+/*
+ * prio_heap.c
+ *
+ * Static-sized priority heap containing pointers. Based on CLRS,
+ * chapter 6.
+ *
+ * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ */
+
+#include <babeltrace/prio_heap.h>
+#include <babeltrace/babeltrace-internal.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#ifndef max_t
+#define max_t(type, a, b) \
+ ((type) (a) > (type) (b) ? (type) (a) : (type) (b))
+#endif
+
+#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++)
+ assert(!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 (likely(heap->alloc_len >= new_len))
+ return 0;
+
+ heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1);
+ new_ptrs = calloc(heap->alloc_len, sizeof(void *));
+ if (unlikely(!new_ptrs))
+ return -ENOMEM;
+ if (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 (unlikely(ret))
+ return ret;
+ heap->len = new_len;
+ return 0;
+}
+
+int 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 heap_replace_max.
+ */
+ return heap_grow(heap, max_t(size_t, 1, alloc_len));
+}
+
+void 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 (unlikely(largest == i))
+ break;
+ tmp = ptrs[i];
+ ptrs[i] = ptrs[largest];
+ ptrs[largest] = tmp;
+ i = largest;
+ }
+ check_heap(heap);
+}
+
+void *heap_replace_max(struct ptr_heap *heap, void *p)
+{
+ void *res;
+
+ if (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 heap_insert(struct ptr_heap *heap, void *p)
+{
+ void **ptrs;
+ size_t pos;
+ int ret;
+
+ ret = heap_set_len(heap, heap->len + 1);
+ if (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 *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 heap_replace_max(heap, heap->ptrs[heap->len]);
+}
+
+void *heap_cherrypick(struct ptr_heap *heap, void *p)
+{
+ size_t pos, len = heap->len;
+
+ for (pos = 0; pos < len; pos++)
+ if (unlikely(heap->ptrs[pos] == p))
+ goto found;
+ return NULL;
+found:
+ if (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;
+}
projects / babeltrace.git / blobdiff