How can I make this work?

[Max Haughton]

On Sunday, 28 February 2021 at 09:18:56 UTC, Rumbu wrote:
> On Sunday, 28 February 2021 at 09:04:49 UTC, Rumbu wrote:
>> On Sunday, 28 February 2021 at 07:05:27 UTC, Jack wrote:
>>> I'm using a windows callback function where the user-defined 
>>> value is passed thought a LPARAM argument type. I'd like to 
>>> pass my D array then access it from that callback function. 
>>> How is the casting from LPARAM to my type array done in that 
>>> case?
>>>
>>> for example, I need something like this to work:
>>>
>>> int[] arr = [1, 2, 3];
>>> long l = cast(long) cast(void*) arr.ptr;
>>> int[] a = cast(int[]) cast(void*) l;
>>
>> LPARAM is not long on 32 bits, it's int. Use LPARAM instead of 
>> long.
>
> And you are passing only the address of the first element this 
> way, loosing the array/slice length. This should work, but keep 
> in mind that you have no warranty that the array stays in 
> memory and it is not garbage collected.
>
> int[] arr = [1, 2, 3];
> LPARAM l = cast(LPARAM)cast(void*)&arr;
> int[] a = *cast(int[]*)(cast(void*)l);

Do the windows APIs expect the length in memory rather than as a 
parameter?

Also Rumbu can you check your email - I may have emailed you on 
an old email address by accident, but it's about the blog and it 
will be from mh240 at ...