Hello,

With current LibRaw, custom IOs can be implemented by subclassing
LibRaw_abstract_datastream. But this is only available with the C++ API, the
C API only alows to open_file() or open_buffer(). In order to give the C API
more flexibility regarding IOs, I've started working on a LibRaw_proxy_datastream
class that would do IOs by calling a simple set of C callbacks provided by caller.
Initial code is here:

https://gitlab.com/tchaik/LibRaw/tree/tchaik/wip/c-datastream

I'd be happy to get your feedbacks regarding this work, and I'm especilly
intereted in knowing if you would be willing to add this to upstream LibRaw.

Thank you very much!
Martin.