// Copyright (c) 2011 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_STATS_COUNTERS_H_
#define BASE_METRICS_STATS_COUNTERS_H_
#include <string>
#include "base/base_export.h"
#include "base/compiler_specific.h"
#include "base/metrics/stats_table.h"
#include "base/time/time.h"
namespace base {
// StatsCounters are dynamically created values which can be tracked in
// the StatsTable. They are designed to be lightweight to create and
// easy to use.
//
// Since StatsCounters can be created dynamically by name, there is
// a hash table lookup to find the counter in the table. A StatsCounter
// object can be created once and used across multiple threads safely.
//
// Example usage:
// {
// StatsCounter request_count("RequestCount");
// request_count.Increment();
// }
//
// Note that creating counters on the stack does work, however creating
// the counter object requires a hash table lookup. For inner loops, it
// may be better to create the counter either as a member of another object
// (or otherwise outside of the loop) for maximum performance.
//
// Internally, a counter represents a value in a row of a StatsTable.
// The row has a 32bit value for each process/thread in the table and also
// a name (stored in the table metadata).
//
// NOTE: In order to make stats_counters usable in lots of different code,
// avoid any dependencies inside this header file.
//
//------------------------------------------------------------------------------
// Define macros for ease of use. They also allow us to change definitions
// as the implementation varies, or depending on compile options.
//------------------------------------------------------------------------------
// First provide generic macros, which exist in production as well as debug.
#define STATS_COUNTER(name, delta) do { \
base::StatsCounter counter(name); \
counter.Add(delta); \
} while (0)
#define SIMPLE_STATS_COUNTER(name) STATS_COUNTER(name, 1)
#define RATE_COUNTER(name, duration) do { \
base::StatsRate hit_count(name); \
hit_count.AddTime(duration); \
} while (0)
// Define Debug vs non-debug flavors of macros.
#ifndef NDEBUG
#define DSTATS_COUNTER(name, delta) STATS_COUNTER(name, delta)
#define DSIMPLE_STATS_COUNTER(name) SIMPLE_STATS_COUNTER(name)
#define DRATE_COUNTER(name, duration) RATE_COUNTER(name, duration)
#else // NDEBUG
#define DSTATS_COUNTER(name, delta) do {} while (0)
#define DSIMPLE_STATS_COUNTER(name) do {} while (0)
#define DRATE_COUNTER(name, duration) do {} while (0)
#endif // NDEBUG
//------------------------------------------------------------------------------
// StatsCounter represents a counter in the StatsTable class.
class BASE_EXPORT StatsCounter {
public:
// Create a StatsCounter object.
explicit StatsCounter(const std::string& name);
virtual ~StatsCounter();
// Sets the counter to a specific value.
void Set(int value);
// Increments the counter.
void Increment() {
Add(1);
}
virtual void Add(int value);
// Decrements the counter.
void Decrement() {
Add(-1);
}
void Subtract(int value) {
Add(-value);
}
// Is this counter enabled?
// Returns false if table is full.
bool Enabled() {
return GetPtr() != NULL;
}
int value() {
int* loc = GetPtr();
if (loc) return *loc;
return 0;
}
protected:
StatsCounter();
// Returns the cached address of this counter location.
int* GetPtr();
std::string name_;
// The counter id in the table. We initialize to -1 (an invalid value)
// and then cache it once it has been looked up. The counter_id is
// valid across all threads and processes.
int32 counter_id_;
};
// A StatsCounterTimer is a StatsCounter which keeps a timer during
// the scope of the StatsCounterTimer. On destruction, it will record
// its time measurement.
class BASE_EXPORT StatsCounterTimer : protected StatsCounter {
public:
// Constructs and starts the timer.
explicit StatsCounterTimer(const std::string& name);
virtual ~StatsCounterTimer();
// Start the timer.
void Start();
// Stop the timer and record the results.
void Stop();
// Returns true if the timer is running.
bool Running();
// Accept a TimeDelta to increment.
virtual void AddTime(TimeDelta time);
protected:
// Compute the delta between start and stop, in milliseconds.
void Record();
TimeTicks start_time_;
TimeTicks stop_time_;
};
// A StatsRate is a timer that keeps a count of the number of intervals added so
// that several statistics can be produced:
// min, max, avg, count, total
class BASE_EXPORT StatsRate : public StatsCounterTimer {
public:
// Constructs and starts the timer.
explicit StatsRate(const std::string& name);
virtual ~StatsRate();
virtual void Add(int value) OVERRIDE;
private:
StatsCounter counter_;
StatsCounter largest_add_;
};
// Helper class for scoping a timer or rate.
template<class T> class StatsScope {
public:
explicit StatsScope<T>(T& timer)
: timer_(timer) {
timer_.Start();
}
~StatsScope() {
timer_.Stop();
}
void Stop() {
timer_.Stop();
}
private:
T& timer_;
};
} // namespace base
#endif // BASE_METRICS_STATS_COUNTERS_H_