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: $VERSION = "2.110"; #------------------------------ =item new FILEHANDLE, [START, [LENGTH]] I Create a new inner-file opened on the given FILEHANDLE, from bytes START to START+LENGTH. Both START and LENGTH default to 0; negative values are silently coerced to zero. Note that FILEHANDLE must be able to seek() and tell(), in addition to whatever other methods you may desire for reading it. =cut sub new { my ($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 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} += $_[1]; } #------------------------------ =item set_start START =item get_start =item add_start NBYTES I Get/set the virtual start position of the inner file. =cut sub set_start { tied(${$_[0]})->{START} = $_[1]; } sub get_start { tied(${$_[0]})->{START}; } sub set_end { tied(${$_[0]})->{LG} = $_[1] - tied(${$_[0]})->{START}; } sub get_end { tied(${$_[0]})->{LG} + tied(${$_[0]})->{START}; } #------------------------------ =item binmode =item close =item flush =item getc =item getline =item print LIST =item printf LIST =item read BUF, NBYTES =item readline =item seek OFFFSET, WHENCE =item tell =item write ARGS... I Standard filehandle methods. =cut sub write { shift->WRITE(@_) } sub print { shift->PRINT(@_) } sub printf { shift->PRINTF(@_) } sub flush { "0 but true"; } sub binmode { 1; } sub getc { return GETC(tied(${$_[0]}) ); } sub read { return READ( tied(${$_[0]}), @_[1,2,3] ); } sub readline { return READLINE( tied(${$_[0]}) ); } sub getline { return READLINE( tied(${$_[0]}) ); } sub close { return CLOSE(tied(${$_[0]}) ); } sub seek { my ($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 undef if ($self->{CRPOS} >= $self->{LG}); ### 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 David F. Skoll (dfs@roaringpenguin.com). =cut