• Pavel Minayev (8/8) Apr 14 2002 Just found out that struct consisting of N bit fields is N bytes long:
• Russ Lewis (9/12) Apr 14 2002 Would probably be clearer if you used
• Walter (6/14) Apr 14 2002 It's an implementation issue whether individual bits get packed or not. ...
• Pavel Minayev (17/21) Apr 14 2002 The
• Walter (6/27) Apr 14 2002 packed?

"Pavel Minayev" <evilone omen.ru> writes:

Just found out that struct consisting of N bit fields is N bytes long:

    struct bits { bit a, b, c }    // bits.length == 3

Why? Since language forbids pointers to bits, why not pack them
as tight as it's possible? D does it in bit arrays, but not in
structs.

I can understand perfomance reasons; then, make some
attribute for this. align(0), maybe?

    struct bits { align(0) bit a, b, c; }    // bits.length == 1

Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:

Pavel Minayev wrote:

 I can understand perfomance reasons; then, make some
 attribute for this. align(0), maybe?

     struct bits { align(0) bit a, b, c; }    // bits.length == 1

Would probably be clearer if you used

    struct bits { align(bit) bit a, b, c; }

but otherwise a very good idea.

--
The Villagers are Online! http://villagersonline.com

.[ (the fox.(quick,brown)) jumped.over(the dog.lazy) ]
.[ (a version.of(English).(precise.more)) is(possible) ]
?[ you want.to(help(develop(it))) ]

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a9bpjf$134d$1 digitaldaemon.com...
 Just found out that struct consisting of N bit fields is N bytes long:

     struct bits { bit a, b, c }    // bits.length == 3

 Why? Since language forbids pointers to bits, why not pack them
 as tight as it's possible? D does it in bit arrays, but not in
 structs.

 I can understand perfomance reasons; then, make some
 attribute for this. align(0), maybe?

     struct bits { align(0) bit a, b, c; }    // bits.length == 1

It's an implementation issue whether individual bits get packed or not. The
main reason for not doing it at the moment is it adds some implementation
complexity. As you pointed out, you can always use bit arrays which will
pack them regardless.

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a9clk5$1sfj$1 digitaldaemon.com...

 It's an implementation issue whether individual bits get packed or not.

The

Does this statement apply to bit arrays as well, or they are always packed?

 main reason for not doing it at the moment is it adds some implementation
 complexity. As you pointed out, you can always use bit arrays which will
 pack them regardless.

Yep, right... but arrays are indexed with integers, and I wanted
to have some descriptive names. The code was:

    class MouseEvent
    {
        struct Buttons
        {
            bit left, right, middle;
        }

        Buttons buttons;

        ...
    }

I don't really care much if it takes 4 bytes instead of 1... but the
latter is preferred, of course.

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a9co75$2022$1 digitaldaemon.com...
 "Walter" <walter digitalmars.com> wrote in message
 news:a9clk5$1sfj$1 digitaldaemon.com...
 It's an implementation issue whether individual bits get packed or not.

 The
 Does this statement apply to bit arrays as well, or they are always

packed?

They're always packed.

 main reason for not doing it at the moment is it adds some


implementation
 complexity. As you pointed out, you can always use bit arrays which will
 pack them regardless.

 Yep, right... but arrays are indexed with integers, and I wanted
 to have some descriptive names. The code was:

     class MouseEvent
     {
         struct Buttons
         {
             bit left, right, middle;
         }

         Buttons buttons;

         ...
     }

 I don't really care much if it takes 4 bytes instead of 1... but the
 latter is preferred, of course.

Of course <g>.