I've been working with libusbx for some time now --I'm primarily very
happy with it-- but one design trait gave me trouble: Being forced to
use C-callbacks for dealing with asynchronous transfers.
It would be *really* nice if there was a "push style" API one could
resort to, like this:
/* inside the main-loop: */
libusb_check_events_timeout_completed(ctx, timeout, &evt_cnt);
for(int i = 0; i < evt_cnt; ++i) {
libusb_transfer *transfer;
libusb_handle_next_transfer(ctx, &transfer);
/* do something with the transfer */
}
The reason I want this is that I'm programming in LuaJIT [1], and
C-callbacks are undesirable for a variety of reasons [2].
It would be *very* helpful if something like the snippet above worked
in a future version of libusbx.
What is your opinion on this proposal?
TL/DR: make asynchronous transfers possible without using C-callbacks. Please?
--Wolfgang
[1] LuaJIT (http://luajit.org/) is a fast interpreter + JIT compiler
for the Lua language. The fact that it offers simple access to C
data-primitives (almost everything, from 64 bit uints to nested
structs/unions; declarations can be copypasted verbatim from C),
combined with its ability to call C functions by pasting their
signature and pointing toward the relevant dll/so makes it a very
appealing alternative to (or an abstraction/convenience layer on top
of) C- especially for rapid prototyping.
Performance is pretty competitive, e.g. calling ZMQ send_msg/recv_msg
functions: LuaJIT 6160911 [msg/s], C++ 6241452 [msg/s] (difference <
2%).
[2] For one, C-callbacks screw with both garbage collection (of the
callback function itself) and prevent JIT compilation of the caller.
PS: libusbx (and Zadig, and the related documentation) was extremely
useful for me- I'd like to thank you people for the effort.
PPS: I'm not opposed to MIT'ing my (currently hacky and incomplete)
LuaJIT-binding after bringing it to shape, especially if anyone is
interested.
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