I have a memory buffer allocated using different methods. It is simply a pointer and a size.

I would like to be able to manage this buffer by treating it as a memory pool or heap. I think I can use allocators to do this but not sure how.

Effectively I want something like new or malloc but it pulls from the memory buffer rather than the program heap.

// Allocated once at program start
void* FancyBuffer = FancyAlloc(1000);


Then when I want to use the buffer I'll do stuff like



auto myptr = FancyMalloc(10);

....

FancyFree(myptr);


or whatever.

The main thing is, I don't want to have to write my own allocator to manage this buffer as it seems that D's allocators would do a better job.

I imagine that most of the time the buffer will not have more than one piece of code using it(no overlapping uses) but since I won't be 100% sure, I need allow for the cases where there might be overlapping usage. (else I wouldn't ever have to worry about "allocating or releasing" from it.

Thanks.

On 2017-03-29 21:19, Enigma wrote:
> I have a memory buffer allocated using different methods. It is simply a
> pointer and a size.
>
Can you maybe just tread it like an array and slice it for allocation?

On 2017-03-29 23:30, Faux Amis wrote:
> On 2017-03-29 21:19, Enigma wrote:
>> I have a memory buffer allocated using different methods. It is simply a
>> pointer and a size.
>>
> Can you maybe just tread it like an array and slice it for allocation?
>
*treat*

On Wednesday, 29 March 2017 at 19:19:48 UTC, Enigma wrote:
> I have a memory buffer allocated using different methods. It is simply a pointer and a size.
>
> I would like to be able to manage this buffer by treating it as a memory pool or heap. I think I can use allocators to do this but not sure how.
>
> Effectively I want something like new or malloc but it pulls from the memory buffer rather than the program heap.
>
> // Allocated once at program start
> void* FancyBuffer = FancyAlloc(1000);
>
>
> Then when I want to use the buffer I'll do stuff like
>
>
>
> auto myptr = FancyMalloc(10);
>
> ....
>
> FancyFree(myptr);
>
>
> or whatever.
>
> The main thing is, I don't want to have to write my own allocator to manage this buffer as it seems that D's allocators would do a better job.
>
> I imagine that most of the time the buffer will not have more than one piece of code using it(no overlapping uses) but since I won't be 100% sure, I need allow for the cases where there might be overlapping usage. (else I wouldn't ever have to worry about "allocating or releasing" from it.
>
> Thanks.

It looks like you are looking for this: http://dlang.org/phobos-prerelease/std_experimental_allocator_building_blocks_region.html.

On Wednesday, 29 March 2017 at 21:36:14 UTC, Petar Kirov [ZombineDev] wrote:
> On Wednesday, 29 March 2017 at 19:19:48 UTC, Enigma wrote:
>> [...]
>
> It looks like you are looking for this: http://dlang.org/phobos-prerelease/std_experimental_allocator_building_blocks_region.html.

But these seem to require passing a mallocator. I simply want to pass an already allocated region/block/buffer and have the allocators use it. I will allocate and free on my own.

On Wed, Mar 29, 2017 at 11:01:12PM +0000, Enigma via Digitalmars-d-learn wrote:
> On Wednesday, 29 March 2017 at 21:36:14 UTC, Petar Kirov [ZombineDev] wrote:
> > On Wednesday, 29 March 2017 at 19:19:48 UTC, Enigma wrote:
> > > [...]
> > 
> > It looks like you are looking for this: http://dlang.org/phobos-prerelease/std_experimental_allocator_building_blocks_region.html.
> 
> But these seem to require passing a mallocator. I simply want to pass an already allocated region/block/buffer and have the allocators use it. I will allocate and free on my own.

Huh?  Where does it say that a mallocator is required?

As far as I can tell, you could simply do this:

	void[] myBuffer = ...;
	auto allocator = Region!()(myBuffer);
	auto p = allocator.allocate(...);

The default parent allocator is NullAllocator, which does nothing, so that leaves the management of myBuffer entirely up to you.


T

-- 
Life would be easier if I had the source code. -- YHL

On Wednesday, 29 March 2017 at 19:19:48 UTC, Enigma wrote:
> I have a memory buffer allocated using different methods. It is simply a pointer and a size.
>
> I would like to be able to manage this buffer by treating it as a memory pool or heap. I think I can use allocators to do this but not sure how.

You can re-task the GC to use an arena if that's suitable:

https://bitbucket.org/infognition/dstuff/src/1dca752af1021ed5998bb041004465674695113f/gcarena.d?fileviewer=file-view-default

On Wednesday, 29 March 2017 at 23:26:04 UTC, H. S. Teoh wrote:
> On Wed, Mar 29, 2017 at 11:01:12PM +0000, Enigma via Digitalmars-d-learn wrote:
>> On Wednesday, 29 March 2017 at 21:36:14 UTC, Petar Kirov [ZombineDev] wrote:
>> > [...]
>> 
>> But these seem to require passing a mallocator. I simply want to pass an already allocated region/block/buffer and have the allocators use it. I will allocate and free on my own.
>
> Huh?  Where does it say that a mallocator is required?
>
> As far as I can tell, you could simply do this:
>
> 	void[] myBuffer = ...;
> 	auto allocator = Region!()(myBuffer);
> 	auto p = allocator.allocate(...);
>
> The default parent allocator is NullAllocator, which does nothing, so that leaves the management of myBuffer entirely up to you.
>
>
> T

Thanks. All the examples show using a size rather than an array so I assumed that was the case.

On Thursday, 30 March 2017 at 11:22:05 UTC, Gary Willoughby wrote:
> On Wednesday, 29 March 2017 at 19:19:48 UTC, Enigma wrote:
>> I have a memory buffer allocated using different methods. It is simply a pointer and a size.
>>
>> I would like to be able to manage this buffer by treating it as a memory pool or heap. I think I can use allocators to do this but not sure how.
>
> You can re-task the GC to use an arena if that's suitable:
>
> https://bitbucket.org/infognition/dstuff/src/1dca752af1021ed5998bb041004465674695113f/gcarena.d?fileviewer=file-view-default

cool. thanks.