#=======================================================================
#
#   THIS IS A REUSED PERL MODULE, FOR PROPER LICENCING TERMS SEE BELOW:
#
#   Copyright Martin Hosken <Martin_Hosken@sil.org>
#
#   Modified for PDF::API2 by Alfred Reibenschuh <alfredreibenschuh@gmx.net>
#
#   No warranty or expression of effectiveness, least of all regarding
#   anyone's safety, is implied in this software or documentation.
#
#   This specific module is licensed under the Perl Artistic License.
#
#=======================================================================
package PDF::Builder::Basic::PDF::File;

use strict;
no warnings qw[ deprecated recursion uninitialized ];

our $VERSION = '3.019'; # VERSION
my $LAST_UPDATE = '3.018'; # manually update whenever code is changed

=head1 NAME

PDF::Builder::Basic::PDF::File - Holds the trailers and cross-reference tables for a PDF file

=head1 SYNOPSIS

 $p = PDF::Builder::Basic::PDF::File->open("filename.pdf", 1);
 $p->new_obj($obj_ref);
 $p->free_obj($obj_ref);
 $p->append_file();
 $p->close_file();
 $p->release();       # IMPORTANT!

=head1 DESCRIPTION

This class keeps track of the directory aspects of a PDF file. There are two
parts to the directory: the main directory object, which is the parent to all
other objects, and a chain of cross-reference tables and corresponding trailer
dictionaries, starting with the main directory object.

=head1 INSTANCE VARIABLES

Within this class hierarchy, rather than making everything visible via methods,
which would be a lot of work, there are various instance variables which are
accessible via associative array referencing. To distinguish instance variables
from content variables (which may come from the PDF content itself), each such
variable will start with a space.

Variables which do not start with a space directly reflect elements in a PDF
dictionary. In the case of a C<PDF::Builder::Basic::PDF::File>, the elements 
reflect those in the trailer dictionary.

Since some variables are not designed for class users to access, variables are
marked in the documentation with B<(R)> to indicate that such an entry should 
only be used as B<read-only> information. B<(P)> indicates that the information 
is B<private>, and not designed for user use at all, but is included in the 
documentation for completeness and to ensure that nobody else tries to use it.

=over

=item newroot

This variable allows the user to create a new root entry to occur in the trailer
dictionary which is output when the file is written or appended. If you wish to
override the root element in the dictionary you have, use this entry to indicate
that without losing the current Root entry. Notice that newroot should point to
a PDF level object and not just to a dictionary which does not have object 
status.

=item INFILE (R)

Contains the filehandle used to read this information into this PDF directory. 
It is an IO object.

=item fname (R)

This is the filename which is reflected by INFILE, or the original IO object 
passed in.

=item update (R)

This indicates that the read file has been opened for update and that at some
point, C<< $p->appendfile() >> can be called to update the file with the 
changes that have been made to the memory representation.

=item maxobj (R)

Contains the first usable object number above any that have already appeared
in the file so far.

=item outlist (P)

This is a list of Objind which are to be output when the next C<appendfile()> 
or C<outfile()> occurs.

=item firstfree (P)

Contains the first free object in the free object list. Free objects are removed
from the front of the list and added to the end.

=item lastfree (P)

Contains the last free object in the free list. It may be the same as the 
C<firstfree> if there is only one free object.

=item objcache (P)

All objects are held in the cache to ensure that a system only has one 
occurrence of each object. In effect, the objind class acts as a container type 
class to hold the PDF object structure, and it would be unfortunate if there 
were two identical place-holders floating around a system.

=item epos (P)

The end location of the read-file.

=back

Each trailer dictionary contains a number of private instance variables which
hold the chain together.

=over

=item loc (P)

Contains the location of the start of the cross-reference table preceding the
trailer.

=item xref (P)

Contains an anonymous array of each cross-reference table entry.

=item prev (P)

A reference to the previous table. Note this differs from the Prev entry which
is in PDF, which contains the location of the previous cross-reference table.

=back

=head1 METHODS

=cut

use Scalar::Util qw(blessed weaken);

use vars qw($cr $irreg_char $reg_char $ws_char $delim_char %types);

$ws_char    = '[ \t\r\n\f\0]';
$delim_char = '[][<>{}()/%]';
$reg_char   = '[^][<>{}()/% \t\r\n\f\0]';
$irreg_char = '[][<>{}()/% \t\r\n\f\0]';
# \015 = x0D = CR or \r, \012 = x0A = LF or \n
# TBD a line-end character is space CR ' \r', space LF ' \n', or CR LF '\r\n'
#     have seen working PDFs with just a CR and space CR
$cr         = '\s*(?:\015|\012|(?:\015\012))';

my $re_comment = qr/(?:\%[^\r\n]*)/;
my $re_whitespace = qr/(?:[ \t\r\n\f\0]|$re_comment)/;

%types = (
    'Page'  => 'PDF::Builder::Basic::PDF::Page',
    'Pages' => 'PDF::Builder::Basic::PDF::Pages',
);

my $readDebug = 0;

use Carp;
use IO::File;

# Now for the basic PDF types
use PDF::Builder::Basic::PDF::Utils;

use PDF::Builder::Basic::PDF::Array;
use PDF::Builder::Basic::PDF::Bool;
use PDF::Builder::Basic::PDF::Dict;
use PDF::Builder::Basic::PDF::Name;
use PDF::Builder::Basic::PDF::Number;
use PDF::Builder::Basic::PDF::Objind;
use PDF::Builder::Basic::PDF::String;
use PDF::Builder::Basic::PDF::Page;
use PDF::Builder::Basic::PDF::Pages;
use PDF::Builder::Basic::PDF::Null;
use POSIX qw(ceil floor);

=head2 PDF::Builder::Basic::PDF::File->new()

Creates a new, empty file object which can act as the host to other PDF objects.
Since there is no file associated with this object, it is assumed that the
object is created in readiness for creating a new PDF file.

=cut

sub new {
    my ($class, $root) = @_;
    my $self = $class->_new();

    unless ($root) {
        $root = PDFDict();
        $root->{'Type'} = PDFName('Catalog');
    }
    $self->new_obj($root);
    $self->{'Root'} = $root;

    return $self;
}

=head2 $p = PDF::Builder::Basic::PDF::File->open($filename, $update, %options)

Opens the file and reads all the trailers and cross reference tables to build
a complete directory of objects.

C<$filename> may be a string or an IO object.

C<$update> specifies whether this file is being opened for updating and editing
(I<TRUE> value), or simply to be read (I<FALSE> or undefined value).

C<%options> may include

=over

=item -diags => 1

If C<-diags> is set to 1, various warning messages will be given if a 
suspicious PDF structure is found, and some fixup may be attempted. There is
no guarantee that any fixup will change the PDF to legitimate, or that there 
won't be other problems found further down the line. If this flag is I<not>
given, and a structural problem is found, it is fairly likely that errors (and
even a program B<crash>) may happen further along. If you experience crashes 
when reading in a PDF file, try running with C<-diags> and see what is reported.

There are many PDF files out "in the wild" which, while failing to conform to
Adobe's standards, appear to be tolerated by PDF Readers. Thus, Builder will no
longer fail on them, but merely comment on their existence.

=back

=cut

sub open {
    my ($class, $filename, $update, %options) = @_;
    my ($fh, $buffer);
    $options{'-diags'} = 0 if not defined $options{'-diags'}; # default

    my $comment = ''; # any comment jammed into the PDF header
    my $self = $class->_new();
    if (ref $filename) {
        $self->{' INFILE'} = $filename;
        if ($update) {
            $self->{' update'} = 1;
            $self->{' OUTFILE'} = $filename;
        }
        $fh = $filename;
    } else {
        die "File '$filename' does not exist!" unless -f $filename;
        $fh = IO::File->new(($update ? '+' : '') . "<$filename") || return;
        $self->{' INFILE'} = $fh;
        if ($update) {
            $self->{' update'} = 1;
            $self->{' OUTFILE'} = $fh;
            $self->{' fname'} = $filename;
        }
    }
    binmode $fh, ':raw';
    $fh->seek(0, 0);            # go to start of file
    $fh->read($buffer, 255);
    unless ($buffer =~ m/^\%PDF\-(\d+\.\d+)(.*?)$cr/mo) {
        die "$filename does not contain a PDF version";
    }
    $self->{' version'} = $1;
    # can't run verCheckInput() yet, as full ' version' not set
    if (defined $2 && length($2) > 0) {
       $comment = $2;  # save for output as comment
       # since we just echo the original header + comment, unless that causes
       # problems in some Readers, we can just leave it be (no call to strip
       # out inline comment and create a separate comment further along).
    }

    $fh->seek(0, 2);            # go to end of file
    my $end = $fh->tell();
    $self->{' epos'} = $end;
    foreach my $offset (1 .. 64) {
    	$fh->seek($end - 16 * $offset, 0);
    	$fh->read($buffer, 16 * $offset);
    	last if $buffer =~ m/startxref($cr|\s*)\d+($cr|\s*)\%\%eof.*?/i;
    }
    unless ($buffer =~ m/startxref[^\d]+([0-9]+)($cr|\s*)\%\%eof.*?/i) {
	if ($options{'-diags'} == 1) {
            warn "Malformed PDF file $filename"; #orig 'die'
        }
    }
    my $xpos = $1;
    $self->{' xref_position'} = $xpos;

    my $tdict = $self->readxrtr($xpos, %options);
    foreach my $key (keys %$tdict) {
        $self->{$key} = $tdict->{$key};
    }

    return $self;
} # end of open()

=head2 $p->release()

Releases ALL of the memory used by the PDF document and all of its
component objects.  After calling this method, do B<NOT> expect to
have anything left in the C<PDF::Builder::Basic::PDF::File> object 
(so if you need to save, be sure to do it before calling this method).

B<NOTE>, that it is important that you call this method on any
C<PDF::Builder::Basic::PDF::File> object when you wish to destroy it and
free up its memory.  Internally, PDF files have an enormous number of
cross-references, and this causes circular references within the
internal data structures. Calling C<release()> causes a brute-force
cleanup of the data structures, freeing up all of the memory. Once
you've called this method, though, don't expect to be able to do
anything else with the C<PDF::Builder::Basic::PDF::File> object; it'll
have B<no> internal state whatsoever.

=cut

# Maintainer's Question: Couldn't this be handled by a DESTROY method
# instead of requiring an explicit call to release()?
sub release {
    my $self = shift();

    return $self unless ref($self);
    my @tofree = values %$self;

    foreach my $key (keys %$self) {
        $self->{$key} = undef;
        delete $self->{$key};
    }

    while (my $item = shift @tofree) {
        if      (blessed($item) and $item->can('release')) {
            $item->release(1);
        } elsif (ref($item) eq 'ARRAY') {
            push @tofree, @$item;
        } elsif (ref($item) eq 'HASH') {
            push @tofree, values %$item;
            foreach my $key (keys %$item) {
                $item->{$key} = undef;
                delete $item->{$key};
            }
        } else {
            $item = undef;
        }
    }

    return;
} # end of release()

=head2 $p->append_file()

Appends the objects for output to the read file and then appends the 
appropriate table.

=cut

sub append_file {
    my $self = shift();
    return unless $self->{' update'};

    my $fh = $self->{' INFILE'};

    # hack to upgrade pdf-version number to support requested features in 
    # higher versions than the pdf was originally created. WARNING: new version
    # must be exactly SAME length as the old (e.g., 1.6 replacing 1.4), or
    # problems are likely with overwriting header. perhaps some day we will
    # need to check the old version being ovewritten, and adjust something to
    # avoid corrupting the file.
    my $version = $self->{' version'} || 1.4;
    $fh->seek(0, 0);
    # assume that any existing EOL after version will be reused
    $fh->print("%PDF-$version");

    my $tdict = PDFDict();
    $tdict->{'Prev'} = PDFNum($self->{' loc'});
    $tdict->{'Info'} = $self->{'Info'};
    if (defined $self->{' newroot'}) {
        $tdict->{'Root'} = $self->{' newroot'};
    } else {
        $tdict->{'Root'} = $self->{'Root'};
    }
    $tdict->{'Size'} = $self->{'Size'};

    foreach my $key (grep { $_ !~ m/^\s/ } keys %$self) {
        $tdict->{$key} = $self->{$key} unless defined $tdict->{$key};
    }

    $fh->seek($self->{' epos'}, 0);
    $self->out_trailer($tdict, $self->{' update'});
    close $self->{' OUTFILE'};

    return;
} # end of append_file()

=head2 $p->out_file($fname)

Writes a PDF file to a file of the given filename, based on the current list of
objects to be output. It creates the trailer dictionary based on information
in C<$self>.

$fname may be a string or an IO object.

=cut

sub out_file {
    my ($self, $fname) = @_;

    $self = $self->create_file($fname);
    $self = $self->close_file();

    return $self;
}

=head2 $p->create_file($fname)

Creates a new output file (no check is made of an existing open file) of
the given filename or IO object. Note, make sure that C<< $p->{' version'} >> 
is set correctly before calling this function.

=cut

sub create_file {
    my ($self, $filename) = @_;
    my $fh;

    $self->{' fname'} = $filename;
    if (ref $filename) {
        $fh = $filename;
    } else {
        $fh = IO::File->new(">$filename") || die "Unable to open $filename for writing";
        binmode($fh,':raw');
    }

    $self->{' OUTFILE'} = $fh;
    $fh->print('%PDF-' . ($self->{' version'} || '1.4') . "\n");
    $fh->print("%\xC6\xCD\xCD\xB5\n");   # and some binary stuff in a comment.

    # PDF spec requires 4 or more "binary" bytes (128 or higher value) in a
    # comment immediately following the PDF-x.y header, to alert reader that
    # there is binary data. Actual values are apparently arbitrary. This DOES
    # mean that other comments can NOT be inserted between the header and the
    # binary comment! PDF::Builder always outputs this comment, so is always
    # claiming binary data (no harm done?).

    return $self;
}

=head2 $p->close_file()

Closes up the open file for output, by outputting the trailer, etc.

=cut

sub close_file {
    my $self = shift();

    my $tdict = PDFDict();
    $tdict->{'Info'} = $self->{'Info'} if defined $self->{'Info'};
    $tdict->{'Root'} = (defined $self->{' newroot'} and $self->{' newroot'} ne '') ? $self->{' newroot'} : $self->{'Root'};

    # remove all freed objects from the outlist, AND the outlist_cache if not updating
    # NO! Don't do that thing! In fact, let out_trailer do the opposite!

    $tdict->{'Size'} = $self->{'Size'} || PDFNum(1);
    $tdict->{'Prev'} = PDFNum($self->{' loc'}) if $self->{' loc'};
    if ($self->{' update'}) {
        foreach my $key (grep ($_ !~ m/^[\s\-]/, keys %$self)) { ## no critic
            $tdict->{$key} = $self->{$key} unless defined $tdict->{$key};
        }

        my $fh = $self->{' INFILE'};
        $fh->seek($self->{' epos'}, 0);
    }

    $self->out_trailer($tdict, $self->{' update'});
    close($self->{' OUTFILE'});
    if ($^O eq 'MacOS' and not ref($self->{' fname'})) {
        MacPerl::SetFileInfo('CARO', 'TEXT', $self->{' fname'});
    }

    return $self;
} # end of close_file()

=head2 ($value, $str) = $p->readval($str, %opts)

Reads a PDF value from the current position in the file. If C<$str> is too 
short, read some more from the current location in the file until the whole 
object is read. This is a recursive call which may slurp in a whole big stream 
(unprocessed).

Returns the recursive data structure read and also the current C<$str> that has 
been read from the file.

=cut

sub readval {
    my ($self, $str, %opts) = @_;
    my $fh = $self->{' INFILE'};
    my ($result, $value);

    my $update = defined($opts{'update'}) ? $opts{'update'} : 1;
    $str = update($fh, $str) if $update;

    $str =~ s/^$ws_char+//;               # Ignore initial white space
    $str =~ s/^\%[^\015\012]*$ws_char+//; # Ignore comments

    if      ($str =~ m/^<</s) {
        # Dictionary
        $str = substr ($str, 2);
        $str = update($fh, $str) if $update;
        $result = PDFDict();

        while ($str !~ m/^>>/) {
            $str =~ s/^$ws_char+//;               # Ignore initial white space
            $str =~ s/^\%[^\015\012]*$ws_char+//; # Ignore comments

            if      ($str =~ s|^/($reg_char+)||) {
                my $key = PDF::Builder::Basic::PDF::Name::name_to_string($1, $self);
                ($value, $str) = $self->readval($str, %opts);
		# per Vadim Repin (RT 131147) CHG 1. His conclusion is that
		# it is highly unlikely, but remotely possible, that there 
		# could be legitimate use of Null objects that should NOT be
		# prevented from bubbling up. If such a case is discovered, we
		# might have to try Klaus Ethgen's more limited (in scope)
		# patch in ./Pages.pm. See full discussion in RT 131147 for
		# details on what's going on and how this fixes it.
               #$result->{$key} = $value;  # original code
                $result->{$key} = $value
		   unless ref($value) eq 'PDF::Builder::Basic::PDF::Null';
            } elsif ($str =~ s|^/$ws_char+||) {
                # fixes a broken key problem of acrobat. -- fredo
                ($value, $str) = $self->readval($str, %opts);
                $result->{'null'} = $value;
            } elsif ($str =~ s|^//|/|) {
                # fixes again a broken key problem of illustrator/enfocus. -- fredo
                ($value, $str) = $self->readval($str, %opts);
                $result->{'null'} = $value;
            } else {
                die "Invalid dictionary key";
            }
            $str = update($fh, $str) if $update; # thanks gareth.jones@stud.man.ac.uk
        }

        $str =~ s/^>>//;
        $str = update($fh, $str) if $update;
        # streams can't be followed by a lone carriage-return.
        # fredo: yes they can !!! -- use the MacOS, Luke.
	    # TBD isn't this covered by $cr as space CR?
        if (($str =~ s/^stream(?:(?:\015\012)|\012|\015)//) and ($result->{'Length'}->val() != 0)) {   # stream
            my $length = $result->{'Length'}->val();
            $result->{' streamsrc'} = $fh;
            $result->{' streamloc'} = $fh->tell() - length($str);

            unless ($opts{'nostreams'}) {
                if ($length > length($str)) {
                    $value = $str;
                    $length -= length($str);
                    read $fh, $str, $length + 11; # slurp the whole stream!
                } else {
                    $value = '';
                }
                $value .= substr($str, 0, $length);
                $result->{' stream'} = $value;
                $result->{' nofilt'} = 1;
                $str = update($fh, $str, 1) if $update;  # tell update we are in-stream and only need an endstream
                $str = substr($str, index($str, 'endstream') + 9);
            }
        }

        if (defined $result->{'Type'} and defined $types{$result->{'Type'}->val()}) {
            bless $result, $types{$result->{'Type'}->val()};
        }
        # gdj: FIXME: if any of the ws chars were crs, then the whole
        # string might not have been read.

    } elsif ($str =~ m/^([0-9]+)(?:$ws_char|$re_comment)+([0-9]+)(?:$ws_char|$re_comment)+R/s) {
        # Indirect Object
        my $num = $1;
        $value = $2;
        $str =~ s/^([0-9]+)(?:$ws_char|$re_comment)+([0-9]+)(?:$ws_char|$re_comment)+R//s;
        unless ($result = $self->test_obj($num, $value)) {
            $result = PDF::Builder::Basic::PDF::Objind->new();
            $result->{' objnum'} = $num;
            $result->{' objgen'} = $value;
            $self->add_obj($result, $num, $value);
        }
        $result->{' parent'} = $self;
        weaken $result->{' parent'};
       #$result->{' realised'} = 0;
       # removed to address changes being lost when an indirect object
       #  is realised twice
        # gdj: FIXME: if any of the ws chars were crs, then the whole
        # string might not have been read.

    } elsif ($str =~ m/^([0-9]+)(?:$ws_char|$re_comment)+([0-9]+)(?:$ws_char|$re_comment)+obj/s) {
        # Object
        my $obj;
        my $num = $1;
        $value = $2;
        $str =~ s/^([0-9]+)(?:$ws_char|$re_comment)+([0-9]+)(?:$ws_char|$re_comment)+obj//s;
        ($obj, $str) = $self->readval($str, %opts);
        if ($result = $self->test_obj($num, $value)) {
            $result->merge($obj);
        } else {
            $result = $obj;
            $self->add_obj($result, $num, $value);
            $result->{' realised'} = 1;
        }
        $str = update($fh, $str) if $update;       # thanks to kundrat@kundrat.sk
        $str =~ s/^endobj//;

    } elsif ($str =~ m|^/($reg_char*)|s) {
        # Name
        $value = $1;
        $str =~ s|^/($reg_char*)||s;
        $result = PDF::Builder::Basic::PDF::Name->from_pdf($value, $self);

    } elsif ($str =~ m/^\(/) {
        # Literal String
        # We now need to find an unbalanced, unescaped right-paren.
        # This can't be done with a regex.
        my $value = '(';
        $str = substr($str, 1);

        my $nested_level = 1;
        while (1) {
            # Ignore everything up to the first escaped or parenthesis character
            if ($str =~ /^([^\\()]+)(.*)/s) {
                $value .= $1;
                $str = $2;
            }

            # Ignore escaped parentheses
            if      ($str =~ /^(\\[()])/) {
                $value .= $1;
                $str = substr($str, 2);

            } elsif ($str =~ /^\(/) {
                # Left parenthesis: increase nesting
                $value .= '(';
                $str = substr($str, 1);
                $nested_level++;

            } elsif ($str =~ /^\)/) {
                # Right parenthesis: decrease nesting
                $value .= ')';
                $str = substr($str, 1);
                $nested_level--;
                last unless $nested_level;

            } elsif ($str =~ /^(\\[^()])/) {
                # Other escaped character
                $value .= $1;
                $str = substr($str, 2);

            } else {
                # If there wasn't an escaped or parenthesis character,
                # read some more.

                # We don't use update because we don't want to remove
                # whitespace or comments.
                $fh->read($str, 255, length($str)) or die 'Unterminated string.';
            }
        } # end while(TRUE) loop

        $result = PDF::Builder::Basic::PDF::String->from_pdf($value);
        # end Literal String check

    } elsif ($str =~ m/^</) {
        # Hex String
        $str =~ s/^<//;
        $fh->read($str, 255, length($str)) while (0 > index($str, '>'));
        ($value, $str) = ($str =~ /^(.*?)>(.*)/s);
        $result = PDF::Builder::Basic::PDF::String->from_pdf('<' . $value . '>');

    } elsif ($str =~ m/^\[/) {
        # Array
        $str =~ s/^\[//;
        $str = update($fh, $str) if $update;
        $result = PDFArray();
        while ($str !~ m/^\]/) {
            $str =~ s/^$ws_char+//;               # Ignore initial white space
            $str =~ s/^\%[^\015\012]*$ws_char+//; # Ignore comments

            ($value, $str) = $self->readval($str, %opts);
            $result->add_elements($value);
            $str = update($fh, $str) if $update;   # str might just be exhausted!
        }
        $str =~ s/^\]//;

    } elsif ($str =~ m/^(true|false)($irreg_char|$)/) {
        # Boolean
        $value = $1;
        $str =~ s/^(?:true|false)//;
        $result = PDF::Builder::Basic::PDF::Bool->from_pdf($value);

    } elsif ($str =~ m/^([+-.0-9]+)($irreg_char|$)/) {
        # Number
        $value = $1;
        $str =~ s/^([+-.0-9]+)//;

        # If $str only consists of whitespace (or is empty), call update to
        # see if this is the beginning of an indirect object or reference
        if ($update and ($str =~ /^$re_whitespace*$/s or $str =~ /^$re_whitespace+[0-9]+$re_whitespace*$/s)) {
	    $str =~ s/^$re_whitespace+/ /s;
	    $str =~ s/$re_whitespace+$/ /s;
            $str = update($fh, $str);
            if ($str =~ m/^$re_whitespace*([0-9]+)$re_whitespace+(?:R|obj)/s) {
                return $self->readval("$value $str", %opts);
            }
        }

        $result = PDF::Builder::Basic::PDF::Number->from_pdf($value);

    } elsif ($str =~ m/^null($irreg_char|$)/) {
        # Null
        $str =~ s/^null//;
        $result = PDF::Builder::Basic::PDF::Null->new();

    } else {
        die "Can't parse `$str' near " . ($fh->tell()) . " length " . length($str) . ".";
    }

    $str =~ s/^$ws_char+//s;
    return ($result, $str);
} # end of readval()

=head2 $ref = $p->read_obj($objind, %opts)

Given an indirect object reference, locate it and read the object returning
the read in object.

=cut

sub read_obj {
    my ($self, $objind, %opts) = @_;

    my $res = $self->read_objnum($objind->{' objnum'}, $objind->{' objgen'}, %opts) || return;
    $objind->merge($res) unless $objind eq $res;

    return $objind;
}

=head2 $ref = $p->read_objnum($num, $gen, %opts)

Returns a fully read object of given number and generation in this file

=cut

sub read_objnum {
    my ($self, $num, $gen, %opts) = @_;

    croak 'Undefined object number in call to read_objnum($num, $gen)' unless defined $num;
    croak 'Undefined object generation in call to read_objnum($num, $gen)' unless defined $gen;
    croak "Invalid object number '$num' in call to read_objnum" unless $num =~ /^[0-9]+$/;
    croak "Invalid object generation '$gen' in call to read_objnum" unless $gen =~ /^[0-9]+$/;

    my $object_location = $self->locate_obj($num, $gen) || return;
    my $object;

    # Compressed object
    if (ref($object_location)) {
        my ($object_stream_num, $object_stream_pos) = @{$object_location};

        my $object_stream = $self->read_objnum($object_stream_num, 0, %opts);
        die 'Cannot find the compressed object stream' unless $object_stream;

        $object_stream->read_stream() if $object_stream->{' nofilt'};

        # An object stream starts with pairs of integers containing object numbers and
        # stream offsets relative to the First key
        my $fh;
        my $pairs;
        unless ($object_stream->{' streamfile'}) {
            $pairs = substr($object_stream->{' stream'}, 0, $object_stream->{'First'}->val());
        } else {
            CORE::open($fh, '<', $object_stream->{' streamfile'});
            read($fh, $pairs, $object_stream->{'First'}->val());
        }
        my @map = split /\s+/, $pairs;

        # Find the offset of the object in the stream
        my $index = $object_stream_pos * 2;
        die "Objind $num does not exist at index $index" unless $map[$index] == $num;
        my $start = $map[$index + 1];

        # Unless this is the last object in the stream, its length is 
        # determined by the offset of the next object.
        my $last_object_in_stream = $map[-2];
        my $length;
        if ($last_object_in_stream == $num) {
            if ($object_stream->{' stream'}) {
                $length = length($object_stream->{' stream'}) - $object_stream->{'First'}->val() - $start;
            } else {
                $length = (-s $object_stream->{' streamfile'}) - $object_stream->{'First'}->val() - $start;
            }
        } else {
            my $next_start = $map[$index + 3];
            $length = $next_start - $start;
        }

        # Read the object from the stream
        my $stream = "$num 0 obj ";
        unless ($object_stream->{' streamfile'}) {
            $stream .= substr($object_stream->{' stream'}, $object_stream->{'First'}->val() + $start, $length);
        } else {
            seek($fh, $object_stream->{'First'}->val() + $start, 0);
            read($fh, $stream, $length, length($stream));
            close $fh;
        }

        ($object) = $self->readval($stream, %opts, update => 0);
        return $object;
    }

    my $current_location = $self->{' INFILE'}->tell();
    $self->{' INFILE'}->seek($object_location, 0);
    ($object) = $self->readval('', %opts);
    $self->{' INFILE'}->seek($current_location, 0);

    return $object;
} # end of read_objnum()

=head2 $objind = $p->new_obj($obj)

Creates a new, free object reference based on free space in the cross reference 
chain. If nothing is free, then think up a new number. If C<$obj>, then turns 
that object into this new object rather than returning a new object.

=cut

sub new_obj {
    my ($self, $base) = @_;
    my $res;

    if (defined $self->{' free'} and scalar @{$self->{' free'}} > 0) {
        $res = shift(@{$self->{' free'}});
        if (defined $base) {
            my ($num, $gen) = @{$self->{' objects'}{$res->uid()}};
            $self->remove_obj($res);
            $self->add_obj($base, $num, $gen);
            return $self->out_obj($base);
        } else {
            $self->{' objects'}{$res->uid()}[2] = 0;
            return $res;
        }
    }

    my $tdict = $self;
    my $i;
    while (defined $tdict) {
        $i = $tdict->{' xref'}{defined($i) ? $i : ''}[0];
        while (defined $i and $i != 0) {
            my ($ni, $ng) = @{$tdict->{' xref'}{$i}};
            unless (defined $self->locate_obj($i, $ng)) {
                if (defined $base) {
                    $self->add_obj($base, $i, $ng);
                    return $base;
                } else {
                    $res = $self->test_obj($i, $ng) || $self->add_obj(PDF::Builder::Basic::PDF::Objind->new(), $i, $ng);
                    $self->out_obj($res);
                    return $res;
                }
            }
            $i = $ni;
        }
        $tdict = $tdict->{' prev'};
    }

    $i = $self->{' maxobj'}++;
    if (defined $base) {
        $self->add_obj($base, $i, 0);
        $self->out_obj($base);
        return $base;
    } else {
        $res = $self->add_obj(PDF::Builder::Basic::PDF::Objind->new(), $i, 0);
        $self->out_obj($res);
        return $res;
    }
}

=head2 $p->out_obj($obj)

Indicates that the given object reference should appear in the output xref
table whether with data or freed.

=cut

sub out_obj {
    my ($self, $obj) = @_;

    # This is why we've been keeping the outlist CACHE around; to speed
    # up this method by orders of magnitude (it saves up from having to
    # grep the full outlist each time through as we'll just do a lookup
    # in the hash) (which is super-fast).
    unless (exists $self->{' outlist_cache'}{$obj}) {
        push @{$self->{' outlist'}}, $obj;
        # weaken $self->{' outlist'}->[-1];
        $self->{' outlist_cache'}{$obj} = 1;
    }

    return $obj;
}

=head2 $p->free_obj($obj)

Marks an object reference for output as being freed.

=cut

sub free_obj {
    my ($self, $obj) = @_;

    push @{$self->{' free'}}, $obj;
    $self->{' objects'}{$obj->uid()}[2] = 1;
    $self->out_obj($obj);

    return;
}

=head2 $p->remove_obj($objind)

Removes the object from all places where we might remember it.

=cut

sub remove_obj {
    my ($self, $objind) = @_;

    # who says it has to be fast
    delete $self->{' objects'}{$objind->uid()};
    delete $self->{' outlist_cache'}{$objind};
    delete $self->{' printed_cache'}{$objind};
    @{$self->{' outlist'}} = grep($_ ne $objind, @{$self->{' outlist'}}); ## no critic
    @{$self->{' printed'}} = grep($_ ne $objind, @{$self->{' printed'}}); ## no critic
    $self->{' objcache'}{$objind->{' objnum'}, $objind->{' objgen'}} = undef
        if $self->{' objcache'}{$objind->{' objnum'}, $objind->{' objgen'}} eq $objind;

    return $self;
}

=head2 $p->ship_out(@objects)

=head2 $p->ship_out()

Ships the given objects (or all objects for output if C<@objects> is empty) to
the currently open output file (assuming there is one). Freed objects are not
shipped, and once an object is shipped it is switched such that this file
becomes its source and it will not be shipped again unless out_obj is called
again. Notice that a shipped out object can be re-output or even freed, but
that it will not cause the data already output to be changed.

=cut

sub ship_out {
    my ($self, @objects) = @_;

    return unless defined $self->{' OUTFILE'};
    my $fh = $self->{' OUTFILE'};
    seek($fh, 0, 2); # go to the end of the file

    @objects = @{$self->{' outlist'}} unless scalar @objects > 0;
    foreach my $objind (@objects) {
        next unless $objind->is_obj($self);
        my $j = -1;
        for (my $i = 0; $i < scalar @{$self->{' outlist'}}; $i++) {
            if ($self->{' outlist'}[$i] eq $objind) {
                $j = $i;
                last;
            }
        }
        next if $j < 0;
        splice(@{$self->{' outlist'}}, $j, 1);
        delete $self->{' outlist_cache'}{$objind};
        next if grep { $_ eq $objind } @{$self->{' free'}};

        map { $fh->print("\%   $_ \n") } split(/$cr/, $objind->{' comments'}) if $objind->{' comments'};
        $self->{' locs'}{$objind->uid()} = $fh->tell();
        my ($objnum, $objgen) = @{$self->{' objects'}{$objind->uid()}}[0..1];
        $fh->printf('%d %d obj ', $objnum, $objgen);
        $objind->outobjdeep($fh, $self);
        $fh->print(" endobj\n");

        # Note that we've output this obj, not forgetting to update
        # the cache of what's printed.
        unless (exists $self->{' printed_cache'}{$objind}) {
            push @{$self->{' printed'}}, $objind;
            $self->{' printed_cache'}{$objind}++;
        }
    }

    return $self;
} # end of ship_out()

=head2 $p->copy($outpdf, \&filter)

Iterates over every object in the file reading the object, calling C<filter> 
with the object, and outputting the result. If C<filter> is not defined, 
just copies input to output.

=cut

sub copy {
    my ($self, $outpdf, $filter) = @_;
    my ($obj, $minl, $mini, $ming);

    foreach my $key (grep { not m/^[\s\-]/ } keys %$self) {
        $outpdf->{$key} = $self->{$key} unless defined $outpdf->{$key};
    }

    my $tdict = $self;
    while (defined $tdict) {
        foreach my $i (sort {$a <=> $b} keys %{$tdict->{' xref'}}) {
            my ($nl, $ng, $nt) = @{$tdict->{' xref'}{$i}};
            next unless $nt eq 'n';

            if ($nl < $minl or $mini == 0) {
                $mini = $i;
                $ming = $ng;
                $minl = $nl;
            }
            unless ($obj = $self->test_obj($i, $ng)) {
                $obj = PDF::Builder::Basic::PDF::Objind->new();
                $obj->{' objnum'} = $i;
                $obj->{' objgen'} = $ng;
                $self->add_obj($obj, $i, $ng);
                $obj->{' parent'} = $self;
                weaken $obj->{' parent'};
                $obj->{' realised'} = 0;
            }
            $obj->realise();
            my $res = defined $filter ? &{$filter}($obj) : $obj;
            $outpdf->new_obj($res) unless (!$res || $res->is_obj($outpdf));
        }
        $tdict = $tdict->{' prev'};
    }

    # test for linearized and remove it from output
    $obj = $self->test_obj($mini, $ming);
    if ($obj->isa('PDF::Builder::Basic::PDF::Dict') && $obj->{'Linearized'}) {
        $outpdf->free_obj($obj);
    }

    return $self;
} # end of copy()

=head1 PRIVATE METHODS & FUNCTIONS

The following methods and functions are considered B<private> to this class. 
This does not mean you cannot use them if you have a need, just that they 
aren't really designed for users of this class.

=head2 $offset = $p->locate_obj($num, $gen)

Returns a file offset to the object asked for by following the chain of cross
reference tables until it finds the one you want.

=cut

sub locate_obj {
    my ($self, $num, $gen) = @_;

    my $tdict = $self;
    while (defined $tdict) {
        if (ref $tdict->{' xref'}{$num}) {
            my $ref = $tdict->{' xref'}{$num};
            return $ref unless scalar(@$ref) == 3;

            if ($ref->[1] == $gen) {
                return $ref->[0] if $ref->[2] eq 'n';
                return;        # if $ref->[2] eq 'f';
            }
        }
        $tdict = $tdict->{' prev'};
    }

    return;
}

=head2 update($fh, $str, $instream)

Keeps reading C<$fh> for more data to ensure that C<$str> has at least a line 
full for C<readval> to work on. At this point we also take the opportunity to 
ignore comments.

=cut

sub update {
    my ($fh, $str, $instream) = @_;

    print STDERR 'fpos=' . tell($fh) . ' strlen=' . length($str) . "\n" if $readDebug;
    if ($instream) {
        # we are inside a (possible binary) stream
        # so we fetch data till we see an 'endstream'
        # -- fredo/2004-09-03
        while ($str !~ m/endstream/ and not $fh->eof()) {
            print STDERR 'fpos=' . tell($fh) . ' strlen=' . length($str) . "\n" if $readDebug;
            $fh->read($str, 314, length($str));
        }
    } else {
        $str =~ s/^$ws_char*//;
        while ($str !~ m/$cr/ and not $fh->eof()) {
            print STDERR 'fpos=' . tell($fh) . ' strlen=' . length($str) . "\n" if $readDebug;
            $fh->read($str, 314, length($str));
            $str =~ s/^$ws_char*//so;
        }
        while ($str =~ m/^\%/) { # restructured by fredo/2003-03-23
            print STDERR 'fpos=' . tell($fh) . ' strlen=' . length($str) . "\n" if $readDebug;
            $fh->read($str, 314, length($str)) while ($str !~ m/$cr/ and not $fh->eof());
            $str =~ s/^\%[^\015\012]*$ws_char*//so; # fixed for reportlab -- fredo
        }
    }

    return $str;
} # end of update()

=head2 $objind = $p->test_obj($num, $gen)

Tests the cache to see whether an object reference (which may or may not have
been getobj()ed) has been cached. Returns it if it has.

=cut

sub test_obj {
    my ($self, $num, $gen) = @_;

    return $self->{' objcache'}{$num, $gen};
}

=head2 $p->add_obj($objind)

Adds the given object to the internal object cache.

=cut

sub add_obj {
    my ($self, $obj, $num, $gen) = @_;

    $self->{' objcache'}{$num, $gen} = $obj;
    $self->{' objects'}{$obj->uid()} = [$num, $gen];
    # weaken $self->{' objcache'}{$num, $gen};
    return $obj;
}

=head2 $tdict = $p->readxrtr($xpos, %options)

Recursive function which reads each of the cross-reference and trailer tables
in turn until there are no more.

Returns a dictionary corresponding to the trailer chain. Each trailer also
includes the corresponding cross-reference table.

The structure of the xref private element in a trailer dictionary is of an
anonymous hash of cross reference elements by object number. Each element
consists of an array of 3 elements corresponding to the three elements read
in [location, generation number, free or used]. See the PDF specification
for details.

See C<open> for options allowed.

=cut

sub _unpack_xref_stream {
    my ($self, $width, $data) = @_;

    return unpack('C', $data)       if $width == 1;
    return unpack('n', $data)       if $width == 2;
    return unpack('N', "\x00$data") if $width == 3;
    return unpack('N', $data)       if $width == 4;
    return unpack('Q', $data)       if $width == 8; # PDF 1.5+?

    die "Invalid column width: $width";
}

sub readxrtr {
    my ($self, $xpos, %options) = @_;
    # $xpos SHOULD be pointing to "xref" keyword
    my ($tdict, $buf, $xmin, $xnum, $xdiff);

    my $fh = $self->{' INFILE'};
    $fh->seek($xpos, 0);
    $fh->read($buf, 22);  # 22 should overlap into first subsection
    $buf = update($fh, $buf); # fix for broken JAWS xref calculation.

    my $xlist = {};

   ## it seems that some products calculate wrong prev entries (short)
   ## so we seek ahead to find one -- fredo; save for now
   #while ($buf !~ m/^xref$cr/i && !eof($fh)) {
   #    $buf =~ s/^(\s+|\S+|.)//i;
   #    $buf = update($fh, $buf);
   #}

    if ($buf =~ s/^xref$cr//i) {   # remove xrefEOL from buffer
        # Plain XRef tables.
        #
        # look to match startobj# count# EOL of first (or only) subsection
        # supposed to be single ASCII space between numbers, but this is
        #   more lenient for some writers, allowing 1 or more whitespace
        my $subsection_count = 0;
        my $entry_format_error = 0;
        my $xrefListEmpty = 0;

        while ($buf =~ m/^$ws_char*([0-9]+)$ws_char+([0-9]+)$ws_char*$cr(.*?)$/s) {
            my $old_buf = $buf;
            $xmin = $1;   # starting object number of this subsection
            $xnum = $2;   # number of entries in this subsection 
            $buf  = $3;   # remainder of buffer
            $subsection_count++;
            # go back and warn if other than single space separating numbers
            unless ($old_buf =~ /^[0-9]+ [0-9]+$cr/) {  #orig 'warn'
		if ($options{'-diags'} == 1) {
                    # See PDF 1.7 section 7.5.4: Cross-Reference Table
                    warn "Malformed xref: subsection header needs a single\n" .
                         "ASCII space between the numbers and no extra spaces.\n";
	        }
            }
            $xdiff = length($buf); # how much remaining in buffer

            # in case xnum == 0 is permitted (or used and tolerated by readers),
            #   skip over entry reads and go to next subsection
            if ($xnum < 1) { 
                if ($options{'-diags'} == 1) { 
                    warn "Xref subsection has 0 entries. Skipped.\n";
		}
                $xrefListEmpty = 1;
                next; 
            }

            # read chunk of entire subsection list
            my $entry_size = 20;
            # test read first entry, see if $cr in expected place, adjust size
            $fh->read($buf, $entry_size * 1 - $xdiff + 15, $xdiff);
            $buf =~ m/^(.*?)$cr/;
            $entry_size = length($1) + 2;
            if ($entry_size != 20 && $options{'-diags'} == 1) {
                warn "Xref entries supposed to be 20 bytes long, are $entry_size.\n";
            }
            $xdiff = length($buf);

            # read remaining entries
            $fh->read($buf, $entry_size * $xnum - $xdiff + 15, $xdiff);
            # each entry is two integers and flag. spec says single ASCII space 
            #   between each field and certain length for each (10, 5, 1), so 
            #   this appears to be more lenient than spec
            # is object 0 supposed to be in subsection 1, or is any place OK?
            while ($xnum-- > 0 and 
                   $buf =~ m/^$ws_char*(\d+)$ws_char+(\d+)$ws_char+([nf])$ws_char*$cr/) {
                # check if format doesn't match spec
                if ($buf =~ m/^\d{10} \d{5} [nf]$cr/ ||
                    $entry_format_error) {
                    # format OK or have already reported format problem
                } else {
		    if ($options{'-diags'} == 1) {
                        warn "Xref entry readable, but doesn't meet PDF spec.\n";
                    }
                    $entry_format_error++;
                }

                $buf =~ s/^$ws_char*(\d+)$ws_char+(\d+)$ws_char+([nf])$ws_char*$cr//;
                # $1 = object's starting offset in file (n) or 
                #      next object in free list (f) [0 if last]
                # $2 = generation number (n) or 65535 for object 0 (f) or
                #      next generation number (f)
                # $3 = flag (n = object in use, f = free)
                # buf reduced by entry just processed
                if (exists $xlist->{$xmin}) {
                    if ($options{'-diags'} == 1) {
                        warn "Duplicate object number $xmin in xref table ignored.\n";
		    }
                } else {
                    $xlist->{$xmin} = [$1, $2, $3];
                    if ($xmin == 0 && $subsection_count > 1 && $options{'-diags'} == 1) {
                        warn "Xref object 0 entry not in first subsection.\n";
                    }
                }
                $xmin++;
            } # traverse one subsection for objects xmin through xmin+xnum-1 
            # go back for next subsection (if any)
        } # loop through xref subsections
        # fall through to here when run out of xref subsections
        # xlist should have two or more object entries, may not be contiguous

        # should have an object 0
        #   at this point, no idea if object 0 was in first subsection (legal?)
        #   could attempt a fixup if no object 0 found. many fixups are quite
        #     risky and could end up corrupting the free list.
        #   there's no guarantee that a proper free list will result, but any
        #     error should hopefully be caught further on
        if (!exists $xlist->{'0'} && !$xrefListEmpty) {
            # for now, 1 subsection starting with 1, and only object 1 in
            #   free list, try to fix up
            if ($subsection_count == 1 && exists $xlist->{'1'}) {
                # apparently a common enough error in PDF writers

                if ($xlist->{'1'}[0] == 0 &&  # only member of free list
                    $xlist->{'1'}[1] == 65535 &&
                    $xlist->{'1'}[2] eq 'f') {
                    # object 1 appears to be the free list head, so shift
                    #   down all objects
		    if ($options{'-diags'} == 1) {
                        warn "xref appears to be mislabeled starting with 1. Shift down all elements.\n";
		    }
                    my $next = 1;
                    while (exists $xlist->{$next}) {
                        $xlist->{$next - 1} = $xlist->{$next};
                        $next++;
                    }
                    delete $xlist->{--$next};

                } else {
                    # if object 1 does not appear to be a free list head, 
                    #   insert a new object 0
		    if ($options{'-diags'} == 1) {
                        warn "Xref appears to be missing object 0. Insert a new one.\n";
		    }
                    $xlist->{'0'} = [0, 65535, 'f'];
                }
            } else {
		if ($options{'-diags'} == 1) {
                    warn "Malformed cross reference list in PDF file $self->{' fname'} -- no object 0 (free list head)\n";
		}
                $xlist->{'0'} = [0, 65535, 'f'];
            }
        } # no object 0 entry

        # build/validate the free list (and no active objects have f flag)
        my @free_list;
        foreach (sort {$a <=> $b} keys %{ $xlist }) {
            # if 'f' flag, is in free list
            if      ($xlist->{$_}[2] eq 'f') {
                if ($xlist->{$_}[1] <= 0 && $options{'-diags'} == 1) {
                    warn "Xref free list entry $_ with bad next generation number.\n";
                } else {
                    push @free_list, $_; # should be in numeric order (0 first)
                }
            } elsif ($xlist->{$_}[2] eq 'n') {
                if ($xlist->{$_}[0] <= 0 && $options{'-diags'} == 1) {
                    warn "Xref active object $_ entry with bad length ".($xlist->{$_}[1])."\n";
                }
                if ($xlist->{$_}[1] < 0 && $options{'-diags'} == 1) {
                    warn "Xref active object $_ entry with bad generation number ".($xlist->{$_}[1])."\n";
                }
            } else {
		if ($options{'-diags'} == 1) {
                    warn "Xref entry has flag that is not 'f' or 'n'.\n";
	        }
            }
        } # go through xlist and build free_list and check entries
        # traverse free list and check that "next object" is also in free list
        my $next_free = 0;  # object 0 should always be in free list
        if ($xlist->{'0'}[1] != 65535 && $options{'-diags'} == 1) {
            warn "Object 0 next generation is not 65535.\n";
        }
        do {
            if ($xlist->{$next_free}[2] ne 'f') {
                if ($options{'-diags'} == 1) {
                    warn "Corrupted free object list: next=$next_free is not a free object.\n";
		}
                $next_free = 0; # force end of free list
            } else { 
                $next_free = $xlist->{$next_free}[0];
            }
            # remove this entry from free list array
            splice(@free_list, index(@free_list, $next_free), 1);
        } while ($next_free && exists $xlist->{$next_free});
        if (scalar @free_list && $options{'-diags'} == 1) {
            warn "Corrupted xref list: object(s) @free_list marked as free, but are not in free chain.\n";
        }

        # done with cross reference table, so go on to trailer
        if ($buf !~ /^\s*trailer\b/i && $options{'-diags'} == 1) {  #orig 'die'
            warn "Malformed trailer in PDF file $self->{' fname'} at " . ($fh->tell() - length($buf));
        }

        $buf =~ s/^\s*trailer\b//i;

        ($tdict, $buf) = $self->readval($buf);

    } elsif ($buf =~ m/^(\d+)\s+(\d+)\s+obj/i) {
        my ($xref_obj, $xref_gen) = ($1, $2);

        # XRef streams
        ($tdict, $buf) = $self->readval($buf);

        unless ($tdict->{' stream'}) {
	    if ($options{'-diags'} == 1) {
                warn "Malformed XRefStm at $xref_obj $xref_gen obj in PDF file $self->{' fname'}";
	    }
        }
        $tdict->read_stream(1);

        my $stream = $tdict->{' stream'};
        my @widths = map { $_->val() } @{$tdict->{'W'}->val()};

        my $start = 0;
        my $last;

        my @index;
        if (defined $tdict->{'Index'}) {
            @index = map { $_->val() } @{$tdict->{'Index'}->val()};
        } else {
            @index = (0, $tdict->{'Size'}->val());
        }

        while (scalar @index) {
            $start = shift(@index);
            $last = $start + shift(@index) - 1;

            for my $i ($start...$last) {
                # Replaced "for $xmin" because it creates a loop-specific local 
                # variable, and we need $xmin to be correct for maxobj below.
                $xmin = $i;

                my @cols;

                for my $w (@widths) {
                    my $data;
                    $data = $self->_unpack_xref_stream($w, substr($stream, 0, $w, '')) if $w;

                    push @cols, $data;
                }

                $cols[0] = 1 unless defined $cols[0];
                if ($cols[0] > 2 && $options{'-diags'} == 1) {
                    warn "Invalid XRefStm entry type ($cols[0]) at $xref_obj $xref_gen obj";
                }

                next if exists $xlist->{$xmin};

                my @objind = ($cols[1], defined($cols[2]) ? $cols[2] : ($xmin ? 0 : 65535));
                push @objind, ($cols[0] == 0? 'f': 'n') if $cols[0] < 2;

                $xlist->{$xmin} = \@objind;
            }
        }

    } else {  #orig 'die'
	if ($options{'-diags'} == 1) {
            warn "Malformed xref in PDF file $self->{' fname'}";
	}
    }

    $tdict->{' loc'} = $xpos;
    $tdict->{' xref'} = $xlist;
    $self->{' maxobj'} = $xmin + 1 if $xmin + 1 > $self->{' maxobj'};
    $tdict->{' prev'} = $self->readxrtr($tdict->{'Prev'}->val(), %options)
        if (defined $tdict->{'Prev'} and $tdict->{'Prev'}->val() != 0);
    delete $tdict->{' prev'} unless defined $tdict->{' prev'};

    return $tdict;
} # end of readxrtr()

=head2 $p->out_trailer($tdict, $update)

=head2 $p->out_trailer($tdict)

Outputs the body and trailer for a PDF file by outputting all the objects in
the ' outlist' and then outputting a xref table for those objects and any
freed ones. It then outputs the trailing dictionary and the trailer code.

=cut

sub out_trailer {
    my ($self, $tdict, $update) = @_;

    my $fh = $self->{' OUTFILE'};

    while (@{$self->{' outlist'}}) {
        $self->ship_out();
    }

    #    $size = @{$self->{' printed'}} + @{$self->{' free'}};
    #    $tdict->{'Size'} = PDFNum($tdict->{'Size'}->val() + $size);
    # PDFSpec 1.3 says for /Size: (Required) Total number of entries in the file's
    # cross-reference table, including the original table and all updates. Which
    # is what the previous two lines implement.
    # But this seems to make Acrobat croak on saving so we try the following from
    # basil.duval@epfl.ch
    $tdict->{'Size'} = PDFNum($self->{' maxobj'});

    my $tloc = $fh->tell();
##  $fh->print("xref\n");
    # instead of directly outputting (fh->print) xreflist, we accumulate in @out
    my @out; 
    my @xreflist = sort { $self->{' objects'}{$a->uid()}[0] <=> $self->{' objects'}{$b->uid()}[0] } (@{$self->{' printed'} || []}, @{$self->{' free'} || []});

    my ($i, $j, $k);
    unless ($update) {
        $i = 1;
        for ($j = 0; $j < @xreflist; $j++) {
            my @inserts;
            $k = $xreflist[$j];
            while ($i < $self->{' objects'}{$k->uid()}[0]) {
                my ($n) = PDF::Builder::Basic::PDF::Objind->new();
                $self->add_obj($n, $i, 0);
                $self->free_obj($n);
                push(@inserts, $n);
                $i++;
            }
            splice(@xreflist, $j, 0, @inserts);
            $j += @inserts;
            $i++;
        }
    }

    my @freelist = sort { $self->{' objects'}{$a->uid()}[0] <=> $self->{' objects'}{$b->uid()}[0] } @{$self->{' free'} || []};

    $j = 0; my $first = -1; $k = 0;
    for ($i = 0; $i <= $#xreflist + 1; $i++) {
        # if ($i == 0) {
        #     $first = $i; $j = $xreflist[0]->{' objnum'};
        #     $fh->printf("0 1\n%010d 65535 f \n", $ff);
        # }
        if ($i > $#xreflist || $self->{' objects'}{$xreflist[$i]->uid()}[0] != $j + 1) {
##          $fh->print(($first == -1 ? "0 " : "$self->{' objects'}{$xreflist[$first]->uid()}[0] ") . ($i - $first) . "\n");
            push @out, ($first == -1 ? "0 " : "$self->{' objects'}{$xreflist[$first]->uid()}[0] ") . ($i - $first) . "\n";
            if ($first == -1) {
##              $fh->printf("%010d 65535 f \n", defined $freelist[$k] ? $self->{' objects'}{$freelist[$k]->uid()}[0] : 0);
                push @out, sprintf("%010d 65535 f \n", defined $freelist[$k] ? $self->{' objects'}{$freelist[$k]->uid()}[0] : 0);
                $first = 0;
            }
            for ($j = $first; $j < $i; $j++) {
                my $xref = $xreflist[$j];
                if (defined $freelist[$k] && defined $xref && "$freelist[$k]" eq "$xref") {
                    $k++;
##                  $fh->print(pack("A10AA5A4",
                    push(@out, pack("A10AA5A4",
                                    sprintf("%010d", (defined $freelist[$k] ?
                                                      $self->{' objects'}{$freelist[$k]->uid()}[0] : 0)), " ",
                                    sprintf("%05d", $self->{' objects'}{$xref->uid()}[1] + 1),
                                    " f \n"));
                } else {
##                  $fh->print(pack("A10AA5A4", sprintf("%010d", $self->{' locs'}{$xref->uid()}), " ",
                    push(@out, pack("A10AA5A4", sprintf("%010d", $self->{' locs'}{$xref->uid()}), " ",
                            sprintf("%05d", $self->{' objects'}{$xref->uid()}[1]),
                            " n \n"));
                }
            }
            $first = $i;
            $j = $self->{' objects'}{$xreflist[$i]->uid()}[0] if ($i < scalar @xreflist);

        } else {
            $j++;
        }
    } # end for loop through xreflists
##  $fh->print("trailer\n");
##  $tdict->outobjdeep($fh, $self);
##  $fh->print("\nstartxref\n$tloc\n%%EOF\n");
## start new code for 117184 fix by Vadim. @out has array of xref content
    if (exists $tdict->{'Type'} and $tdict->{'Type'}->val() eq 'XRef') {

        my (@index, @stream);
        for (@out) {  # @out is the accumulated cross reference list
            my @a = split;
            @a == 2 ? push @index, @a : push @stream, \@a;
        }
        my $i = $self->{' maxobj'}++;
        $self->add_obj($tdict, $i, 0);
        $self->out_obj($tdict);

        push @index, $i, 1;
        push @stream, [ $tloc, 0, 'n' ];

        my $len = $tloc > 0xFFFF ? 4 : 2;           # don't expect files > 4 Gb
        my $tpl = $tloc > 0xFFFF ? 'CNC' : 'CnC';   # don't expect gennum > 255, it's absurd.
                                                    # Adobe doesn't use them anymore anyway
        my $sstream = '';
        my @prev = ( 0 ) x ( $len + 2 );  # init prev to all 0's
        for (@stream) {
	    # OK to zero out gennum of 65535 for a cross reference stream, 
	    # rather than just truncating to 255 -- Vadim
	    $_->[ 1 ] = 0 if $_->[ 1 ] == 65535 and
	                     $_->[ 2 ] eq 'f';
            # make sure is 0..255, since will pack with 'C' code -- Phil
	    if ($_->[1] > 0xFF) {
		print "generation number ".($_->[1])." in entry '$_->[0] $_->[1] $_->[2]' exceeds 256, reduced to ".($_->[1] & 0x00FF)."\n";
	    }
	    $_->[ 1 ] &= 0x00FF;  
            my @line = unpack 'C*', pack $tpl, $_->[ 2 ] eq 'n'? 1 : 0, @{ $_ }[ 0 .. 1 ];

            $sstream .= pack 'C*', 2, # prepend filtering method, "PNG Up"
                map {($line[ $_ ] - $prev[ $_ ] + 256) % 256} 0 .. $#line;
            @prev    = @line;
        }
	# build a dictionary for the cross reference stream
        $tdict->{'Size'} = PDFNum($i + 1);
        $tdict->{'Index'} = PDFArray(map { PDFNum($_) } @index);
        $tdict->{'W'} = PDFArray(map { PDFNum($_) } 1, $len, 1);
        $tdict->{'Filter'} = PDFName('FlateDecode');

	# it's compressed
        $tdict->{'DecodeParms'} = PDFDict();
        $tdict->{'DecodeParms'}->val()->{'Predictor'} = PDFNum(12);
        $tdict->{'DecodeParms'}->val()->{'Columns'} = PDFNum($len + 2);

        $sstream = PDF::Builder::Basic::PDF::Filter::FlateDecode->new()->outfilt($sstream, 1);
        $tdict->{' stream'} = $sstream;
        $tdict->{' nofilt'} = 1;
        delete $tdict->{'Length'};
        $self->ship_out();
    } else {
	# delete may be moved later by Vadim closer to where XRefStm created
	delete $tdict->{'XRefStm'};
	# almost the original code
        $fh->print("xref\n", @out, "trailer\n");
        $tdict->outobjdeep($fh, $self);
        $fh->print("\n");
    }
    $fh->print("startxref\n$tloc\n%%EOF\n");
## end of new code

    return;
} # end of out_trailer()

=head2 PDF::Builder::Basic::PDF::File->_new()

Creates a very empty PDF file object (used by new() and open())

=cut

sub _new {
    my $class = shift();
    my $self = {};

    bless $self, $class;
    $self->{' outlist'}       = [];
    $self->{' outlist_cache'} = {};     # A cache of what's in the 'outlist'
    $self->{' maxobj'}        = 1;
    $self->{' objcache'}      = {};
    $self->{' objects'}       = {};

    return $self;
}

1;

=head1 AUTHOR

Martin Hosken Martin_Hosken@sil.org

Copyright Martin Hosken 1999 and onwards

No warranty or expression of effectiveness, least of all regarding anyone's
safety, is implied in this software or documentation.
