Update //base to chromium 9659b08ea5a34f889dc4166217f438095ddc10d2

base/metrics/statistics_recorder.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.
 
 // StatisticsRecorder holds all Histograms and BucketRanges that are used by
 // Histograms in the system. It provides a general place for
 // Histograms/BucketRanges to register, and supports a global API for accessing
 // (i.e., dumping, or graphing) the data.
 
 #ifndef BASE_METRICS_STATISTICS_RECORDER_H_
 #define BASE_METRICS_STATISTICS_RECORDER_H_
 
 #include <list>
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/lazy_instance.h"
+#include "base/metrics/histogram_base.h"
 
 namespace base {
 
 class BucketRanges;
-class HistogramBase;
 class Lock;
 
 class BASE_EXPORT StatisticsRecorder {
  public:
   typedef std::vector<HistogramBase*> Histograms;
 
   // Initializes the StatisticsRecorder system. Safe to call multiple times.
   static void Initialize();
 
   // Find out if histograms can now be registered into our list.
@@ skipping 31 matching lines @@
   // Find a histogram by name. It matches the exact name. This method is thread
   // safe.  It returns NULL if a matching histogram is not found.
   static HistogramBase* FindHistogram(const std::string& name);
 
   // GetSnapshot copies some of the pointers to registered histograms into the
   // caller supplied vector (Histograms). Only histograms which have |query| as
   // a substring are copied (an empty string will process all registered
   // histograms).
   static void GetSnapshot(const std::string& query, Histograms* snapshot);
 
+  typedef base::Callback<void(HistogramBase::Sample)> OnSampleCallback;
+
+  // SetCallback sets the callback to notify when a new sample is recorded on
+  // the histogram referred to by |histogram_name|. The call to this method can
+  // be be done before or after the histogram is created. This method is thread
+  // safe. The return value is whether or not the callback was successfully set.
+  static bool SetCallback(const std::string& histogram_name,
+                          const OnSampleCallback& callback);
+
+  // ClearCallback clears any callback set on the histogram referred to by
+  // |histogram_name|. This method is thread safe.
+  static void ClearCallback(const std::string& histogram_name);
+
+  // FindCallback retrieves the callback for the histogram referred to by
+  // |histogram_name|, or a null callback if no callback exists for this
+  // histogram. This method is thread safe.
+  static OnSampleCallback FindCallback(const std::string& histogram_name);
+
  private:
+  // HistogramNameRef holds a weak const ref to the name field of the associated
+  // Histogram object, allowing re-use of the underlying string storage for the
+  // map keys. The wrapper is required as using "const std::string&" as the key
+  // results in compile errors.
+  struct HistogramNameRef {
+    explicit HistogramNameRef(const std::string& name) : name_(name){};
+
+    // Operator < is necessary to use this type as a std::map key.
+    bool operator<(const HistogramNameRef& other) const {
+      return name_ < other.name_;
+    }
+
+    // Weak, owned by the associated Histogram object.
+    const std::string& name_;
+  };
+
   // We keep all registered histograms in a map, from name to histogram.
-  typedef std::map<std::string, HistogramBase*> HistogramMap;
+  typedef std::map<HistogramNameRef, HistogramBase*> HistogramMap;
+
+  // We keep a map of callbacks to histograms, so that as histograms are
+  // created, we can set the callback properly.
+  typedef std::map<std::string, OnSampleCallback> CallbackMap;
 
   // We keep all |bucket_ranges_| in a map, from checksum to a list of
   // |bucket_ranges_|.  Checksum is calculated from the |ranges_| in
   // |bucket_ranges_|.
   typedef std::map<uint32, std::list<const BucketRanges*>*> RangesMap;
 
   friend struct DefaultLazyInstanceTraits<StatisticsRecorder>;
   friend class HistogramBaseTest;
   friend class HistogramSnapshotManagerTest;
   friend class HistogramTest;
   friend class JsonPrefStoreTest;
   friend class SparseHistogramTest;
   friend class StatisticsRecorderTest;
   FRIEND_TEST_ALL_PREFIXES(HistogramDeltaSerializationTest,
                            DeserializeHistogramAndAddSamples);
 
   // The constructor just initializes static members. Usually client code should
   // use Initialize to do this. But in test code, you can friend this class and
   // call destructor/constructor to get a clean StatisticsRecorder.
   StatisticsRecorder();
   ~StatisticsRecorder();
 
   static void DumpHistogramsToVlog(void* instance);
 
   static HistogramMap* histograms_;
+  static CallbackMap* callbacks_;
   static RangesMap* ranges_;
 
   // Lock protects access to above maps.
   static base::Lock* lock_;
 
   DISALLOW_COPY_AND_ASSIGN(StatisticsRecorder);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_STATISTICS_RECORDER_H_