crc32c for ruby

crc32er.rb

require 'digest/crc32c' #  gem install digest-crc
p 'syntax: something to get digested! [output it with trailing 4 byte digest, in ruby string syntax]'
checksum = Digest::CRC32c.checksum(ARGV[0])
p checksum
out = ARGV[0].dup.bytes # assume it starts ascii :|
for n in [24, 16, 8, 0]
  next_byte = (checksum >> n & 0xff)
  out << next_byte
  p "x%x" % next_byte
end
p out
p 'total bytes:'
p out.to_a.join(',')
File.open("raw_bytes", "wb") do |f|
  out.each{|b|
    f.print b.chr
  }
end
puts "wrote raw_bytes file" # can send to tape device or what have you

NB that some implementations do the bytes in the reverse order than this :| (LT08 is reverse this, T10K uses the above)

If I'm reading this correctly, this is reversing the byte order, which can be done more succinctly with Ruby's built-in pack:

cksum = Digest::CRC32c.file(filepath).checksum # or Digest::CRC32c.checksum(string)
cksum_big_endian = [cksum].pack('L>') # pack as 32-bit BE int
# `cksum_big_endian` is a raw byte string
Base64.encode64(cksum_big_endian).chomp # These checksums are commonly expressed in base64 encoding