MIME::Base64(3p) Perl Programmers Reference Guide MIME::Base64(3p)

MIME::Base64(3p) Perl Programmers Reference Guide MIME::Base64(3p) #

MIME::Base64(3p) Perl Programmers Reference Guide MIME::Base64(3p)

NNAAMMEE #

 MIME::Base64 - Encoding and decoding of base64 strings

SSYYNNOOPPSSIISS #

  use MIME::Base64;

  $encoded = encode_base64('Aladdin:open sesame');
  $decoded = decode_base64($encoded);

DDEESSCCRRIIPPTTIIOONN #

 This module provides functions to encode and decode strings into and from
 the base64 encoding specified in RFC 2045 - _M_I_M_E _(_M_u_l_t_i_p_u_r_p_o_s_e _I_n_t_e_r_n_e_t
 _M_a_i_l _E_x_t_e_n_s_i_o_n_s_). 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 eennccooddee__bbaassee6644(()) 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 ddeeccooddee__bbaassee6644(()) 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.

EEXXAAMMPPLLEESS #

 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;

CCOOPPYYRRIIGGHHTT #

 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)

SSEEEE AALLSSOO #

 MIME::QuotedPrint

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

perl v5.36.3 2023-02-15 MIME::Base64(3p)