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package IO::InnerFile;
=head1 NAME
IO::InnerFile - define a file inside another file
=head1 SYNOPSIS
### Read a subset of a file:
$inner = IO::InnerFile->new($fh, $start, $length);
while (<$inner>) {
...
}
=head1 DESCRIPTION
If you have a filehandle that can seek() and tell(), then you
can open an IO::InnerFile on a range of the underlying file.
=head1 PUBLIC INTERFACE
=over
=cut
use Symbol;
# The package version, both in 1.23 style *and* usable by MakeMaker:
$VERSION = "2.111";
#------------------------------
=item new FILEHANDLE, [START, [LENGTH]]
I<Class method, constructor.>
Create a new inner-file opened on the given FILEHANDLE,
from bytes START to START+LENGTH. Both START and LENGTH
default to 0; negative values are silently coerced to zero.
Note that FILEHANDLE must be able to seek() and tell(), in addition
to whatever other methods you may desire for reading it.
=cut
sub new {
my ($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');
}
#------------------------------
=item set_length LENGTH
=item get_length
=item add_length NBYTES
I<Instance methods.>
Get/set the virtual length of the inner file.
=cut
sub set_length { tied(${$_[0]})->{LG} = $_[1]; }
sub get_length { tied(${$_[0]})->{LG}; }
sub add_length { tied(${$_[0]})->{LG} += $_[1]; }
#------------------------------
=item set_start START
=item get_start
=item add_start NBYTES
I<Instance methods.>
Get/set the virtual start position of the inner file.
=cut
sub set_start { tied(${$_[0]})->{START} = $_[1]; }
sub get_start { tied(${$_[0]})->{START}; }
sub set_end { tied(${$_[0]})->{LG} = $_[1] - tied(${$_[0]})->{START}; }
sub get_end { tied(${$_[0]})->{LG} + tied(${$_[0]})->{START}; }
#------------------------------
=item binmode
=item close
=item flush
=item getc
=item getline
=item print LIST
=item printf LIST
=item read BUF, NBYTES
=item readline
=item seek OFFFSET, WHENCE
=item tell
=item write ARGS...
I<Instance methods.>
Standard filehandle methods.
=cut
sub write { shift->WRITE(@_) }
sub print { shift->PRINT(@_) }
sub printf { shift->PRINTF(@_) }
sub flush { "0 but true"; }
sub fileno { }
sub binmode { 1; }
sub getc { return GETC(tied(${$_[0]}) ); }
sub read { return READ( tied(${$_[0]}), @_[1,2,3] ); }
sub readline { return READLINE( tied(${$_[0]}) ); }
sub getline { return READLINE( tied(${$_[0]}) ); }
sub close { return CLOSE(tied(${$_[0]}) ); }
sub seek {
my ($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__
=back
=head1 VERSION
$Id: InnerFile.pm,v 1.4 2005/02/10 21:21:53 dfs Exp $
=head1 AUTHOR
Original version by Doru Petrescu (pdoru@kappa.ro).
Documentation and by Eryq (eryq@zeegee.com).
Currently maintained by Dianne Skoll (dfs@roaringpenguin.com).
=cut