module Base32H

This module provides Base32H encoding and decoding functions.

Constants

VERSION

Public Instance Methods

decode(str) click to toggle source

Decodes a Base32H number to its integer representation.

@param str [#to_s] the number to decode

@return [Integer] the decoded integer

# File lib/base32h.rb, line 130
def decode(str)
  res = str.to_s.chars.reverse.reduce({acc: 0, exp: 0}) do |state, char|
    digit = decode_digit(char)
    if digit.nil?
      state
    else
      {acc: state[:acc] + (digit * 32**state[:exp]),
       exp: state[:exp] + 1}
    end
  end
  res[:acc]
end

decode_bin(str) click to toggle source

Decodes a Base32H binary into a string of packed unsigned bytes.

@param str [String] the binary to decode

@return [String] the decoded binary

# File lib/base32h.rb, line 149
def decode_bin(str)
  data = str.chars.reject {|c| decode_digit(c).nil?}
  extra = data.length % 8
  data = (['0'] * (8 - extra)) + data if extra > 0
  out = []
  data.each_slice(8) do |s|
    chunk = u40_to_bytes decode(s.join '')
    out += chunk
  end
  out.pack('C*')
end

decode_digit(d) click to toggle source

Decodes a single Base32H digit to its integer representation. Returns nil if the input is not a Base32H digit.

@param d [#to_s] the digit to decode

@return [Integer] the digit's value

# File lib/base32h.rb, line 119
def decode_digit(d)
  d = d.to_s
  digits.find_index {|i| i.include? d}
end

digits() click to toggle source

The complete list of Base32H digits, as an array of strings. The index of the array is the numeric value of the digit(s) in the string at that index. The first character in each string is the “canonical” digit (i.e. the one that Base32H-conformant encoders must emit for that value); all other characters (if present) are “aliases” (i.e. alternate forms of that digit that Base32H-conformant decoders must accept and correctly decode to that value).

@example

Base32H.digits[27] #=> 'VvUu'

@return [Array<String>] the full list of digits

# File lib/base32h.rb, line 22
def digits
  ['0Oo',
   '1Ii',
   '2',
   '3',
   '4',
   '5Ss',
   '6',
   '7',
   '8',
   '9',
   'Aa',
   'Bb',
   'Cc',
   'Dd',
   'Ee',
   'Ff',
   'Gg',
   'Hh',
   'Jj',
   'Kk',
   'Ll',
   'Mm',
   'Nn',
   'Pp',
   'Qq',
   'Rr',
   'Tt',
   'VvUu',
   'Ww',
   'Xx',
   'Yy',
   'Zz']
end

encode(int) click to toggle source

Encodes an integer to its Base32H representation.

@param int [#to_i] the integer to encode

@return [String] the encoded number

# File lib/base32h.rb, line 79
def encode(int)
  rem = int.to_i.abs
  out = []
  return '0' if rem == 0
  while rem > 0 do
    out.unshift(encode_digit(rem % 32))
    rem /= 32
  end
  out.join ''
end

encode_bin(bin) click to toggle source

Encodes a (binary) string to its Base32H representation.

@param bin [String] the string/binary to encode

@return [String] the encoded binary

# File lib/base32h.rb, line 96
def encode_bin(bin)
  data = bin.unpack('C*')
  extra = data.length % 5
  data = ([0] * (5 - extra)) + data if extra > 0
  out = []
  data.each_slice(5) do |s|
    chunk = bytes_to_u40 s
    out.push encode(chunk).rjust(8, '0')
  end
  out.join ''
end

encode_digit(d) click to toggle source

Encodes an integer between 0 and 31 (inclusive) to its Base32H representation. Returns nil for input values outside that range.

@param d [#to_i] the integer value of the requested digit

@return [String, NilClass] the resulting digit

# File lib/base32h.rb, line 67
def encode_digit(d)
  d = d.to_i
  return nil unless (0..31).include? d
  digits[d][0]
end

Private Instance Methods

bytes_to_u40(bytes) click to toggle source

# File lib/base32h.rb, line 177
def bytes_to_u40(bytes)
  bytes.reverse.reduce({acc:0,exp:0}) do |s,b|
    {acc: s[:acc] + (b * 2**(8*s[:exp])),
     exp: s[:exp] + 1}
  end[:acc]
end

u40_to_bytes(int) click to toggle source

@!endgroup

# File lib/base32h.rb, line 165
def u40_to_bytes(int)
  rem = int.to_i.abs
  out = []
  while rem > 0 do
    out.unshift(rem % 256)
    rem /= 256
  end
  pad = 5 - out.length
  out = ([0] * pad) + out if pad > 0
  out
end