http://tcllib.sourceforge.net/doc/base64.html
Background: Base64 is a way to encode arbitrary binary data in such a way that the result contains only printable characters and are thus able to pass unchanged even through old applications which are not 8bit-ASCII clean.
Base64 is related to UUencoding in that it uses the same mechanism of distributing the bits in 3 bytes into 4 bytes. But it uses a different table to map the resulting data into printable characters.
The above means that base64 encoded data takes one-third more space than the data before the conversion.
Base 64 encode/decode has been retired now - the Tcllib module is the recommended one.
Category Package, subset Tcllib