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used a union after reading warnings about potential g++ optimizations

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This commit is contained in:
Jeff Hill
2001-05-22 01:39:35 +00:00
parent 6440ee39e8
commit bc4bd0216e
1 changed files with 76 additions and 26 deletions
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102
src/libCom/osi/os/default/osiWireFormat.h
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@@ -26,7 +26,7 @@
// network byte stream.
//
// this endian test should vanish during optimization
// this endian test will hopefully vanish during optimization
// and therefore be executed only at compile time
inline bool osiLittleEndian ()
{
@@ -34,7 +34,6 @@ inline bool osiLittleEndian ()
epicsUInt32 uint;
epicsUInt8 uchar[4];
} osiWireFormatEndianTest;
osiWireFormatEndianTest.uint = 1;
if ( osiWireFormatEndianTest.uchar[0] == 1 ) {
return true;
@@ -44,41 +43,92 @@ inline bool osiLittleEndian ()
}
}
inline void osiConvertToWireFormat ( const epicsFloat32 &value, unsigned char *pWire )
inline void osiConvertToWireFormat ( const epicsFloat32 &value, epicsUInt8 *pWire )
{
const epicsUInt32 * pValue = reinterpret_cast < const epicsUInt32 * > ( &value );
pWire[0u] = static_cast < unsigned char > ( *pValue >> 24u );
pWire[1u] = static_cast < unsigned char > ( *pValue >> 16u );
pWire[2u] = static_cast < unsigned char > ( *pValue >> 8u );
pWire[3u] = static_cast < unsigned char > ( *pValue >> 0u );
union {
epicsUInt32 utmp;
epicsFloat32 ftmp;
};
ftmp = value;
pWire[0] = static_cast < unsigned char > ( utmp >> 24u );
pWire[1] = static_cast < unsigned char > ( utmp >> 16u );
pWire[2] = static_cast < unsigned char > ( utmp >> 8u );
pWire[3] = static_cast < unsigned char > ( utmp >> 0u );
}
inline void osiConvertToWireFormat ( const epicsFloat64 &value, unsigned char *pWire )
inline void osiConvertToWireFormat ( const epicsFloat64 &value, epicsUInt8 *pWire )
{
const epicsUInt32 *pValue = reinterpret_cast < const epicsUInt32 *> ( &value );
const epicsUInt32 * pValue = reinterpret_cast < const epicsUInt32 *> ( &value );
union {
epicsUInt8 btmp[8];
epicsFloat64 ftmp;
};
ftmp = value;
// this endian test should vanish during optimization
if ( osiLittleEndian () ) {
// little endian
pWire[0u] = static_cast < unsigned char > ( pValue[1] >> 24u );
pWire[1u] = static_cast < unsigned char > ( pValue[1] >> 16u );
pWire[2u] = static_cast < unsigned char > ( pValue[1] >> 8u );
pWire[3u] = static_cast < unsigned char > ( pValue[1] >> 0u );
pWire[4u] = static_cast < unsigned char > ( pValue[0] >> 24u );
pWire[5u] = static_cast < unsigned char > ( pValue[0] >> 16u );
pWire[6u] = static_cast < unsigned char > ( pValue[0] >> 8u );
pWire[7u] = static_cast < unsigned char > ( pValue[0] >> 0u );
pWire[0] = btmp[7];
pWire[1] = btmp[6];
pWire[2] = btmp[5];
pWire[3] = btmp[4];
pWire[4] = btmp[3];
pWire[5] = btmp[2];
pWire[6] = btmp[1];
pWire[7] = btmp[0];
}
else {
// big endian
pWire[0u] = static_cast < unsigned char > ( pValue[0] >> 24u );
pWire[1u] = static_cast < unsigned char > ( pValue[0] >> 16u );
pWire[2u] = static_cast < unsigned char > ( pValue[0] >> 8u );
pWire[3u] = static_cast < unsigned char > ( pValue[0] >> 0u );
pWire[4u] = static_cast < unsigned char > ( pValue[1] >> 24u );
pWire[5u] = static_cast < unsigned char > ( pValue[1] >> 16u );
pWire[6u] = static_cast < unsigned char > ( pValue[1] >> 8u );
pWire[7u] = static_cast < unsigned char > ( pValue[1] >> 0u );
pWire[0] = btmp[0];
pWire[1] = btmp[1];
pWire[2] = btmp[2];
pWire[3] = btmp[3];
pWire[4] = btmp[4];
pWire[5] = btmp[5];
pWire[6] = btmp[6];
pWire[7] = btmp[7];
}
}
inline void osiConvertFromWireFormat ( epicsFloat32 &value, epicsUInt8 *pWire )
{
union {
epicsUInt32 utmp;
epicsFloat32 ftmp;
};
utmp = pWire[0] << 24u;
utmp |= pWire[1] << 16u;
utmp |= pWire[2] << 8u;
utmp |= pWire[3] << 0u;
value = ftmp;
}
inline void osiConvertFromWireFormat ( epicsFloat64 &value, epicsUInt8 *pWire )
{
union {
epicsUInt8 btmp[8];
epicsFloat64 ftmp;
};
if ( osiLittleEndian () ) {
btmp[7] = pWire[0];
btmp[6] = pWire[1];
btmp[5] = pWire[2];
btmp[4] = pWire[3];
btmp[3] = pWire[4];
btmp[2] = pWire[5];
btmp[1] = pWire[6];
btmp[0] = pWire[7];
}
else {
btmp[0] = pWire[0];
btmp[1] = pWire[1];
btmp[2] = pWire[2];
btmp[3] = pWire[3];
btmp[4] = pWire[4];
btmp[5] = pWire[5];
btmp[6] = pWire[6];
btmp[7] = pWire[7];
}
value = ftmp;
}
#endif // osiWireFormat