BitStream
¶ ↑
BitStream
is a mixin to write data structures of bit streams such as picture, music, movie files, and e.t.c.. You can refer contents of bit streams even when you are defining the data structures. With the function, you can write a data structure easily that the header contains the data length of the body field.
Installation¶ ↑
gem install bitstream
Sample¶ ↑
gzip.rb: A metadata definition of a gzip file. ( www.gzip.org/zlib/rfc-gzip.html )
require 'bitstream' class Gzip include BitStream byte_order :little_endian FHCRC = 1 << 1 FEXTRA = 1 << 2 FNAME = 1 << 3 FCOMMENT = 1 << 4 fields do unsigned :id1, 8 unsigned :id2, 8 unsigned :cm, 8 unsigned :flg, 8 unsigned :mtime, 32 unsigned :xfl, 8 unsigned :os, 8 if (flg & FEXTRA) != 0 unsigned :xlen, 16 string :extra_field, xlen end if (flg & FNAME) != 0 # cstring means a NULL-terminated string. cstring :original_file_name end if (flg & FCOMMENT) != 0 # cstring means a NULL-terminated string. cstring :file_comment end if (flg & FHCRC) != 0 unsigned :crc16, 16 end end end
gzip-viewer.rb: A viewer of the original file name of a gzip file.
require_relative 'gzip' gzip = nil File.open(ARGV[0], "rb") do |file| gzip = Gzip.create(file.read) end if gzip.respond_to? :original_file_name puts "original_file_name:#{gzip.original_file_name}" else puts "The gzip does not contain its original file name." end
Documentation¶ ↑
In preparation.
License¶ ↑
This library is distributed under the dual license of the Ruby license (in the narrow sense) and the 2-clause BSD license. Please see www.ruby-lang.org and BSDL. Copyright © 2011, 2012 Natsuki Kawai.