-/*
- * SPDX-License-Identifier: MIT
- *
- * Copyright 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * Static-sized priority heap containing pointers. Based on CLRS,
- * chapter 6.
- */
-
-#include "common/macros.h"
-#include "common/assert.h"
-#include <errno.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include "common/prio-heap.h"
-
-#ifdef DEBUG_HEAP
-void check_heap(const struct ptr_heap *heap)
-{
- size_t i;
-
- if (!heap->len)
- return;
-
- for (i = 1; i < heap->len; i++)
- BT_ASSERT_DBG(!heap->gt(heap->ptrs[i], heap->ptrs[0]));
-}
-#endif
-
-static
-size_t parent(size_t i)
-{
- return (i - 1) >> 1;
-}
-
-static
-size_t left(size_t i)
-{
- return (i << 1) + 1;
-}
-
-static
-size_t right(size_t i)
-{
- return (i << 1) + 2;
-}
-
-/*
- * Copy of heap->ptrs pointer is invalid after heap_grow.
- */
-static
-int heap_grow(struct ptr_heap *heap, size_t new_len)
-{
- void **new_ptrs;
-
- if (G_LIKELY(heap->alloc_len >= new_len))
- return 0;
-
- heap->alloc_len = bt_max_t(size_t, new_len, heap->alloc_len << 1);
- new_ptrs = calloc(heap->alloc_len, sizeof(void *));
- if (G_UNLIKELY(!new_ptrs))
- return -ENOMEM;
- if (G_LIKELY(heap->ptrs))
- memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *));
- free(heap->ptrs);
- heap->ptrs = new_ptrs;
- return 0;
-}
-
-static
-int heap_set_len(struct ptr_heap *heap, size_t new_len)
-{
- int ret;
-
- ret = heap_grow(heap, new_len);
- if (G_UNLIKELY(ret))
- return ret;
- heap->len = new_len;
- return 0;
-}
-
-int bt_heap_init(struct ptr_heap *heap, size_t alloc_len,
- int gt(void *a, void *b))
-{
- heap->ptrs = NULL;
- heap->len = 0;
- heap->alloc_len = 0;
- heap->gt = gt;
- /*
- * Minimum size allocated is 1 entry to ensure memory allocation
- * never fails within bt_heap_replace_max.
- */
- return heap_grow(heap, bt_max_t(size_t, 1, alloc_len));
-}
-
-void bt_heap_free(struct ptr_heap *heap)
-{
- free(heap->ptrs);
-}
-
-static void heapify(struct ptr_heap *heap, size_t i)
-{
- void **ptrs = heap->ptrs;
- size_t l, r, largest;
-
- for (;;) {
- void *tmp;
-
- l = left(i);
- r = right(i);
- if (l < heap->len && heap->gt(ptrs[l], ptrs[i]))
- largest = l;
- else
- largest = i;
- if (r < heap->len && heap->gt(ptrs[r], ptrs[largest]))
- largest = r;
- if (G_UNLIKELY(largest == i))
- break;
- tmp = ptrs[i];
- ptrs[i] = ptrs[largest];
- ptrs[largest] = tmp;
- i = largest;
- }
- check_heap(heap);
-}
-
-void *bt_heap_replace_max(struct ptr_heap *heap, void *p)
-{
- void *res;
-
- if (G_UNLIKELY(!heap->len)) {
- (void) heap_set_len(heap, 1);
- heap->ptrs[0] = p;
- check_heap(heap);
- return NULL;
- }
-
- /* Replace the current max and heapify */
- res = heap->ptrs[0];
- heap->ptrs[0] = p;
- heapify(heap, 0);
- return res;
-}
-
-int bt_heap_insert(struct ptr_heap *heap, void *p)
-{
- void **ptrs;
- size_t pos;
- int ret;
-
- ret = heap_set_len(heap, heap->len + 1);
- if (G_UNLIKELY(ret))
- return ret;
- ptrs = heap->ptrs;
- pos = heap->len - 1;
- while (pos > 0 && heap->gt(p, ptrs[parent(pos)])) {
- /* Move parent down until we find the right spot */
- ptrs[pos] = ptrs[parent(pos)];
- pos = parent(pos);
- }
- ptrs[pos] = p;
- check_heap(heap);
- return 0;
-}
-
-void *bt_heap_remove(struct ptr_heap *heap)
-{
- switch (heap->len) {
- case 0:
- return NULL;
- case 1:
- (void) heap_set_len(heap, 0);
- return heap->ptrs[0];
- }
- /* Shrink, replace the current max by previous last entry and heapify */
- heap_set_len(heap, heap->len - 1);
- /* len changed. previous last entry is at heap->len */
- return bt_heap_replace_max(heap, heap->ptrs[heap->len]);
-}
-
-void *bt_heap_cherrypick(struct ptr_heap *heap, void *p)
-{
- size_t pos, len = heap->len;
-
- for (pos = 0; pos < len; pos++)
- if (G_UNLIKELY(heap->ptrs[pos] == p))
- goto found;
- return NULL;
-found:
- if (G_UNLIKELY(heap->len == 1)) {
- (void) heap_set_len(heap, 0);
- check_heap(heap);
- return heap->ptrs[0];
- }
- /* Replace p with previous last entry and heapify. */
- heap_set_len(heap, heap->len - 1);
- /* len changed. previous last entry is at heap->len */
- heap->ptrs[pos] = heap->ptrs[heap->len];
- heapify(heap, pos);
- return p;
-}
-
-int bt_heap_copy(struct ptr_heap *dst, struct ptr_heap *src)
-{
- int ret;
-
- ret = bt_heap_init(dst, src->alloc_len, src->gt);
- if (ret < 0)
- goto end;
-
- ret = heap_set_len(dst, src->len);
- if (ret < 0)
- goto end;
-
- memcpy(dst->ptrs, src->ptrs, src->len * sizeof(void *));
-
-end:
- return ret;
-}
projects / babeltrace.git / commitdiff
