tar.pm

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

### the gnu tar specification:
### http://www.gnu.org/software/tar/manual/tar.html
###
### and the pax format spec, which tar derives from:
### http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html

package Archive::Tar;
require 5.005_03;

use strict;
use vars qw[$DEBUG $error $VERSION $WARN $FOLLOW_SYMLINK $CHOWN $CHMOD
            $DO_NOT_USE_PREFIX $HAS_PERLIO $HAS_IO_STRING
            $INSECURE_EXTRACT_MODE
         ];

$DEBUG                  = 0;
$WARN                   = 1;
$FOLLOW_SYMLINK         = 0;
$VERSION                = "1.38";
$CHOWN                  = 1;
$CHMOD                  = 1;
$DO_NOT_USE_PREFIX      = 0;
$INSECURE_EXTRACT_MODE  = 0;

BEGIN {
    use Config;
    $HAS_PERLIO = $Config::Config{useperlio};

    ### try and load IO::String anyway, so you can dynamically
    ### switch between perlio and IO::String
    eval {
        require IO::String;
        import IO::String;
    };
    $HAS_IO_STRING = $@ ? 0 : 1;

}

use Cwd;
use IO::File;
use Carp                qw(carp croak);
use File::Spec          ();
use File::Spec::Unix    ();
use File::Path          ();

use Archive::Tar::File;
use Archive::Tar::Constant;

=head1 NAME

Archive::Tar - module for manipulations of tar archives

=head1 SYNOPSIS

    use Archive::Tar;
    my $tar = Archive::Tar->new;

    $tar->read('origin.tgz',1);
    $tar->extract();

    $tar->add_files('file/foo.pl', 'docs/README');
    $tar->add_data('file/baz.txt', 'This is the contents now');

    $tar->rename('oldname', 'new/file/name');

    $tar->write('files.tar');

=head1 DESCRIPTION

Archive::Tar provides an object oriented mechanism for handling tar
files.  It provides class methods for quick and easy files handling
while also allowing for the creation of tar file objects for custom
manipulation.  If you have the IO::Zlib module installed,
Archive::Tar will also support compressed or gzipped tar files.

An object of class Archive::Tar represents a .tar(.gz) archive full
of files and things.

=head1 Object Methods

=head2 Archive::Tar->new( [$file, $compressed] )

Returns a new Tar object. If given any arguments, C<new()> calls the
C<read()> method automatically, passing on the arguments provided to
the C<read()> method.

If C<new()> is invoked with arguments and the C<read()> method fails
for any reason, C<new()> returns undef.

=cut

my $tmpl = {
    _data   => [ ],
    _file   => 'Unknown',
};

### install get/set accessors for this object.
for my $key ( keys %$tmpl ) {
    no strict 'refs';
    *{__PACKAGE__."::$key"} = sub {
        my $self = shift;
        $self->{$key} = $_[0] if @_;
        return $self->{$key};
    }
}

sub new {
    my $class = shift;
    $class = ref $class if ref $class;

    ### copying $tmpl here since a shallow copy makes it use the
    ### same aref, causing for files to remain in memory always.
    my $obj = bless { _data => [ ], _file => 'Unknown' }, $class;

    if (@_) {
        unless ( $obj->read( @_ ) ) {
            $obj->_error(qq[No data could be read from file]);
            return;
        }
    }

    return $obj;
}

=head2 $tar->read ( $filename|$handle, $compressed, {opt => 'val'} )

Read the given tar file into memory.
The first argument can either be the name of a file or a reference to
an already open filehandle (or an IO::Zlib object if it's compressed)
The second argument indicates whether the file referenced by the first
argument is compressed.

The C<read> will I<replace> any previous content in C<$tar>!

The second argument may be considered optional if IO::Zlib is
installed, since it will transparently Do The Right Thing.
Archive::Tar will warn if you try to pass a compressed file if
IO::Zlib is not available and simply return.

Note that you can currently B<not> pass a C<gzip> compressed
filehandle, which is not opened with C<IO::Zlib>, nor a string
containing the full archive information (either compressed or
uncompressed). These are worth while features, but not currently
implemented. See the C<TODO> section.

The third argument can be a hash reference with options. Note that
all options are case-sensitive.

=over 4

=item limit

Do not read more than C<limit> files. This is useful if you have
very big archives, and are only interested in the first few files.

=item extract

If set to true, immediately extract entries when reading them. This
gives you the same memory break as the C<extract_archive> function.
Note however that entries will not be read into memory, but written
straight to disk.

=back

All files are stored internally as C<Archive::Tar::File> objects.
Please consult the L<Archive::Tar::File> documentation for details.

Returns the number of files read in scalar context, and a list of
C<Archive::Tar::File> objects in list context.

=cut

sub read {
    my $self = shift;
    my $file = shift;
    my $gzip = shift || 0;
    my $opts = shift || {};

    unless( defined $file ) {
        $self->_error( qq[No file to read from!] );
        return;
    } else {
        $self->_file( $file );
    }

    my $handle = $self->_get_handle($file, $gzip, READ_ONLY->( ZLIB ) )
                    or return;

    my $data = $self->_read_tar( $handle, $opts ) or return;

    $self->_data( $data );

    return wantarray ? @$data : scalar @$data;
}

sub _get_handle {
    my $self = shift;
    my $file = shift;   return unless defined $file;
                        return $file if ref $file;

    my $gzip = shift || 0;
    my $mode = shift || READ_ONLY->( ZLIB ); # default to read only

    my $fh; my $bin;

    ### only default to ZLIB if we're not trying to /write/ to a handle ###
    if( ZLIB and $gzip || MODE_READ->( $mode ) ) {

        ### IO::Zlib will Do The Right Thing, even when passed
        ### a plain file ###
        $fh = new IO::Zlib;

    } else {
        if( $gzip ) {
            $self->_error(qq[Compression not available - Install IO::Zlib!]);
            return;

        } else {
            $fh = new IO::File;
            $bin++;
        }
    }

    unless( $fh->open( $file, $mode ) ) {
        $self->_error( qq[Could not create filehandle for '$file': $!!] );
        return;
    }

    binmode $fh if $bin;

    return $fh;
}

sub _read_tar {
    my $self    = shift;
    my $handle  = shift or return;
    my $opts    = shift || {};

    my $count   = $opts->{limit}    || 0;
    my $extract = $opts->{extract}  || 0;

    ### set a cap on the amount of files to extract ###
    my $limit   = 0;
    $limit = 1 if $count > 0;

    my $tarfile = [ ];
    my $chunk;
    my $read = 0;
    my $real_name;  # to set the name of a file when
                    # we're encountering @longlink
    my $data;

    LOOP:
    while( $handle->read( $chunk, HEAD ) ) {
        ### IO::Zlib doesn't support this yet
        my $offset = eval { tell $handle } || 'unknown';

        unless( $read++ ) {
            my $gzip = GZIP_MAGIC_NUM;
            if( $chunk =~ /$gzip/ ) {
                $self->_error( qq[Cannot read compressed format in tar-mode] );
                return;
            }
        }

        ### if we can't read in all bytes... ###
        last if length $chunk != HEAD;

        ### Apparently this should really be two blocks of 512 zeroes,
        ### but GNU tar sometimes gets it wrong. See comment in the
        ### source code (tar.c) to GNU cpio.
        next if $chunk eq TAR_END;

        ### according to the posix spec, the last 12 bytes of the header are
        ### null bytes, to pad it to a 512 byte block. That means if these
        ### bytes are NOT null bytes, it's a corrrupt header. See:
        ### www.koders.com/c/fidCE473AD3D9F835D690259D60AD5654591D91D5BA.aspx
        ### line 111
        {   my $nulls = join '', "\0" x 12;
            unless( $nulls eq substr( $chunk, 500, 12 ) ) {
                $self->_error( qq[Invalid header block at offset $offset] );
                next LOOP;
            }
        }

        ### pass the realname, so we can set it 'proper' right away
        ### some of the heuristics are done on the name, so important
        ### to set it ASAP
        my $entry;
        {   my %extra_args = ();
            $extra_args{'name'} = $$real_name if defined $real_name;
            
            unless( $entry = Archive::Tar::File->new(   chunk => $chunk, 
                                                        %extra_args ) 
            ) {
                $self->_error( qq[Couldn't read chunk at offset $offset] );
                next LOOP;
            }
        }

        ### ignore labels:
        ### http://www.gnu.org/manual/tar/html_node/tar_139.html
        next if $entry->is_label;

        if( length $entry->type and ($entry->is_file || $entry->is_longlink) ) {

            if ( $entry->is_file && !$entry->validate ) {
                ### sometimes the chunk is rather fux0r3d and a whole 512
                ### bytes ends up in the ->name area.
                ### clean it up, if need be
                my $name = $entry->name;
                $name = substr($name, 0, 100) if length $name > 100;
                $name =~ s/\n/ /g;

                $self->_error( $name . qq[: checksum error] );
                next LOOP;
            }

            my $block = BLOCK_SIZE->( $entry->size );

            $data = $entry->get_content_by_ref;

            ### just read everything into memory
            ### can't do lazy loading since IO::Zlib doesn't support 'seek'
            ### this is because Compress::Zlib doesn't support it =/
            ### this reads in the whole data in one read() call.
            if( $handle->read( $$data, $block ) < $block ) {
                $self->_error( qq[Read error on tarfile (missing data) '].
                                    $entry->full_path ."' at offset $offset" );
                next LOOP;
            }

            ### throw away trailing garbage ###
            substr ($$data, $entry->size) = "" if defined $$data;

            ### part II of the @LongLink munging -- need to do /after/
            ### the checksum check.
            if( $entry->is_longlink ) {
                ### weird thing in tarfiles -- if the file is actually a
                ### @LongLink, the data part seems to have a trailing ^@
                ### (unprintable) char. to display, pipe output through less.
                ### but that doesn't *always* happen.. so check if the last
                ### character is a control character, and if so remove it
                ### at any rate, we better remove that character here, or tests
                ### like 'eq' and hashlook ups based on names will SO not work
                ### remove it by calculating the proper size, and then
                ### tossing out everything that's longer than that size.

                ### count number of nulls
                my $nulls = $$data =~ tr/\0/\0/;

                ### cut data + size by that many bytes
                $entry->size( $entry->size - $nulls );
                substr ($$data, $entry->size) = "";
            }
        }

        ### clean up of the entries.. posix tar /apparently/ has some
        ### weird 'feature' that allows for filenames > 255 characters
        ### they'll put a header in with as name '././@LongLink' and the
        ### contents will be the name of the /next/ file in the archive
        ### pretty crappy and kludgy if you ask me

        ### set the name for the next entry if this is a @LongLink;
        ### this is one ugly hack =/ but needed for direct extraction
        if( $entry->is_longlink ) {
            $real_name = $data;
            next LOOP;
        } elsif ( defined $real_name ) {
            $entry->name( $$real_name );
            $entry->prefix('');
            undef $real_name;
        }

        $self->_extract_file( $entry ) if $extract
                                            && !$entry->is_longlink
                                            && !$entry->is_unknown
                                            && !$entry->is_label;

        ### Guard against tarfiles with garbage at the end
	    last LOOP if $entry->name eq '';

        ### push only the name on the rv if we're extracting
        ### -- for extract_archive
        push @$tarfile, ($extract ? $entry->name : $entry);

        if( $limit ) {
            $count-- unless $entry->is_longlink || $entry->is_dir;
            last LOOP unless $count;
        }
    } continue {
        undef $data;
    }

    return $tarfile;
}

=head2 $tar->contains_file( $filename )

Check if the archive contains a certain file.
It will return true if the file is in the archive, false otherwise.

Note however, that this function does an exact match using C<eq>
on the full path. So it cannot compensate for case-insensitive file-
systems or compare 2 paths to see if they would point to the same
underlying file.

=cut

sub contains_file {
    my $self = shift;
    my $full = shift;
    
    return unless defined $full;

    ### don't warn if the entry isn't there.. that's what this function
    ### is for after all.
    local $WARN = 0;
    return 1 if $self->_find_entry($full);
    return;
}

=head2 $tar->extract( [@filenames] )

Write files whose names are equivalent to any of the names in
C<@filenames> to disk, creating subdirectories as necessary. This
might not work too well under VMS.
Under MacPerl, the file's modification time will be converted to the
MacOS zero of time, and appropriate conversions will be done to the
path.  However, the length of each element of the path is not
inspected to see whether it's longer than MacOS currently allows (32
characters).

If C<extract> is called without a list of file names, the entire
contents of the archive are extracted.

Returns a list of filenames extracted.

=cut

sub extract {
    my $self    = shift;
    my @args    = @_;
    my @files;

    # use the speed optimization for all extracted files
    local($self->{cwd}) = cwd() unless $self->{cwd};

    ### you requested the extraction of only certian files
    if( @args ) {
        for my $file ( @args ) {
            
            ### it's already an object?
            if( UNIVERSAL::isa( $file, 'Archive::Tar::File' ) ) {
                push @files, $file;
                next;

            ### go find it then
            } else {
            
                my $found;
                for my $entry ( @{$self->_data} ) {
                    next unless $file eq $entry->full_path;
    
                    ### we found the file you're looking for
                    push @files, $entry;
                    $found++;