_bittest, _bittest64

Artikel
08/03/2021

Microsoft Specific

Generates the bt instruction, which examines the bit in position b of address a, and returns the value of that bit.

Syntax

unsigned char _bittest(
   long const *a,
   long b
);
unsigned char _bittest64(
   __int64 const *a,
   __int64 b
);

Parameters

a
[in] A pointer to the memory to examine.

b
[in] The bit position to test.

Return value

The bit at the position specified.

Requirements

Intrinsic	Architecture	Header
`_bittest`	x86, ARM, x64, ARM64	<intrin.h>
`_bittest64`	ARM64, x64	<intrin.h>

Remarks

This routine is only available as an intrinsic.

Example

// bittest.cpp
// processor: x86, ARM, x64

#include <stdio.h>
#include <intrin.h>

long num = 78002;

int main()
{
    unsigned char bits[32];
    long nBit;

    printf_s("Number: %d\n", num);

    for (nBit = 0; nBit < 31; nBit++)
    {
        bits[nBit] = _bittest(&num, nBit);
    }

    printf_s("Binary representation:\n");
    while (nBit--)
    {
        if (bits[nBit])
            printf_s("1");
        else
            printf_s("0");
    }
}

Number: 78002
Binary representation:
0000000000000010011000010110010

END Microsoft Specific

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