57 lines
2.0 KiB
C++
57 lines
2.0 KiB
C++
// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "cast/streaming/ntp_time.h"
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#include "util/osp_logging.h"
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namespace openscreen {
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namespace cast {
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namespace {
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// The number of seconds between 1 January 1900 and 1 January 1970.
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constexpr NtpSeconds kTimeBetweenNtpEpochAndUnixEpoch{INT64_C(2208988800)};
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} // namespace
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NtpTimeConverter::NtpTimeConverter(Clock::time_point now,
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std::chrono::seconds since_unix_epoch)
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: start_time_(now),
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since_ntp_epoch_(
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std::chrono::duration_cast<NtpSeconds>(since_unix_epoch) +
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kTimeBetweenNtpEpochAndUnixEpoch) {}
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NtpTimeConverter::~NtpTimeConverter() = default;
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NtpTimestamp NtpTimeConverter::ToNtpTimestamp(
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Clock::time_point time_point) const {
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const Clock::duration time_since_start = time_point - start_time_;
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const auto whole_seconds =
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std::chrono::duration_cast<NtpSeconds>(time_since_start);
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const auto remainder =
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std::chrono::duration_cast<NtpFraction>(time_since_start - whole_seconds);
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return AssembleNtpTimestamp(since_ntp_epoch_ + whole_seconds, remainder);
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}
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Clock::time_point NtpTimeConverter::ToLocalTime(NtpTimestamp timestamp) const {
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auto ntp_seconds = NtpSecondsPart(timestamp);
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// Year 2036 wrap-around check: If the NTP timestamp appears to be a
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// point-in-time before 1970, assume the 2036 wrap-around has occurred, and
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// adjust to compensate.
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if (ntp_seconds <= kTimeBetweenNtpEpochAndUnixEpoch) {
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constexpr NtpSeconds kNtpSecondsPerEra{INT64_C(1) << 32};
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ntp_seconds += kNtpSecondsPerEra;
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}
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const auto whole_seconds = ntp_seconds - since_ntp_epoch_;
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const auto seconds_since_start =
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Clock::to_duration(whole_seconds) + start_time_;
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const auto remainder = Clock::to_duration(NtpFractionPart(timestamp));
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return seconds_since_start + remainder;
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}
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} // namespace cast
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} // namespace openscreen
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