Convert plaintext list of URLs to firefox session restore file

links-to-sess.bash

#!/bin/bash

{
    echo '{"version":["sessionrestore",1],"windows":[{"tabs":['
    while read url; do
        echo '{'
        echo '"entries":[{"url":"'$url'"}]'
        echo '},'
    done <links
    echo '{}'
    echo ']'
    echo '}]'
    echo '}'
} >links.1

read size _ < <(wc -c links.1)

a=$((size % 256))
b=$(((size / 256) % 256))
c=$(((size / 256 / 256) % 256))

{
    printf 'mozLz40\0'
    printf '\x'$(printf '%x' $a)
    printf '\x'$(printf '%x' $b)
    printf '\x'$(printf '%x' $c)
    printf '\0'
    lz4 --no-frame-crc <links.1 | tail -c+12 | head -c-4
} >sessionstore.jsonlz4