For a bijective base: 7 bits -> Decode 0xxxxxxx and add 0 (unchanged) 14 bits -> Decode 10xxxxxx xxxxxxxx and add 0x80 21 bits -> Decode 110xxxxx x

For a bijective base: 7 bits -> Decode 0xxxxxxx and add 0 (unchanged) 14 bits -> Decode 10xxxxxx xxxxxxxx and add 0x80 21 bits -> Decode 110xxxxx xxxxxxxx xxxxxxxx and add 0x4080 In a non-bijective base vs a bijective base: 7 bits encode 0 to 2&7 - 1 vs. 0 to 2^7 -1 14 bits encode 0 to 2^14 - 1 vs. 2^7 to 2^14 + 2^7 - 1 21 bits encode 0 to 2^21 - 1 vs. 2^14 + 2^7 to 2^21 + 2^14 + 2^7 - 1 ... In the bijective decoding routine, you need to special-case the maximum length case to check for numeric overflow.