[HarfBuzz] [Feature Request] Custom allocator support

[Jamie Dale]

Since there was no movement here I went ahead and hacked in our allocator
by redefining malloc, calloc, realloc, and free to point to extern'd
functions that I define in our application. This yielded some performance
benefits for us, so I'm hoping that a more standard HarfBuzz solution might
appear at some point :)

If you're not keen on the idea of allowing the allocator to be swapped out
at runtime, would you at least allow it to be extern'd at compile time? I'm
not familiar with HarfBuzz coding standards, but I'd propose adding
something like a HAVE_EXTERNAL_ALLOCATOR define to control this, and then
define your own allocator functions that you'd use in place of malloc, etc.

Basically, something like this (I currently have this code in hb-private.hh
):

/* Define our allocation functions. These may be provided by an
 * external source when HAVE_EXTERNAL_ALLOCATOR is defined. */
#ifdef HAVE_EXTERNAL_ALLOCATOR
extern void* _hb_malloc(size_t);
extern void* _hb_calloc(size_t, size_t);
extern void* _hb_realloc(void*, size_t);
extern void _hb_free(void*);
#define hb_malloc _hb_malloc
#define hb_calloc _hb_calloc
#define hb_realloc _hb_realloc
#define hb_free _hb_free
#else
#define hb_malloc malloc
#define hb_calloc calloc
#define hb_realloc realloc
#define hb_free free
#endif

You'd then replace calls to malloc, calloc, realloc, and free from within
HarfBuzz to use hb_malloc, hb_calloc, hb_realloc, and hb_free.

This is basically the code I already have, except I redefined malloc, calloc
, realloc, and free rather than create the hb_* variants, as I didn't want
to change too much HarfBuzz code.

Thoughts?

On 31 August 2015 at 22:17, Jamie Dale <jamiedale88+harfbuzz at gmail.com>
wrote:

> Hey,
>
> I'm not sure if this is correct place to post/discuss feature requests...
> hopefully it is.
>
> Our project makes use of a custom memory allocator, and we like to ensure
> that our third-party libraries are using this where possible, as our
> allocator can offer significantly better performance, and can also allow us
> better memory profiling and debugging support.
>
> A look through the HarfBuzz source code would suggest that it doesn't
> currently support custom memory allocators, and instead just directly calls
> the standard malloc/free/etc functions. I was wondering if you'd ever
> considered (or would consider) adding a way to override this behaviour?
>
> In my case, I'd just need a single global override to be set before my
> first call to any other HarfBuzz code... basically something like
> the FT_Memory struct from FreeType:
>
> http://www.freetype.org/freetype2/docs/reference/ft2-system_interface.html#FT_Memory
>
> Thanks,
> Jamie.
>
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