| title | _bittestandset, _bittestandset64 | Microsoft Docs | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ms.custom | ||||||||||||||
| ms.date | 11/04/2016 | |||||||||||||
| ms.reviewer | ||||||||||||||
| ms.suite | ||||||||||||||
| ms.technology |
|
|||||||||||||
| ms.tgt_pltfrm | ||||||||||||||
| ms.topic | article | |||||||||||||
| f1_keywords |
|
|||||||||||||
| dev_langs |
|
|||||||||||||
| helpviewer_keywords |
|
|||||||||||||
| ms.assetid | 6d6c8670-fea0-4c1c-9aad-2bb842715203 | |||||||||||||
| caps.latest.revision | 16 | |||||||||||||
| author | corob-msft | |||||||||||||
| ms.author | corob | |||||||||||||
| manager | ghogen | |||||||||||||
| translation.priority.ht |
|
Microsoft Specific
Generate an instruction which examines bit b of the address a, returns its current value, and sets the bit to 1.
unsigned char _bittestandset(
long *a,
long b
);
unsigned char _bittestandset64(
__int64 *a,
__int64 b
);
[in, out] a
A pointer to the memory to examine.
[in] b
The bit position to test.
The bit at the position specified.
| Intrinsic | Architecture |
|---|---|
_bittestandset |
x86, ARM, [!INCLUDEvcprx64] |
_bittestandset64 |
[!INCLUDEvcprx64] |
Header file <intrin.h>
This routine is only available as an intrinsic.
// bittestandset.cpp
// processor: x86, ARM, x64
// This example uses several of the _bittest family of intrinsics
// to implement a Flags class that allows bit level access to an
// integer field.
#include <stdio.h>
#include <intrin.h>
#pragma intrinsic(_bittestandset, _bittestandreset,\
_bittestandcomplement, _bittest)
class Flags
{
private:
long flags;
long* oldValues;
public:
Flags() : flags(0)
{
oldValues = new long[32];
}
~Flags()
{
delete oldValues;
}
void SetFlagBit(long nBit)
{
// We omit range checks on the argument
oldValues[nBit] = _bittestandset(&flags, nBit);
printf_s("Flags: 0x%x\n", flags);
}
void ClearFlagBit(long nBit)
{
oldValues[nBit] = _bittestandreset(&flags, nBit);
printf_s("Flags: 0x%x\n", flags);
}
unsigned char GetFlagBit(long nBit)
{
unsigned char result = _bittest(&flags, nBit);
printf_s("Flags: 0x%x\n", flags);
return result;
}
void RestoreFlagBit(long nBit)
{
if (oldValues[nBit])
oldValues[nBit] = _bittestandset(&flags, nBit);
else
oldValues[nBit] = _bittestandreset(&flags, nBit);
printf_s("Flags: 0x%x\n", flags);
}
unsigned char ToggleBit(long nBit)
{
unsigned char result = _bittestandcomplement(&flags, nBit);
printf_s("Flags: 0x%x\n", flags);
return result;
}
};
int main()
{
Flags f;
f.SetFlagBit(1);
f.SetFlagBit(2);
f.SetFlagBit(3);
f.ClearFlagBit(3);
f.ToggleBit(1);
f.RestoreFlagBit(2);
}
Flags: 0x2
Flags: 0x6
Flags: 0xe
Flags: 0x6
Flags: 0x4
Flags: 0x0
END Microsoft Specific