Serialize/Deserialize support in HistogramBase

base/metrics/histogram_base.h

Index: base/metrics/histogram_base.h
diff --git a/base/metrics/histogram_base.h b/base/metrics/histogram_base.h
index 302795a73fc7a4072bb4fc26ccb86461a5f790c0..53cb3e9b9400fa76ad7be3ff5eba61f674cf13c0 100644
--- a/base/metrics/histogram_base.h
+++ b/base/metrics/histogram_base.h
@@ -11,9 +11,13 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 
+class Pickle;
+class PickleIterator;
+
 namespace base {
 
 class DictionaryValue;
+class HistogramBase;
 class HistogramSamples;
 class ListValue;
 
@@ -32,6 +36,13 @@ enum BASE_EXPORT HistogramType {
 
 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 {
@@ -69,14 +80,22 @@ class BASE_EXPORT HistogramBase {
   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;
@@ -91,6 +110,9 @@ class BASE_EXPORT HistogramBase {
   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;