BLI_heap.c

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * 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.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * The Original Code is: none of this file.
 *
 * Contributor(s): Brecht Van Lommel
 *
 * ***** END GPL LICENSE BLOCK *****
 * A heap / priority queue ADT.
 */

#include <string.h>

#include "MEM_guardedalloc.h"
#include "BLI_memarena.h"
#include "BLI_heap.h"

/***/

struct HeapNode {
    void *ptr;
    float value;
    int index;
};

struct Heap {
    unsigned int size;
    unsigned int bufsize;
    MemArena *arena;
    HeapNode *freenodes;
    HeapNode *nodes;
    HeapNode **tree;
};

#define SWAP(type, a, b) \
    { type sw_ap; sw_ap=(a); (a)=(b); (b)=sw_ap; }
#define HEAP_PARENT(i) ((i-1)>>1)
#define HEAP_LEFT(i)   ((i<<1)+1)
#define HEAP_RIGHT(i)  ((i<<1)+2)
#define HEAP_COMPARE(a, b) (a->value < b->value)
#define HEAP_EQUALS(a, b) (a->value == b->value)
#define HEAP_SWAP(heap, i, j) \
{                                                                             \
    SWAP(int, heap->tree[i]->index, heap->tree[j]->index);                    \
    SWAP(HeapNode*, heap->tree[i], heap->tree[j]);                            \
}

/***/

Heap *BLI_heap_new(void)
{
    Heap *heap = (Heap*)MEM_callocN(sizeof(Heap), "BLIHeap");
    heap->bufsize = 1;
    heap->tree = (HeapNode**)MEM_mallocN(sizeof(HeapNode*), "BLIHeapTree");
    heap->arena = BLI_memarena_new(1<<16, "heap arena");

    return heap;
}

void BLI_heap_free(Heap *heap, HeapFreeFP ptrfreefp)
{
    int i;

    if (ptrfreefp)
        for (i = 0; i < heap->size; i++)
            ptrfreefp(heap->tree[i]->ptr);
    
    MEM_freeN(heap->tree);
    BLI_memarena_free(heap->arena);
    MEM_freeN(heap);
}

static void BLI_heap_down(Heap *heap, int i)
{
    while (1) {
        int size = heap->size, smallest;
        int l = HEAP_LEFT(i);
        int r = HEAP_RIGHT(i);

        smallest = ((l < size) && HEAP_COMPARE(heap->tree[l], heap->tree[i]))? l: i;

        if ((r < size) && HEAP_COMPARE(heap->tree[r], heap->tree[smallest]))
            smallest = r;
        
        if (smallest == i)
            break;

        HEAP_SWAP(heap, i, smallest);
        i = smallest;
    }
}

static void BLI_heap_up(Heap *heap, int i)
{
    while (i > 0) {
        int p = HEAP_PARENT(i);

        if (HEAP_COMPARE(heap->tree[p], heap->tree[i]))
            break;

        HEAP_SWAP(heap, p, i);
        i = p;
    }
}

HeapNode *BLI_heap_insert(Heap *heap, float value, void *ptr)
{
    HeapNode *node;

    if ((heap->size + 1) > heap->bufsize) {
        int newsize = heap->bufsize*2;
        HeapNode **newtree;

        newtree = (HeapNode**)MEM_mallocN(newsize*sizeof(*newtree), "BLIHeapTree");
        memcpy(newtree, heap->tree, sizeof(HeapNode*)*heap->size);
        MEM_freeN(heap->tree);

        heap->tree = newtree;
        heap->bufsize = newsize;
    }

    if (heap->freenodes) {
        node = heap->freenodes;
        heap->freenodes = (HeapNode*)(((HeapNode*)heap->freenodes)->ptr);
    }
    else
        node = (HeapNode*)BLI_memarena_alloc(heap->arena, sizeof *node);

    node->value = value;
    node->ptr = ptr;
    node->index = heap->size;

    heap->tree[node->index] = node;

    heap->size++;

    BLI_heap_up(heap, heap->size-1);

    return node;
}

int BLI_heap_empty(Heap *heap)
{
    return (heap->size == 0);
}

int BLI_heap_size(Heap *heap)
{
    return heap->size;
}

HeapNode *BLI_heap_top(Heap *heap)
{
    return heap->tree[0];
}

void *BLI_heap_popmin(Heap *heap)
{
    void *ptr = heap->tree[0]->ptr;

    heap->tree[0]->ptr = heap->freenodes;
    heap->freenodes = heap->tree[0];

    if (heap->size == 1)
        heap->size--;
    else {
        HEAP_SWAP(heap, 0, heap->size-1);
        heap->size--;

        BLI_heap_down(heap, 0);
    }

    return ptr;
}

void BLI_heap_remove(Heap *heap, HeapNode *node)
{
    int i = node->index;

    while (i > 0) {
        int p = HEAP_PARENT(i);

        HEAP_SWAP(heap, p, i);
        i = p;
    }

    BLI_heap_popmin(heap);
}

float BLI_heap_node_value(HeapNode *node)
{
    return node->value;
}

void *BLI_heap_node_ptr(HeapNode *node)
{
    return node->ptr;
}