##
## UTF-5 library for Ruby
##   (draft-jseng-utf5-01.txt)
## Nov 9, 2000 by yoshidam
##

require 'uconv'

module Uconv
  UTF5TRANS = "0123456789ABCDEFGHIJKLMNOPQRSTUV"

  def self._uarytoutf5(uary)
    ret = ""
    uary.each do |u|
      if u < 0x10
        len = 1
      elsif u < 0x100
        len = 2
      elsif u < 0x1000
        len = 3
      elsif u < 0x10000
        len = 4
      elsif u < 0x100000
        len = 5
      elsif u < 0x1000000
        len = 6
      elsif u < 0x10000000
        len = 7
      elsif u < 0x80000000
        len = 8
      else
        raise "invalid ucs-4"
      end

      for i in 1..len
        c = (u >> (4*(len - i))) & 0xf
        c |= 0x10 if i == 1
        ret << UTF5TRANS[c]
      end
    end
    ret
  end

  def self._utf5touary(utf5)
    ret = []
    start = 1
    cc = nil
    utf5.each_byte do |c|
      v = UTF5TRANS.index(c.chr)
      raise "invalid utf-5" unless v
      if v >= 0x10
        ret << cc if cc
        cc = v & 0xf
      else
        cc = (cc << 4) | v
      end
    end
    ret << cc if cc
    ret
  end

  def self.u8tou5(utf8)
    _uarytoutf5(utf8.unpack("U*"))
  end

  def self.u5tou8(utf5)
    _utf5touary(utf5).pack("U*")
  end
end