Arena.addCloseAction and the implementation of a custom allocator

[Maurizio Cimadamore]

Hi,
you can still do that, using MemorySegment::ofAddress:

|public MemorySegment allocate(long byteSize, long byteAlignment) { if 
(byteAlignment > MAX_ALIGNMENT) { throw new IllegalArgumentException(); 
} try { var arena = Arena.ofAuto(); long address = 
(long)MALLOC.invokeExact(byteSize); // I assume this should work since 
other reinterpret casts like unsigned <-> int is legal here return 
MemorySegment.ofAddresss(address, byteSize, arena, () -> { try { 
FREE.invokeExact(address); } catch(Throwable e) { throw new 
RuntimeException(e); } }); } catch(Throwable e) { throw new 
RuntimeException(e); } } |

That is, there is a new overload in |MemorySegment::ofAddress| that does 
exactly what you want.

I hope this helps.

Cheers
Maurizio

On 04/03/2023 10:10, Quân Anh Mai wrote:

> Hi,
>
> I noticed that the method Arena::addCloseAction has been dropped from 
> the API. May I ask in that case what is the way to create a 
> custom allocator that manages its allocated memory? With the method, I 
> believe it can be achieved with something like this:
>
> public MemorySegment allocate(long byteSize, long byteAlignment) {
>     if (byteAlignment > MAX_ALIGNMENT) {
>         throw new IllegalArgumentException();
>     }
>
>     try {
>         var arena = Arena.ofAuto();
>         long address = (long)MALLOC.invokeExact(byteSize); // I assume 
> this should work since other reinterpret casts like unsigned <-> int 
> is legal here
>         arena.addCloseAction(() -> {
>                 try {
>                     FREE.invokeExact(address);
>                 } catch(Throwable e) {
>                     throw new RuntimeException(e);
>                 }
>         });
>         return MemorySegment.ofAddress(address, byteSize, arena);
>     } catch(Throwable e) {
>         throw new RuntimeException(e);
>     }
> }
>
> Thanks a lot,
> Quan Anh

​
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