#!/usr/bin/ruby

def dumpgrib1 line
  #puts [line.size, ("\0" + line[0,3]).unpack('N').first]
  ofs = 4
  isec = 1
  while ofs < line.size
    secl = ("\0" + line[ofs,3]).unpack('N').first
    sec = line[ofs,secl]
    h = {
      :p1 => sec[18],
      :p2 => sec[19],
      :timerange => sec[20],
      :parameter => sec[8],
      :leveltype => sec[9],
      :level => sec[10,2].unpack('n').first
    }
    p h
    return if isec == 1
    ofs += secl
    isec += 1
  end
end

def dumpgrib line
  case line[3]
  when 1 then dumpgrib1(line)
  #when 2 then dumpgrib2
  else raise "unsupported grib edition #{line[3]}"
  end
end

def dumpfile fnam
  File.open(fnam, 'rb') {|fp|
    fp.binmode
    fp.each('GRIB') {|line|
      next unless /7777/ === line
      dumpgrib line
    }
  }
end

for file in ARGV
  dumpfile file
end