koreader/platform/common/spinning_zsync

#!/bin/sh

# Figure out whether that's a delta or a full download given the number of arguments passed...
if [ $# -lt 7 ]; then
    ZSYNC_MESSAGE="Downloading update data"
else
    ZSYNC_MESSAGE="Computing zsync delta"
fi

# Small zsync wrapper so we can get a pretty spinner while it works...
./fbink -q -y -7 -pmh "${ZSYNC_MESSAGE} !"
# Clear any potential leftover from the local OTA tarball creation.
./fbink -q -y -6 -pm ' '

# Spin in the background while we work ;).
(
    # See https://stackoverflow.com/questions/2685435 for inspiration
    # as well as https://www.npmjs.com/package/cli-spinners
    # & https://github.com/swelljoe/spinner
    # http://www.fileformat.info/info/unicode/block/block_elements/list.htm
    ##
    # Simple bars, they look better when a bit smoother, with a snappier interval (~250ms)
    #SPINNER="<22> ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ ▇ ▆ ▅ ▄ ▃ ▂ ▁"
    #SPINNER="<22> ▏ ▎ ▍ ▌ ▋ ▊ ▉ █ ▉ ▊ ▋ ▌ ▍ ▎ ▏"
    # Spinning blocks
    SPINNER="▖ ▘ ▝ ▗"
    #SPINNER="▜ ▟ ▙ ▛"
    # Snaking blocks
    #SPINNER="▌ ▀ ▐ ▄"
    #SPINNER="▌ ▛ ▀ ▜ ▐ ▟ ▄ ▙"
    while :; do
        for spin in ${SPINNER}; do
            usleep 500000 2>/dev/null || sleep 0.5
            # NOTE: Throw stderr to the void because I'm cheating w/ U+FFFD for a blank character,
            #       which FBInk replaces by a blank, but not before shouting at us on stderr ;).
            ./fbink -q -y -7 -pmh "${ZSYNC_MESSAGE} ${spin}" 2>/dev/null
        done
    done
) &

# Launch zsync, and remember its exit code...
./zsync "$@"
rc=$?

# Kill the spinner subshell now that we're done
kill -15 $!

# And return with zsync's exit code, not kill's ;).
exit ${rc}