I am having float value in Variant, Initially this variant is a bstr type. I am using VariantChangeType to change to float type. and then I am getting float value from it and then i am converting into byte vector format.
If variant has float values this works fine. If variant is having INF values, VariantChangeType gets failed. So i am getting 0 from variant.fltVal.
How to Changetype to float if variant having INF or NAN values? I want to get INF or NAN values in float.
Convert(_variant_t varVal,vector<byte> dataArr)
{
HRESULT hr = VariantChangeType( varVal&, &varVal, 0 , VT_R4 );
// Above code is failing if varVal.bstr contains 1.#INF" values
UINT size = 4;
if ( data && dataItem.vt != VT_EMPTY )
{
float value = dataItem.fltVal;
BYTE tmpBuf[4];
me开发者_运维问答mcpy(tmpBuf, &value, sizeof(value));
for( int i = size - 1 ; i >= 0 ; i-- )
{
data->push_back(tmpBuf[i]);
}
retVal = TRUE;
}
}
in pseudo-language:
if ( varVal.bstr.contains("1.#INF" ) ) {
// assign plus infinity to your variant see http://stackoverflow.com/questions/2538339/infinity-in-msvc
} else if ( varVal.bstr.contains("-1.#INF" ) ) {
// assign minus infinity to your variant see http://stackoverflow.com/questions/2538339/infinity-in-msvc
} else if ( varVal.bstr.contains("NaN" ) {
// assign NaN to your variant see http://stackoverflow.com/questions/235386/using-nan-in-c
} else {
// your original working code for regular float values
}
Please pay attention because it is a fragile solution: it relies on the string representations of infinity and NaN and maybe Microsoft can change them without warning.
This is an unofficial yet authoritative information by Raymond Chen:
What does -1.#IND mean?: A survey of how the Visual C runtime library prints special floating point values, even if it is not related to VARIANT
.
Output Meaning 1#INF Positive infinity -1#INF Negative infinity 1#SNAN Positive signaling NaN -1#SNAN Negative signaling NaN 1#QNAN Positive quiet NaN -1#QNAN Negative quiet NaN 1#IND Positive indefinite NaN -1#IND Negative indefinite NaN
An official information is printf
Type Field Characters.
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