a.rb

def current_map_id world = nil
  return false unless File.exist?(nbt_path("data/idcounts.dat", world))
  file = File.open(nbt_path("data/idcounts.dat", world))
  cstrio = StringIO.new("rw")
  gz = Zlib::GzipWriter.new(cstrio)
  gz.write file.read
  gz.close
  cstrio.reopen("r")
  cstrio.rewind
  NBTFile.load(cstrio)
end

gistfile1.txt

[28] pry(#<Mcl::HMclImageMaps>)> cstrio = StringIO.new("rw")
=> #<StringIO:0x007f92164baed8>
[29] pry(#<Mcl::HMclImageMaps>)> gz = Zlib::GzipWriter.new(cstrio)
=> #<Zlib::GzipWriter:0x007f9216499170>
[30] pry(#<Mcl::HMclImageMaps>)> file = File.open(nbt_path("data/idcounts.dat", world))
=> #<File:/Volumes/code/_private/mcl/_server/world/data/idcounts.dat>
[31] pry(#<Mcl::HMclImageMaps>)> gz.write file.read
=> 12
[32] pry(#<Mcl::HMclImageMaps>)> file.rewind
=> 0
[33] pry(#<Mcl::HMclImageMaps>)> file.read
=> "\n\u0000\u0000\u0002\u0000\u0003map\u0000\u0000\u0000"
[34] pry(#<Mcl::HMclImageMaps>)> cstrio
=> #<StringIO:0x007f92164baed8>
[35] pry(#<Mcl::HMclImageMaps>)> cstrio.length
=> 10
[36] pry(#<Mcl::HMclImageMaps>)> gz.close
=> #<StringIO:0x007f92164baed8>
[37] pry(#<Mcl::HMclImageMaps>)> cstrio.length
=> 32
[38] pry(#<Mcl::HMclImageMaps>)> cstrio.rewind
=> 0
[39] pry(#<Mcl::HMclImageMaps>)> cstrio.read
IOError: not opened for reading
from (pry):45:in `read'
[40] pry(#<Mcl::HMclImageMaps>)> cstrio.reopen
=> #<StringIO:0x007f92164baed8>
[41] pry(#<Mcl::HMclImageMaps>)> cstrio.read
=> ""
[42] pry(#<Mcl::HMclImageMaps>)> cstrio.length
=> 0