Dpkg::Compression::FileHandle(3pelibdpkg-pDpkg::Compression::FileHandle(3perl)
NAME
Dpkg::Compression::FileHandle - class dealing transparently with file
compression
SYNOPSIS
use Dpkg::Compression::FileHandle;
my ($fh, @lines);
$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();
$fh = Dpkg::Compression::FileHandle->new(filename => 'sample.gz');
@lines = <$fh>;
close $fh;
$fh = Dpkg::Compression::FileHandle->new();
open($fh, '<', 'sample.bz2');
@lines = <$fh>;
close $fh;
$fh = Dpkg::Compression::FileHandle->new();
$fh->open('sample.xz', 'r');
@lines = $fh->getlines();
$fh->close();
DESCRIPTION
Dpkg::Compression::FileHandle is a class 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 "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 "set_filename" method).
Once a file has been opened, the filehandle must be closed before being
able to open another file.
STANDARD FUNCTIONS
The standard functions acting on filehandles should accept a
Dpkg::Compression::FileHandle object transparently including "open"
(only when using the variant with 3 parameters), "close", "binmode",
"eof", "fileno", "getc", "print", "printf", "read", "sysread", "say",
"write", "syswrite", "seek", "sysseek", "tell".
Note however that "seek" and "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.
FileHandle METHODS
The class inherits from IO::File so all methods that work on this class
should work for Dpkg::Compression::FileHandle too. There may be
exceptions though.
PUBLIC METHODS
$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.
$fh->ensure_open($mode, %opts)
Ensure the file is opened in the requested mode ("r" for read and
"w" for write). The options are passed down to the compressor's
spawn() call, if one is used. 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.
$fh->set_compression($comp)
Defines the compression method used. $comp should one of the
methods supported by 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.
$fh->set_compression_level($level)
Indicate the desired compression level. It should be a value
accepted by the function "compression_is_valid_level" of
Dpkg::Compression.
$fh->set_filename($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).
$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 enabled while the compression method is set to
"auto". The returned filename includes the extension of the
compression method if "add_comp_ext" is enabled.
$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
get_filename method.
$real_fh = $fh->get_filehandle()
Returns the real underlying filehandle. Useful if you want to pass
it along in a derived class.
DERIVED CLASSES
If you want to create a class that inherits from
Dpkg::Compression::FileHandle you must be aware that the object is a
reference to a GLOB that is returned by Symbol::gensym() and as such
it's not a HASH.
You can store internal data in a hash but you have to use
"*$self-"{...}> to access the associated hash like in the example
below:
sub set_option {
my ($self, $value) = @_;
*$self->{option} = $value;
}
CHANGES
Version 1.01 (dpkg 1.17.11)
New argument: $fh->ensure_open() accepts an %opts argument.
Version 1.00 (dpkg 1.15.6)
Mark the module as public.
1.21.1 2024-02-Dpkg::Compression::FileHandle(3perl)
Generated by dwww version 1.14 on Fri Jan 24 01:51:15 CET 2025.