Custom allocator

[abnara]

Builder’s custom init function provides mechanism to provide custom allocator to flatcc builder.

The flatcc_builder_alloc_fun contains alloc and free calls. This allows multiple flatcc builders in a project to have different alloc and free functions. This just requires a new function to be sent during init.

Any reason why the same was functionality was not extended to flatcc_builder_emit_fun?
Theoretically, flatcc_builder_custom_init and emitter.c can be modified to make it behave similar to alloc_fun. But does this cause any known issues?

Similarly refmap and json_printer don’t expose this functionality.

[abnara]

Does someone know about this?

[mikkelfj]

Sorry for inactivity. If you are still interested, I can dig into this.

I think the answer is that the builder is a core feature, and the emitter, while also being extremely important, is on its own replaceable, so if you need custom allocation you can write a new emitter. If there are we an allocator plugin directly in the builder for the emitter, it might not work so well if other emitters were added, although the default emitter has a few privileges as I recall, being the default.

As for refmap and json_printer, this is probably to not overengineer the solution. There are FLATCC_ALLOC... defines or something like that that can be used. These are to replace malloc and friends.

the builder has a much more elaborate allocation structure with maybe 6-7 different allocation types that can be fine tuned to different stack sizes if you are very limited on memory. A custom emitter could just use a fixed memory block on an embedded device, or a FLATCC redefined general allocator. And the same goes for refmap and json_printer.

It is possible I have overlooked replacing malloc with FLATCC_ALLOC but I doubt it.

https://github.com/dvidelabs/flatcc/blob/master/include/flatcc/flatcc_alloc.h