Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #include "webrtc/modules/rtp_rtcp/source/time_util.h"
      12             : 
      13             : #include <algorithm>
      14             : 
      15             : namespace webrtc {
      16             : namespace {
      17             : // TODO(danilchap): Make generic, optimize and move to base.
      18           0 : inline int64_t DivideRoundToNearest(int64_t x, uint32_t y) {
      19             :   // Caller ensure x is positive by converting unsigned value into it.
      20             :   // So this Divide doesn't need to handle negative argument case.
      21           0 :   return (x + y / 2) / y;
      22             : }
      23             : }  // namespace
      24             : 
      25           0 : int64_t CompactNtpRttToMs(uint32_t compact_ntp_interval) {
      26             :   // Interval to convert expected to be positive, e.g. rtt or delay.
      27             :   // Because interval can be derived from non-monotonic ntp clock,
      28             :   // it might become negative that is indistinguishable from very large values.
      29             :   // Since very large rtt/delay are less likely than non-monotonic ntp clock,
      30             :   // those values consider to be negative and convert to minimum value of 1ms.
      31           0 :   if (compact_ntp_interval > 0x80000000)
      32           0 :     return 1;
      33             :   // Convert to 64bit value to avoid multiplication overflow.
      34           0 :   int64_t value = static_cast<int64_t>(compact_ntp_interval);
      35             :   // To convert to milliseconds need to divide by 2^16 to get seconds,
      36             :   // then multiply by 1000 to get milliseconds. To avoid float operations,
      37             :   // multiplication and division swapped.
      38           0 :   int64_t ms = DivideRoundToNearest(value * 1000, 1 << 16);
      39             :   // Rtt value 0 considered too good to be true and increases to 1.
      40           0 :   return std::max<int64_t>(ms, 1);
      41             : }
      42             : }  // namespace webrtc