convenience wrapper. Reimplement the same trivial wrapper in Go.
Libusb wrappers
ways of calling out to cgo.
extracted from the device. Makes testing easier.
a fake libusb xfer underneath.
Change the interface a bit.
add a data() method, to avoid reaching into any xfer fields.
to sync on c.done channel before exiting.
newUSBTransfer.
descriptor in the transfer struct.