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fix calculation of pad bits length while decoding #18

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fix calculation of pad bits length while decoding #18

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2 changes: 1 addition & 1 deletion lib/base32.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ def initialize(bytes)
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
p = n == 0 ? 5 : (bytes.length * 5) % (n * 8)
c = bytes.inject(0) do |m,o|
i = Base32.table.index(o.chr)
raise ArgumentError, "invalid character '#{o.chr}'" if i.nil?
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19 changes: 19 additions & 0 deletions test/base32_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,11 @@ def assert_decoding(encoded, plain)
assert_equal(plain, decoded)
end

def assert_hex_decoding(encoded, hex)
plain = [hex].pack('H*')
assert_decoding(encoded, plain)
end

def assert_encoding(encoded, plain)
actual = Base32.encode(plain)
assert_equal(encoded, actual)
Expand Down Expand Up @@ -121,4 +126,18 @@ def test_encode_decode_with_alternate_table
Base32.table = Base32::TABLE # so as not to ruin other tests
end

def test_decoding_ignores_pad_bits
assert_hex_decoding('M', '') # (01100)
assert_hex_decoding('MU', '65') # 01100 101(00)
assert_hex_decoding('MV', '65') # 01100 101(01)
assert_hex_decoding('MVS', '65') # 01100 101(01 10010)
assert_hex_decoding('MVSA', '6564') # 01100 10101 10010 0(0000)
assert_hex_decoding('MVSJ', '6564') # 01100 10101 10010 0(1001)
assert_hex_decoding('MVSJO', '656497') # 01100 10101 10010 01001 0111(0)
assert_hex_decoding('MVSJP', '656497') # 01100 10101 10010 01001 0111(1)
assert_hex_decoding('MVSJOA', '656497') # 01100 10101 10010 01001 0111(0 00000)
assert_hex_decoding('MVSJOY', '656497') # 01100 10101 10010 01001 0111(0 11000)
assert_hex_decoding('MVSJOYQ', '65649762') # 01100 10101 10010 01001 01110 11000 10(000)
assert_hex_decoding('MVSJOYX', '65649762') # 01100 10101 10010 01001 01110 11000 10(111)
end
end