import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

tools/memory-profiler/CompactTraceTable.h

@@ -0,0 +1,116 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef memory_profiler_CompactTraceTable_h
+#define memory_profiler_CompactTraceTable_h
+
+#include "mozilla/HashFunctions.h"
+
+#include "nsDataHashtable.h"
+#include "nsTArray.h"
+
+namespace mozilla {
+
+struct TrieNode final
+{
+  uint32_t parentIdx;
+  uint32_t nameIdx;
+  bool operator==(const TrieNode t) const
+  {
+    return parentIdx == t.parentIdx && nameIdx == t.nameIdx;
+  }
+  uint32_t Hash() const
+  {
+    return HashGeneric(parentIdx, nameIdx);
+  }
+};
+
+// This class maps a Node of type T to its parent's index in the
+// map. When serializing, the map is traversed and put into an ordered
+// array of Nodes.
+template<typename KeyClass, typename T>
+class NodeIndexMap final
+{
+public:
+  uint32_t Insert(const T& e)
+  {
+    uint32_t index = mMap.Count();
+    if (!mMap.Get(e, &index)) {
+      mMap.Put(e, index);
+    }
+    return index;
+  }
+
+  nsTArray<T> Serialize() const
+  {
+    nsTArray<T> v;
+    v.SetLength(mMap.Count());
+    for (auto iter = mMap.ConstIter(); !iter.Done(); iter.Next()) {
+      v[iter.Data()] = iter.Key();
+    }
+    return v;
+  }
+
+  uint32_t Size() const
+  {
+    return mMap.Count();
+  }
+
+  void Clear()
+  {
+    mMap.Clear();
+  }
+private:
+  nsDataHashtable<KeyClass, uint32_t> mMap;
+};
+
+// Backtraces are stored in a trie to save spaces.
+// Function names are stored in an unique table and TrieNodes contain indexes
+// into that table.
+// The trie is implemented with a hash table; children are stored in
+// traces[TrieNode{parent node index, branch/function name index}].
+class CompactTraceTable final
+{
+public:
+  CompactTraceTable()
+  {
+    mNames.Insert(nsAutoCString("(unknown)"));
+    mTraces.Insert(TrieNode{0, 0});
+  }
+
+  nsTArray<nsCString> GetNames() const
+  {
+    return mNames.Serialize();
+  }
+
+  nsTArray<TrieNode> GetTraces() const
+  {
+    return mTraces.Serialize();
+  }
+
+  // Returns an ID to a stacktrace.
+  uint32_t Insert(const nsTArray<nsCString>& aRawStacktrace)
+  {
+    uint32_t parent = 0;
+    for (auto& frame: aRawStacktrace) {
+      parent = mTraces.Insert(TrieNode{parent, mNames.Insert(frame)});
+    }
+    return parent;
+  }
+
+  void Reset()
+  {
+    mNames.Clear();
+    mTraces.Clear();
+  }
+private:
+  NodeIndexMap<nsCStringHashKey, nsCString> mNames;
+  NodeIndexMap<nsGenericHashKey<TrieNode>, TrieNode> mTraces;
+};
+
+} // namespace mozilla
+
+#endif // memory_profiler_CompactTraceTable_h