dpkg-1.16.1.1/scripts/Dpkg/Compression/FileHandle.pm - nest-learning-thermostat/5.1.6/dpkg - Git at Google

 # Copyright © 2008-2010 Raphaël Hertzog <hertzog@debian.org>
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.

 package Dpkg::Compression::FileHandle;

 use strict;
 use warnings;

 our $VERSION = "1.00";

 use Dpkg::Compression;
 use Dpkg::Compression::Process;
 use Dpkg::Gettext;
 use Dpkg::ErrorHandling;
 use POSIX qw(WIFSIGNALED WTERMSIG SIGPIPE);

 use base qw(FileHandle Tie::Handle);

 # Useful reference to understand some kludges required to
 # have the object behave like a filehandle
 # http://blog.woobling.org/2009/10/are-filehandles-objects.html

 =encoding utf8

 =head1 NAME

 Dpkg::Compression::FileHandle - object dealing transparently with file compression

 =head1 SYNOPSIS

     use Dpkg::Compression::FileHandle;

     $fh = Dpkg::Compression::FileHandle->new(filename=>"sample.gz");
     print $fh "Something\n";
     close $fh;

     $fh = Dpkg::Compression::FileHandle->new();
     open($fh, ">", "sample.bz2");
     print $fh "Something\n";
     close $fh;

     $fh = Dpkg::Compression::FileHandle->new();
     $fh->open("sample.xz", "w");
     $fh->print("Something\n");
     $fh->close();

     $fh = Dpkg::Compression::FileHandle->new(filename=>"sample.gz");
     my @lines = <$fh>;
     close $fh;

     $fh = Dpkg::Compression::FileHandle->new();
     open($fh, "<", "sample.bz2");
     my @lines = <$fh>;
     close $fh;

     $fh = Dpkg::Compression::FileHandle->new();
     $fh->open("sample.xz", "r");
     my @lines = $fh->getlines();
     $fh->close();

 =head1 DESCRIPTION

 Dpkg::Compression::FileHandle is an object that can be used
 like any filehandle and that deals transparently with compressed
 files. By default, the compression scheme is guessed from the filename
 but you can override this behaviour with the method C<set_compression>.

 If you don't open the file explicitly, it will be auto-opened on the
 first read or write operation based on the filename set at creation time
 (or later with the C<set_filename> method).

 Once a file has been opened, the filehandle must be closed before being
 able to open another file.

 =head1 STANDARD FUNCTIONS

 The standard functions acting on filehandles should accept a
 Dpkg::Compression::FileHandle object transparently including
 C<open> (only when using the variant with 3 parameters), C<close>,
 C<binmode>, C<eof>, C<fileno>, C<getc>, C<print>, C<printf>, C<read>,
 C<sysread>, C<say>, C<write>, C<syswrite>, C<seek>, C<sysseek>, C<tell>.

 Note however that C<seek> and C<sysseek> will only work on uncompressed
 files as compressed files are really pipes to the compressor programs
 and you can't seek on a pipe.

 =head1 FileHandle METHODS

 The object inherits from FileHandle so all methods that work on this
 object should work for Dpkg::Compression::FileHandle too. There
 may be exceptions though.

 =head1 PUBLIC METHODS

 =over 4

 =item my $fh = Dpkg::Compression::FileHandle->new(%opts)

 Creates a new filehandle supporting on-the-fly compression/decompression.
 Supported options are "filename", "compression", "compression_level" (see
 respective set_* functions) and "add_comp_ext". If "add_comp_ext"
 evaluates to true, then the extension corresponding to the selected
 compression scheme is automatically added to the recorded filename. It's
 obviously incompatible with automatic detection of the compression method.

 =cut

 # Object methods
 sub new {
     my ($this, %args) = @_;
     my $class = ref($this) || $this;
     my $self = FileHandle->new();
     # Tying is required to overload the open functions and to auto-open
     # the file on first read/write operation
     tie *$self, $class, $self;
     bless $self, $class;
     # Initializations
     *$self->{"compression"} = "auto";
     *$self->{"compressor"} = Dpkg::Compression::Process->new();
     *$self->{"add_comp_ext"} = $args{"add_compression_extension"} ||
 	    $args{"add_comp_ext"} || 0;
     *$self->{"allow_sigpipe"} = 0;
     if (exists $args{"filename"}) {
 	$self->set_filename($args{"filename"});
     }
     if (exists $args{"compression"}) {
 	$self->set_compression($args{"compression"});
     }
     if (exists $args{"compression_level"}) {
 	$self->set_compression_level($args{"compression_level"});
     }
     return $self;
 }

 =item $fh->ensure_open($mode)

 Ensure the file is opened in the requested mode ("r" for read and "w" for
 write). Opens the file with the recorded filename if needed. If the file
 is already open but not in the requested mode, then it errors out.

 =cut

 sub ensure_open {
     my ($self, $mode) = @_;
     if (exists *$self->{"mode"}) {
 	return if *$self->{"mode"} eq $mode;
 	internerr("ensure_open requested incompatible mode: $mode");
     } else {
 	if ($mode eq "w") {
 	    $self->open_for_write();
 	} elsif ($mode eq "r") {
 	    $self->open_for_read();
 	} else {
 	    internerr("invalid mode in ensure_open: $mode");
 	}
     }
 }

 ##
 ## METHODS FOR TIED HANDLE
 ##
 sub TIEHANDLE {
     my ($class, $self) = @_;
     return $self;
 }

 sub WRITE {
     my ($self, $scalar, $length, $offset) = @_;
     $self->ensure_open("w");
     return *$self->{'file'}->write($scalar, $length, $offset);
 }

 sub READ {
     my ($self, $scalar, $length, $offset) = @_;
     $self->ensure_open("r");
     return *$self->{'file'}->read($scalar, $length, $offset);
 }

 sub READLINE {
     my ($self) = shift;
     $self->ensure_open("r");
     return *$self->{"file"}->getlines() if wantarray;
     return *$self->{"file"}->getline();
 }

 sub OPEN {
     my ($self) = shift;
     if (scalar(@_) == 2) {
 	my ($mode, $filename) = @_;
 	$self->set_filename($filename);
 	if ($mode eq ">") {
 	    $self->open_for_write();
 	} elsif ($mode eq "<") {
 	    $self->open_for_read();
 	} else {
 	    internerr("Unsupported open mode on Dpkg::Compression::FileHandle: $mode");
 	}
     } else {
 	internerr("Dpkg::Compression::FileHandle only supports open() with 3 parameters");
     }
     return 1; # Always works (otherwise errors out)
 }

 sub CLOSE {
     my ($self) = shift;
     my $ret = 1;
     if (defined *$self->{'file'}) {
 	$ret = *$self->{'file'}->close(@_) if *$self->{'file'}->opened();
     } else {
 	$ret = 0;
     }
     $self->cleanup();
     return $ret;
 }

 sub FILENO {
     my ($self) = shift;
     return *$self->{"file"}->fileno(@_) if defined *$self->{"file"};
     return undef;
 }

 sub EOF {
     my ($self) = shift;
     return *$self->{"file"}->eof(@_) if defined *$self->{"file"};
     return 1;
 }

 sub SEEK {
     my ($self) = shift;
     return *$self->{"file"}->seek(@_) if defined *$self->{"file"};
     return 0;
 }

 sub TELL {
     my ($self) = shift;
     return *$self->{"file"}->tell(@_) if defined *$self->{"file"};
     return -1;
 }

 sub BINMODE {
     my ($self) = shift;
     return *$self->{"file"}->binmode(@_) if defined *$self->{"file"};
     return undef;
 }

 ##
 ## NORMAL METHODS
 ##

 =item $fh->set_compression($comp)

 Defines the compression method used. $comp should one of the methods supported by
 B<Dpkg::Compression> or "none" or "auto". "none" indicates that the file is
 uncompressed and "auto" indicates that the method must be guessed based
 on the filename extension used.

 =cut

 sub set_compression {
     my ($self, $method) = @_;
     if ($method ne "none" and $method ne "auto") {
 	*$self->{"compressor"}->set_compression($method);
     }
     *$self->{"compression"} = $method;
 }

 =item $fh->set_compression_level($level)

 Indicate the desired compression level. It should be a value accepted
 by the function C<compression_is_valid_level> of B<Dpkg::Compression>.

 =cut

 sub set_compression_level {
     my ($self, $level) = @_;
     *$self->{"compressor"}->set_compression_level($level);
 }

 =item $fh->set_filename($name, [$add_comp_ext])

 Use $name as filename when the file must be opened/created. If
 $add_comp_ext is passed, it indicates whether the default extension
 of the compression method must be automatically added to the filename
 (or not).

 =cut

 sub set_filename {
     my ($self, $filename, $add_comp_ext) = @_;
     *$self->{"filename"} = $filename;
     # Automatically add compression extension to filename
     if (defined($add_comp_ext)) {
 	*$self->{"add_comp_ext"} = $add_comp_ext;
     }
     if (*$self->{"add_comp_ext"} and $filename =~ /\.$compression_re_file_ext$/) {
 	warning("filename %s already has an extension of a compressed file " .
 	        "and add_comp_ext is active", $filename);
     }
 }

 =item my $file = $fh->get_filename()

 Returns the filename that would be used when the filehandle must
 be opened (both in read and write mode). This function errors out
 if "add_comp_ext" is enableactivated while the compression method is set
 to "auto". The returned filename includes the extension of the compression
 method if "add_comp_ext" is enabled.

 =cut

 sub get_filename {
     my $self = shift;
     my $comp = *$self->{"compression"};
     if (*$self->{'add_comp_ext'}) {
 	if ($comp eq "auto") {
 	    internerr("automatic detection of compression is " .
 	              "incompatible with add_comp_ext");
 	} elsif ($comp eq "none") {
 	    return *$self->{"filename"};
 	} else {
 	    return *$self->{"filename"} . "." .
 	           compression_get_property($comp, "file_ext");
 	}
     } else {
 	return *$self->{"filename"};
     }
 }

 =item $ret = $fh->use_compression()

 Returns "0" if no compression is used and the compression method used
 otherwise. If the compression is set to "auto", the value returned
 depends on the extension of the filename obtained with the B<get_filename>
 method.

 =cut

 sub use_compression {
     my ($self) = @_;
     my $comp = *$self->{"compression"};
     if ($comp eq "none") {
 	return 0;
     } elsif ($comp eq "auto") {
 	$comp = compression_guess_from_filename($self->get_filename());
 	*$self->{"compressor"}->set_compression($comp) if $comp;
     }
     return $comp;
 }

 =item my $real_fh = $fh->get_filehandle()

 Returns the real underlying filehandle. Useful if you want to pass it
 along in a derived object.

 =cut

 sub get_filehandle {
     my ($self) = @_;
     return *$self->{"file"} if exists *$self->{"file"};
 }

 ## INTERNAL METHODS

 sub open_for_write {
     my ($self) = @_;
     error("Can't reopen an already opened compressed file") if exists *$self->{"mode"};
     my $filehandle;
     if ($self->use_compression()) {
 	*$self->{'compressor'}->compress(from_pipe => \$filehandle,
 		to_file => $self->get_filename());
     } else {
 	CORE::open($filehandle, ">", $self->get_filename) ||
 		syserr(_g("cannot write %s"), $self->get_filename());
     }
     *$self->{"mode"} = "w";
     *$self->{"file"} = $filehandle;
 }

 sub open_for_read {
     my ($self) = @_;
     error("Can't reopen an already opened compressed file") if exists *$self->{"mode"};
     my $filehandle;
     if ($self->use_compression()) {
 	*$self->{'compressor'}->uncompress(to_pipe => \$filehandle,
 		from_file => $self->get_filename());
         *$self->{'allow_sigpipe'} = 1;
     } else {
 	CORE::open($filehandle, "<", $self->get_filename) ||
 		syserr(_g("cannot read %s"), $self->get_filename());
     }
     *$self->{"mode"} = "r";
     *$self->{"file"} = $filehandle;
 }

 sub cleanup {
     my ($self) = @_;
     my $cmdline = *$self->{"compressor"}{"cmdline"} || "";
     *$self->{"compressor"}->wait_end_process(nocheck => *$self->{'allow_sigpipe'});
     if (*$self->{'allow_sigpipe'}) {
         unless (($? == 0) || (WIFSIGNALED($?) && (WTERMSIG($?) == SIGPIPE))) {
             subprocerr($cmdline);
         }
 	*$self->{'allow_sigpipe'} = 0;
     }
     delete *$self->{"mode"};
     delete *$self->{"file"};
 }

 =back

 =head1 DERIVED OBJECTS

 If you want to create an object that inherits from
 Dpkg::Compression::FileHandle you must be aware that
 the object is a reference to a GLOB that is returned by Symbol::gensym()
 and as such it's not a HASH.

 You can store internal data in a hash but you have to use
 C<*$self->{...}> to access the associated hash like in the example below:

     sub set_option {
 	my ($self, $value) = @_;
 	*$self->{"option"} = $value;
     }


 =head1 AUTHOR

 Raphaël Hertzog <hertzog@debian.org>

 =cut
 1;
	# Copyright © 2008-2010 Raphaël Hertzog <hertzog@debian.org>
	#
	# This program is free software; you can redistribute it and/or modify
	# it under the terms of the GNU General Public License as published by
	# the Free Software Foundation; either version 2 of the License, or
	# (at your option) any later version.
	#
	# This program is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	# GNU General Public License for more details.
	#
	# You should have received a copy of the GNU General Public License
	# along with this program. If not, see <http://www.gnu.org/licenses/>.

	package Dpkg::Compression::FileHandle;

	use strict;
	use warnings;

	our $VERSION = "1.00";

	use Dpkg::Compression;
	use Dpkg::Compression::Process;
	use Dpkg::Gettext;
	use Dpkg::ErrorHandling;
	use POSIX qw(WIFSIGNALED WTERMSIG SIGPIPE);

	use base qw(FileHandle Tie::Handle);

	# Useful reference to understand some kludges required to
	# have the object behave like a filehandle
	# http://blog.woobling.org/2009/10/are-filehandles-objects.html

	=encoding utf8

	=head1 NAME

	Dpkg::Compression::FileHandle - object dealing transparently with file compression

	=head1 SYNOPSIS

	use Dpkg::Compression::FileHandle;

	$fh = Dpkg::Compression::FileHandle->new(filename=>"sample.gz");
	print $fh "Something\n";
	close $fh;

	$fh = Dpkg::Compression::FileHandle->new();
	open($fh, ">", "sample.bz2");
	print $fh "Something\n";
	close $fh;

	$fh = Dpkg::Compression::FileHandle->new();
	$fh->open("sample.xz", "w");
	$fh->print("Something\n");
	$fh->close();

	$fh = Dpkg::Compression::FileHandle->new(filename=>"sample.gz");
	my @lines = <$fh>;
	close $fh;

	$fh = Dpkg::Compression::FileHandle->new();
	open($fh, "<", "sample.bz2");
	my @lines = <$fh>;
	close $fh;

	$fh = Dpkg::Compression::FileHandle->new();
	$fh->open("sample.xz", "r");
	my @lines = $fh->getlines();
	$fh->close();

	=head1 DESCRIPTION

	Dpkg::Compression::FileHandle is an object that can be used
	like any filehandle and that deals transparently with compressed
	files. By default, the compression scheme is guessed from the filename
	but you can override this behaviour with the method C<set_compression>.

	If you don't open the file explicitly, it will be auto-opened on the
	first read or write operation based on the filename set at creation time
	(or later with the C<set_filename> method).

	Once a file has been opened, the filehandle must be closed before being
	able to open another file.

	=head1 STANDARD FUNCTIONS

	The standard functions acting on filehandles should accept a
	Dpkg::Compression::FileHandle object transparently including
	C<open> (only when using the variant with 3 parameters), C<close>,
	C<binmode>, C<eof>, C<fileno>, C<getc>, C<print>, C<printf>, C<read>,
	C<sysread>, C<say>, C<write>, C<syswrite>, C<seek>, C<sysseek>, C<tell>.

	Note however that C<seek> and C<sysseek> will only work on uncompressed
	files as compressed files are really pipes to the compressor programs
	and you can't seek on a pipe.

	=head1 FileHandle METHODS

	The object inherits from FileHandle so all methods that work on this
	object should work for Dpkg::Compression::FileHandle too. There
	may be exceptions though.

	=head1 PUBLIC METHODS

	=over 4

	=item my $fh = Dpkg::Compression::FileHandle->new(%opts)

	Creates a new filehandle supporting on-the-fly compression/decompression.
	Supported options are "filename", "compression", "compression_level" (see
	respective set_* functions) and "add_comp_ext". If "add_comp_ext"
	evaluates to true, then the extension corresponding to the selected
	compression scheme is automatically added to the recorded filename. It's
	obviously incompatible with automatic detection of the compression method.

	=cut

	# Object methods
	sub new {
	my ($this, %args) = @_;
	my $class = ref($this) \|\| $this;
	my $self = FileHandle->new();
	# Tying is required to overload the open functions and to auto-open
	# the file on first read/write operation
	tie *$self, $class, $self;
	bless $self, $class;
	# Initializations
	*$self->{"compression"} = "auto";
	*$self->{"compressor"} = Dpkg::Compression::Process->new();
	*$self->{"add_comp_ext"} = $args{"add_compression_extension"} \|\|
	$args{"add_comp_ext"} \|\| 0;
	*$self->{"allow_sigpipe"} = 0;
	if (exists $args{"filename"}) {
	$self->set_filename($args{"filename"});
	}
	if (exists $args{"compression"}) {
	$self->set_compression($args{"compression"});
	}
	if (exists $args{"compression_level"}) {
	$self->set_compression_level($args{"compression_level"});
	}
	return $self;
	}

	=item $fh->ensure_open($mode)

	Ensure the file is opened in the requested mode ("r" for read and "w" for
	write). Opens the file with the recorded filename if needed. If the file
	is already open but not in the requested mode, then it errors out.

	=cut

	sub ensure_open {
	my ($self, $mode) = @_;
	if (exists *$self->{"mode"}) {
	return if *$self->{"mode"} eq $mode;
	internerr("ensure_open requested incompatible mode: $mode");
	} else {
	if ($mode eq "w") {
	$self->open_for_write();
	} elsif ($mode eq "r") {
	$self->open_for_read();
	} else {
	internerr("invalid mode in ensure_open: $mode");
	}
	}
	}

	##
	## METHODS FOR TIED HANDLE
	##
	sub TIEHANDLE {
	my ($class, $self) = @_;
	return $self;
	}

	sub WRITE {
	my ($self, $scalar, $length, $offset) = @_;
	$self->ensure_open("w");
	return *$self->{'file'}->write($scalar, $length, $offset);
	}

	sub READ {
	my ($self, $scalar, $length, $offset) = @_;
	$self->ensure_open("r");
	return *$self->{'file'}->read($scalar, $length, $offset);
	}

	sub READLINE {
	my ($self) = shift;
	$self->ensure_open("r");
	return *$self->{"file"}->getlines() if wantarray;
	return *$self->{"file"}->getline();
	}

	sub OPEN {
	my ($self) = shift;
	if (scalar(@_) == 2) {
	my ($mode, $filename) = @_;
	$self->set_filename($filename);
	if ($mode eq ">") {
	$self->open_for_write();
	} elsif ($mode eq "<") {
	$self->open_for_read();
	} else {
	internerr("Unsupported open mode on Dpkg::Compression::FileHandle: $mode");
	}
	} else {
	internerr("Dpkg::Compression::FileHandle only supports open() with 3 parameters");
	}
	return 1; # Always works (otherwise errors out)
	}

	sub CLOSE {
	my ($self) = shift;
	my $ret = 1;
	if (defined *$self->{'file'}) {
	$ret = $self->{'file'}->close(@_) if $self->{'file'}->opened();
	} else {
	$ret = 0;
	}
	$self->cleanup();
	return $ret;
	}

	sub FILENO {
	my ($self) = shift;
	return $self->{"file"}->fileno(@_) if defined $self->{"file"};
	return undef;
	}

	sub EOF {
	my ($self) = shift;
	return $self->{"file"}->eof(@_) if defined $self->{"file"};
	return 1;
	}

	sub SEEK {
	my ($self) = shift;
	return $self->{"file"}->seek(@_) if defined $self->{"file"};
	return 0;
	}

	sub TELL {
	my ($self) = shift;
	return $self->{"file"}->tell(@_) if defined $self->{"file"};
	return -1;
	}

	sub BINMODE {
	my ($self) = shift;
	return $self->{"file"}->binmode(@_) if defined $self->{"file"};
	return undef;
	}

	##
	## NORMAL METHODS
	##

	=item $fh->set_compression($comp)

	Defines the compression method used. $comp should one of the methods supported by
	B<Dpkg::Compression> or "none" or "auto". "none" indicates that the file is
	uncompressed and "auto" indicates that the method must be guessed based
	on the filename extension used.

	=cut

	sub set_compression {
	my ($self, $method) = @_;
	if ($method ne "none" and $method ne "auto") {
	*$self->{"compressor"}->set_compression($method);
	}
	*$self->{"compression"} = $method;
	}

	=item $fh->set_compression_level($level)

	Indicate the desired compression level. It should be a value accepted
	by the function C<compression_is_valid_level> of B<Dpkg::Compression>.

	=cut

	sub set_compression_level {
	my ($self, $level) = @_;
	*$self->{"compressor"}->set_compression_level($level);
	}

	=item $fh->set_filename($name, [$add_comp_ext])

	Use $name as filename when the file must be opened/created. If
	$add_comp_ext is passed, it indicates whether the default extension
	of the compression method must be automatically added to the filename
	(or not).

	=cut

	sub set_filename {
	my ($self, $filename, $add_comp_ext) = @_;
	*$self->{"filename"} = $filename;
	# Automatically add compression extension to filename
	if (defined($add_comp_ext)) {
	*$self->{"add_comp_ext"} = $add_comp_ext;
	}
	if (*$self->{"add_comp_ext"} and $filename =~ /\.$compression_re_file_ext$/) {
	warning("filename %s already has an extension of a compressed file " .
	"and add_comp_ext is active", $filename);
	}
	}

	=item my $file = $fh->get_filename()

	Returns the filename that would be used when the filehandle must
	be opened (both in read and write mode). This function errors out
	if "add_comp_ext" is enableactivated while the compression method is set
	to "auto". The returned filename includes the extension of the compression
	method if "add_comp_ext" is enabled.

	=cut

	sub get_filename {
	my $self = shift;
	my $comp = *$self->{"compression"};
	if (*$self->{'add_comp_ext'}) {
	if ($comp eq "auto") {
	internerr("automatic detection of compression is " .
	"incompatible with add_comp_ext");
	} elsif ($comp eq "none") {
	return *$self->{"filename"};
	} else {
	return *$self->{"filename"} . "." .
	compression_get_property($comp, "file_ext");
	}
	} else {
	return *$self->{"filename"};
	}
	}

	=item $ret = $fh->use_compression()

	Returns "0" if no compression is used and the compression method used
	otherwise. If the compression is set to "auto", the value returned
	depends on the extension of the filename obtained with the B<get_filename>
	method.

	=cut

	sub use_compression {
	my ($self) = @_;
	my $comp = *$self->{"compression"};
	if ($comp eq "none") {
	return 0;
	} elsif ($comp eq "auto") {
	$comp = compression_guess_from_filename($self->get_filename());
	*$self->{"compressor"}->set_compression($comp) if $comp;
	}
	return $comp;
	}

	=item my $real_fh = $fh->get_filehandle()

	Returns the real underlying filehandle. Useful if you want to pass it
	along in a derived object.

	=cut

	sub get_filehandle {
	my ($self) = @_;
	return $self->{"file"} if exists $self->{"file"};
	}

	## INTERNAL METHODS

	sub open_for_write {
	my ($self) = @_;
	error("Can't reopen an already opened compressed file") if exists *$self->{"mode"};
	my $filehandle;
	if ($self->use_compression()) {
	*$self->{'compressor'}->compress(from_pipe => \$filehandle,
	to_file => $self->get_filename());
	} else {
	CORE::open($filehandle, ">", $self->get_filename) \|\|
	syserr(_g("cannot write %s"), $self->get_filename());
	}
	*$self->{"mode"} = "w";
	*$self->{"file"} = $filehandle;
	}

	sub open_for_read {
	my ($self) = @_;
	error("Can't reopen an already opened compressed file") if exists *$self->{"mode"};
	my $filehandle;
	if ($self->use_compression()) {
	*$self->{'compressor'}->uncompress(to_pipe => \$filehandle,
	from_file => $self->get_filename());
	*$self->{'allow_sigpipe'} = 1;
	} else {
	CORE::open($filehandle, "<", $self->get_filename) \|\|
	syserr(_g("cannot read %s"), $self->get_filename());
	}
	*$self->{"mode"} = "r";
	*$self->{"file"} = $filehandle;
	}

	sub cleanup {
	my ($self) = @_;
	my $cmdline = *$self->{"compressor"}{"cmdline"} \|\| "";
	$self->{"compressor"}->wait_end_process(nocheck => $self->{'allow_sigpipe'});
	if (*$self->{'allow_sigpipe'}) {
	unless (($? == 0) \|\| (WIFSIGNALED($?) && (WTERMSIG($?) == SIGPIPE))) {
	subprocerr($cmdline);
	}
	*$self->{'allow_sigpipe'} = 0;
	}
	delete *$self->{"mode"};
	delete *$self->{"file"};
	}

	=back

	=head1 DERIVED OBJECTS

	If you want to create an object that inherits from
	Dpkg::Compression::FileHandle you must be aware that
	the object is a reference to a GLOB that is returned by Symbol::gensym()
	and as such it's not a HASH.

	You can store internal data in a hash but you have to use
	C<*$self->{...}> to access the associated hash like in the example below:

	sub set_option {
	my ($self, $value) = @_;
	*$self->{"option"} = $value;
	}


	=head1 AUTHOR

	Raphaël Hertzog <hertzog@debian.org>

	=cut
	1;