Class: Xid::Base32

Inherits:
Object
  • Object
show all
Defined in:
lib/xid/base32.rb

Constant Summary collapse

ENCODE_HEX = 
'0123456789abcdefghijklmnopqrstuv'.freeze
PAD_CHAR = 
'='.freeze

Class Method Summary collapse

Class Method Details

.b32decode(src) ⇒ Object 



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# File 'lib/xid/base32.rb', line 19

def b32decode(src)
  decode(src, ENCODE_HEX)
end

.b32encode(src) ⇒ Object 



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# File 'lib/xid/base32.rb', line 14

def b32encode(src)
  src = src.scan(/.{1}/m).map(&:ord)
  encode(src, ENCODE_HEX)
end

.decode(src, str_map) ⇒ Object 



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# File 'lib/xid/base32.rb', line 77

def decode(src, str_map)
  src.downcase!

  end_loop = false
  result = []
  while src && !src.empty? && !end_loop
    dst = [0] * 5
    dbuf = [0] * 8
    src_len = 8

    (0..8).each do |i|
      if i >= src.length
        src_len = i
        end_loop = true
        break
      end
      char = src[i]
      if char == PAD_CHAR
        end_loop = true
        src_len = i
        break
      else
        dbuf[i] = decode_hex_map[char]
      end
    end

    if src_len >= 8
      dst[4] = (dbuf[6] << 5) | (dbuf[7])
    end
    if src_len >= 7
      dst[3] = (dbuf[4] << 7) | (dbuf[5] << 2) | (dbuf[6] >> 3)
    end
    if src_len >= 5
      dst[2] = (dbuf[3] << 4) | (dbuf[4] >> 1)
    end
    if src_len >= 4
      dst[1] = (dbuf[1] << 6) | (dbuf[2] << 1) | (dbuf[3] >> 4)
    end
    if src_len >= 2
      dst[0] = (dbuf[0] << 3) | (dbuf[1] >> 2)
    end

    dst = dst.map { |x| x & 0xff }

    if src_len == 2
      dst = dst[0]
    elsif src_len == 4
      dst = dst[0..1]
    elsif src_len == 5
      dst = dst[0..2]
    elsif src_len == 7
      dst = dst[0..3]
    elsif src_len == 8
      dst = dst[0..4]
    end

    result += dst
    src = src[8..src.length]
  end

  result
end

.decode_hex_map ⇒ Object 



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# File 'lib/xid/base32.rb', line 10

def decode_hex_map
  Hash[ENCODE_HEX.chars.each_with_index.map { |x, i| [x, i] }]
end

.encode(src_str, str_map) ⇒ Object 



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# File 'lib/xid/base32.rb', line 23

def encode(src_str, str_map)
  return '' if src_str.empty?

  dst = []
  src_len = 0
  while src_str && !src_str.empty?
    src_len = src_str.length
    next_byte = [0] * 8

    if src_len > 4
      next_byte[7] = src_str[4] & 0x1f
      next_byte[6] = src_str[4] >> 5
    end
    if src_len > 3
      next_byte[6] = next_byte[6] | (src_str[3] << 3) & 0x1f
      next_byte[5] = (src_str[3] >> 2) & 0x1f
      next_byte[4] = src_str[3] >> 7
    end
    if src_len > 2
      next_byte[4] = next_byte[4] | (src_str[2] << 1) & 0x1f
      next_byte[3] = (src_str[2] >> 4) & 0x1f
    end
    if src_len > 1
      next_byte[3] = next_byte[3] | (src_str[1] << 4) & 0x1f
      next_byte[2] = (src_str[1] >> 1) & 0x1f
      next_byte[1] = (src_str[1] >> 6) & 0x1f
    end
    if src_len > 0
      next_byte[1] = next_byte[1] | (src_str[0] << 2) & 0x1f
      next_byte[0] = src_str[0] >> 3
    end

    next_byte.each do |nb|
      dst << str_map[nb]
    end
    src_str = src_str[5..src_str.length]
  end

  dst[-1] = '=' if src_len < 5
  if src_len < 4
    dst[-2] = '='
    dst[-3] = '='
  end
  if src_len < 3
    dst[-4] = '='
  end
  if src_len < 2
    dst[-5] = '='
    dst[-6] = '='
  end

  dst.join('')
end