1 /* 2 * Copyright (c) 2015 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 #ifndef SYSTEM_WRAPPERS_INCLUDE_NTP_TIME_H_ 11 #define SYSTEM_WRAPPERS_INCLUDE_NTP_TIME_H_ 12 13 #include <cmath> 14 #include <cstdint> 15 #include <limits> 16 17 #include "rtc_base/numerics/safe_conversions.h" 18 19 namespace webrtc { 20 21 class NtpTime { 22 public: 23 static constexpr uint64_t kFractionsPerSecond = 0x100000000; NtpTime()24 NtpTime() : value_(0) {} NtpTime(uint64_t value)25 explicit NtpTime(uint64_t value) : value_(value) {} NtpTime(uint32_t seconds,uint32_t fractions)26 NtpTime(uint32_t seconds, uint32_t fractions) 27 : value_(seconds * kFractionsPerSecond + fractions) {} 28 29 NtpTime(const NtpTime&) = default; 30 NtpTime& operator=(const NtpTime&) = default; uint64_t()31 explicit operator uint64_t() const { return value_; } 32 Set(uint32_t seconds,uint32_t fractions)33 void Set(uint32_t seconds, uint32_t fractions) { 34 value_ = seconds * kFractionsPerSecond + fractions; 35 } Reset()36 void Reset() { value_ = 0; } 37 ToMs()38 int64_t ToMs() const { 39 static constexpr double kNtpFracPerMs = 4.294967296E6; // 2^32 / 1000. 40 const double frac_ms = static_cast<double>(fractions()) / kNtpFracPerMs; 41 return 1000 * static_cast<int64_t>(seconds()) + 42 static_cast<int64_t>(frac_ms + 0.5); 43 } 44 // NTP standard (RFC1305, section 3.1) explicitly state value 0 is invalid. Valid()45 bool Valid() const { return value_ != 0; } 46 seconds()47 uint32_t seconds() const { 48 return rtc::dchecked_cast<uint32_t>(value_ / kFractionsPerSecond); 49 } fractions()50 uint32_t fractions() const { 51 return rtc::dchecked_cast<uint32_t>(value_ % kFractionsPerSecond); 52 } 53 54 private: 55 uint64_t value_; 56 }; 57 58 inline bool operator==(const NtpTime& n1, const NtpTime& n2) { 59 return static_cast<uint64_t>(n1) == static_cast<uint64_t>(n2); 60 } 61 inline bool operator!=(const NtpTime& n1, const NtpTime& n2) { 62 return !(n1 == n2); 63 } 64 65 // Converts `int64_t` milliseconds to Q32.32-formatted fixed-point seconds. 66 // Performs clamping if the result overflows or underflows. Int64MsToQ32x32(int64_t milliseconds)67inline int64_t Int64MsToQ32x32(int64_t milliseconds) { 68 // TODO(bugs.webrtc.org/10893): Change to use `rtc::saturated_cast` once the 69 // bug has been fixed. 70 double result = 71 std::round(milliseconds * (NtpTime::kFractionsPerSecond / 1000.0)); 72 73 // Explicitly cast values to double to avoid implicit conversion warnings 74 // The conversion of the std::numeric_limits<int64_t>::max() triggers 75 // -Wimplicit-int-float-conversion warning in clang 10.0.0 without explicit 76 // cast 77 if (result <= static_cast<double>(std::numeric_limits<int64_t>::min())) { 78 return std::numeric_limits<int64_t>::min(); 79 } 80 81 if (result >= static_cast<double>(std::numeric_limits<int64_t>::max())) { 82 return std::numeric_limits<int64_t>::max(); 83 } 84 85 return rtc::dchecked_cast<int64_t>(result); 86 } 87 88 // Converts `int64_t` milliseconds to UQ32.32-formatted fixed-point seconds. 89 // Performs clamping if the result overflows or underflows. Int64MsToUQ32x32(int64_t milliseconds)90inline uint64_t Int64MsToUQ32x32(int64_t milliseconds) { 91 // TODO(bugs.webrtc.org/10893): Change to use `rtc::saturated_cast` once the 92 // bug has been fixed. 93 double result = 94 std::round(milliseconds * (NtpTime::kFractionsPerSecond / 1000.0)); 95 96 // Explicitly cast values to double to avoid implicit conversion warnings 97 // The conversion of the std::numeric_limits<int64_t>::max() triggers 98 // -Wimplicit-int-float-conversion warning in clang 10.0.0 without explicit 99 // cast 100 if (result <= static_cast<double>(std::numeric_limits<uint64_t>::min())) { 101 return std::numeric_limits<uint64_t>::min(); 102 } 103 104 if (result >= static_cast<double>(std::numeric_limits<uint64_t>::max())) { 105 return std::numeric_limits<uint64_t>::max(); 106 } 107 108 return rtc::dchecked_cast<uint64_t>(result); 109 } 110 111 // Converts Q32.32-formatted fixed-point seconds to `int64_t` milliseconds. Q32x32ToInt64Ms(int64_t q32x32)112inline int64_t Q32x32ToInt64Ms(int64_t q32x32) { 113 return rtc::dchecked_cast<int64_t>( 114 std::round(q32x32 * (1000.0 / NtpTime::kFractionsPerSecond))); 115 } 116 117 // Converts UQ32.32-formatted fixed-point seconds to `int64_t` milliseconds. UQ32x32ToInt64Ms(uint64_t q32x32)118inline int64_t UQ32x32ToInt64Ms(uint64_t q32x32) { 119 return rtc::dchecked_cast<int64_t>( 120 std::round(q32x32 * (1000.0 / NtpTime::kFractionsPerSecond))); 121 } 122 123 } // namespace webrtc 124 #endif // SYSTEM_WRAPPERS_INCLUDE_NTP_TIME_H_ 125