manpagez: man(ual) pages & more
man MIME::Base64(3)
Home | html | info | man
MIME::Base64(3pm)      Perl Programmers Reference Guide      MIME::Base64(3pm)




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 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 primary functions are provided:

       encode_base64( $bytes )
       encode_base64( $bytes, $eol );
           Encode data by calling the encode_base64() function.  The first
           argument is the byte string to encode.  The second argument is the
           line-ending sequence to use.  It is optional and defaults to "\n".
           The returned encoded string is broken into lines of no more than 76
           characters 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 to be broken into lines.

           The function will croak with "Wide character in subroutine entry"
           if $bytes contains characters with code above 255.  The base64
           encoding is only defined for single-byte characters.  Use the
           Encode module to select the byte encoding you want.

       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 subset is
           silently ignored.  Characters occurring after a '=' padding
           character are never decoded.

       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);

       Additional functions not exported by default:

       encode_base64url( $bytes )
       decode_base64url( $str )
           Encode and decode according to the base64 scheme for "URL
           applications" [1].  This is a variant of the base64 encoding which
           does not use padding, does not break the string into multiple lines
           and use the characters "-" and "_" instead of "+" and "/" to avoid
           using reserved URL characters.

       encoded_base64_length( $bytes )
       encoded_base64_length( $bytes, $eol )
           Returns the length that the encoded string would have without
           actually encoding it.  This will return the same value as
           "length(encode_base64($bytes))", but should be more efficient.

       decoded_base64_length( $str )
           Returns the length that the decoded string would have without
           actually decoding it.  This will return the same value as
           "length(decode_base64($str))", but should be more efficient.


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 every line contains a multiple of
       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 base64 encoding is only
       defined for single-byte characters.  The solution is to use the Encode
       module to select the byte encoding you want.  For example:

           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, 2010 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 uses code from metamail.  Copyright 1991 Bell
       Communications Research, Inc. (Bellcore)


SEE ALSO

       MIME::QuotedPrint(3)

       [1] <http://en.wikipedia.org/wiki/Base64#URL_applications>



perl v5.24.0                      2016-03-01                 MIME::Base64(3pm)

perl 5.24 - Generated Thu Nov 17 18:37:59 CST 2016
© manpagez.com 2000-2017
Individual documents may contain additional copyright information.