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installed optimization for machines that dont have hardware floating point

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This commit is contained in:
Jeff Hill
2002-05-13 20:59:26 +00:00
parent 05b948519d
commit a09a1f2beb
1 changed files with 52 additions and 16 deletions
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68
src/libCom/osi/epicsTime.cpp
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@@ -68,6 +68,8 @@ public:
double ntpEpochOffset; // seconds
#endif
double time_tSecPerTick; // seconds (both NTP and EPICS use int sec)
unsigned long epicsEpochOffsetAsAnUnsignedLong;
bool useDiffTimeOptimization;
};
static const epicsTimeLoadTimeInit lti;
@@ -115,6 +117,16 @@ epicsTimeLoadTimeInit::epicsTimeLoadTimeInit ()
this->epicsEpochOffset = difftime (epicsEpoch, ansiEpoch) - secWest;
}
if ( this->time_tSecPerTick == 1.0 && this->epicsEpochOffset <= ULONG_MAX &&
this->epicsEpochOffset >= 0 ) {
this->useDiffTimeOptimization = true;
this->epicsEpochOffsetAsAnUnsignedLong = static_cast < unsigned long > ( this->epicsEpochOffset );
}
else {
this->useDiffTimeOptimization = false;
this->epicsEpochOffsetAsAnUnsignedLong = 0;
}
#ifdef NTP_SUPPORT
/* unfortunately, on NT mktime cant calculate a time_t for a date before 1970 */
{
@@ -151,31 +163,49 @@ inline void epicsTime::addNanoSec (long nSecAdj)
//
// epicsTime (const time_t_wrapper &tv)
//
epicsTime::epicsTime (const time_t_wrapper &ansiTimeTicks)
epicsTime::epicsTime ( const time_t_wrapper & ansiTimeTicks )
{
static double uLongMax = static_cast<double> (ULONG_MAX);
double sec;
//
// map time_t, which ansi C defines as some arithmetic type, into type double
// try to directly map time_t into an unsigned long integer because this is
// faster on systems w/o hardware floating point and a simple integer type time_t.
//
sec = ansiTimeTicks.ts * lti.time_tSecPerTick - lti.epicsEpochOffset;
if ( lti.useDiffTimeOptimization ) {
if ( ansiTimeTicks.ts > 0 && ansiTimeTicks.ts <= ULONG_MAX ) {
unsigned long ticks = static_cast < unsigned long > ( ansiTimeTicks.ts );
if ( ticks >= lti.epicsEpochOffsetAsAnUnsignedLong ) {
this->secPastEpoch = ticks - lti.epicsEpochOffsetAsAnUnsignedLong;
}
else {
this->secPastEpoch = ( ULONG_MAX - lti.epicsEpochOffsetAsAnUnsignedLong ) + ticks;
}
this->nSec = 0;
return;
}
}
//
// otherwise map time_t, which ANSI C and POSIX define as any arithmetic type,
// into type double
//
double sec = ansiTimeTicks.ts * lti.time_tSecPerTick - lti.epicsEpochOffset;
//
// map into the the EPICS time stamp range (which allows rollover)
//
if (sec < 0.0) {
if (sec < -uLongMax) {
sec = sec + static_cast<unsigned long>(-sec/uLongMax)*uLongMax;
if ( sec < 0.0 ) {
if ( sec < -uLongMax ) {
sec = sec + static_cast<unsigned long> ( -sec / uLongMax ) * uLongMax;
}
sec += uLongMax;
}
else if (sec > uLongMax) {
sec = sec - static_cast<unsigned long>(sec/uLongMax)*uLongMax;
else if ( sec > uLongMax ) {
sec = sec - static_cast<unsigned long> ( sec / uLongMax ) * uLongMax;
}
this->secPastEpoch = static_cast <unsigned long> (sec);
this->nSec = static_cast <unsigned long> ( (sec-this->secPastEpoch) * nSecPerSec );
this->secPastEpoch = static_cast <unsigned long> ( sec );
this->nSec = static_cast <unsigned long> ( ( sec-this->secPastEpoch ) * nSecPerSec );
}
epicsTime::epicsTime (const epicsTimeStamp &ts)
@@ -222,16 +252,22 @@ void epicsTime::synchronize () {} // depricated
//
epicsTime::operator time_t_wrapper () const
{
double tmp;
time_t_wrapper wrap;
tmp = (this->secPastEpoch + lti.epicsEpochOffset) / lti.time_tSecPerTick;
tmp += (this->nSec / lti.time_tSecPerTick) / nSecPerSec;
if ( lti.useDiffTimeOptimization ) {
if ( this->secPastEpoch < ULONG_MAX - lti.epicsEpochOffset ) {
wrap.ts = static_cast <time_t> ( this->secPastEpoch + lti.epicsEpochOffset );
return wrap;
}
}
//
// map type double into time_t which ansi C defines as some arithmetic type
//
wrap.ts = static_cast <time_t> (tmp);
double tmp = (this->secPastEpoch + lti.epicsEpochOffset) / lti.time_tSecPerTick;
tmp += (this->nSec / lti.time_tSecPerTick) / nSecPerSec;
wrap.ts = static_cast <time_t> ( tmp );
return wrap;
}