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=head1 NAME |
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Net::FCP::Util - utility functions. |
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=head1 SYNOPSIS |
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use Net::FCP::Util; |
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=head1 DESCRIPTION |
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=over 4 |
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=cut |
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package Net::FCP::Util; |
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use Carp (); |
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use Digest::SHA1; |
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use MIME::Base64 (); |
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no warnings; |
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=item log2 $num[, $minlog] |
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Calculate the (integer) log2 of a number, rounded up. If C<$minlog> is |
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given it will be the minimum value returned. |
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=cut |
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sub log2($;$) { # n, minlog |
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$_[0] && length sprintf "%$_[1]b", $_[0] - 1; |
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} |
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# the above line is much faster than the equivalent |
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# below, which illustrates a fine point of perl... |
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# my ($n, $b) = @_; |
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# $b++ while 1 << $b < $n; |
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# $b; |
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=item encode_mpi $num |
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Encode the given number as a multiple-precision number (2 byte bitlength + bytes) |
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=cut |
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sub encode_mpi($) { |
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my $num = pack "N", $_[0]; |
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my $len = log2 $_[0], 1; |
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$num =~ s/^\x00+//; |
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pack "n a*", $len, $num; |
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} |
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=item decode_base64 $string |
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Decode freenet's perverted version of base64. |
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=cut |
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sub decode_base64($) { |
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my $s = shift; |
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$s =~ y%~\-%+/%; |
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MIME::Base64::decode_base64 "$s======"; |
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} |
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=item encode_base64 $data |
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Encode into freenet's perverted version of base64. |
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=cut |
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sub encode_base64($) { |
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my $s = MIME::Base64::encode_base64 shift, ""; |
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$s =~ s/=+$//; |
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$s =~ y%+/%~\-%; |
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$s; |
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} |
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=item generate_chk_hash $metadata, $data |
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Generate and return they hash portion (the part after the comma, the |
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crypto key) that would be used in the CHK (as binary). This can be used to |
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verify contents of a CHK, since this key is a hash over the data. |
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(This function assumes a 128 bit key, which seems standard in freenet). |
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=cut |
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sub generate_chk_hash($$) { |
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my $d = new Digest::SHA1; |
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$d->add ($_[0]); |
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$d->add ($_[1]); |
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$d = $d->digest; |
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my $k = new Digest::SHA1; |
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$k->add ("\x00" x 1); # only one iteration |
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$k->add ($d); |
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substr $k->digest, 0, 16; # extract leading 128 bit |
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} |
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=item extract_chk_hash $uri |
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Extract the hash portion (the part after the comma, the crypto key) of a |
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CHK (in binary). Useful to compare against the output of generate_chk_key. |
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=cut |
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sub extract_chk_hash($) { |
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$_[0] =~ /CHK\@[a-zA-Z0-9~\-]{31},([a-zA-Z0-9~\-]{22})/ |
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or Carp::croak "unable to parse CHK key from '$_[0]'"; |
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decode_base64 $1; |
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} |
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=back |
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=head1 SEE ALSO |
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L<Net::FCP>. |
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=head1 BUGS |
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Not heavily tested. |
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=head1 AUTHOR |
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Marc Lehmann <pcg@goof.com> |
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http://www.goof.com/pcg/marc/ |
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=cut |
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1; |
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