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#ifndef IMPALA_UTIL_PROGRESS_UPDATER_H
#define IMPALA_UTIL_PROGRESS_UPDATER_H

#include <string>
#include <boost/cstdint.hpp>

#include "common/atomic.h"

namespace impala {

/// Utility class to update progress. This is split out so a different
/// logging level can be set for these updates (GLOG_module)
/// This class is thread safe after Init() is called.
/// Example usage:
///   ProgressUpdater updater;
///   updater.Init("Task", 100, 10);  // 100 items, print every 10%
///   updater.Update(15);  // 15 done, prints 15%
///   updater.Update(3);   // 18 done, doesn't print
///   update.Update(5);    // 23 done, prints 23%
class ProgressUpdater {
 public:

  ProgressUpdater();

  /// Initialize this ProgressUpdater with:
  /// 'label' - label that is printed with each update.
  /// 'total' - maximum number of work items
  /// 'update_period' - how often the progress is printed expressed as a percentage
  void Init(const std::string& label, int64_t total, int update_period = 1);

  /// Sets the GLOG level for this progress updater. By default, this will use 2 but
  /// objects can override it.
  void set_logging_level(int level) { logging_level_ = level; }

  /// 'delta' more of the work has been complete. Will potentially output to
  /// VLOG_PROGRESS. Init() must be called before Update().
  void Update(int64_t delta);

  /// Returns true if all tasks are done.
  bool done() const { return num_complete() >= total_; }

  int64_t total() const { return total_; }
  int64_t num_complete() const { return num_complete_.Load(); }
  int64_t remaining() const { return total() - num_complete(); }

  /// Returns a string representation of the current progress
  std::string ToString() const;

 private:
  /// Label printed with each update.
  std::string label_;

  /// GLOG level for updates.
  int logging_level_;

  /// Total number of work items. -1 before Init().
  int64_t total_;

  /// Number of percentage points between outputs.
  int update_period_;

  /// Number of completed work items.
  AtomicInt64 num_complete_;

  /// Percentage when the last output was generated.
  AtomicInt32 last_output_percentage_;
};

}

#endif