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fix to drift in usecTimestampNow() caused when computer sleeps

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This commit is contained in:
ZappoMan 2014-11-21 13:33:53 -08:00
parent 9c9381e57e
commit bd2adf08e3
1 changed files with 39 additions and 20 deletions
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59
libraries/shared/src/SharedUtil.cpp
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@ -46,31 +46,50 @@ quint64 usecTimestampNow(bool wantDebug) {
TIME_REFERENCE = QDateTime::currentMSecsSinceEpoch() * 1000; // ms to usec
timestampTimer.start();
usecTimestampNowIsInitialized = true;
} else {
// We've seen the QElapsedTimer begin to introduce dramatic errors if it's been
// continuously running for a long time. So we will periodically reset it.
const quint64 SECS_TO_NSECS = 1000000000;
const quint64 RESET_AFTER_ELAPSED_SECS = 60 * 60; // 1 hour: 60 minutes * 60 seconds
const quint64 RESET_AFTER_ELAPSED_NSECS = RESET_AFTER_ELAPSED_SECS * SECS_TO_NSECS;
const quint64 nsecsElapsed = timestampTimer.nsecsElapsed();
if (nsecsElapsed > RESET_AFTER_ELAPSED_NSECS) {
quint64 msecsElapsed = timestampTimer.restart();
quint64 usecsElapsed = nsecsElapsed / 1000; // nsec to usec
TIME_REFERENCE += usecsElapsed;
if (wantDebug) {
qDebug() << "usecTimestampNow() - resetting QElapsedTimer. ";
qDebug() << " RESET_AFTER_ELAPSED_NSECS:" << RESET_AFTER_ELAPSED_NSECS;
qDebug() << " nsecsElapsed:" << nsecsElapsed;
qDebug() << " msecsElapsed:" << msecsElapsed;
qDebug() << " usecsElapsed:" << usecsElapsed;
}
}
}
quint64 now;
quint64 nsecsElapsed = timestampTimer.nsecsElapsed();
quint64 usecsElapsed = nsecsElapsed / 1000; // nsec to usec
quint64 now = TIME_REFERENCE + usecsElapsed + ::usecTimestampNowAdjust;
// QElapsedTimer may not advance if the CPU has gone to sleep. In which case it
// will begin to deviate from real time. We detect that here, and reset if necessary
quint64 msecsCurrentTime = QDateTime::currentMSecsSinceEpoch();
quint64 msecsEstimate = (TIME_REFERENCE + usecsElapsed) / 1000; // usecs to msecs
int possibleSkew = msecsEstimate - msecsCurrentTime;
const int TOLERANCE = 10000; // up to 10 seconds of skew is tolerated
if (abs(possibleSkew) > TOLERANCE) {
// reset our TIME_REFERENCE and timer
TIME_REFERENCE = QDateTime::currentMSecsSinceEpoch() * 1000; // ms to usec
timestampTimer.restart();
now = TIME_REFERENCE + ::usecTimestampNowAdjust;
if (wantDebug) {
qDebug() << "usecTimestampNow() - resetting QElapsedTimer. ";
qDebug() << " msecsCurrentTime:" << msecsCurrentTime;
qDebug() << " msecsEstimate:" << msecsEstimate;
qDebug() << " possibleSkew:" << possibleSkew;
qDebug() << " TOLERANCE:" << TOLERANCE;
qDebug() << " nsecsElapsed:" << nsecsElapsed;
qDebug() << " usecsElapsed:" << usecsElapsed;
QDateTime currentLocalTime = QDateTime::currentDateTime();
quint64 msecsNow = now / 1000; // usecs to msecs
QDateTime nowAsString;
nowAsString.setMSecsSinceEpoch(msecsNow);
qDebug() << " now:" << now;
qDebug() << " msecsNow:" << msecsNow;
qDebug() << " nowAsString:" << nowAsString.toString("yyyy-MM-dd hh:mm:ss.zzz");
qDebug() << " currentLocalTime:" << currentLocalTime.toString("yyyy-MM-dd hh:mm:ss.zzz");
}
} else {
now = TIME_REFERENCE + usecsElapsed + ::usecTimestampNowAdjust;
}
if (wantDebug) {
QDateTime currentLocalTime = QDateTime::currentDateTime();