Thanks Isaac,

your readbit function does the trick.

Cheers Justin


2009/7/22 Isaac Marino Bavaresco <isaacbavaresco@yahoo.com.br>

> You could write a function or macro to do this.
> Use a char array as the underlying type and abstract the bit access in
> the function/macro:
>
> Ex.:
> void SetBit( char *v, int n )
>    {
>    v[n>>3] |=3D 1 << ( n & 7 );
>    }
>
> void ClrBit( char *v, int n )
>    {
>    v[n>>3] &=3D ~( 1 << ( n & 7 ));
>    }
>
> int ReadBit( char *v, int n )
>    {
>    return ( v[n>>3] & ( 1 << ( n & 7 ))) ? 1 : 0;
>    }
>
> Justin Richards escreveu:
> > was tagged [tech]
> >
> > 2009/7/21 Justin Richards <justin.richards@gmail.com>
> >
> >
> >> In C18 a union can be described as follows
> >>
> >> typedef union _IP_ADDR
> >> {
> >>     BYTE        v[4];
> >>     DWORD       Val;
> >> } IP_ADDR;
> >>
> >>
> >> Then memory may be referenced as follows [after a variable IP of type
> >> IP_ADDR is declared]
> >> i=3D3;
> >> IP.v[i];
> >>
> >> Can a similar member reference be used with bits.
> >>
> >> That is instead of referencing a bit member in the union below as
> >>
> >> iomask.bits.b0;
> >>
> >> Can it be referenced as
> >>
> >> iomask.bits[i]; or perhaps iomask.bits.b[i];
> >>
> >> Experimenting with the compiler seems to indicate that it is not
> possible.
> >>
> >> Pointers to examples etc would be greatly appreciated or even what to
> >> google for.
> >>
> >>       union
> >>         {
> >>             struct
> >>             {
> >>                 unsigned char b0:1;
> >>                 unsigned char b1:1;
> >>                 unsigned char b2:1;
> >>                 unsigned char b3:1;
> >>                 unsigned char b4:1;
> >>                 unsigned char b5:1;
> >>                 unsigned char b6:1;
> >>                 unsigned char b7:1;
> >>             } bits;
> >>             BYTE val;
> >>         } iomask;
> >>
> >> Cheers Justin
> >>
> >>
> >>
> >>
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