Converting void* to D array

[CraigDillabaugh via Digitalmars-d-learn]

On Wednesday, 15 April 2015 at 11:18:03 UTC, Steven Schveighoffer 
wrote:
> On 4/15/15 12:47 AM, Daniel Kozak wrote:
>> On Wednesday, 15 April 2015 at 04:43:39 UTC, Daniel Kozák 
>> wrote:
>>>
>>> On Wed, 15 Apr 2015 04:24:20 +0000
>>> Craig Dillabaugh via Digitalmars-d-learn
>>> <digitalmars-d-learn at puremagic.com> wrote:
>>>
>>>> Hi.
>>>> I want to call a C library function that returns a data 
>>>> buffer as a
>>>> void*.  How do I convert the resulting void* into something 
>>>> I can
>>>> process in D?
>>>>
>>>> //I have the following function from the GDAL C library.
>>>> extern(C) CPLErr GDALReadBlock( GDALRasterBandH, int, int, 
>>>> void* );
>>>>
>>>>
>>>> So I have (GByte is defined in the GDAL library):
>>>>
>>>> void* buffer = malloc( GByte.sizeof * x_block_size * 
>>>> y_block_size );
>>>>
>>>> I fill the buffer (and ignore any errors :o)
>>>>
>>>> GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock, 
>>>> buffer );
>>>>
>>>>
>>>> Now, how can I access the data in buffer?
>>> Or you probably can do it like this:
>>>
>>> auto buffer = new GByte[xblock*yblock];
>>>
>>> GDALReadBlock( AGDALRasterBandHInstance, xblock, yblock,
>>> (cast void*)buffer.ptr );
>> But in this case memory will be scan by GC. Which probably is 
>> not
>> something what you want.
>
> Depends on what GByte is. If it doesn't contain pointers (I'm 
> assuming its probably ubyte?), then it won't be scanned.
>
> If you still want to use malloc, but in a safe way, you can do:
>
> immutable blocksize = GByte.sizeof * x_block_size * 
> y_block_size;
> auto buffer = malloc(blocksize)[0..blocksize];
>
> Also, you don't need to cast pointers to void *. Should be able 
> to do:
>
> GDALReadBlock(AGDALRasterBandHInstance, xblock, yblock, 
> buffer.ptr);
>
> -Steve

Thanks for the pointers (no pun intended!)

Just out of curiosity, what is the type of 'buffer'?  'malloc' 
returns a void* but using the .ptr suggests 'buffer' is an array. 
  Is the return of malloc automatically converted to an array?