Serialize/Deserialize support in HistogramBase

base/metrics/histogram_base.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 BASE_METRICS_HISTOGRAM_BASE_H_
 #define BASE_METRICS_HISTOGRAM_BASE_H_
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 
+class Pickle;
+class PickleIterator;
+
 namespace base {
 
 class DictionaryValue;
+class HistogramBase;
 class HistogramSamples;
 class ListValue;
 
 ////////////////////////////////////////////////////////////////////////////////
 // These enums are used to facilitate deserialization of histograms from other
 // processes into the browser. If you create another class that inherits from
 // HistogramBase, add new histogram types and names below.
 
 enum BASE_EXPORT HistogramType {
   HISTOGRAM,
   LINEAR_HISTOGRAM,
   BOOLEAN_HISTOGRAM,
   CUSTOM_HISTOGRAM,
   SPARSE_HISTOGRAM,
 };
 
 std::string HistogramTypeToString(HistogramType type);
 
+// Create or find existing histogram that matches the pickled info.
+// Returns NULL if the pickled data has problems.
+HistogramBase* DeserializeHistogramInfo(PickleIterator* iter);

[Ilya Sherman, 2013/01/09 05:48:37]

nit: Please tuck this into an anonymous namespace in the implementation file.

[kaiwang, 2013/01/10 23:02:24]

It's used by unittest.
Although this is not directly used by client, I think it at least makes the
histogram more feature complete... Don't see the harm putting it here...

+
+// Create or find existing histogram and add the samples from pickle.
+bool DeserializeHistogramAndAddSamples(PickleIterator* iter);

[Ilya Sherman, 2013/01/09 05:48:37]

nit: Why does this function need a return value?  histogram_synchronizer doesn't
seem to make use of the value, and I'm not 100% sure what true vs. false
means...

[kaiwang, 2013/01/10 23:02:24]

Done.

+
 ////////////////////////////////////////////////////////////////////////////////
 
 class BASE_EXPORT HistogramBase {
  public:
   typedef int Sample;  // Used for samples.
   typedef int Count;   // Used to count samples.
 
   static const Sample kSampleType_MAX;  // INT_MAX
 
   enum Flags {
@@ skipping 17 matching lines @@
   std::string histogram_name() const { return histogram_name_; }
 
   // Operations with Flags enum.
   int32 flags() const { return flags_; }
   void SetFlags(int32 flags);
   void ClearFlags(int32 flags);
 
   virtual HistogramType GetHistogramType() const = 0;
 
   // Whether the histogram has construction arguments as parameters specified.
-  // For histograms that don't have the concept of minimum, maximum or
-  // bucket_count, this function always returns false.
+  // For histograms that don't have the concept of |minimum|, |maximum| or
+  // |bucket_count|, this function always returns false.
   virtual bool HasConstructionArguments(Sample minimum,
                                         Sample maximum,
                                         size_t bucket_count) const = 0;
 
   virtual void Add(Sample value) = 0;
 
+  virtual void AddSamples(const HistogramSamples& samples) = 0;
+  virtual bool AddSamplesFromPickle(PickleIterator* iter) = 0;
+
+  // Serialize the histogram info into |pickle|.
+  // Note. This only serializes the construction arguments of the histogram, but

[Ilya Sherman, 2013/01/09 05:48:37]

nit: "Note." -> "Note:"; "but not" -> "but does not"

[kaiwang, 2013/01/10 23:02:24]

Done.

+  // not serialize the samples.
+  bool SerializeInfo(Pickle* pickle) const;
+
   // Snapshot the current complete set of sample data.
   // Override with atomic/locked snapshot if needed.
   virtual scoped_ptr<HistogramSamples> SnapshotSamples() const = 0;
 
   // The following methods provide graphical histogram displays.
   virtual void WriteHTMLGraph(std::string* output) const = 0;
   virtual void WriteAscii(std::string* output) const = 0;
 
   // Produce a JSON representation of the histogram. This is implemented with
   // the help of GetParameters and GetCountAndBucketData; overwrite them to
   // customize the output.
   void WriteJSON(std::string* output) const;
 
 protected:
+  // Subclasses should implement this function to make SerializeInfo work.
+  virtual bool SerializeInfoImpl(Pickle* pickle) const = 0;
+
   // Writes information about the construction parameters in |params|.
   virtual void GetParameters(DictionaryValue* params) const = 0;
 
   // Writes information about the current (non-empty) buckets and their sample
   // counts to |buckets| and the total sample count to |count|.
   virtual void GetCountAndBucketData(Count* count,
                                      ListValue* buckets) const = 0;
  private:
   const std::string histogram_name_;
   int32 flags_;
 
   DISALLOW_COPY_AND_ASSIGN(HistogramBase);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_BASE_H_