heap.c

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/* LIBDGL -- a Directed Graph Library implementation
 * SPDX-FileCopyrightText: 2002 Roberto Micarelli
 * SPDX-FileCopyrightText: GRASS Development Team
 * SPDX-License-Identifier: GPL-2.0-or-later
 */
 
/* best view tabstop=4
 */
#include <stdio.h>
#include <stdlib.h>
 
#include "type.h"
#include "heap.h"
 
void dglHeapInit(dglHeap_s *pheap)
{
    pheap->index = 0;
    pheap->count = 0;
    pheap->block = 256;
    pheap->pnode = NULL;
}
 
void dglHeapFree(dglHeap_s *pheap, dglHeapCancelItem_fn pfnCancelItem)
{
    int iItem;
 
    if (pheap->pnode) {
        if (pfnCancelItem) {
            for (iItem = 0; iItem <= pheap->index; iItem++) {
                pfnCancelItem(pheap, &pheap->pnode[iItem]);
            }
        }
        free(pheap->pnode);
    }
    pheap->pnode = NULL;
}
 
int dglHeapInsertMin(dglHeap_s *pheap, long key, unsigned char flags,
                     dglHeapData_u value)
{
    long i;
 
    if (pheap->index >= pheap->count - 1) {
        pheap->count += pheap->block;
        if ((pheap->pnode = realloc(pheap->pnode, sizeof(dglHeapNode_s) *
                                                      pheap->count)) == NULL)
            return -1;
    }
 
    i = ++pheap->index;
 
    while (i != 1 && key < pheap->pnode[i / 2].key) {
        pheap->pnode[i] = pheap->pnode[i / 2];
        i /= 2;
    }
 
    pheap->pnode[i].key = key;
    pheap->pnode[i].flags = flags;
    pheap->pnode[i].value = value;
 
    return i;
}
 
int dglHeapExtractMin(dglHeap_s *pheap, dglHeapNode_s *pnoderet)
{
    dglHeapNode_s temp;
    long iparent, ichild;
 
    if (pheap->index == 0)
        return 0; /* empty heap */
 
    *pnoderet = pheap->pnode[1];
 
    temp = pheap->pnode[pheap->index--];
 
    iparent = 1;
    ichild = 2;
 
    while (ichild <= pheap->index) {
        if (ichild < pheap->index &&
            pheap->pnode[ichild].key > pheap->pnode[ichild + 1].key) {
            ichild++;
        }
        if (temp.key <= pheap->pnode[ichild].key)
            break;
 
        pheap->pnode[iparent] = pheap->pnode[ichild];
        iparent = ichild;
        ichild *= 2;
    }
    pheap->pnode[iparent] = temp;
 
    return 1;
}
 
int dglHeapInsertMax(dglHeap_s *pheap, long key, unsigned char flags,
                     dglHeapData_u value)
{
    long i;
 
    if (pheap->index >= pheap->count - 1) {
        pheap->count += pheap->block;
        if ((pheap->pnode = realloc(pheap->pnode, sizeof(dglHeapNode_s) *
                                                      pheap->count)) == NULL)
            return -1;
    }
 
    i = ++pheap->index;
 
    while (i != 1 && key > pheap->pnode[i / 2].key) {
        pheap->pnode[i] = pheap->pnode[i / 2];
        i /= 2;
    }
 
    pheap->pnode[i].key = key;
    pheap->pnode[i].flags = flags;
    pheap->pnode[i].value = value;
 
    return i;
}
 
int dglHeapExtractMax(dglHeap_s *pheap, dglHeapNode_s *pnoderet)
{
    dglHeapNode_s temp;
    long iparent, ichild;
 
    if (pheap->index == 0)
        return 0; /* empty heap */
 
    *pnoderet = pheap->pnode[1];
 
    temp = pheap->pnode[pheap->index--];
 
    iparent = 1;
    ichild = 2;
 
    while (ichild <= pheap->index) {
        if (ichild < pheap->index &&
            pheap->pnode[ichild].key < pheap->pnode[ichild + 1].key) {
            ichild++;
        }
        if (temp.key >= pheap->pnode[ichild].key)
            break;
 
        pheap->pnode[iparent] = pheap->pnode[ichild];
        iparent = ichild;
        ichild *= 2;
    }
    pheap->pnode[iparent] = temp;
 
    return 1;
}