On Fri, 09 Sep 2011 17:43:04 +0200, Timon Gehr wrote:
> On 09/09/2011 05:19 PM, teo wrote:
>> Here is an example of what I am after:
>>
>> struct DATA
>> {
>> ubyte D1;
>> ubyte D2;
>> ubyte D3;
>> ubyte D4;
>> }
>>
>> void main()
>> {
>> ubyte[16] a = [ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
>> 0x01,
>> 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 ];
>> auto b = (cast(DATA*)a.ptr)[0 .. 4];
>> auto c = (cast(DATA[]*)b.ptr)[0 .. 2][0 .. 2];
>> }
>>
>> I need to have a DATA[2][2]. That code compiles but gives me a
>> segmentation fault.
>
> If you actually want a dynamic DATA[2][] array of length 2, this works:
> auto b=(*(cast(DATA[2][2]*)a.ptr))[];
>
> Otherwise:
>
> A simple reinterpret cast should do:
> auto b=*(cast(DATA[2][2]*)a.ptr);
>
> but note that this copies the data, because static arrays have value
> semantics.
>
> If you want to have refer the new array to the same location, you can
> use a union.
>
> void main(){
> union Myunion{
> ubyte[16] a = [ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
0x01,
> 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 ];
> DATA[2][2] b;
> }
> Myunion myunion;
> assert(*(cast(DATA[2][2]*)myunion.a.ptr)==myunion.b);
> }
Thank you Timon for the good explanation.
Just one more question (I suspect the answer will be no, but let me ask):
is it possible to directly cast to ubyte[][]?
