1MIME::Base64(3pm)      Perl Programmers Reference Guide      MIME::Base64(3pm)
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NAME

6       MIME::Base64 - Encoding and decoding of base64 strings
7

SYNOPSIS

9        use MIME::Base64;
10
11        $encoded = encode_base64('Aladdin:open sesame');
12        $decoded = decode_base64($encoded);
13

DESCRIPTION

15       This module provides functions to encode and decode strings into and
16       from the base64 encoding specified in RFC 2045 - MIME (Multipurpose
17       Internet Mail Extensions). The base64 encoding is designed to represent
18       arbitrary sequences of octets in a form that need not be humanly read‐
19       able. A 65-character subset ([A-Za-z0-9+/=]) of US-ASCII is used,
20       enabling 6 bits to be represented per printable character.
21
22       The following functions are provided:
23
24       encode_base64($str)
25       encode_base64($str, $eol);
26           Encode data by calling the encode_base64() function.  The first
27           argument is the string to encode.  The second argument is the line-
28           ending sequence to use.  It is optional and defaults to "\n".  The
29           returned encoded string is broken into lines of no more than 76
30           characters each and it will end with $eol unless it is empty.  Pass
31           an empty string as second argument if you do not want the encoded
32           string to be broken into lines.
33
34       decode_base64($str)
35           Decode a base64 string by calling the decode_base64() function.
36           This function takes a single argument which is the string to decode
37           and returns the decoded data.
38
39           Any character not part of the 65-character base64 subset is
40           silently ignored.  Characters occurring after a '=' padding charac‐
41           ter are never decoded.
42
43           If the length of the string to decode, after ignoring non-base64
44           chars, is not a multiple of 4 or if padding occurs too early, then
45           a warning is generated if perl is running under "-w".
46
47       If you prefer not to import these routines into your namespace, you can
48       call them as:
49
50           use MIME::Base64 ();
51           $encoded = MIME::Base64::encode($decoded);
52           $decoded = MIME::Base64::decode($encoded);
53

DIAGNOSTICS

55       The following warnings can be generated if perl is invoked with the
56       "-w" switch:
57
58       Premature end of base64 data
59           The number of characters to decode is not a multiple of 4.  Legal
60           base64 data should be padded with one or two "=" characters to make
61           its length a multiple of 4.  The decoded result will be the same
62           whether the padding is present or not.
63
64       Premature padding of base64 data
65           The '=' padding character occurs as the first or second character
66           in a base64 quartet.
67
68       The following exception can be raised:
69
70       Wide character in subroutine entry
71           The string passed to encode_base64() contains characters with code
72           above 255.  The base64 encoding is only defined for single-byte
73           characters.  Use the Encode module to select the byte encoding you
74           want.
75

EXAMPLES

77       If you want to encode a large file, you should encode it in chunks that
78       are a multiple of 57 bytes.  This ensures that the base64 lines line up
79       and that you do not end up with padding in the middle. 57 bytes of data
80       fills one complete base64 line (76 == 57*4/3):
81
82          use MIME::Base64 qw(encode_base64);
83
84          open(FILE, "/var/log/wtmp") or die "$!";
85          while (read(FILE, $buf, 60*57)) {
86              print encode_base64($buf);
87          }
88
89       or if you know you have enough memory
90
91          use MIME::Base64 qw(encode_base64);
92          local($/) = undef;  # slurp
93          print encode_base64(<STDIN>);
94
95       The same approach as a command line:
96
97          perl -MMIME::Base64 -0777 -ne 'print encode_base64($_)' <file
98
99       Decoding does not need slurp mode if every line contains a multiple of
100       four base64 chars:
101
102          perl -MMIME::Base64 -ne 'print decode_base64($_)' <file
103
104       Perl v5.8 and better allow extended Unicode characters in strings.
105       Such strings cannot be encoded directly, as the base64 encoding is only
106       defined for single-byte characters.  The solution is to use the Encode
107       module to select the byte encoding you want.  For example:
108
109           use MIME::Base64 qw(encode_base64);
110           use Encode qw(encode);
111
112           $encoded = encode_base64(encode("UTF-8", "\x{FFFF}\n"));
113           print $encoded;
114

116       Copyright 1995-1999, 2001-2004 Gisle Aas.
117
118       This library is free software; you can redistribute it and/or modify it
119       under the same terms as Perl itself.
120
121       Distantly based on LWP::Base64 written by Martijn Koster
122       <m.koster@nexor.co.uk> and Joerg Reichelt <j.reichelt@nexor.co.uk> and
123       code posted to comp.lang.perl <3pd2lp$6gf@wsinti07.win.tue.nl> by Hans
124       Mulder <hansm@wsinti07.win.tue.nl>
125
126       The XS implementation uses code from metamail.  Copyright 1991 Bell
127       Communications Research, Inc. (Bellcore)
128

SEE ALSO

130       MIME::QuotedPrint
131
132
133
134perl v5.8.8                       2001-09-21                 MIME::Base64(3pm)
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