[FFmpeg-devel] [PATCH] [RFC][WIP] avutil/buffer: add add a dynamnic size buffer pool API

[wm4]

On Tue, 27 Mar 2018 14:16:15 -0300
James Almer <jamrial at gmail.com> wrote:

> On 3/20/2018 7:44 PM, James Almer wrote:
> > On 3/16/2018 3:21 PM, James Almer wrote:  
> >> Signed-off-by: James Almer <jamrial at gmail.com>
> >> ---
> >> This is a proof of concept for a dynamic size buffer pool API.
> >>
> >> For the purpose of easy testing and reviewing I replaced the current
> >> linked list used to keep a pool of fixed size buffers with the tree
> >> based pool that will be used to keep a pool of varying size buffers,
> >> instead of adding a new set of functions exclusively for the new API.
> >> The final committed work doesn't necessarely have to do the above, as
> >> there's no real benefit using a tree when you only need a fixed size
> >> buffer pool, other than simplying things.
> >>
> >> I'm open to suggestions about how to introduce this. Completely
> >> separate set of functions and struct names? Sharing the struct and
> >> init/uninit functions and only adding a new get() one like in this
> >> patch?
> >> Any preferences with function/struct naming, for that matter?  
> > 
> > Ping?  
> 
> No comments or preferences at all on how to introduce this?

Well, it's a pretty big mess (so many things to consider). That's
mostly about the implementation details.

I think the API you picked is relatively nice. It feels weird that a
pool that is initialized with a size has a function to allocate buffers
with a different size. So if you want some bikeshedding, sure, I can
provide you with some colors:

 AVDynamicBufferPool *av_dynamic_buffer_pool_create(alloc_fn, free_fn);
 AVBufferRef *av_dynamic_buffer_pool_get(AVDynamicBufferPool *pool,
                                         size_t size);
 void av_dynamic_buffer_pool_uininit(AVDynamicBufferPool **pool);

or:

 // sets *pool if it was NULL
 // (where to put alloc/free FNs for custom alloc?)
 AVBufferRef *av_dynamic_buffer_pool_get(AVDynamicBufferPool **pool,
                                         size_t size);
 void av_dynamic_buffer_pool_uininit(AVDynamicBufferPool **pool);

or:

  // sets *pool if it was NULL
  // free the pool with av_buffer_unref()
  AVBufferRef *av_dynamic_buffer_pool_get(AVBufferRef **pool,
                                         size_t size);

or just force the API user to pass size=0 to av_buffer_pool_init() and
enforce the use of the correct alloc function (fixed size/dynamic size)
at runtime.