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 => $output [,OPTS]
or die "gunzip failed: $GunzipError\n";
The functional interface needs Perl5.005 or better.
"gunzip" expects at least two parameters, $input and $output.
The $input parameter
The parameter, $input, is used to define the source of the compressed data.
It can take one of the following forms:
- A filename
- If the $input 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 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 is a scalar reference, the input data will be
read from $$input.
- An array reference
- If $input is an array reference, each element in the array
must be a filename.
The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid
filenames before any data is uncompressed.
- An Input FileGlob string
- If $input is a string that is delimited by the characters
"<" and ">" "gunzip" will assume that
it is an input fileglob string. The input is the list of files that
match the fileglob.
See File::GlobMapper for more details.
If the $input parameter is any other type, "undef" will be returned.
The $output parameter
The parameter $output is used to control the destination of the uncompressed
data. This parameter can take one of these forms.
- A filename
- If the $output parameter is a simple scalar, it is assumed
to be a filename. This file will be opened for writing and the
uncompressed data will be written to it.
- A filehandle
- If the $output parameter is a filehandle, the uncompressed
data will be written to it. The string '-' can be used as an alias for
standard output.
- A scalar reference
- If $output is a scalar reference, the uncompressed data
will be stored in $$output.
- An Array Reference
- If $output is an array reference, the uncompressed data
will be pushed onto the array.
- An Output FileGlob
- If $output 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 is an fileglob string, $input must also be a fileglob string.
Anything else is an error.
See File::GlobMapper for more details.
If the $output parameter is any other type, "undef" will be returned.
Notes¶
When $input maps to multiple compressed files/buffers and $output is a single
file/buffer, after uncompression $output 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 the 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 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
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.
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.
$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 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) 2005-2012 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.