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IO::Uncompress::Gunzip(3)      User Contributed Perl Documentation      IO::Uncompress::Gunzip(3)



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 con-
       form 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 Inter-
       face" 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 $input => $output [, OPTS]

       "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.

            If the fileglob does not match any files ...

            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.

       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 filehan-
            dles.

            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"
            TODO

       "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 compressed 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::Gun-
       zip 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 $$output.

       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/bufffer 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 over-
            written 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

       getHeaderInfo

       Usage is

           $hdr  = $z->getHeaderInfo();
           @hdrs = $z->getHeaderInfo();

       This method returns either a hash reference (in scalar context) or a list or hash refer-
       ences (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 back-
       ward.

       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 cur-
       rent 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 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 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::Uncom-
       press::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 cre-
       ated, 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 encoun-
       tered.

       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 com-
       pressed 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 con-
       structor.

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::Uncompress::Gunzip::FAQ

SEE ALSO
       Compress::Zlib, IO::Compress::Gzip, IO::Compress::Deflate, IO::Uncompress::Inflate,
       IO::Compress::RawDeflate, IO::Uncompress::RawInflate, IO::Compress::Bzip2, IO::Uncom-
       press::Bunzip2, IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncom-
       press::UnLzf, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress

       Compress::Zlib::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  and Mark
       Adler .

       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, .

MODIFICATION HISTORY
       See the Changes file.

COPYRIGHT AND LICENSE
       Copyright (c) 2005-2009 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 v5.8.8                                 2009-03-28                  IO::Uncompress::Gunzip(3)