This program is designed to encode and decode a typical Base64 stream from an input stream.
make
then
cp b64 /usr/local/bin
For manpage:
cp manpage/b64.1.gz /usr/local/share/man/man1
Usage: b64 [-e] [-d ASCII/binary] [-i if] [-o of]
There are a few technical explanations in the header files. Otherwise, there is some info here as well.
Default input stream is stdin.
Default output stream is stdout.
fgetc() loads 3 bytes into a 32-bit variable to force big-endian byte order. Then, B64 encoding is performed using a 6-bit mask and bit shifts and the ASCII-encoded characters are sent to the output stream.
For decoding, a 32-bit variable is loaded with 3 bytes using fgetc() to force a big-endian byte order. Then, depending on whether the output is specified to be either ASCII or binary, the decoded data will be sent to the output stream.
base64 provided by GNU coreutilsis 4 times faster and I attribute this to the
superfluous i/o calls in my program.