Filtered events.

chrome/common/extensions/value_counter.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_COMMON_EXTENSIONS_VALUE_COUNTER_H_
+#define CHROME_COMMON_EXTENSIONS_VALUE_COUNTER_H_
+#pragma once
+
+#include "base/memory/linked_ptr.h"
+
+#include <vector>
+
+namespace base {
+class Value;
+}
+
+namespace extensions {
+
+// Keeps a running count of Values, like map<Value, int>. Adding / removing
+// values increments / decrements the count associated with a given Value.
+//
+// Add() and Remove() are linear in the number of Values in the ValueCounter,
+// because there is no operator<() defined on Value, so we must iterate to find
+// whether a Value is equal to an existing one.
+class ValueCounter {
+ public:
+  ValueCounter();
+  ~ValueCounter();
+
+  // Adds |value| to the set and returns how many equal values are in the set
+  // after. Does not take ownership of |value|. In the case where a Value equal
+  // to |value| doesn't already exist in this map, this function makes a
+  // DeepCopy() of |value|.
+  int Add(const base::Value& value);
+
+  // Removes |value| from the set and returns how many equal values are in
+  // the set after.
+  int Remove(const base::Value& value);
+
+  // Same as Add() but only performs the add if the value isn't present.
+  int AddIfMissing(const base::Value& value);
+
+ private:
+  class Entry {
+   public:
+    explicit Entry(const base::Value& value);
+    ~Entry();
+
+    int Increment();
+    int Decrement();
+
+    const base::Value* value() const { return value_.get(); }
+    int count() const { return count_; }
+
+   private:
+    linked_ptr<base::Value> value_;
+    int count_;
+
+    DISALLOW_COPY_AND_ASSIGN(Entry);
+  };
+  typedef std::vector<linked_ptr<Entry> > EntryList;
+
+  int AddImpl(const base::Value& value, bool increment);
+
+  EntryList entries_;
+
+  DISALLOW_COPY_AND_ASSIGN(ValueCounter);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_COMMON_EXTENSIONS_VALUE_COUNTER_H_