Provided by: libio-compress-perl_2.063-1_all 
NAME
IO::Uncompress::Gunzip - Read RFC 1952 files/buffers
SYNOPSIS
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
my $status = gunzip $input => $output [,OPTS]
or die "gunzip failed: $GunzipError\n";
my $z = new IO::Uncompress::Gunzip $input [OPTS]
or die "gunzip failed: $GunzipError\n";
$status = $z->read($buffer)
$status = $z->read($buffer, $length)
$status = $z->read($buffer, $length, $offset)
$line = $z->getline()
$char = $z->getc()
$char = $z->ungetc()
$char = $z->opened()
$status = $z->inflateSync()
$data = $z->trailingData()
$status = $z->nextStream()
$data = $z->getHeaderInfo()
$z->tell()
$z->seek($position, $whence)
$z->binmode()
$z->fileno()
$z->eof()
$z->close()
$GunzipError ;
# IO::File mode
<$z>
read($z, $buffer);
read($z, $buffer, $length);
read($z, $buffer, $length, $offset);
tell($z)
seek($z, $position, $whence)
binmode($z)
fileno($z)
eof($z)
close($z)
DESCRIPTION
This module provides a Perl interface that allows the reading of files/buffers that conform to RFC 1952.
For writing RFC 1952 files/buffers, see the companion module IO::Compress::Gzip.
Functional Interface
A top-level function, "gunzip", is provided to carry out "one-shot" uncompression between buffers and/or
files. For finer control over the uncompression process, see the "OO Interface" section.
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
gunzip $input_filename_or_reference => $output_filename_or_reference [,OPTS]
or die "gunzip failed: $GunzipError\n";
The functional interface needs Perl5.005 or better.
gunzip $input_filename_or_reference => $output_filename_or_reference [, OPTS]
"gunzip" expects at least two parameters, $input_filename_or_reference and $output_filename_or_reference.
The $input_filename_or_reference parameter
The parameter, $input_filename_or_reference, is used to define the source of the compressed data.
It can take one of the following forms:
A filename
If the <$input_filename_or_reference> parameter is a simple scalar, it is assumed to be a filename.
This file will be opened for reading and the input data will be read from it.
A filehandle
If the $input_filename_or_reference parameter is a filehandle, the input data will be read from it.
The string '-' can be used as an alias for standard input.
A scalar reference
If $input_filename_or_reference is a scalar reference, the input data will be read from
$$input_filename_or_reference.
An array reference
If $input_filename_or_reference is an array reference, each element in the array must be a filename.
The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid filenames before any data is
uncompressed.
An Input FileGlob string
If $input_filename_or_reference is a string that is delimited by the characters "<" and ">" "gunzip"
will assume that it is an input fileglob string. The input is the list of files that match the
fileglob.
See File::GlobMapper for more details.
If the $input_filename_or_reference parameter is any other type, "undef" will be returned.
The $output_filename_or_reference parameter
The parameter $output_filename_or_reference is used to control the destination of the uncompressed data.
This parameter can take one of these forms.
A filename
If the $output_filename_or_reference parameter is a simple scalar, it is assumed to be a filename.
This file will be opened for writing and the uncompressed data will be written to it.
A filehandle
If the $output_filename_or_reference parameter is a filehandle, the uncompressed data will be
written to it. The string '-' can be used as an alias for standard output.
A scalar reference
If $output_filename_or_reference is a scalar reference, the uncompressed data will be stored in
$$output_filename_or_reference.
An Array Reference
If $output_filename_or_reference is an array reference, the uncompressed data will be pushed onto
the array.
An Output FileGlob
If $output_filename_or_reference is a string that is delimited by the characters "<" and ">"
"gunzip" will assume that it is an output fileglob string. The output is the list of files that
match the fileglob.
When $output_filename_or_reference is an fileglob string, $input_filename_or_reference must also be
a fileglob string. Anything else is an error.
See File::GlobMapper for more details.
If the $output_filename_or_reference parameter is any other type, "undef" will be returned.
Notes
When $input_filename_or_reference maps to multiple compressed files/buffers and
$output_filename_or_reference is a single file/buffer, after uncompression $output_filename_or_reference
will contain a concatenation of all the uncompressed data from each of the input files/buffers.
Optional Parameters
Unless specified below, the optional parameters for "gunzip", "OPTS", are the same as those used with the
OO interface defined in the "Constructor Options" section below.
"AutoClose => 0|1"
This option applies to any input or output data streams to "gunzip" that are filehandles.
If "AutoClose" is specified, and the value is true, it will result in all input and/or output
filehandles being closed once "gunzip" has completed.
This parameter defaults to 0.
"BinModeOut => 0|1"
When writing to a file or filehandle, set "binmode" before writing to the file.
Defaults to 0.
"Append => 0|1"
The behaviour of this option is dependent on the type of output data stream.
• A Buffer
If "Append" is enabled, all uncompressed data will be append to the end of the output buffer.
Otherwise the output buffer will be cleared before any uncompressed data is written to it.
• A Filename
If "Append" is enabled, the file will be opened in append mode. Otherwise the contents of the
file, if any, will be truncated before any uncompressed data is written to it.
• A Filehandle
If "Append" is enabled, the filehandle will be positioned to the end of the file via a call to
"seek" before any uncompressed data is written to it. Otherwise the file pointer will not be
moved.
When "Append" is specified, and set to true, it will append all uncompressed data to the output data
stream.
So when the output is a filehandle it will carry out a seek to the eof before writing any
uncompressed data. If the output is a filename, it will be opened for appending. If the output is a
buffer, all uncompressed data will be appended to the existing buffer.
Conversely when "Append" is not specified, or it is present and is set to false, it will operate as
follows.
When the output is a filename, it will truncate the contents of the file before writing any
uncompressed data. If the output is a filehandle its position will not be changed. If the output is
a buffer, it will be wiped before any uncompressed data is output.
Defaults to 0.
"MultiStream => 0|1"
If the input file/buffer contains multiple compressed data streams, this option will uncompress the
whole lot as a single data stream.
Defaults to 0.
"TrailingData => $scalar"
Returns the data, if any, that is present immediately after the compressed data stream once
uncompression is complete.
This option can be used when there is useful information immediately following the compressed data
stream, and you don't know the length of the compressed data stream.
If the input is a buffer, "trailingData" will return everything from the end of the compressed data
stream to the end of the buffer.
If the input is a filehandle, "trailingData" will return the data that is left in the filehandle
input buffer once the end of the compressed data stream has been reached. You can then use the
filehandle to read the rest of the input file.
Don't bother using "trailingData" if the input is a filename.
If you know the length of the compressed data stream before you start uncompressing, you can avoid
having to use "trailingData" by setting the "InputLength" option.
Examples
To read the contents of the file "file1.txt.gz" and write the uncompressed data to the file "file1.txt".
use strict ;
use warnings ;
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
my $input = "file1.txt.gz";
my $output = "file1.txt";
gunzip $input => $output
or die "gunzip failed: $GunzipError\n";
To read from an existing Perl filehandle, $input, and write the uncompressed data to a buffer, $buffer.
use strict ;
use warnings ;
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
use IO::File ;
my $input = new IO::File "<file1.txt.gz"
or die "Cannot open 'file1.txt.gz': $!\n" ;
my $buffer ;
gunzip $input => \$buffer
or die "gunzip failed: $GunzipError\n";
To uncompress all files in the directory "/my/home" that match "*.txt.gz" and store the compressed data
in the same directory
use strict ;
use warnings ;
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
gunzip '</my/home/*.txt.gz>' => '</my/home/#1.txt>'
or die "gunzip failed: $GunzipError\n";
and if you want to compress each file one at a time, this will do the trick
use strict ;
use warnings ;
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
for my $input ( glob "/my/home/*.txt.gz" )
{
my $output = $input;
$output =~ s/.gz// ;
gunzip $input => $output
or die "Error compressing '$input': $GunzipError\n";
}
OO Interface
Constructor
The format of the constructor for IO::Uncompress::Gunzip is shown below
my $z = new IO::Uncompress::Gunzip $input [OPTS]
or die "IO::Uncompress::Gunzip failed: $GunzipError\n";
Returns an "IO::Uncompress::Gunzip" object on success and undef on failure. The variable $GunzipError
will contain an error message on failure.
If you are running Perl 5.005 or better the object, $z, returned from IO::Uncompress::Gunzip can be used
exactly like an IO::File filehandle. This means that all normal input file operations can be carried out
with $z. For example, to read a line from a compressed file/buffer you can use either of these forms
$line = $z->getline();
$line = <$z>;
The mandatory parameter $input is used to determine the source of the compressed data. This parameter can
take one of three forms.
A filename
If the $input parameter is a scalar, it is assumed to be a filename. This file will be opened for
reading and the compressed data will be read from it.
A filehandle
If the $input parameter is a filehandle, the compressed data will be read from it. The string '-'
can be used as an alias for standard input.
A scalar reference
If $input is a scalar reference, the compressed data will be read from $$input.
Constructor Options
The option names defined below are case insensitive and can be optionally prefixed by a '-'. So all of
the following are valid
-AutoClose
-autoclose
AUTOCLOSE
autoclose
OPTS is a combination of the following options:
"AutoClose => 0|1"
This option is only valid when the $input parameter is a filehandle. If specified, and the value is
true, it will result in the file being closed once either the "close" method is called or the
IO::Uncompress::Gunzip object is destroyed.
This parameter defaults to 0.
"MultiStream => 0|1"
Allows multiple concatenated compressed streams to be treated as a single compressed stream.
Decompression will stop once either the end of the file/buffer is reached, an error is encountered
(premature eof, corrupt compressed data) or the end of a stream is not immediately followed by the
start of another stream.
This parameter defaults to 0.
"Prime => $string"
This option will uncompress the contents of $string before processing the input file/buffer.
This option can be useful when the compressed data is embedded in another file/data structure and it
is not possible to work out where the compressed data begins without having to read the first few
bytes. If this is the case, the uncompression can be primed with these bytes using this option.
"Transparent => 0|1"
If this option is set and the input file/buffer is not compressed data, the module will allow
reading of it anyway.
In addition, if the input file/buffer does contain compressed data and there is non-compressed data
immediately following it, setting this option will make this module treat the whole file/buffer as a
single data stream.
This option defaults to 1.
"BlockSize => $num"
When reading the compressed input data, IO::Uncompress::Gunzip will read it in blocks of $num bytes.
This option defaults to 4096.
"InputLength => $size"
When present this option will limit the number of compressed bytes read from the input file/buffer
to $size. This option can be used in the situation where there is useful data directly after the
compressed data stream and you know beforehand the exact length of the compressed data stream.
This option is mostly used when reading from a filehandle, in which case the file pointer will be
left pointing to the first byte directly after the compressed data stream.
This option defaults to off.
"Append => 0|1"
This option controls what the "read" method does with uncompressed data.
If set to 1, all uncompressed data will be appended to the output parameter of the "read" method.
If set to 0, the contents of the output parameter of the "read" method will be overwritten by the
uncompressed data.
Defaults to 0.
"Strict => 0|1"
This option controls whether the extra checks defined below are used when carrying out the
decompression. When Strict is on, the extra tests are carried out, when Strict is off they are not.
The default for this option is off.
1. If the FHCRC bit is set in the gzip FLG header byte, the CRC16 bytes in the header must match
the crc16 value of the gzip header actually read.
2. If the gzip header contains a name field (FNAME) it consists solely of ISO 8859-1 characters.
3. If the gzip header contains a comment field (FCOMMENT) it consists solely of ISO 8859-1
characters plus line-feed.
4. If the gzip FEXTRA header field is present it must conform to the sub-field structure as
defined in RFC 1952.
5. The CRC32 and ISIZE trailer fields must be present.
6. The value of the CRC32 field read must match the crc32 value of the uncompressed data actually
contained in the gzip file.
7. The value of the ISIZE fields read must match the length of the uncompressed data actually read
from the file.
"ParseExtra => 0|1" If the gzip FEXTRA header field is present and this option is set, it will force the
module to check that it conforms to the sub-field structure as defined in RFC 1952.
If the "Strict" is on it will automatically enable this option.
Defaults to 0.
Examples
TODO
Methods
read
Usage is
$status = $z->read($buffer)
Reads a block of compressed data (the size of the compressed block is determined by the "Buffer" option
in the constructor), uncompresses it and writes any uncompressed data into $buffer. If the "Append"
parameter is set in the constructor, the uncompressed data will be appended to the $buffer parameter.
Otherwise $buffer will be overwritten.
Returns the number of uncompressed bytes written to $buffer, zero if eof or a negative number on error.
read
Usage is
$status = $z->read($buffer, $length)
$status = $z->read($buffer, $length, $offset)
$status = read($z, $buffer, $length)
$status = read($z, $buffer, $length, $offset)
Attempt to read $length bytes of uncompressed data into $buffer.
The main difference between this form of the "read" method and the previous one, is that this one will
attempt to return exactly $length bytes. The only circumstances that this function will not is if end-of-
file or an IO error is encountered.
Returns the number of uncompressed bytes written to $buffer, zero if eof or a negative number on error.
getline
Usage is
$line = $z->getline()
$line = <$z>
Reads a single line.
This method fully supports the use of the variable $/ (or $INPUT_RECORD_SEPARATOR or $RS when "English"
is in use) to determine what constitutes an end of line. Paragraph mode, record mode and file slurp mode
are all supported.
getc
Usage is
$char = $z->getc()
Read a single character.
ungetc
Usage is
$char = $z->ungetc($string)
inflateSync
Usage is
$status = $z->inflateSync()
TODO
getHeaderInfo
Usage is
$hdr = $z->getHeaderInfo();
@hdrs = $z->getHeaderInfo();
This method returns either a hash reference (in scalar context) or a list or hash references (in array
context) that contains information about each of the header fields in the compressed data stream(s).
Name The contents of the Name header field, if present. If no name is present, the value will be undef.
Note this is different from a zero length name, which will return an empty string.
Comment
The contents of the Comment header field, if present. If no comment is present, the value will be
undef. Note this is different from a zero length comment, which will return an empty string.
tell
Usage is
$z->tell()
tell $z
Returns the uncompressed file offset.
eof
Usage is
$z->eof();
eof($z);
Returns true if the end of the compressed input stream has been reached.
seek
$z->seek($position, $whence);
seek($z, $position, $whence);
Provides a sub-set of the "seek" functionality, with the restriction that it is only legal to seek
forward in the input file/buffer. It is a fatal error to attempt to seek backward.
Note that the implementation of "seek" in this module does not provide true random access to a compressed
file/buffer. It works by uncompressing data from the current offset in the file/buffer until it reaches
the uncompressed offset specified in the parameters to "seek". For very small files this may be
acceptable behaviour. For large files it may cause an unacceptable delay.
The $whence parameter takes one the usual values, namely SEEK_SET, SEEK_CUR or SEEK_END.
Returns 1 on success, 0 on failure.
binmode
Usage is
$z->binmode
binmode $z ;
This is a noop provided for completeness.
opened
$z->opened()
Returns true if the object currently refers to a opened file/buffer.
autoflush
my $prev = $z->autoflush()
my $prev = $z->autoflush(EXPR)
If the $z object is associated with a file or a filehandle, this method returns the current autoflush
setting for the underlying filehandle. If "EXPR" is present, and is non-zero, it will enable flushing
after every write/print operation.
If $z is associated with a buffer, this method has no effect and always returns "undef".
Note that the special variable $| cannot be used to set or retrieve the autoflush setting.
input_line_number
$z->input_line_number()
$z->input_line_number(EXPR)
Returns the current uncompressed line number. If "EXPR" is present it has the effect of setting the line
number. Note that setting the line number does not change the current position within the file/buffer
being read.
The contents of $/ are used to determine what constitutes a line terminator.
fileno
$z->fileno()
fileno($z)
If the $z object is associated with a file or a filehandle, "fileno" will return the underlying file
descriptor. Once the "close" method is called "fileno" will return "undef".
If the $z object is associated with a buffer, this method will return "undef".
close
$z->close() ;
close $z ;
Closes the output file/buffer.
For most versions of Perl this method will be automatically invoked if the IO::Uncompress::Gunzip object
is destroyed (either explicitly or by the variable with the reference to the object going out of scope).
The exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these cases, the "close" method will
be called automatically, but not until global destruction of all live objects when the program is
terminating.
Therefore, if you want your scripts to be able to run on all versions of Perl, you should call "close"
explicitly and not rely on automatic closing.
Returns true on success, otherwise 0.
If the "AutoClose" option has been enabled when the IO::Uncompress::Gunzip object was created, and the
object is associated with a file, the underlying file will also be closed.
nextStream
Usage is
my $status = $z->nextStream();
Skips to the next compressed data stream in the input file/buffer. If a new compressed data stream is
found, the eof marker will be cleared and $. will be reset to 0.
Returns 1 if a new stream was found, 0 if none was found, and -1 if an error was encountered.
trailingData
Usage is
my $data = $z->trailingData();
Returns the data, if any, that is present immediately after the compressed data stream once uncompression
is complete. It only makes sense to call this method once the end of the compressed data stream has been
encountered.
This option can be used when there is useful information immediately following the compressed data
stream, and you don't know the length of the compressed data stream.
If the input is a buffer, "trailingData" will return everything from the end of the compressed data
stream to the end of the buffer.
If the input is a filehandle, "trailingData" will return the data that is left in the filehandle input
buffer once the end of the compressed data stream has been reached. You can then use the filehandle to
read the rest of the input file.
Don't bother using "trailingData" if the input is a filename.
If you know the length of the compressed data stream before you start uncompressing, you can avoid having
to use "trailingData" by setting the "InputLength" option in the constructor.
Importing
No symbolic constants are required by this IO::Uncompress::Gunzip at present.
:all Imports "gunzip" and $GunzipError. Same as doing this
use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;
EXAMPLES
Working with Net::FTP
See IO::Compress::FAQ
SEE ALSO
Compress::Zlib, IO::Compress::Gzip, IO::Compress::Deflate, IO::Uncompress::Inflate,
IO::Compress::RawDeflate, IO::Uncompress::RawInflate, IO::Compress::Bzip2, IO::Uncompress::Bunzip2,
IO::Compress::Lzma, IO::Uncompress::UnLzma, IO::Compress::Xz, IO::Uncompress::UnXz, IO::Compress::Lzop,
IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::UnLzf, IO::Uncompress::AnyInflate,
IO::Uncompress::AnyUncompress
IO::Compress::FAQ
File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib
For RFC 1950, 1951 and 1952 see http://www.faqs.org/rfcs/rfc1950.html,
http://www.faqs.org/rfcs/rfc1951.html and http://www.faqs.org/rfcs/rfc1952.html
The zlib compression library was written by Jean-loup Gailly gzip@prep.ai.mit.edu and Mark Adler
madler@alumni.caltech.edu.
The primary site for the zlib compression library is http://www.zlib.org.
The primary site for gzip is http://www.gzip.org.
AUTHOR
This module was written by Paul Marquess, pmqs@cpan.org.
MODIFICATION HISTORY
See the Changes file.
COPYRIGHT AND LICENSE
Copyright (c) 2005-2013 Paul Marquess. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.
perl v5.18.1 2013-09-02 IO::Uncompress::Gunzip(3pm)