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// 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/gtest_prod_util.h"
#include "base/lazy_instance.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.
static bool IsActive();
// Register, or add a new histogram to the collection of statistics. If an
// identically named histogram is already registered, then the argument
// |histogram| will deleted. The returned value is always the registered
// histogram (either the argument, or the pre-existing registered histogram).
static HistogramBase* RegisterOrDeleteDuplicate(HistogramBase* histogram);
// Register, or add a new BucketRanges. If an identically BucketRanges is
// already registered, then the argument |ranges| will deleted. The returned
// value is always the registered BucketRanges (either the argument, or the
// pre-existing one).
static const BucketRanges* RegisterOrDeleteDuplicateRanges(
const BucketRanges* ranges);
// Methods for appending histogram data to a string. Only histograms which
// have |query| as a substring are written to |output| (an empty string will
// process all registered histograms).
static void WriteHTMLGraph(const std::string& query, std::string* output);
static void WriteGraph(const std::string& query, std::string* output);
// Returns the histograms with |query| as a substring as JSON text (an empty
// |query| will process all registered histograms).
static std::string ToJSON(const std::string& query);
// Method for extracting histograms which were marked for use by UMA.
static void GetHistograms(Histograms* output);
// Method for extracting BucketRanges used by all histograms registered.
static void GetBucketRanges(std::vector<const BucketRanges*>* output);
// 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);
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<HistogramNameRef, HistogramBase*> HistogramMap;
// 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 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_
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