120 lines
2 KiB
C
120 lines
2 KiB
C
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/* Licensed under BSD-MIT - see LICENSE file for details */
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#include <ccan/heap/heap.h>
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/*
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* Allocating memory in chunks greater than needed does not yield measurable
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* speedups of the test program when linking against glibc 2.15.
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*
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* When the data array has to be shrunk though, limiting calls to realloc
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* does help a little bit (~7% speedup), hence the following parameter.
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*/
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#define HEAP_MEM_HYSTERESIS 4096
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static inline void swap(struct heap *h, size_t i, size_t j)
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{
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void *foo = h->data[i];
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h->data[i] = h->data[j];
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h->data[j] = foo;
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}
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static void __up(struct heap *h, size_t j)
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{
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size_t i; /* parent */
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while (j) {
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i = (j - 1) / 2;
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if (h->less(h->data[j], h->data[i])) {
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swap(h, i, j);
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j = i;
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} else {
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break;
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}
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}
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}
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int heap_push(struct heap *h, void *data)
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{
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if (h->len == h->cap) {
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void *m = realloc(h->data, (h->cap + 1) * sizeof(void *));
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if (m == NULL)
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return -1;
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h->data = m;
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h->cap++;
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}
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h->data[h->len++] = data;
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__up(h, h->len - 1);
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return 0;
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}
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static void __down(struct heap *h, size_t i)
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{
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size_t l, r, j; /* left, right, min child */
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while (1) {
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l = 2 * i + 1;
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if (l >= h->len)
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break;
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r = l + 1;
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if (r >= h->len)
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j = l;
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else
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j = h->less(h->data[l], h->data[r]) ? l : r;
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if (h->less(h->data[j], h->data[i])) {
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swap(h, i, j);
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i = j;
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} else {
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break;
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}
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}
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}
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void *heap_pop(struct heap *h)
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{
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void *ret = h->data[0];
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void *m;
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swap(h, 0, --h->len);
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if (h->len) {
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__down(h, 0);
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if (h->len == h->cap - HEAP_MEM_HYSTERESIS) {
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m = realloc(h->data, h->len * sizeof(void *));
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if (m == NULL)
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return NULL;
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h->data = m;
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h->cap = h->len;
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}
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}
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return ret;
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}
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struct heap *heap_init(heap_less_func_t less)
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{
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struct heap *heap = calloc(1, sizeof(*heap));
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if (heap == NULL)
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return NULL;
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heap->less = less;
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return heap;
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}
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void heap_ify(struct heap *h, heap_less_func_t less)
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{
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int i;
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if (less)
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h->less = less;
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for (i = h->len / 2 - 1; i >= 0; i--)
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__down(h, i);
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}
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void heap_free(struct heap *heap)
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{
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free(heap->data);
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free(heap);
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}
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