hindex: Fix incomplete iteration bug.

hindex_next() make the completely wrong assumption that head nodes within
a bucket were sorted in ascending order by hash.  This commit removes
that assumption.

Also add a test that would have found the problem.

Signed-off-by: ZhengLingyun <konghuarukhr@163.com>
[blp@nicira.com changed how hindex_head_node() is implemented and
 other code details]
Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/lib/hindex.c b/lib/hindex.c
index dc0f1b7..fd4199a 100644 (file)
--- a/lib/hindex.c
+++ b/lib/hindex.c
@@ -287,6 +287,19 @@ hindex_node_with_hash(const struct hindex *hindex, size_t hash)
     return node;
 }
 
+/* Returns the head node in 'hindex' with the given 'hash'.  'hindex' must
+ * contain a head node with the given hash. */
+static struct hindex_node *
+hindex_head_node(const struct hindex *hindex, size_t hash)
+{
+    struct hindex_node *node = hindex->buckets[hash & hindex->mask];
+
+    while (node->hash != hash) {
+        node = node->d;
+    }
+    return node;
+}
+
 static struct hindex_node *
 hindex_next__(const struct hindex *hindex, size_t start)
 {
@@ -312,13 +325,23 @@ hindex_first(const struct hindex *hindex)
  * null pointer if 'node' is the last node in 'hindex'.
  *
  * If the hash index has been reallocated since 'node' was visited, some nodes
- * may be skipped or visited twice.  (Removing 'node' from the hash index does
- * not prevent calling this function, since node->next is preserved, although
- * freeing 'node' of course does.) */
+ * may be skipped or visited twice. */
 struct hindex_node *
 hindex_next(const struct hindex *hindex, const struct hindex_node *node)
 {
-    return (node->s ? node->s
-            : node->d && node->d->hash != node->hash ? node->d
-            : hindex_next__(hindex, (node->hash & hindex->mask) + 1));
+    struct hindex_node *head;
+
+    /* If there's a node with the same hash, return it. */
+    if (node->s) {
+        return node->s;
+    }
+
+    /* If there's another node in the same bucket, return it. */
+    head = hindex_head_node(hindex, node->hash);
+    if (head->d) {
+        return head->d;
+    }
+
+    /* Return the first node in the next (or later) bucket. */
+    return hindex_next__(hindex, (node->hash & hindex->mask) + 1);
 }

diff --git a/tests/test-hindex.c b/tests/test-hindex.c
index 7a3ef72..f0a8b93 100644 (file)
--- a/tests/test-hindex.c
+++ b/tests/test-hindex.c
@@ -178,6 +178,12 @@ mod2_hash(int value)
     return value % 2;
 }
 
+static size_t
+multipart_hash(int value)
+{
+    return (mod4_hash(value) << 16) | (constant_hash(value) & 0xFFFF);
+}
+
 /* Tests basic hindex insertion and deletion. */
 static void
 test_hindex_insert_delete(hash_func *hash)
@@ -298,6 +304,7 @@ run_test(void (*function)(hash_func *))
         mod4_hash,
         mod3_hash,
         mod2_hash,
+        multipart_hash,
     };
     size_t i;