$ctx->add_bits("\xF0\xA0", 12);

Most digest algorithms are byte based.  For those it is not possible
to add bits that are not a multiple of 8, and the add_bits() method
will croak if you try.

=item $ctx->digest

Return the binary digest for the message.

Note that the C<digest> operation is effectively a destructive,
read-once operation. Once it has been performed, the $ctx object is
automatically C<reset> and can be used to calculate another digest
value.  Call $ctx->clone->digest if you want to calculate the digest
without reseting the digest state.

=item $ctx->hexdigest

Same as $ctx->digest, but will return the digest in hexadecimal form.

=item $ctx->b64digest

Same as $ctx->digest, but will return the digest as a base64 encoded
string.

=back

=head1 Digest speed

This table should give some indication on the relative speed of
different algorithms.  It is sorted by throughput based on a benchmark
done with of some implementations of this API:

 Algorithm      Size    Implementation                  MB/s

 MD4            128     Digest::MD4 v1.3               165.0
 MD5            128     Digest::MD5 v2.33               98.8
 SHA-256        256     Digest::SHA2 v1.1.0             66.7
 SHA-1          160     Digest::SHA v4.3.1              58.9
 SHA-1          160     Digest::SHA1 v2.10              48.8
 SHA-256        256     Digest::SHA v4.3.1              41.3
 Haval-256      256     Digest::Haval256 v1.0.4         39.8
 SHA-384        384     Digest::SHA2 v1.1.0             19.6
 SHA-512        512     Digest::SHA2 v1.1.0             19.3
 SHA-384        384     Digest::SHA v4.3.1              19.2
 SHA-512        512     Digest::SHA v4.3.1              19.2
 Whirlpool      512     Digest::Whirlpool v1.0.2        13.0
 MD2            128     Digest::MD2 v2.03                9.5

 Adler-32        32     Digest::Adler32 v0.03            1.3
 CRC-16          16     Digest::CRC v0.05                1.1
 CRC-32          32     Digest::CRC v0.05                1.1
 MD5            128     Digest::Perl::MD5 v1.5           1.0
 CRC-CCITT       16     Digest::CRC v0.05                0.8

These numbers was achieved Apr 2004 with ActivePerl-5.8.3 running
under Linux on a P4 2.8 GHz CPU.  The last 5 entries differ by being
pure perl implementations of the algorithms, which explains why they
are so slow.

=head1 SEE ALSO

L<Digest::Adler32>, L<Digest::CRC>, L<Digest::Haval256>,
L<Digest::HMAC>, L<Digest::MD2>, L<Digest::MD4>, L<Digest::MD5>,
L<Digest::SHA>, L<Digest::SHA1>, L<Digest::SHA2>, L<Digest::Whirlpool>

New digest implementations should consider subclassing from L<Digest::base>.

L<MIME::Base64>

=head1 AUTHOR

Gisle Aas <gisle@aas.no>

The C<Digest::> interface is based on the interface originally
developed by Neil Winton for his C<MD5> module.

This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

    Copyright 1998-2001,2003-2004 Gisle Aas.
    Copyright 1995-1996 Neil Winton.

=cut