Re: D and memory mapped devices
On 2017-06-14 11:04, Rene Zwanenburg wrote: I've casted void buffers to structs containing bitfields to read pre-existing binary files, and that worked just fine. I don't see why it would be different for memory mapped devices. What do yo mean by 'do more'? This bitfield discussion came up in a DStep issue [1]. The bitfields mixin will generate a field to store the bits in, which I think was surprising for Russel. Although, currently there are no other way to specify which other field should be used for storage. Another issue that came up is that you can use the default generated constructor or the struct initializer syntax to bypass the generate methods and set the underlying storage field directly. [1] https://github.com/jacob-carlborg/dstep/issues/151 -- /Jacob Carlborg
Re: D and memory mapped devices
On Wednesday, 14 June 2017 at 08:10:57 UTC, Russel Winder wrote: This would appear a priori to not allow for actual memory mapped devices using it, or am I missing something? I believe the only case where it might matter is if the device was sensitive to the read/write size (1/2/4 bytes). Otherwise, the generated code should be functionally the same as C bitfields.
Re: D and memory mapped devices
On 6/14/17 4:10 AM, Russel Winder via Digitalmars-d-learn wrote:
In C and C++ you often use bitfields to control devices with memory
mapped hardware control and data words. So for example:
typedef struct some_device {
unsigned int flob: 3;
unsigned int adob: 2;
unsigned int: 3;
unsigned int data: 8;
} some_device;
Clearly D has no bitfields. I know of std.bitfield, so somethign like:
struct some_device {
uint a;
mixin(bitfields!(
uint, "flob", 3,
uint, "adob", 2,
uint, "someMadeUpNameBecauseBlankIsNotAcceptable", 3,
uint, "data", 8));
}
but the bitfields mixin template appears to do more than add all the
bit twiddling functions to emulate the bitfields. This would appear a
priori to not allow for actual memory mapped devices using it, or am I
missing something?
Why not? It should work just the same as C's bitfields, but with more
configurability. It all depends on how the hardware register works, as
they often don't act like normal memory. One thing D does miss is the
volatile keyword.
Have you tried it? It might just work :)
-Steve
Re: D and memory mapped devices
On Wednesday, 14 June 2017 at 08:10:57 UTC, Russel Winder wrote: but the bitfields mixin template appears to do more than add all the bit twiddling functions to emulate the bitfields. This would appear a priori to not allow for actual memory mapped devices using it, or am I missing something? I've casted void buffers to structs containing bitfields to read pre-existing binary files, and that worked just fine. I don't see why it would be different for memory mapped devices. What do yo mean by 'do more'?
D and memory mapped devices
In C and C++ you often use bitfields to control devices with memory
mapped hardware control and data words. So for example:
typedef struct some_device {
unsigned int flob: 3;
unsigned int adob: 2;
unsigned int: 3;
unsigned int data: 8;
} some_device;
Clearly D has no bitfields. I know of std.bitfield, so somethign like:
struct some_device {
uint a;
mixin(bitfields!(
uint, "flob", 3,
uint, "adob", 2,
uint, "someMadeUpNameBecauseBlankIsNotAcceptable", 3,
uint, "data", 8));
}
but the bitfields mixin template appears to do more than add all the
bit twiddling functions to emulate the bitfields. This would appear a
priori to not allow for actual memory mapped devices using it, or am I
missing something?
--
Russel.
=
Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net
41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk
London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder
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