How to make a HANDLE in D without casting and stuff:
<code>
interface iface{
    void doSomething(HANDLE h);
}
class A : iface {
    override void doSomething(HANDLE h) {
        assert(validPointer(h));
        h.foo = bar;
    }
}
class B : iface {
    someVar table[];
    override void doSomething(HANDLE h) {
        assert(table.isInBounds(h));
        table[h].foo = bar;
}
</code>

Module/class -scoped alias would be great like:
<code>
#a.d
private alias uintptr_t HANDLE;

#b.d
private alias someVar HANDLE;
</code>

but alias is resolved too early for that. How to make it properly then? Union or something else?

Thanks,
Mariusz Gliwiński

On 19/01/2011 12:27, Mariusz Gliwiński wrote:
> How to make a HANDLE in D without casting and stuff:
> <code>
> interface iface{
> void doSomething(HANDLE h);
> }
> class A : iface {
> override void doSomething(HANDLE h) {
> assert(validPointer(h));
> h.foo = bar;
> }
> }
> class B : iface {
> someVar table[];
> override void doSomething(HANDLE h) {
> assert(table.isInBounds(h));
> table[h].foo = bar;
> }
> </code>
>
> Module/class -scoped alias would be great like:
> <code>
> #a.d
> private alias uintptr_t HANDLE;
>
> #b.d
> private alias someVar HANDLE;
> </code>
>
> but alias is resolved too early for that. How to make it properly then?
> Union or something else?
>
> Thanks,
> Mariusz Gliwiński

Traditionally:

struct dummy;

alias dummy* HANDLE;

void doSomething(HANDLE h) {
}

Just don't provide a body for dummy to keep it abstract.

-- 
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk

2011-01-19 19:23, Simon wrote:
> Traditionally:
>
> struct dummy;
>
> alias dummy* HANDLE;
>
> void doSomething(HANDLE h) {
> }
>
> Just don't provide a body for dummy to keep it abstract.
So, if I understood  correctly I can't transparently swap pointer with integer of the same size? Fair enough, but:
#iface.d
struct _handle;
alias _handle* HANDLE;

#a.d
struct _handle {
    uintptr_t val;
}
class A : iface {
    void doSomething(HANDLE h) {
        assert(node.val < _t.length);    //HERE
    }
}

states:
a.d (HERE): Error: struct _handle is forward referenced

Which means that he doesn't really see _handle defined, even if it's defined few lines above. Am i doing something wrong?

Thanks,
Mariusz Gliwiński

On 20/01/2011 02:20, Mariusz Gliwiński wrote:
> 2011-01-19 19:23, Simon wrote:
>> Traditionally:
>>
>> struct dummy;
>>
>> alias dummy* HANDLE;
>>
>> void doSomething(HANDLE h) {
>> }
>>
>> Just don't provide a body for dummy to keep it abstract.
> So, if I understood correctly I can't transparently swap pointer with
> integer of the same size?

You could use a uintptr_t but you shouldn't.
Using a pointer keeps your interface type safe.

>
Fair enough, but:
> #iface.d
> struct _handle;
> alias _handle* HANDLE;
>
> #a.d
> struct _handle {
> uintptr_t val;
> }
> class A : iface {
> void doSomething(HANDLE h) {
> assert(node.val < _t.length); //HERE
> }
> }
>
> states:
> a.d (HERE): Error: struct _handle is forward referenced
>
> Which means that he doesn't really see _handle defined, even if it's
> defined few lines above. Am i doing something wrong?
>
> Thanks,
> Mariusz Gliwiński

You'll have to use casts in the implementation of your lib.

so:

#iface.d

struct _handle;
alias _handle* HANDLE;

#a.d

struct actualData {
	uintptr_t val;
}

class A : iface {
  void doSomething(HANDLE h) {
     auto ad = cast(actualData*)h;
  }
}

I don't know of any more elegant way of doing it.

D's module system has some draw backs when it comes to trying to fully encapsulate a library.

-- 
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk