I was looking for a not %02x way of converting binary to hex String, and I stumbled upon the implementation in PrettyBytes.swift.

I'm not 100% sure about the Sequence conformance of non-contiguous DataProtocol, but it seemed to me that the self on line 46 should be the ignored parameter $0 (or maybe eliminate the region logic since looping over self most likely would have taken non-contiguous memory regions into account?), otherwise the code reads:

For each segment of the data buffer, loop over the entirety of data buffer and convert each byte to two hex chars.

Unless non-contiguous DataProtocol has non-stable indices and iterators, this code will over/re-iterate the data buffer.