package PDF::API2::Basic::PDF::Filter::RunLengthDecode;
our $VERSION = '2.023'; # VERSION
use base 'PDF::API2::Basic::PDF::Filter';
use strict;
use warnings;
# Maintainer's Note: RunLengthDecode is described in the PDF 1.7 spec
# in section 7.4.5.
sub outfilt {
my ($self, $input, $include_eod) = @_;
my $output;
while ($input ne '') {
my ($unrepeated, $repeated);
# Look for a repeated character (which can be repeated up to
# 127 times)
if ($input =~ m/^(.*?)((.)\3{1,127})(.*)$/so) {
$unrepeated = $1;
$repeated = $2;
$input = $4;
}
else {
$unrepeated = $input;
}
# Print any non-repeating bytes at the beginning of the input
# in chunks of up to 128 bytes, prefixed with a run-length (0
# to 127, signifying 1 to 128 bytes)
while (length($unrepeated) > 127) {
$output .= pack('C', 127) . substr($unrepeated, 0, 128);
substr($unrepeated, 0, 128) = '';
}
$output .= pack('C', length($unrepeated) - 1) . $unrepeated if length($unrepeated) > 0;
# Then print the number of times the repeated byte was
# repeated (using the formula "257 - length" to give a result
# in the 129-255 range) followed by the byte to be repeated
if (length($repeated)) {
$output .= pack('C', 257 - length($repeated)) . substr($repeated, 0, 1);
}
}
# A byte value of 128 signifies that we're done.
$output .= "\x80" if $include_eod;
return $output;
}
sub infilt {
my ($self, $input, $is_terminated) = @_;
my ($output, $length);
# infilt may be called multiple times, and is expected to continue
# where it left off
if (exists $self->{'incache'}) {
$input = $self->{'incache'} . $input;
delete $self->{'incache'};
}
while (length($input)) {
# Read a length byte
$length = unpack("C", $input);
# A "length" of 128 represents the end of the document
if ($length == 128) {
return $output;
}
# Any other length needs to be followed by at least one other byte
if (length($input) == 1 and not $is_terminated) {
die "Premature end to RunLengthEncoded data";
}
# A length of 129-255 represents a repeated string
# (number of repeats = 257 - length)
if ($length > 128) {
if (length($input) == 1) {
# Out of data. Defer until the next call.
$self->{'incache'} = $input;
return $output;
}
$output .= substr($input, 1, 1) x (257 - $length);
substr($input, 0, 2) = '';
}
# Any other length (under 128) represents a non-repeated
# stream of bytes (with a length of 0 to 127 representing 1 to
# 128 bytes)
else {
if (length($input) < $length + 2) {
# Insufficient data. Defer until the next call.
$self->{'incache'} = $input;
return $output;
}
$output .= substr($input, 1, $length + 1);
substr($input, 0, $length + 2) = '';
}
}
return $output;
}
1;