text: /*
   *  Copyright 2005 The WebRTC Project Authors. All rights reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #ifndef RTC_BASE_TIME_UTILS_H_
  #define RTC_BASE_TIME_UTILS_H_
  
  #include <stdint.h>
  #include <time.h>
  #include <string>
  
  #include "rtc_base/checks.h"
  #include "rtc_base/strings/string_builder.h"
  
  namespace rtc {
  
  static const int64_t kNumMillisecsPerSec = INT64_C(1000);
  static const int64_t kNumMicrosecsPerSec = INT64_C(1000000);
  static const int64_t kNumNanosecsPerSec = INT64_C(1000000000);
  
  static const int64_t kNumMicrosecsPerMillisec =
      kNumMicrosecsPerSec / kNumMillisecsPerSec;
  static const int64_t kNumNanosecsPerMillisec =
      kNumNanosecsPerSec / kNumMillisecsPerSec;
  static const int64_t kNumNanosecsPerMicrosec =
      kNumNanosecsPerSec / kNumMicrosecsPerSec;
  
  // TODO(honghaiz): Define a type for the time value specifically.
  
  class ClockInterface {
   public:
    virtual ~ClockInterface() {}
    virtual int64_t TimeNanos() const = 0;
  };
  
  // Sets the global source of time. This is useful mainly for unit tests.
  //
  // Returns the previously set ClockInterface, or nullptr if none is set.
  //
  // Does not transfer ownership of the clock. SetClockForTesting(nullptr)
  // should be called before the ClockInterface is deleted.
  //
  // This method is not thread-safe; it should only be used when no other thread
  // is running (for example, at the start/end of a unit test, or start/end of
  // main()).
  //
  // TODO(deadbeef): Instead of having functions that access this global
  // ClockInterface, we may want to pass the ClockInterface into everything
  // that uses it, eliminating the need for a global variable and this function.
  ClockInterface* SetClockForTesting(ClockInterface* clock);
  
  // Returns previously set clock, or nullptr if no custom clock is being used.
  ClockInterface* GetClockForTesting();
  
  #if defined(WINUWP)
  // Synchronizes the current clock based upon an NTP server's epoch in
  // milliseconds.
  void SyncWithNtp(int64_t time_from_ntp_server_ms);
  #endif  // defined(WINUWP)
  
  // Returns the actual system time, even if a clock is set for testing.
  // Useful for timeouts while using a test clock, or for logging.
  int64_t SystemTimeNanos();
  int64_t SystemTimeMillis();
  
  // Returns the current time in milliseconds in 32 bits.
  uint32_t Time32();
  
  // Returns the current time in milliseconds in 64 bits.
  int64_t TimeMillis();
  // Deprecated. Do not use this in any new code.
  inline int64_t Time() {
    return TimeMillis();
  }
  
  // Returns the current time in microseconds.
  int64_t TimeMicros();
  
  // Returns the current time in nanoseconds.
  int64_t TimeNanos();
  
  // Returns a future timestamp, 'elapsed' milliseconds from now.
  int64_t TimeAfter(int64_t elapsed);
  
  // Number of milliseconds that would elapse between 'earlier' and 'later'
  // timestamps.  The value is negative if 'later' occurs before 'earlier'.
  int64_t TimeDiff(int64_t later, int64_t earlier);
  int32_t TimeDiff32(uint32_t later, uint32_t earlier);
  
  // The number of milliseconds that have elapsed since 'earlier'.
  inline int64_t TimeSince(int64_t earlier) {
    return TimeMillis() - earlier;
  }
  
  // The number of milliseconds that will elapse between now and 'later'.
  inline int64_t TimeUntil(int64_t later) {
    return later - TimeMillis();
  }
  
  class TimestampWrapAroundHandler {
   public:
    TimestampWrapAroundHandler();
  
    int64_t Unwrap(uint32_t ts);
  
   private:
    uint32_t last_ts_;
    int64_t num_wrap_;
  };
  
  // Convert from tm, which is relative to 1900-01-01 00:00 to number of
  // seconds from 1970-01-01 00:00 ("epoch"). Don't return time_t since that
  // is still 32 bits on many systems.
  int64_t TmToSeconds(const tm& tm);
  
  // Return the number of microseconds since January 1, 1970, UTC.
  // Useful mainly when producing logs to be correlated with other
  // devices, and when the devices in question all have properly
  // synchronized clocks.
  //
  // Note that this function obeys the system's idea about what the time
  // is. It is not guaranteed to be monotonic; it will jump in case the
  // system time is changed, e.g., by some other process calling
  // settimeofday. Always use rtc::TimeMicros(), not this function, for
  // measuring time intervals and timeouts.
  int64_t TimeUTCMicros();
  
  // Return the number of milliseconds since January 1, 1970, UTC.
  // See above.
  int64_t TimeUTCMillis();
  
  // Interval of time from the range [min, max] inclusive.
  class IntervalRange {
   public:
    IntervalRange() : min_(0), max_(0) {}
    IntervalRange(int min, int max) : min_(min), max_(max) {
      RTC_DCHECK_LE(min, max);
    }
  
    int min() const { return min_; }
    int max() const { return max_; }
  
    std::string ToString() const {
      rtc::StringBuilder ss;
      ss << "[" << min_ << "," << max_ << "]";
      return ss.Release();
    }
  
    bool operator==(const IntervalRange& o) const {
      return min_ == o.min_ && max_ == o.max_;
    }
  
    bool operator!=(const IntervalRange& o) const { return !operator==(o); }
  
   private:
    int min_;
    int max_;
  };
  
  }  // namespace rtc
  
  #endif  // RTC_BASE_TIME_UTILS_H_
  