base 64
<file format, algorithm> A file format using 64 ASCII characters to
encode the six bit binary data values 0-63.
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.
Base 64 is used when transmitting binary data through text-only media such as
electronic mail, and has largely replaced the older uuencode encoding.
(2004-07-17)
Nearby terms:
baroque « barrel shifter « base « base 64 »
baseband » base class » baseline
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