1Dpkg::Compression::FileHandle(3perlli)bdpkg-peDrplkg::Compression::FileHandle(3perl)
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NAME

6       Dpkg::Compression::FileHandle - class dealing transparently with file
7       compression
8

SYNOPSIS

10           use Dpkg::Compression::FileHandle;
11
12           my ($fh, @lines);
13
14           $fh = Dpkg::Compression::FileHandle->new(filename => 'sample.gz');
15           print $fh "Something\n";
16           close $fh;
17
18           $fh = Dpkg::Compression::FileHandle->new();
19           open($fh, '>', 'sample.bz2');
20           print $fh "Something\n";
21           close $fh;
22
23           $fh = Dpkg::Compression::FileHandle->new();
24           $fh->open('sample.xz', 'w');
25           $fh->print("Something\n");
26           $fh->close();
27
28           $fh = Dpkg::Compression::FileHandle->new(filename => 'sample.gz');
29           @lines = <$fh>;
30           close $fh;
31
32           $fh = Dpkg::Compression::FileHandle->new();
33           open($fh, '<', 'sample.bz2');
34           @lines = <$fh>;
35           close $fh;
36
37           $fh = Dpkg::Compression::FileHandle->new();
38           $fh->open('sample.xz', 'r');
39           @lines = $fh->getlines();
40           $fh->close();
41

DESCRIPTION

43       Dpkg::Compression::FileHandle is a class that can be used like any
44       filehandle and that deals transparently with compressed files. By
45       default, the compression scheme is guessed from the filename but you
46       can override this behaviour with the method "set_compression".
47
48       If you don't open the file explicitly, it will be auto-opened on the
49       first read or write operation based on the filename set at creation
50       time (or later with the "set_filename" method).
51
52       Once a file has been opened, the filehandle must be closed before being
53       able to open another file.
54

STANDARD FUNCTIONS

56       The standard functions acting on filehandles should accept a
57       Dpkg::Compression::FileHandle object transparently including "open"
58       (only when using the variant with 3 parameters), "close", "binmode",
59       "eof", "fileno", "getc", "print", "printf", "read", "sysread", "say",
60       "write", "syswrite", "seek", "sysseek", "tell".
61
62       Note however that "seek" and "sysseek" will only work on uncompressed
63       files as compressed files are really pipes to the compressor programs
64       and you can't seek on a pipe.
65

FileHandle METHODS

67       The class inherits from IO::File so all methods that work on this class
68       should work for Dpkg::Compression::FileHandle too. There may be
69       exceptions though.
70

PUBLIC METHODS

72       $fh = Dpkg::Compression::FileHandle->new(%opts)
73           Creates a new filehandle supporting on-the-fly
74           compression/decompression.  Supported options are "filename",
75           "compression", "compression_level" (see respective set_* functions)
76           and "add_comp_ext". If "add_comp_ext" evaluates to true, then the
77           extension corresponding to the selected compression scheme is
78           automatically added to the recorded filename. It's obviously
79           incompatible with automatic detection of the compression method.
80
81       $fh->ensure_open($mode, %opts)
82           Ensure the file is opened in the requested mode ("r" for read and
83           "w" for write). The options are passed down to the compressor's
84           spawn() call, if one is used. Opens the file with the recorded
85           filename if needed. If the file is already open but not in the
86           requested mode, then it errors out.
87
88       $fh->set_compression($comp)
89           Defines the compression method used. $comp should one of the
90           methods supported by Dpkg::Compression or "none" or "auto". "none"
91           indicates that the file is uncompressed and "auto" indicates that
92           the method must be guessed based on the filename extension used.
93
94       $fh->set_compression_level($level)
95           Indicate the desired compression level. It should be a value
96           accepted by the function "compression_is_valid_level" of
97           Dpkg::Compression.
98
99       $fh->set_filename($name, [$add_comp_ext])
100           Use $name as filename when the file must be opened/created. If
101           $add_comp_ext is passed, it indicates whether the default extension
102           of the compression method must be automatically added to the
103           filename (or not).
104
105       $file = $fh->get_filename()
106           Returns the filename that would be used when the filehandle must be
107           opened (both in read and write mode). This function errors out if
108           "add_comp_ext" is enabled while the compression method is set to
109           "auto". The returned filename includes the extension of the
110           compression method if "add_comp_ext" is enabled.
111
112       $ret = $fh->use_compression()
113           Returns "0" if no compression is used and the compression method
114           used otherwise. If the compression is set to "auto", the value
115           returned depends on the extension of the filename obtained with the
116           get_filename method.
117
118       $real_fh = $fh->get_filehandle()
119           Returns the real underlying filehandle. Useful if you want to pass
120           it along in a derived class.
121

DERIVED CLASSES

123       If you want to create a class that inherits from
124       Dpkg::Compression::FileHandle you must be aware that the object is a
125       reference to a GLOB that is returned by Symbol::gensym() and as such
126       it's not a HASH.
127
128       You can store internal data in a hash but you have to use
129       "*$self-"{...}> to access the associated hash like in the example
130       below:
131
132           sub set_option {
133               my ($self, $value) = @_;
134               *$self->{option} = $value;
135           }
136

CHANGES

138   Version 1.01 (dpkg 1.17.11)
139       New argument: $fh->ensure_open() accepts an %opts argument.
140
141   Version 1.00 (dpkg 1.15.6)
142       Mark the module as public.
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1461.21.9                            2022-08-0D4pkg::Compression::FileHandle(3perl)
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