Add heap debug option, fix heap.

[lttng-modules.git] / lib / prio_heap / prio_heap.c

diff --git a/lib/prio_heap/prio_heap.c b/lib/prio_heap/prio_heap.c
index 29af3033812f98ba770ee28b855959b8dca82bfd..f6b8158055c5b13da34fde1978ecb92a83396db6 100644 (file)
--- a/lib/prio_heap/prio_heap.c
+++ b/lib/prio_heap/prio_heap.c
@@ -19,22 +19,35 @@
 #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;
 }
 
 /*
@@ -96,26 +109,24 @@ 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)
@@ -125,6 +136,7 @@ void *heap_replace_max(struct ptr_heap *heap, void *p)
        if (!heap->len) {
                (void) heap_set_len(heap, 1);
                heap->ptrs[0] = p;
+               check_heap(heap);
                return NULL;
        }
 
@@ -145,28 +157,14 @@ int heap_insert(struct ptr_heap *heap, void *p)
        if (ret)
                return ret;
        ptrs = heap->ptrs;
-       /* Add the element to the end */
-       ptrs[heap->len - 1] = p;
        pos = heap->len - 1;
-       /* Bubble it up to the appropriate position. */
-       for (;;) {
-               if (pos > 0 && heap->gt(ptrs[pos], ptrs[parent(pos)])) {
-                       void *tmp;
-
-                       /* Need to exchange */
-                       tmp = ptrs[pos];
-                       ptrs[pos] = ptrs[parent(pos)];
-                       ptrs[parent(pos)] = tmp;
-                       pos = parent(pos);
-                       /*
-                        * No need to rebalance: if we are larger than
-                        * our parent, we are necessarily larger than
-                        * its other child.
-                        */
-               } else {
-                       break;
-               }
+       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;
 }
 
@@ -181,7 +179,8 @@ void *heap_remove(struct ptr_heap *heap)
        }
        /* Shrink, replace the current max by previous last entry and heapify */
        heap_set_len(heap, heap->len - 1);
-       return heap_replace_max(heap, 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)
@@ -195,11 +194,13 @@ void *heap_cherrypick(struct ptr_heap *heap, void *p)
 found:
        if (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);
-       heap->ptrs[pos] = heap->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;
 }