These are very similar to the considerations that were discussed in RFC 3548, which documented Base32 and Base64. I assume they were pretty well known at the ti

These are very similar to the considerations that were discussed in RFC 3548, which documented Base32 and Base64. I assume they were pretty well known at the time the code you linked to was written. https://tools.ietf.org/html/rfc3548 https://tools.ietf.org/html/rfc3548