added conversion between epicsTime and win32 FILETIME

2002-09-04 16:30:37 +00:00
parent f5cbac744e
commit 6ec7ac0e16
9 changed files with 224 additions and 86 deletions
--- a/src/libCom/osi/epicsTime.cpp
+++ b/src/libCom/osi/epicsTime.cpp
@@ -418,6 +418,104 @@ epicsTime::epicsTime (const aitTimeStamp &ts)
    *this = epicsTime (this->secPastEpoch+secAdj, this->nSec+nSecAdj);
 }

+static const FILETIME epicsEpochInFileTime = { 0x18d64000, 0x01b41e2a };
+
+static inline bool fileTimeGreaterThanOrEqual ( const FILETIME & lhs, const FILETIME & rhs ) 
+{
+    if ( lhs.dwHighDateTime > rhs.dwHighDateTime ) {
+        return true;
+    }
+    else if ( lhs.dwHighDateTime < rhs.dwHighDateTime ) {
+        return false;
+    }
+    else if ( lhs.dwLowDateTime >= rhs.dwLowDateTime ) {
+        return true;
+    }
+    return false;
+}
+
+epicsTime::operator _FILETIME () const
+{
+    static const DWORD dwordMax = 0xffffffff;
+    static const double ticksPerLowWord = 
+        static_cast < double > ( dwordMax ) + 1;
+    static const double ftNanoSecPerTick = 100;
+    static const double ftTicksPerSec = 1e7;
+
+    // compute the ticks past the epics epoch in file time ticks
+    double ftTicks = this->secPastEpoch * ftTicksPerSec + this->nSec / ftNanoSecPerTick;
+    FILETIME ftTicksPastEpicsEpoch;
+    ftTicksPastEpicsEpoch.dwHighDateTime = static_cast < DWORD > ( ftTicks / ticksPerLowWord );
+    double lowPart = ftTicks - ftTicksPastEpicsEpoch.dwHighDateTime * ticksPerLowWord;
+    ftTicksPastEpicsEpoch.dwLowDateTime = static_cast < DWORD > ( lowPart );
+
+    // add the EPICS epoch offset
+    FILETIME result;
+    result.dwHighDateTime = 
+        epicsEpochInFileTime.dwHighDateTime + ftTicksPastEpicsEpoch.dwHighDateTime;
+    if ( epicsEpochInFileTime.dwLowDateTime  > dwordMax - ftTicksPastEpicsEpoch.dwLowDateTime ) {
+        // carry
+        result.dwHighDateTime++; 
+        double tmp = epicsEpochInFileTime.dwLowDateTime;
+        tmp += ftTicksPastEpicsEpoch.dwLowDateTime;
+        result.dwLowDateTime = static_cast < DWORD > ( tmp - dwordMax );
+    }
+    else {
+        result.dwLowDateTime = 
+            epicsEpochInFileTime.dwLowDateTime + ftTicksPastEpicsEpoch.dwLowDateTime;
+    }
+    return result;
+}
+
+epicsTime::epicsTime ( const _FILETIME & ts )
+{
+    static const DWORD dwordMax = 0xffffffff;
+
+    if ( fileTimeGreaterThanOrEqual ( ts , epicsEpochInFileTime ) ) {
+        // remove epics epoch offset from the incoming file time
+        FILETIME ftTicksPastEpicsEpoch;
+        ftTicksPastEpicsEpoch.dwHighDateTime = 
+            ts.dwHighDateTime - epicsEpochInFileTime.dwHighDateTime;
+        if ( ts.dwLowDateTime >= epicsEpochInFileTime.dwLowDateTime ) {
+            ftTicksPastEpicsEpoch.dwLowDateTime = 
+                ts.dwLowDateTime - epicsEpochInFileTime.dwLowDateTime;
+        }
+        else {
+            // borrow 
+            ftTicksPastEpicsEpoch.dwHighDateTime--;
+            ftTicksPastEpicsEpoch.dwLowDateTime = 
+                ( dwordMax - epicsEpochInFileTime.dwLowDateTime ) 
+                + ts.dwLowDateTime + 1;
+        }
+
+        // adjust between file time ticks and EPICS time ticks
+        static const double ticksPerLowWord = 
+            static_cast < double > ( dwordMax ) + 1;
+        static const double ftTicksPerSec = 1e7;
+        static const double epicsTicksPerSec = 1e9;
+        double ftTicksPastEpicsEpochFP = 
+            ticksPerLowWord * ftTicksPastEpicsEpoch.dwHighDateTime +
+            ftTicksPastEpicsEpoch.dwLowDateTime;
+        double epicsTicksPastEpicsEpoch = ftTicksPastEpicsEpochFP *
+            ( epicsTicksPerSec / ftTicksPerSec );
+        this->secPastEpoch = static_cast < unsigned long > 
+                        ( epicsTicksPastEpicsEpoch / nSecPerSec );
+        double nSec = epicsTicksPastEpicsEpoch - 
+                this->secPastEpoch * epicsTime::nSecPerSec;
+        this->nSec = static_cast < unsigned long > ( nSec );
+    }
+    else {
+	    this->secPastEpoch = 0;
+        this->nSec = 0;
+    }
+}
+
+epicsTime & epicsTime::operator = ( const _FILETIME & rhs )
+{
+    *this = epicsTime ( rhs );
+    return *this;
+}
+
 //
 // epicsTime::ntpTimeStamp ()
 //