Fold leaks that are referenced by other leaks

Find leaks that have no references at all, or are only referenced by
other leaks in the same strongly connected component, and hide all
referenced leaks.

Bug: 27208635
Change-Id: Ifbfd14e24e2ba0f8af7c1b887e57f34362720f2d
diff --git a/libmemunreachable/LeakFolding.h b/libmemunreachable/LeakFolding.h
new file mode 100644
index 0000000..e181f27
--- /dev/null
+++ b/libmemunreachable/LeakFolding.h
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LIBMEMUNREACHABLE_LEAK_FOLDING_H_
+#define LIBMEMUNREACHABLE_LEAK_FOLDING_H_
+
+#include "HeapWalker.h"
+
+class LeakFolding {
+ public:
+  LeakFolding(Allocator<void> allocator, HeapWalker& heap_walker)
+   : allocator_(allocator), heap_walker_(heap_walker),
+     leak_map_(allocator), leak_graph_(allocator), leak_scc_(allocator) {}
+
+  bool FoldLeaks();
+
+  struct Leak {
+    const Range range;
+    size_t referenced_count;
+    size_t referenced_size;
+  };
+
+  bool Leaked(allocator::vector<Leak>& leaked, size_t limit,
+      size_t* num_leaks_out, size_t* leak_bytes_out);
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(LeakFolding);
+  Allocator<void> allocator_;
+  HeapWalker& heap_walker_;
+
+  struct SCCInfo {
+   public:
+    Node<SCCInfo> node;
+
+    size_t count;
+    size_t size;
+
+    size_t cuumulative_count;
+    size_t cuumulative_size;
+
+    bool dominator;
+    SCCInfo* accumulator;
+
+    SCCInfo(Allocator<SCCInfo> allocator) : node(this, allocator),
+        count(0), size(0), cuumulative_count(0), cuumulative_size(0),
+        dominator(false), accumulator(nullptr) {}
+   private:
+    SCCInfo(SCCInfo&&) = delete;
+    DISALLOW_COPY_AND_ASSIGN(SCCInfo);
+  };
+
+  struct LeakInfo {
+   public:
+    Node<LeakInfo> node;
+
+    const Range range;
+
+    SCCInfo* scc;
+
+    LeakInfo(const Range& range, Allocator<LeakInfo> allocator)
+        : node(this, allocator), range(range),
+          scc(nullptr) {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(LeakInfo);
+  };
+
+  void ComputeDAG();
+  void AccumulateLeaks(SCCInfo* dominator);
+
+  allocator::map<LeakInfo, Range, compare_range> leak_map_;
+  Graph<LeakInfo> leak_graph_;
+  allocator::vector<Allocator<SCCInfo>::unique_ptr> leak_scc_;
+};
+
+#endif // LIBMEMUNREACHABLE_LEAK_FOLDING_H_