modules/include/module_common_types_public.h

/*
 *  Copyright (c) 2017 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 MODULES_INCLUDE_MODULE_COMMON_TYPES_PUBLIC_H_
#define MODULES_INCLUDE_MODULE_COMMON_TYPES_PUBLIC_H_

#include <limits>

#include "absl/types/optional.h"

namespace webrtc {

template <typename U>
inline bool IsNewer(U value, U prev_value) {
  static_assert(!std::numeric_limits<U>::is_signed, "U must be unsigned");
  // kBreakpoint is the half-way mark for the type U. For instance, for a
  // uint16_t it will be 0x8000, and for a uint32_t, it will be 0x8000000.
  constexpr U kBreakpoint = (std::numeric_limits<U>::max() >> 1) + 1;
  // Distinguish between elements that are exactly kBreakpoint apart.
  // If t1>t2 and |t1-t2| = kBreakpoint: IsNewer(t1,t2)=true,
  // IsNewer(t2,t1)=false
  // rather than having IsNewer(t1,t2) = IsNewer(t2,t1) = false.
  if (value - prev_value == kBreakpoint) {
    return value > prev_value;
  }
  return value != prev_value &&
         static_cast<U>(value - prev_value) < kBreakpoint;
}

// NB: Doesn't fulfill strict weak ordering requirements.
//     Mustn't be used as std::map Compare function.
inline bool IsNewerSequenceNumber(uint16_t sequence_number,
                                  uint16_t prev_sequence_number) {
  return IsNewer(sequence_number, prev_sequence_number);
}

// NB: Doesn't fulfill strict weak ordering requirements.
//     Mustn't be used as std::map Compare function.
inline bool IsNewerTimestamp(uint32_t timestamp, uint32_t prev_timestamp) {
  return IsNewer(timestamp, prev_timestamp);
}

inline uint16_t LatestSequenceNumber(uint16_t sequence_number1,
                                     uint16_t sequence_number2) {
  return IsNewerSequenceNumber(sequence_number1, sequence_number2)
             ? sequence_number1
             : sequence_number2;
}

inline uint32_t LatestTimestamp(uint32_t timestamp1, uint32_t timestamp2) {
  return IsNewerTimestamp(timestamp1, timestamp2) ? timestamp1 : timestamp2;
}

}  // namespace webrtc
#endif  // MODULES_INCLUDE_MODULE_COMMON_TYPES_PUBLIC_H_