• =?UTF-8?B?Tm9yZGzDtnc=?= (25/25) Apr 30 2017 Have anybody found a way to do transitive packing of bitfields?
• Stefan Koch (3/28) Apr 30 2017 You'd have to write your own template to do it; it's easy though
• Per =?UTF-8?B?Tm9yZGzDtnc=?= (4/41) Apr 30 2017 Yeah, I thought so too. The question then becomes I have to write

=?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

Have anybody found a way to do transitive packing of bitfields?

For instance, in


import std.bitmanip : bitfields;

struct X
{
     // one bit too many to fit in one byte
     mixin(bitfields!(bool, `a`, 1,
                      bool, `b`, 1,
                      ubyte, `c`, 7,
                      ubyte, `_pad`, 7);
}

struct Y
{
     // one unused bit
     mixin(bitfields!(ubyte, `d`, 7,
                      ubyte, `_pad`, 1);
}

struct XY
{
     X x;
     Y y;
}


`XY` will currently occupy 4 bytes, when only 1+1+7+7=16 bits are 
actually used in `a`, `b`, `c` and `d`.

Rust just got support for this.

Stefan Koch <uplink.coder googlemail.com> writes:

On Sunday, 30 April 2017 at 11:02:52 UTC, Nordlöw wrote:
 Have anybody found a way to do transitive packing of bitfields?

 For instance, in


 import std.bitmanip : bitfields;

 struct X
 {
     // one bit too many to fit in one byte
     mixin(bitfields!(bool, `a`, 1,
                      bool, `b`, 1,
                      ubyte, `c`, 7,
                      ubyte, `_pad`, 7);
 }

 struct Y
 {
     // one unused bit
     mixin(bitfields!(ubyte, `d`, 7,
                      ubyte, `_pad`, 1);
 }

 struct XY
 {
     X x;
     Y y;
 }


 `XY` will currently occupy 4 bytes, when only 1+1+7+7=16 bits 
 are actually used in `a`, `b`, `c` and `d`.

 Rust just got support for this.

You'd have to write your own template to do it; it's easy though 
:)

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

On Sunday, 30 April 2017 at 13:22:49 UTC, Stefan Koch wrote:
 On Sunday, 30 April 2017 at 11:02:52 UTC, Nordlöw wrote:
 Have anybody found a way to do transitive packing of bitfields?

 For instance, in


 import std.bitmanip : bitfields;

 struct X
 {
     // one bit too many to fit in one byte
     mixin(bitfields!(bool, `a`, 1,
                      bool, `b`, 1,
                      ubyte, `c`, 7,
                      ubyte, `_pad`, 7);
 }

 struct Y
 {
     // one unused bit
     mixin(bitfields!(ubyte, `d`, 7,
                      ubyte, `_pad`, 1);
 }

 struct XY
 {
     X x;
     Y y;
 }


 `XY` will currently occupy 4 bytes, when only 1+1+7+7=16 bits 
 are actually used in `a`, `b`, `c` and `d`.

 Rust just got support for this.

 You'd have to write your own template to do it; it's easy 
 though :)

Yeah, I thought so too. The question then becomes I have to write 
my own version of bitfields that can introspect the bitsize of 
it's arguments via some new trait bitsizeOf.