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package IO::InnerFile;
use strict;
use warnings;
use Symbol;
our $VERSION = '2.113';
sub new {
my ($class, $fh, $start, $lg) = @_;
$start = 0 if (!$start or ($start < 0));
$lg = 0 if (!$lg or ($lg < 0));
### Create the underlying "object":
my $a = {
FH => $fh,
CRPOS => 0,
START => $start,
LG => $lg,
};
### Create a new filehandle tied to this object:
$fh = gensym;
tie(*$fh, $class, $a);
return bless($fh, $class);
}
sub TIEHANDLE {
my ($class, $data) = @_;
return bless($data, $class);
}
sub DESTROY {
my ($self) = @_;
$self->close() if (ref($self) eq 'SCALAR');
}
sub set_length { tied(${$_[0]})->{LG} = $_[1]; }
sub get_length { tied(${$_[0]})->{LG}; }
sub add_length { tied(${$_[0]})->{LG} += $_[1]; }
sub set_start { tied(${$_[0]})->{START} = $_[1]; }
sub get_start { tied(${$_[0]})->{START}; }
sub set_end { tied(${$_[0]})->{LG} = $_[1] - tied(${$_[0]})->{START}; }
sub get_end { tied(${$_[0]})->{LG} + tied(${$_[0]})->{START}; }
sub write { shift->WRITE(@_) }
sub print { shift->PRINT(@_) }
sub printf { shift->PRINTF(@_) }
sub flush { "0 but true"; }
sub fileno { }
sub binmode { 1; }
sub getc { return GETC(tied(${$_[0]}) ); }
sub read { return READ( tied(${$_[0]}), @_[1,2,3] ); }
sub readline { return READLINE( tied(${$_[0]}) ); }
sub getline { return READLINE( tied(${$_[0]}) ); }
sub close { return CLOSE(tied(${$_[0]}) ); }
sub seek {
my ($self, $ofs, $whence) = @_;
$self = tied( $$self );
$self->{CRPOS} = $ofs if ($whence == 0);
$self->{CRPOS}+= $ofs if ($whence == 1);
$self->{CRPOS} = $self->{LG} + $ofs if ($whence == 2);
$self->{CRPOS} = 0 if ($self->{CRPOS} < 0);
$self->{CRPOS} = $self->{LG} if ($self->{CRPOS} > $self->{LG});
return 1;
}
sub tell {
return tied(${$_[0]})->{CRPOS};
}
sub WRITE {
die "inner files can only open for reading\n";
}
sub PRINT {
die "inner files can only open for reading\n";
}
sub PRINTF {
die "inner files can only open for reading\n";
}
sub GETC {
my ($self) = @_;
return 0 if ($self->{CRPOS} >= $self->{LG});
my $data;
### Save and seek...
my $old_pos = $self->{FH}->tell;
$self->{FH}->seek($self->{CRPOS}+$self->{START}, 0);
### ...read...
my $lg = $self->{FH}->read($data, 1);
$self->{CRPOS} += $lg;
### ...and restore:
$self->{FH}->seek($old_pos, 0);
$self->{LG} = $self->{CRPOS} unless ($lg);
return ($lg ? $data : undef);
}
sub READ {
my ($self, $undefined, $lg, $ofs) = @_;
$undefined = undef;
return 0 if ($self->{CRPOS} >= $self->{LG});
$lg = $self->{LG} - $self->{CRPOS} if ($self->{CRPOS} + $lg > $self->{LG});
return 0 unless ($lg);
### Save and seek...
my $old_pos = $self->{FH}->tell;
$self->{FH}->seek($self->{CRPOS}+$self->{START}, 0);
### ...read...
$lg = $self->{FH}->read($_[1], $lg, $_[3] );
$self->{CRPOS} += $lg;
### ...and restore:
$self->{FH}->seek($old_pos, 0);
$self->{LG} = $self->{CRPOS} unless ($lg);
return $lg;
}
sub READLINE {
my ($self) = @_;
return $self->_readline_helper() unless wantarray;
my @arr;
while(defined(my $line = $self->_readline_helper())) {
push(@arr, $line);
}
return @arr;
}
sub _readline_helper {
my ($self) = @_;
return undef if ($self->{CRPOS} >= $self->{LG});
# Handle slurp mode (CPAN ticket #72710)
if (! defined($/)) {
my $text;
$self->READ($text, $self->{LG} - $self->{CRPOS});
return $text;
}
### Save and seek...
my $old_pos = $self->{FH}->tell;
$self->{FH}->seek($self->{CRPOS}+$self->{START}, 0);
### ...read...
my $text = $self->{FH}->getline;
### ...and restore:
$self->{FH}->seek($old_pos, 0);
#### If we detected a new EOF ...
unless (defined $text) {
$self->{LG} = $self->{CRPOS};
return undef;
}
my $lg=length($text);
$lg = $self->{LG} - $self->{CRPOS} if ($self->{CRPOS} + $lg > $self->{LG});
$self->{CRPOS} += $lg;
return substr($text, 0,$lg);
}
sub CLOSE { %{$_[0]}=(); }
1;
__END__
__END__
=head1 NAME
IO::InnerFile - define a file inside another file
=head1 SYNOPSIS
use strict;
use warnings;
use IO::InnerFile;
# Read a subset of a file:
my $fh = _some_file_handle;
my $start = 10;
my $length = 50;
my $inner = IO::InnerFile->new($fh, $start, $length);
while (my $line = <$inner>) {
# ...
}
=head1 DESCRIPTION
If you have a file handle that can C<seek> and C<tell>, then you
can open an L<IO::InnerFile> on a range of the underlying file.
=head1 CONSTRUCTORS
L<IO::InnerFile> implements the following constructors.
=head2 new
my $inner = IO::InnerFile->new($fh);
$inner = IO::InnerFile->new($fh, 10);
$inner = IO::InnerFile->new($fh, 10, 50);
Create a new L<IO::InnerFile> opened on the given file handle.
The file handle supplied B<MUST> be able to both C<seek> and C<tell>.
The second and third parameters are start and length. Both are defaulted
to zero (C<0>). Negative values are silently coerced to zero.
=head1 METHODS
L<IO::InnerFile> implements the following methods.
=head2 add_length
$inner->add_length(30);
Add to the virtual length of the inner file by the number given in bytes.
=head2 add_start
$inner->add_start(30);
Add to the virtual position of the inner file by the number given in bytes.
=head2 binmode
$inner->binmode();
This is a NOOP method just to satisfy the normal L<IO::File> interface.
=head2 close
=head2 fileno
$inner->fileno();
This is a NOOP method just to satisfy the normal L<IO::File> interface.
=head2 flush
$inner->flush();
This is a NOOP method just to satisfy the normal L<IO::File> interface.
=head2 get_end
my $num_bytes = $inner->get_end();
Get the virtual end position of the inner file in bytes.
=head2 get_length
my $num_bytes = $inner->get_length();
Get the virtual length of the inner file in bytes.
=head2 get_start
my $num_bytes = $inner->get_start();
Get the virtual position of the inner file in bytes.
=head2 getc
=head2 getline
=head2 print LIST
=head2 printf
=head2 read
=head2 readline
=head2 seek
=head2 set_end
$inner->set_end(30);
Set the virtual end of the inner file in bytes (this basically just alters the length).
=head2 set_length
$inner->set_length(30);
Set the virtual length of the inner file in bytes.
=head2 set_start
$inner->set_start(30);
Set the virtual start position of the inner file in bytes.
=head2 tell
=head2 write
=head1 AUTHOR
Eryq (F<eryq@zeegee.com>).
President, ZeeGee Software Inc (F<http://www.zeegee.com>).
=head1 CONTRIBUTORS
Dianne Skoll (F<dfs@roaringpenguin.com>).
=head1 COPYRIGHT & LICENSE
Copyright (c) 1997 Erik (Eryq) Dorfman, ZeeGee Software, Inc. All rights reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
=cut
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