#!/usr/bin/env ruby
# dsgrep [FILES...] - find lines with high entropy
# 
# This tool works like grep; use radare2 or binwalk for binary files!

THRESHOLD = Float(ENV["DSTHRES"]) rescue 5

def entropy(s)
  s = s.b
  (0..255).sum { |e|
    px = s.count(e.chr).to_f / s.size
    px > 0 ? (-px)*Math.log2(px) : 0
  }
end

while line = gets
  next  if line.size < 6 || line.size > 100

  if entropy(line) >= THRESHOLD
    if ARGV.size > 1
      print "#{ARGF.filename}:#{ARGF.file.lineno}:"
    end
    puts line
  end

end