Now with cancel button and an actual progress bar. For simplicity, we do
two passes on the progress bar, one for loading the NAND into memory and
one for extracting it. The user directory is likely on an SSD, making
the extraction pass invisibly fast.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Use std::string(cstring, strnlen(cstring, max_length)) instead of
trying to remove extra null characters manually, which is a bit
ugly and error prone.
And indeed, the original code contained a bug which would cause
extra NULLs to not be removed at all if the string did not
end with a NULL -- causing issues down the road when constructing
paths for sub-entries.
