To convert data to base 64, the first byte is placed in the

most significant eight bits of a 24-bit buffer, the next in

the middle eight, and the third in the least significant eight

bits. If there a fewer than three bytes to encode, the

corresponding buffer bits will be zero. The buffer is then

used, six bits at a time, most significant first, as indices

into the string

"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

and the indicated character output. If there were only one or

two input bytes, the output is padded with two or one "="

characters respectively. This prevents extra bits being added

to the reconstructed data. The process then repeats on the

remaining input data.