FAQ 9.18 How do I decode a MIME/BASE64 string?


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This is an excerpt from the latest version perlfaq9.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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9.18: How do I decode a MIME/BASE64 string?

The "MIME-Base64" package (available from CPAN) handles this as well as
the MIME/QP encoding. Decoding BASE64 becomes as simple as:

use MIME::Base64;
$decoded = decode_base64($encoded);

The "MIME-Tools" package (available from CPAN) supports extraction with
decoding of BASE64 encoded attachments and content directly from email
messages.

If the string to decode is short (less than 84 bytes long) a more direct
approach is to use the "unpack()" function's "u" format after minor
transliterations:

tr#A-Za-z0-9+/##cd; # remove non-base64 chars
tr#A-Za-z0-9+/# -_#; # convert to uuencoded format
$len = pack("c", 32 + 0.75*length); # compute length byte
print unpack("u", $len . $_); # uudecode and print



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