1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef CHROME_COMMON_EXTENSIONS_VALUE_COUNTER_H_ 6 #define CHROME_COMMON_EXTENSIONS_VALUE_COUNTER_H_ 7 8 #include "base/memory/linked_ptr.h" 9 10 #include <vector> 11 12 namespace base { 13 class Value; 14 } 15 16 namespace extensions { 17 18 // Keeps a running count of Values, like map<Value, int>. Adding / removing 19 // values increments / decrements the count associated with a given Value. 20 // 21 // Add() and Remove() are linear in the number of Values in the ValueCounter, 22 // because there is no operator<() defined on Value, so we must iterate to find 23 // whether a Value is equal to an existing one. 24 class ValueCounter { 25 public: 26 ValueCounter(); 27 ~ValueCounter(); 28 29 // Adds |value| to the set and returns how many equal values are in the set 30 // after. Does not take ownership of |value|. In the case where a Value equal 31 // to |value| doesn't already exist in this map, this function makes a 32 // DeepCopy() of |value|. 33 int Add(const base::Value& value); 34 35 // Removes |value| from the set and returns how many equal values are in 36 // the set after. 37 int Remove(const base::Value& value); 38 39 // Same as Add() but only performs the add if the value isn't present. 40 int AddIfMissing(const base::Value& value); 41 42 private: 43 class Entry { 44 public: 45 explicit Entry(const base::Value& value); 46 ~Entry(); 47 48 int Increment(); 49 int Decrement(); 50 value()51 const base::Value* value() const { return value_.get(); } count()52 int count() const { return count_; } 53 54 private: 55 linked_ptr<base::Value> value_; 56 int count_; 57 58 DISALLOW_COPY_AND_ASSIGN(Entry); 59 }; 60 typedef std::vector<linked_ptr<Entry> > EntryList; 61 62 int AddImpl(const base::Value& value, bool increment); 63 64 EntryList entries_; 65 66 DISALLOW_COPY_AND_ASSIGN(ValueCounter); 67 }; 68 69 } // namespace extensions 70 71 #endif // CHROME_COMMON_EXTENSIONS_VALUE_COUNTER_H_ 72