_t *)heap->tree;
# define OFFSET(i) (i * (uint)sizeof(HeapSimpleNode))
# define NODE(offset) (*(HeapSimpleNode *)(tree_buf + (offset)))
#else
HeapSimpleNode *const tree = heap->tree;
# define OFFSET(i) (i)
# define NODE(i) tree[i]
#endif
#define HEAP_LEFT_OFFSET(i) (((i) << 1) + OFFSET(1))
const uint size = OFFSET(heap->size);
/* Pull the active node values into locals. This allows spilling
* the data from registers instead of literally swapping nodes. */
float active_val = init->value;
void *active_ptr = init->ptr;
/* Prepare the first iteration and spill value. */
uint i = OFFSET(start_i);
NODE(i).value = active_val;
for (;;) {
const uint l = HEAP_LEFT_OFFSET(i);
const uint r = l + OFFSET(1); /* right */
/* Find the child with the smallest value. */
uint smallest = i;
if (LIKELY(l < size) && NODE(l).value < active_val) {
smallest = l;
}
if (LIKELY(r < size) && NODE(r).value < NODE(smallest).value) {
smallest = r;
}
if (UNLIKELY(smallest == i)) {
break;
}
/* Move the smallest child into the current node.
* Skip padding: for some reason that makes it faster here. */
NODE(i).value = NODE(smallest).value;
NODE(i).ptr = NODE(smallest).ptr;
/* Proceed to next iteration and spill value. */
i = smallest;
NODE(i).value = active_val;
}
/* Spill the pointer into the final position of the node. */
NODE(i).ptr = active_ptr;
#undef NODE
#undef OFFSET
#undef HEAP_LEFT_OFFSET
}
static void heapsimple_up(HeapSimple *heap, uint i, float active_val, void *active_ptr)
{
HeapSimpleNode *const tree = heap->tree;
while (LIKELY(i > 0)) {
const uint p = HEAP_PARENT(i);
if (active_val >= tree[p].value) {
break;
}
tree[i] = tree[p];
i = p;
}
tree[i].value = active_val;
tree[i].ptr = active_ptr;
}
/** \} */
/* -------------------------------------------------------------------- */
/** \name Public HeapSimple API
* \{ */
HeapSimple *BLI_heapsimple_new_ex(uint tot_reserve)
{
HeapSimple *heap = MEM_mallocN(sizeof(HeapSimple), __func__);
/* ensure we have at least one so we can keep doubling it */
heap->size = 0;
heap->bufsize = MAX2(1u, tot_reserve);
heap->tree = MEM_mallocN(heap->bufsize * sizeof(HeapSimpleNode), "BLIHeapSimpleTree");
return heap;
}
HeapSimple *BLI_heapsimple_new(void)
{
return BLI_heapsimple_new_ex(1);
}
void BLI_heapsimple_free(HeapSimple *heap, HeapSimpleFreeFP ptrfreefp)
{
if (ptrfreefp) {
for (uint i = 0; i < heap->size; i++) {
ptrfreefp(heap->tree[i].ptr);
}
}
MEM_freeN(heap->tree);
MEM_freeN(heap);
}
void BLI_heapsimple_clear(HeapSimple *heap, HeapSimpleFreeFP ptrfreefp)
{
if (ptrfreefp) {
for (uint i = 0; i < heap->size; i++) {
ptrfreefp(heap->tree[i].ptr);
}
}
heap->size = 0;
}
void BLI_heapsimple_insert(HeapSimple *heap, float value, void *ptr)
{
if (UNLIKELY(heap->size >= heap->bufsize)) {
heap->bufsize *= 2;
heap->tree = MEM_reallocN(heap->tree, heap->bufsize * sizeof(*heap->tree));
}
heapsimple_up(heap, heap->size++, value, ptr);
}
bool BLI_heapsimple_is_empty(const HeapSimple *heap)
{
return (heap->size == 0);
}
uint BLI_heapsimple_len(const HeapSimple *heap)
{
return heap->size;
}
float BLI_heapsimple_top_value(const HeapSimple *heap)
{
BLI_assert(heap->size != 0);
return heap->tree[0].value;
}
void *BLI_heapsimple_pop_min(HeapSimple *heap)
{
BLI_assert(heap->size != 0);
void *ptr = heap->tree[0].ptr;
if (--heap->size) {
heapsimple_down(heap, 0, &heap->tree[heap->size]);
}
return ptr;
}
/** \} */
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