Reading bits using bitwise operators from 32 bit integer

[madhu542]

Hi,

I have a 32 bit integer variable with some value (eg: 4545) in it, now I want to read first 8 bits into uint8_t and second 8 bits into another uint8_t and so on till the last 8 bits.

I am thinking of using bitwise operators, can anyone give some examples how to do this?


Thanks for your help!

-Madhu.

[VictorN]

Microsoft already made the most of the work for you. Have a look at Window Macros
What you need are HIBYTE, HIWORD. LOBYTE. LOWORD

[madhu542]

Okay, but I need this in C under Linux platform.

[VictorN]

Okay, but I need this in C under Linux platform.

Then why do you ask it in the Windows forum?

C++ and WinAPI Discuss Windows API related issues using C++ (and Visual C++). This is a non-MFC forum.

There is another forum for linux:

C++ (Non Visual C++ Issues) Ask or answer C and C++ questions not related to Visual C++. This includes Console programming, Linux programming, or general ANSI C++.

As for your question - use bitwise operator & with 0x000000FF to extract the lowest byte, then shift the original "32 bit integer" 8 bits to the right and so on...

[Igor Vartanov]

Okay, but I need this in C under Linux platform.

// bitwise.cpp
#include <stdio.h>

typedef union U32
{
    unsigned u32;
    struct {
    unsigned short w2;
    unsigned short w1;
    } w32;
    struct {
    unsigned char b4;
    unsigned char b3;
    unsigned char b2;
    unsigned char b1;
    } b32;
} U32;

typedef struct {
    unsigned b4:8;
    unsigned b3:8;
    unsigned b2:8;
    unsigned b1:8;
} bb32;

int main()
{
    U32 uni32;
    
    uni32.u32 = 0x01020304;
    bb32& bb  = *(bb32*)&uni32.u32;
    
    printf ("&#37;08x\n", uni32.u32);
    printf ("%04x:%04x\n", uni32.w32.w1, uni32.w32.w2);
    printf ("%02x:%02x:%02x:%02x\n", uni32.b32.b1, uni32.b32.b2, uni32.b32.b3, uni32.b32.b4);
    printf ("%02x:%02x:%02x:%02x\n", bb.b1, bb.b2, bb.b3, bb.b4);
    
    return 0;
}

igor@igor-desktop:~/Temp$ g++ bitwise.cpp -o bitwise.out
igor@igor-desktop:~/Temp$ ./bitwise.out 
01020304
0102:0304
01:02:03:04
01:02:03:04