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/*
* Copyright 2006 Serge van den Boom <svdb@stack.nl>
*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "heap.h"
#include <assert.h>
#include <math.h>
#include <stdlib.h>
#include "port.h"
static inline size_t nextPower2(size_t x);
static void
Heap_resize(Heap *heap, size_t size) {
heap->entries = realloc(heap->entries, size * sizeof (HeapValue *));
heap->size = size;
}
// Heap inv: comparator(parent, child) <= 0 for every child of every parent.
Heap *
Heap_new(HeapValue_Comparator comparator, size_t initialSize, size_t minSize,
double minFillQuotient) {
Heap *heap;
assert(minFillQuotient >= 0.0);
heap = malloc(sizeof (Heap));
if (initialSize < minSize)
initialSize = minSize;
heap->comparator = comparator;
heap->minSize = minSize;
heap->minFillQuotient = minFillQuotient;
heap->size = nextPower2(initialSize);
heap->minFill = ceil(((double) (heap->size >> 1))
* heap->minFillQuotient);
heap->entries = malloc(heap->size * sizeof (HeapValue *));
heap->numEntries = 0;
return heap;
}
void
Heap_delete(Heap *heap) {
free(heap->entries);
free(heap);
}
void
Heap_add(Heap *heap, HeapValue *value) {
size_t i;
if (heap->numEntries >= heap->size)
Heap_resize(heap, heap->size * 2);
i = heap->numEntries;
heap->numEntries++;
while (i > 0) {
size_t parentI = (i - 1) / 2;
if (heap->comparator(heap->entries[parentI], value) <= 0)
break;
heap->entries[i] = heap->entries[parentI];
heap->entries[i]->index = i;
i = parentI;
}
heap->entries[i] = value;
heap->entries[i]->index = i;
}
HeapValue *
Heap_first(const Heap *heap) {
assert(heap->numEntries > 0);
return heap->entries[0];
}
static void
Heap_removeByIndex(Heap *heap, size_t i) {
assert(heap->numEntries > i);
heap->numEntries--;
if (heap->numEntries != 0) {
// Restore the heap invariant. We're shifting entries into the
// gap that was created until we find the place where we can
// insert the last entry.
HeapValue *lastEntry = heap->entries[heap->numEntries];
for (;;) {
size_t childI = i * 2 + 1;
// The two children are childI and 'childI + 1'.
if (childI + 1 >= heap->numEntries) {
// There is no right child.
if (childI >= heap->numEntries) {
// There is no left child either.
break;
}
} else {
if (heap->comparator(heap->entries[childI + 1],
heap->entries[childI]) < 0) {
// The right child is the child with the lowest value.
childI++;
}
}
// childI is now the child with the lowest value.
if (heap->comparator(lastEntry, heap->entries[childI]) <= 0) {
// The last entry goes here.
break;
}
// Move the child into the gap.
heap->entries[i] = heap->entries[childI];
heap->entries[i]->index = i;
// and repeat for the child.
i = childI;
}
// Fill the gap with the last entry.
heap->entries[i] = lastEntry;
heap->entries[i]->index = i;
}
// Resize if necessary:
if (heap->numEntries < heap->minFill &&
heap->numEntries > heap->minSize)
Heap_resize(heap, heap->size / 2);
}
HeapValue *
Heap_pop(Heap *heap) {
HeapValue *result;
assert(heap->numEntries > 0);
result = heap->entries[0];
Heap_removeByIndex(heap, 0);
return result;
}
size_t
Heap_count(const Heap *heap) {
return heap->numEntries;
}
bool
Heap_hasMore(const Heap *heap) {
return heap->numEntries > 0;
}
void
Heap_remove(Heap *heap, HeapValue *value) {
Heap_removeByIndex(heap, value->index);
}
// Adapted from "Hackers Delight"
// Returns the smallest power of two greater or equal to x.
static inline size_t
nextPower2(size_t x) {
x--;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
# if (SIZE_MAX > 0xffff)
x |= x >> 16;
# if (SIZE_MAX > 0xffffffff)
x |= x >> 32;
# endif
# endif
return x + 1;
}
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