base64(3)
NAME
MIME::Base64 - Encoding and decoding of base64 strings
SYNOPSIS
use MIME::Base64;
$encoded = encode_base64('Aladdin:open sesame');
$decoded = decode_base64($encoded);
DESCRIPTION
This module provides functions to encode and decode
strings into the Base64 encoding specified in RFC 2045 MIME (Multipurpose Internet Mail Extensions). The Base64
encoding is designed to represent arbitrary sequences of
octets in a form that need not be humanly readable. A
65-character subset ([A-Za-z0-9+/=]) of US-ASCII is used,
enabling 6 bits to be represented per printable character.
The following functions are provided:
- encode_base64($str, [$eol])
- Encode data by calling the encode_base64() function.
The first argument is the string to encode. The sec
ond argument is the line ending sequence to use (it is
optional and defaults to "0). The returned encoded
string is broken into lines of no more than 76 charac
ters each and it will end with $eol unless it is
empty. Pass an empty string as second argument if you
do not want the encoded string broken into lines. - decode_base64($str)
- Decode a base64 string by calling the decode_base64()
function. This function takes a single argument which
is the string to decode and returns the decoded data. - Any character not part of the 65-character base64 sub
set set is silently ignored. Characters occuring
after a '=' padding character are never decoded. - If the length of the string to decode (after ignoring
non-base64 chars) is not a multiple of 4 or padding
occurs too ealy, then a warning is generated if perl
is running under "-w". - If you prefer not to import these routines into your
namespace you can call them as:
use MIME::Base64 ();
$encoded = MIME::Base64::encode($decoded);
$decoded = MIME::Base64::decode($encoded);
DIAGNOSTICS
The following warnings might be generated if perl is
invoked with the "-w" switch:
- Premature end of base64 data
- The number of characters to decode is not a multiple
of 4. Legal base64 data should be padded with one or
two "=" characters to make its length a multiple of 4.
The decoded result will anyway be as if the padding
was there. - Premature padding of base64 data
- The '=' padding character occurs as the first or sec
ond character in a base64 quartet.
EXAMPLES
- If you want to encode a large file, you should encode it
in chunks that are a multiple of 57 bytes. This ensures
that the base64 lines line up and that you do not end up
with padding in the middle. 57 bytes of data fills one
complete base64 line (76 == 57*4/3): - use MIME::Base64 qw(encode_base64);
- open(FILE, "/var/log/wtmp") or die "$!";
while (read(FILE, $buf, 60*57)) {print encode_base64($buf); - }
- or if you know you have enough memory
use MIME::Base64 qw(encode_base64);
local($/) = undef; # slurp
print encode_base64(<STDIN>);- The same approach as a command line:
perl -MMIME::Base64 -0777 -ne 'print encode_base64($_)'- <file
- Decoding does not need slurp mode if all the lines con
tains a multiple of 4 base64 chars:
perl -MMIME::Base64 -ne 'print decode_base64($_)' <file
COPYRIGHT
Copyright 1995-1999, 2001 Gisle Aas.
This library is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.
Distantly based on LWP::Base64 written by Martijn Koster
<m.koster@nexor.co.uk> and Joerg Reichelt
<j.reichelt@nexor.co.uk> and code posted to comp.lang.perl
<3pd2lp$6gf@wsinti07.win.tue.nl> by Hans Mulder
<hansm@wsinti07.win.tue.nl>
- The XS implementation use code from metamail. Copyright
1991 Bell Communications Research, Inc. (Bellcore)