Algorithm-Hamming-Perl

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Perl.pm  view on Meta::CPAN

	$Hamming8semi{$char} = $Hamming8raw{$key};
}
%Hamming8rev = reverse(%Hamming8semi);	


# hamming_faster - this subroutine builds two large hashes of,
#		%Hamming8by2	  2 byte data -> 3 byte Hamming code
#		%Hamming8by2rev	  3 byte Hamming code -> 2 byte data
#	for faster encodings and decodings. Running this subroutine is 
#	optional. If it is used then conversions are faster, however more 
#	memory is used to store the hashes, and a couple of seconds is added 
#	to the startup time. If it is not used, conversions are slower -
#	taking up to 5 times the usual time. A good measure is the data you
#	with to encode - more than 1 Mb would benifit from this subroutine.
#
sub hamming_faster {

	#
	#  Step through 0,0 to 255,255 to build a hash that can convert
	#  any 2 byte combinations.
	#

Perl.pm  view on Meta::CPAN

}
	

# hamming - this turns data into hamming code. This has been written 
#  	with memory and CPU efficiency in mind (without resorting to C).
#
sub hamming {
	my $data = shift;	# input data
	my $pos;		# counter to step through data string
	my $char_in1;		# first input byte
	my $char_in2;		# second input byte
	my $chars_in;		# both input bytes
	my $ham_text;		# hamming code in binary text "0101.."
	my $char_out;		# hamming code as bytes
	my $output = "";	# full output hamming code as bytes

	my $length = length($data);
	
	#
	#  Step through the $data 2 bytes at a time, generating a
	#  Hamming encoded $output.

Perl.pm  view on Meta::CPAN

# unhamming_err - this turns hamming code into data. This has been written 
# 	with memory and CPU efficiencu in mind (without resorting to C).
#
sub unhamming_err {
	my $data = shift;	# input data
	my $pos;		# counter to step through data string
	my $err;		# corrected bit error
	my $chars_in;		# input bytes
	my $ham_text;		# hamming code in binary text "0101..", 2 bytes
	my $ham_text1;		# hamming code for first byte
	my $ham_text2;		# hamming code for second byte
	my $char_out1;		# output data byte 1
	my $char_out2;		# output data byte 2
	my $output = "";	# full output data as bytes
	my $err_all = 0;	# count of corrected bit errors

	my $length = length($data);
	
	# 
	#  Step through the $data 3 bytes at a time, decoding it back into
	#  the $output data.

Perl.pm  view on Meta::CPAN

=head1 OTHER SUBROUTINES

=over 4

=item Algorithm::Hamming::Perl::hamming_faster ()

This is an optional subroutine that will speed Hamming encoding if it is
run once at the start of the program. It does this by using a larger (hash)
cache of preprocessed results. The disadvantage is that it uses more memory,
and can add several seconds to invocation time. Only use this if you are
encoding more than 1 Mb of data.

=back

=head1 INSTALLATION

   perl Makefile.PL
   make
   make test
   make install

README  view on Meta::CPAN

         Returns the original data from the provided Hamming
         code, and a number counting the number of bytes that
         were corrected. Single bit errors are auto corrected.

OTHER SUBROUTINES
     Algorithm::Hamming::Perl::hamming_faster ()
         This is an optional subroutine that will speed Hamming
         encoding if it is run once at the start of the program.
         It does this by using a larger (hash) cache of
         preprocessed results. The disadvantage is that it uses
         more memory, and can add several seconds to invocation
         time. Only use this if you are encoding more than 1 Mb
         of data.

INSTALLATION
        perl Makefile.PL
        make
        make test
        make install

DEPENDENCIES

example03  view on Meta::CPAN

$infile = $ARGV[0];
$outfile = $ARGV[1];

### Open filehandles
open(IN,"$infile") || die "ERROR: Can't open $infile: $!\n";
open(OUT,">$outfile") || die "ERROR: Can't open $outfile: $!\n";
binmode(IN);
binmode(OUT);

### Use optional faster (but bigger) cache - adds several seconds to startup!
Algorithm::Hamming::Perl::hamming_faster();


### Process data
while (read(IN,$buffer,3072)) {
	$hamcode = hamming($buffer);
	print OUT $hamcode;
}

close IN;

example04  view on Meta::CPAN

$infile = $ARGV[0];
$outfile = $ARGV[1];

### Open filehandles
open(IN,"$infile") || die "ERROR: Can't open $infile: $!\n";
open(OUT,">$outfile") || die "ERROR: Can't open $outfile: $!\n";
binmode(IN);
binmode(OUT);

### Use optional faster (but bigger) cache - adds several seconds to startup!
Algorithm::Hamming::Perl::hamming_faster();


### Process data
while (read(IN,$buffer,3072)) {
	$data = unhamming($buffer);
	print OUT $data;
}

close IN;