X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=lib%2Fprio_heap%2Fprio_heap.c;h=f6b8158055c5b13da34fde1978ecb92a83396db6;hb=0b6d2ab30831e9385a4796d45012ebb749a63cae;hp=58d5d6ae9df05a112026196b252a204cbd432407;hpb=c8d547f07b97ba82c3a8275af6fbbe248b061855;p=lttng-modules.git

diff --git a/lib/prio_heap/prio_heap.c b/lib/prio_heap/prio_heap.c
index 58d5d6ae..f6b81580 100644
--- a/lib/prio_heap/prio_heap.c
+++ b/lib/prio_heap/prio_heap.c
@@ -19,24 +19,40 @@
 #include <linux/slab.h>
 #include "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++)
+		WARN_ON_ONCE(!heap->gt(heap->ptrs[i], heap->ptrs[0]));
+}
+#endif
+
 static
 size_t parent(size_t i)
 {
-	return i >> 1;
+	return (i -1) >> 1;
 }
 
 static
 size_t left(size_t i)
 {
-	return i << 1;
+	return (i << 1) + 1;
 }
 
 static
 size_t right(size_t i)
 {
-	return (i << 1) + 1;
+	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)
 {
@@ -93,94 +109,98 @@ static void heapify(struct ptr_heap *heap, size_t i)
 	size_t l, r, largest;
 
 	for (;;) {
+		void *tmp;
+
 		l = left(i);
 		r = right(i);
-		if (l <= heap->len && ptrs[l] > ptrs[i])
+		if (l < heap->len && heap->gt(ptrs[l], ptrs[i]))
 			largest = l;
 		else
 			largest = i;
-		if (r <= heap->len && ptrs[r] > ptrs[largest])
+		if (r < heap->len && heap->gt(ptrs[r], ptrs[largest]))
 			largest = r;
-		if (largest != i) {
-			void *tmp;
-
-			tmp = ptrs[i];
-			ptrs[i] = ptrs[largest];
-			ptrs[largest] = tmp;
-			i = largest;
-			continue;
-		} else {
+		if (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;
-	void **ptrs = heap->ptrs;
 
 	if (!heap->len) {
 		(void) heap_set_len(heap, 1);
-		ptrs[0] = p;
+		heap->ptrs[0] = p;
+		check_heap(heap);
 		return NULL;
 	}
 
 	/* Replace the current max and heapify */
-	res = ptrs[0];
-	ptrs[0] = p;
+	res = heap->ptrs[0];
+	heap->ptrs[0] = p;
 	heapify(heap, 0);
 	return res;
 }
 
 int heap_insert(struct ptr_heap *heap, void *p)
 {
-	void **ptrs = heap->ptrs;
+	void **ptrs;
+	size_t pos;
 	int ret;
 
 	ret = heap_set_len(heap, heap->len + 1);
 	if (ret)
 		return ret;
-	/* Add the element to the end */
-	ptrs[heap->len - 1] = p;
-	/* rebalance */
-	heapify(heap, 0);
+	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)
 {
-	void **ptrs = heap->ptrs;
-
 	switch (heap->len) {
 	case 0:
 		return NULL;
 	case 1:
 		(void) heap_set_len(heap, 0);
-		return ptrs[0];
+		return heap->ptrs[0];
 	}
 	/* Shrink, replace the current max by previous last entry and heapify */
 	heap_set_len(heap, heap->len - 1);
-	return heap_replace_max(heap, ptrs[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)
 {
-	void **ptrs = heap->ptrs;
 	size_t pos, len = heap->len;
 
 	for (pos = 0; pos < len; pos++)
-		if (ptrs[pos] == p)
+		if (heap->ptrs[pos] == p)
 			goto found;
 	return NULL;
 found:
 	if (heap->len == 1) {
 		(void) heap_set_len(heap, 0);
-		return ptrs[0];
+		check_heap(heap);
+		return heap->ptrs[0];
 	}
 	/* Replace p with previous last entry and heapify. */
 	heap_set_len(heap, heap->len - 1);
-	ptrs[pos] = ptrs[heap->len - 1];
+	/* len changed. previous last entry is at heap->len */
+	heap->ptrs[pos] = heap->ptrs[heap->len];
 	heapify(heap, pos);
 	return p;
 }