Test Data Group
Reports if a value is a safe zero, a zero with an extreme exponent, a subnormal, a safe nonzero, a normal with no leading zero, or an infinity or NaN and if the value is positive or negative. Safe means leading zero digits and a non-extreme exponent. A subnormal can appear as either an extreme nonzero or safe nonzero. The exact meaning of some masks depends on the particular CPU model.
long _d64_test_data_group (_Decimal64, unsigned long mask);
long _d128_test_data_group (_Decimal128, unsigned long mask);
One of the values listed in Table 3.