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Give up trying to calculat epicsEpochOffset, which is a constant.

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Also fixed incorrect NTP timescale conversion constant.
This commit is contained in:
Andrew Johnson
2008-03-14 20:50:39 +00:00
parent 4deb3a92c9
commit 3a40dddccb
1 changed files with 13 additions and 38 deletions
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src/libCom/osi/epicsTime.cpp
+13 -38
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@@ -49,13 +49,13 @@ static const unsigned nSecPerUSec = 1000u;
static const unsigned nSecPerSec = nSecPerUSec * uSecPerSec;
static const unsigned nSecFracDigits = 9u;
static const unsigned tmEpochYear = 1900;
static const unsigned ansiEpochYear = 1970;
static const unsigned epicsEpochYear = 1990;
static const unsigned epochMonth = 0; // January
static const unsigned epochDayOfTheMonth = 1; // the 1st
// Timescale conversion data
static const unsigned int POSIX_TIME_AT_EPICS_EPOCH = 631152000u;
static const unsigned long NTP_TIME_AT_POSIX_EPOCH = 2208988800ul;
static const unsigned long NTP_TIME_AT_EPICS_EPOCH =
NTP_TIME_AT_POSIX_EPOCH + POSIX_TIME_AT_EPICS_EPOCH;
//
// epicsTime (const unsigned long secIn, const unsigned long nSecIn)
@@ -87,32 +87,9 @@ epicsTimeLoadTimeInit::epicsTimeLoadTimeInit ()
time_t t_one = static_cast<time_t> (1);
this->time_tSecPerTick = difftime (t_one, t_zero);
/* We calculate the difference in seconds between the ANSI and EPICS
* epochs (1970-1-1, 1990-1-1). However mktime() takes a local time
* and adds a timezone-specified Daylight Savings Time offset to the
* result it returns. Luckily we only need the time difference in
* seconds between the two epochs, so the two DST corrections cancel
* each other out. We offset the local time used by 12 hours so the
* ANSI result can never go negative whatever timezone we're in.
*/
struct tm tmEpoch;
tmEpoch.tm_sec = 0;
tmEpoch.tm_min = 0;
tmEpoch.tm_hour = 12;
tmEpoch.tm_mday = epochDayOfTheMonth;
tmEpoch.tm_mon = epochMonth;
tmEpoch.tm_isdst = 0;
tmEpoch.tm_year = ansiEpochYear - tmEpochYear;
time_t ansiEpoch = mktime(&tmEpoch);
assert(ansiEpoch != (time_t) -1);
tmEpoch.tm_year = epicsEpochYear - tmEpochYear;
time_t epicsEpoch = mktime(&tmEpoch);
assert(epicsEpoch != (time_t) -1);
this->epicsEpochOffset = difftime (epicsEpoch, ansiEpoch);
/* Convert our epoch offset into time_t units */
this->epicsEpochOffset =
(double) POSIX_TIME_AT_EPICS_EPOCH / this->time_tSecPerTick;
if (this->time_tSecPerTick == 1.0 &&
this->epicsEpochOffset <= ULONG_MAX &&
@@ -379,10 +356,8 @@ epicsTime::epicsTime (const struct timeval &ts)
this->addNanoSec (ts.tv_usec * nSecPerUSec);
}
// 631152000 (at posix epic) + 2272060800 (btw posix and epics epoch) +
// 15 ( leap seconds )
static const unsigned long epicsEpocSecsPastEpochNTP = 2903212815u;
static const double NTP_FRACTION_DENOMINATOR = (static_cast<double>(0xffffffff) + 1.0);
static const double NTP_FRACTION_DENOMINATOR = 1.0 + 0xffffffff;
struct l_fp { /* NTP time stamp */
epicsUInt32 l_ui; /* sec past NTP epoch */
@@ -395,7 +370,7 @@ struct l_fp { /* NTP time stamp */
epicsTime::operator l_fp () const
{
l_fp ts;
ts.l_ui = this->secPastEpoch + epicsEpocSecsPastEpochNTP;
ts.l_ui = this->secPastEpoch + NTP_TIME_AT_EPICS_EPOCH;
ts.l_uf = static_cast < unsigned long >
( ( this->nSec * NTP_FRACTION_DENOMINATOR ) / nSecPerSec );
return ts;
@@ -406,7 +381,7 @@ epicsTime::operator l_fp () const
//
epicsTime::epicsTime ( const l_fp & ts )
{
this->secPastEpoch = ts.l_ui - epicsEpocSecsPastEpochNTP;
this->secPastEpoch = ts.l_ui - NTP_TIME_AT_EPICS_EPOCH;
this->nSec = static_cast < unsigned long >
( ( ts.l_uf / NTP_FRACTION_DENOMINATOR ) * nSecPerSec );
}
@@ -531,7 +506,7 @@ size_t epicsTime::strftime (
// look for "%0<n>f" at the end (used for fractional second formatting)
char strftimePrefixBuf [256];
bool fracFmtFound;
unsigned long fracWid;
unsigned long fracWid = 0;
pFmt = fracFormatFind (
pFmt,
strftimePrefixBuf, sizeof ( strftimePrefixBuf ),