The Int64ShrlMod32 function performs a right logical shift operation on an unsigned 64-bit integer value. The function provides improved shifting code for right logical shifts where the shift count is in the range 0 - 31.
DWORDLONG Int64ShrlMod32(
|
DWORDLONG Value, |
// specifies unsigned 64-bit integer to shift right logically |
|
DWORD ShiftCount |
// specifies a shift count in the range 0 - 31 |
|
); |
The return value is the unsigned 64-bit integer result of the right logical shift operation.
The shift count is the number of bit positions that the value’s bits move.
In a right logical shift operation on an unsigned value, the value’s bits move to the right, and vacated bits on the left side of the value are set to zero.
A compiler can generate optimal code for a right logical shift operation when the shift count is a constant. However, if the shift count is a variable whose range of values is unknown, the compiler must assume the worst case, leading to non-optimal code: code that calls a subroutine, or code that is inline but branches. By restricting the shift count to the range 0 - 31, the Int64ShrlMod32 function lets the compiler generate optimal or near-optimal code.
Please note that the Int64ShrlMod32 function’s Value parameter and return value are 64-bit values, not LARGE_INTEGER structures.