Ruby code to convert an Integer to a Binary Coded Decimal (BCD) array of bytes

ruby-int-to-bcd.rb

  # Convert an Integer to a "Packed" Binary Coded Decimal (BCD) formatted array of bytes
  # http://en.wikipedia.org/wiki/Binary-coded_decimal
  def int_to_bcd_bytes(int)
    # BCD format takes each digit of an integer value and encodes it into a nibble (4 bits)
    # It maintains the order of the original digits, so 15 would be 00010101
    # Since we're dealing with nibbles, we have to zero-pad-left if the number has an odd number of digits
    # Decimal digit   Binary
    #   0             0000
    #   1             0001
    #   2             0010
    #   3             0011
    #   4             0100
    #   5             0101
    #   6             0110
    #   7             0111
    #   8             1000
    #   9             1001

    bcd_string = ''
    s = int.to_s
    s = '0' + s if s.length.odd?
    s.chars.each do |digit|
      bcd_string += sprintf("%04b", digit) # digit encoded as nibble
    end
    bcd_bytes = [bcd_string].pack("B*").unpack("C*")
  end

Hello,

The code can be simplified. When converting an integer to string, the string you get is valid BCD. There is no need to go through the string once more before the final pack-unpack. Hence, you need to treat string characters as hex values during packing.

def int_to_bcd_bytes(int)
  bcd_string = int.to_s
  bcd_string.insert(0, '0') if bcd_string.length.odd?
  [bcd_string].pack('H*').unpack('C*')
end

Command line examples:

2.1.1 :117 > result = int_to_bcd_bytes(0); puts "#{result} - #{result.collect { |i| '%02X' % i }}"
[0] - ["00"]
 => nil 
2.1.1 :118 > result = int_to_bcd_bytes(1); puts "#{result} - #{result.collect { |i| '%02X' % i }}"
[1] - ["01"]
 => nil 
2.1.1 :119 > result = int_to_bcd_bytes(10); puts "#{result} - #{result.collect { |i| '%02X' % i }}"
[16] - ["10"]
 => nil 
2.1.1 :120 > result = int_to_bcd_bytes(110); puts "#{result} - #{result.collect { |i| '%02X' % i }}"
[1, 16] - ["01", "10"]
 => nil 
2.1.1 :121 > result = int_to_bcd_bytes(9910); puts "#{result} - #{result.collect { |i| '%02X' % i }}"
[153, 16] - ["99", "10"]
 => nil