_bittestandcomplement, _bittestandcomplement64
Microsoft Specific
Generate the btc instruction, which examines bit b of the address a, returns its current value, and sets the bit to its complement.
unsigned char _bittestandcomplement(
long *a,
long b
);
unsigned char _bittestandcomplement64(
__int64 *a,
__int64 b
);
Parameters
- [in, out] a
A pointer to the memory to examine.
- [in] b
The bit position to test.
Return Value
The bit at the position specified.
Requirements
| Intrinsic | Architecture |
|---|---|
_bittestandcomplement |
x86, IPF, x64 |
_bittestandcomplement64 |
IPF, x64 |
Header file <intrin.h>
Remarks
On the IPF architecture, the btc instruction is not available, so this intrinsic is a custom function that imitates the behavior of btc. This custom function might be slower than a hand-written inline function because it includes overhead, such as handling the case where b is negative, that might be unnecessary in specific cases.
This routine is only available as an intrinsic.
Example
// bittestandcomplement.cpp
// processor: x86, IPF, x64
#include <stdio.h>
#include <intrin.h>
#pragma intrinsic(_bittestandcomplement)
#ifdef _M_AMD64
#pragma intrinsic(_bittestandcomplement64)
#endif
int main()
{
long i = 1;
__int64 i64 = 0x1I64;
unsigned char result;
printf("Initial value: %d\n", i);
printf("Testing bit 1\n");
result = _bittestandcomplement(&i, 1);
printf("Value changed to %d, Result: %d\n", i, result);
#ifdef _M_AMD64
printf("Testing bit 0\n");
result = _bittestandcomplement64(&i64, 0);
printf("Value changed to %I64d, Result: %d\n", i64, result);
#endif
}
Sample Output
Initial value: 1
Testing bit 1
Value changed to 3, Result: 0
Testing bit 0
Value changed to 0, Result: 1