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require 'openssl'
# Module for encoding and decoding in Base32 per RFC 3548
module Base32
TABLE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'.freeze
class Chunk
def initialize(bytes)
@bytes = bytes
end
def decode
bytes = @bytes.take_while {|c| c != 61} # strip padding
n = (bytes.length * 5.0 / 8.0).floor
p = bytes.length < 8 ? 5 - (n * 8) % 5 : 0
c = bytes.inject(0) {|m,o| (m << 5) + Base32.table.index(o.chr)} >> p
(0..n-1).to_a.reverse.collect {|i| ((c >> i * 8) & 0xff).chr}
end
def encode
n = (@bytes.length * 8.0 / 5.0).ceil
p = n < 8 ? 5 - (@bytes.length * 8) % 5 : 0
c = @bytes.inject(0) {|m,o| (m << 8) + o} << p
[(0..n-1).to_a.reverse.collect {|i| Base32.table[(c >> i * 5) & 0x1f].chr},
("=" * (8-n))]
end
end
def self.chunks(str, size)
result = []
bytes = str.bytes
while bytes.any? do
result << Chunk.new(bytes.take(size))
bytes = bytes.drop(size)
end
result
end
def self.encode(str)
chunks(str, 5).collect(&:encode).flatten.join
end
def self.decode(str)
chunks(str, 8).collect(&:decode).flatten.join
end
def self.random_base32(length=16, padding=true)
random = ''
OpenSSL::Random.random_bytes(length).each_byte do |b|
random << self.table[b % 32]
end
padding ? random.ljust((length / 8.0).ceil * 8, '=') : random
end
def self.table=(table)
raise ArgumentError, "Table must have 32 unique characters" unless self.table_valid?(table)
@table = table
end
def self.table
@table || TABLE
end
def self.table_valid?(table)
table.bytes.to_a.size == 32 && table.bytes.to_a.uniq.size == 32
end
end
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