holes.rb

#!/usr/bin/ruby

require 'json'

CLUSTER_SIZE = 65536

map = JSON.parse(IO.read('map.txt')).select { |e| e['offset'] }.sort { |x, y| x['offset'] <=> y['offset'] }

ofs = 0
max_gap = 0
output = []
for e in map
    gap = (e['offset'] - ofs) / CLUSTER_SIZE
    if gap > 0
        output << "Gap of #{gap} clusters between #{ofs} and #{e['offset']}"
        max_gap = gap if gap > max_gap
    end
    ofs = e['offset'] + e['length']
end

IO.write("/tmp/gaps.txt", output * $/)
puts "Maximum gap: #{max_gap} clusters"