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MAN page from RedHat EL 3 perl-MIME-Base64-revival-3.09-2.el3.i386.rpm

Base64

Section: User Contributed Perl Documentation (3)
Updated: 2010-01-25
Index 

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 and from thebase64 encoding specified in RFC 2045 - MIME (Multipurpose InternetMail Extensions). The base64 encoding is designed to representarbitrary sequences of octets in a form that need not be humanlyreadable. 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($str)
encode_base64($str, $eol);
Encode data by calling the encode_base64() function. The firstargument is the string to encode. The second argument is theline-ending sequence to use. It is optional and defaults to ``\n''. Thereturned encoded string is broken into lines of no more than 76characters each and it will end with $eol unless it is empty. Pass anempty string as second argument if you do not want the encoded stringto be broken into lines.
decode_base64($str)
Decode a base64 string by calling the decode_base64() function. Thisfunction takes a single argument which is the string to decode andreturns the decoded data.

Any character not part of the 65-character base64 subset issilently ignored. Characters occurring after a '=' padding characterare never decoded.

If the length of the string to decode, after ignoringnon-base64 chars, is not a multiple of 4 or if padding occurs too early,then a warning is generated if perl is running under "-w".

If you prefer not to import these routines into your namespace, you cancall them as:

    use MIME::Base64 ();    $encoded = MIME::Base64::encode($decoded);    $decoded = MIME::Base64::decode($encoded);
 

DIAGNOSTICS

The following warnings can 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. Legalbase64 data should be padded with one or two ``='' characters to makeits length a multiple of 4. The decoded result will be the samewhether the padding is present or not.
Premature padding of base64 data
The '=' padding character occurs as the first or second characterin a base64 quartet.

The following exception can be raised:

Wide character in subroutine entry
The string passed to encode_base64() contains characters with codeabove 255. The base64 encoding is only defined for single-bytecharacters. Use the Encode module to select the byte encoding youwant.
 

EXAMPLES

If you want to encode a large file, you should encode it in chunksthat are a multiple of 57 bytes. This ensures that the base64 linesline up and that you do not end up with padding in the middle. 57bytes 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 every line contains a multipleof four base64 chars:

   perl -MMIME::Base64 -ne 'print decode_base64($_)' <file

Perl v5.8 and better allow extended Unicode characters in strings.Such strings cannot be encoded directly, as the base64encoding is only defined for single-byte characters. The solution isto use the Encode module to select the byte encoding you want. Forexample:

    use MIME::Base64 qw(encode_base64);    use Encode qw(encode);

    $encoded = encode_base64(encode("UTF-8", "\x{FFFF}\n"));    print $encoded;
 

COPYRIGHT

Copyright 1995-1999, 2001-2004 Gisle Aas.

This library is free software; you can redistribute it and/ormodify 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.reicheltAATTnexor.co.uk> andcode posted to comp.lang.perl <3pd2lp$6gfAATTwsinti07.win.tue.nl> by HansMulder <hansmAATTwsinti07.win.tue.nl>

The XS implementation uses code from metamail. Copyright 1991 BellCommunications Research, Inc. (Bellcore) 

SEE ALSO

MIME::QuotedPrint


 

Index

NAME
SYNOPSIS
DESCRIPTION
DIAGNOSTICS
EXAMPLES
COPYRIGHT
SEE ALSO

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