Using histograms for timing statistics.

  Histogram class and test cases added.
  Modified make file to add test cases and class file.
  Added a guard to avoid race condition in Cumulative logger that
  was possible race between Addlogger and Dump() functions.

Change-Id: I060a0d65648c7120963856624e7008c0aa681eb7
diff --git a/src/base/timing_logger.h b/src/base/timing_logger.h
new file mode 100644
index 0000000..d3f7ef4
--- /dev/null
+++ b/src/base/timing_logger.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_SRC_TIMING_LOGGER_H_
+#define ART_SRC_TIMING_LOGGER_H_
+
+#include "base/histogram.h"
+#include "base/macros.h"
+#include "base/mutex.h"
+
+#include <string>
+#include <vector>
+
+namespace art {
+
+class CumulativeLogger;
+
+class TimingLogger {
+ public:
+  explicit TimingLogger(const std::string &name, bool precise);
+  void AddSplit(const std::string &label);
+  void Dump(std::ostream &os) const;
+  void Reset();
+  uint64_t GetTotalNs() const;
+
+ protected:
+  std::string name_;
+  bool precise_;
+  std::vector<uint64_t> times_;
+  std::vector<std::string> labels_;
+
+  friend class CumulativeLogger;
+};
+
+class CumulativeLogger {
+
+ public:
+
+  explicit CumulativeLogger(const std::string &name);
+  void prepare_stats();
+  ~CumulativeLogger();
+  void Start();
+  void End();
+  void Reset();
+  void Dump(std::ostream &os) LOCKS_EXCLUDED(lock_);
+  uint64_t GetTotalNs() const;
+  void SetName(const std::string &name);
+  void AddLogger(const TimingLogger &logger) LOCKS_EXCLUDED(lock_);
+
+ private:
+
+  void AddPair(const std::string &label, uint64_t delta_time)
+      EXCLUSIVE_LOCKS_REQUIRED(lock_);
+  void DumpHistogram(std::ostream &os) EXCLUSIVE_LOCKS_REQUIRED(lock_);
+  uint64_t GetTotalTime() const;
+  static const uint64_t kAdjust = 1000;
+  std::vector<Histogram<uint64_t> *> histograms_ GUARDED_BY(lock_);
+  std::string name_;
+  mutable Mutex lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
+  size_t index_ GUARDED_BY(lock_);
+  size_t iterations_ GUARDED_BY(lock_);
+
+  DISALLOW_COPY_AND_ASSIGN(CumulativeLogger);
+};
+
+}  // namespace art
+
+#endif  // ART_SRC_TIMING_LOGGER_H_