Add SampleMap and use it in SparseHistogram

base/metrics/sample_map.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.
+
+// SampleMap implements HistogramSamples interface. It is used by the
+// SparseHistogram class to store samples.
+
+#ifndef BASE_METRICS_SAMPLE_MAP_H_
+#define BASE_METRICS_SAMPLE_MAP_H_
+
+#include <map>
+
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram_base.h"
+#include "base/metrics/histogram_samples.h"
+
+namespace base {
+
+class BASE_EXPORT_PRIVATE SampleMap : public HistogramSamples {
+ public:
+  SampleMap();
+  virtual ~SampleMap();
+
+  // HistogramSamples implementation:
+  virtual void Accumulate(HistogramBase::Sample value,
+                          HistogramBase::Count count) OVERRIDE;
+  virtual HistogramBase::Count GetCount(
+      HistogramBase::Sample value) const OVERRIDE;
+  virtual HistogramBase::Count TotalCount() const OVERRIDE;
+  virtual scoped_ptr<SampleCountIterator> Iterator() const OVERRIDE;
+
+  void ResetRedundantCount(HistogramBase::Count count);
+
+ protected:
+  virtual bool AddSubtractImpl(
+      SampleCountIterator* iter,
+      HistogramSamples::Operator op) OVERRIDE;  // |op| is ADD or SUBTRACT.
+
+ private:
+  std::map<HistogramBase::Sample, HistogramBase::Count> sample_counts_;
+
+  DISALLOW_COPY_AND_ASSIGN(SampleMap);
+};
+
+class BASE_EXPORT_PRIVATE SampleMapIterator : public SampleCountIterator {
+ public:
+  typedef std::map<HistogramBase::Sample, HistogramBase::Count>
+      SampleToCountMap;

[Ilya Sherman, 2012/10/05 03:29:24]

nit: Do we really want a public typedef?  If we move these classes into the
base::metrics:: namespace, we'd have std::map<Sample, Count>, which isn't
terribly long.

[kaiwang, 2012/10/05 04:02:38]

This is exactly what I suggested to Jim

[jar (doing other things), 2012/10/05 16:55:19]

I agree the "rightish" thing is to indeed create a base::metrics namespace, and
move a lot of stuff into that namespace. That is a bigger change, and should not
be mixed with this CL.  

For now, it was really bothering me to have to read as many as three lines (that
should be one) because this was not shorter... so making it a typedef even in
this class seemed quite helpful (my style perspective... which I know offends
your sensibilities a bit... and also leaves Kai wandering between two code
reviewers).

If/when we move into metrics, we can all be happy.... but for now, I really
think line wraps to 3 lines in a declaration was too much.

On 2012/10/05 03:29:24, Ilya Sherman wrote:

+
+  SampleMapIterator(const SampleToCountMap& sample_counts);
+  virtual ~SampleMapIterator();
+
+  // SampleCountIterator implementation:
+  virtual bool Done() const OVERRIDE;
+  virtual void Next() OVERRIDE;
+  virtual void Get(HistogramBase::Sample* min,
+                   HistogramBase::Sample* max,
+                   HistogramBase::Count* count) const OVERRIDE;
+ private:
+  SampleToCountMap::const_iterator iter_;
+  const SampleToCountMap::const_iterator end_;
+};
+
+}  // namespace base
+
+#endif  // BASE_METRICS_SAMPLE_MAP_H_