Thread overview
Allocating byte aligned array
Sep 27
timvol
Sep 27
timvol
Sep 29
Igor
September 27
Hi guys,
how can I allocate an (e.g. 16) byte aligned array?
In C I can do the following:

    void *mem = malloc(1024+15);
    void *ptr = ((uintptr_t)mem+15) & ~ (uintptr_t)0x0F;
    memset_16aligned(ptr, 0, 1024);
    free(mem);

I think in D it looks similar to this:

    auto mem = new ubyte[1024+15];
    auto ptr = (mem.ptr + 15) & ~ (...???...) 0x0F;

How to fill ...???... ?
Without a cast, the compiler tells me that I the types are incompatible (ubyte* and int).

What's the correct syntax here?

PS: I don't want to use the experimental branch that provides alignedAllocate().
September 27
On 09/27/2017 02:39 PM, timvol wrote:
> Hi guys,
> how can I allocate an (e.g. 16) byte aligned array?
> In C I can do the following:
>
>     void *mem = malloc(1024+15);
>     void *ptr = ((uintptr_t)mem+15) & ~ (uintptr_t)0x0F;
>     memset_16aligned(ptr, 0, 1024);
>     free(mem);
>
> I think in D it looks similar to this:
>
>     auto mem = new ubyte[1024+15];
>     auto ptr = (mem.ptr + 15) & ~ (...???...) 0x0F;
>
> How to fill ...???... ?
> Without a cast, the compiler tells me that I the types are incompatible
> (ubyte* and int).
>
> What's the correct syntax here?
>
> PS: I don't want to use the experimental branch that provides
> alignedAllocate().

void main() {
    auto mem = new ubyte[1024+15];
    auto ptr = cast(ubyte*)(cast(ulong)(mem.ptr + 15) & ~0x0FUL);
    auto arr = ptr[0..1024];
}

Ali

September 27
On Wednesday, 27 September 2017 at 21:44:48 UTC, Ali Çehreli wrote:
> On 09/27/2017 02:39 PM, timvol wrote:
>> [...]
>
> void main() {
>     auto mem = new ubyte[1024+15];
>     auto ptr = cast(ubyte*)(cast(ulong)(mem.ptr + 15) & ~0x0FUL);
>     auto arr = ptr[0..1024];
> }
>
> Ali

Works perfect. Thank you!
September 29
On Wednesday, 27 September 2017 at 21:48:35 UTC, timvol wrote:
> On Wednesday, 27 September 2017 at 21:44:48 UTC, Ali Çehreli wrote:
>> On 09/27/2017 02:39 PM, timvol wrote:
>>> [...]
>>
>> void main() {
>>     auto mem = new ubyte[1024+15];
>>     auto ptr = cast(ubyte*)(cast(ulong)(mem.ptr + 15) & ~0x0FUL);
>>     auto arr = ptr[0..1024];
>> }
>>
>> Ali
>
> Works perfect. Thank you!

I know you can also use this with static arrays:

align(16) ubyte[1024] mem;

But I guess align directive doesn't work with dynamic arrays...