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Compress::Bzip2(3)    User Contributed Perl Documentation   Compress::Bzip2(3)




NAME

       Compress::Bzip2 - Interface to Bzip2 compression library


SYNOPSIS

           use Compress::Bzip2 qw(:all :constant :utilities :gzip);

           ($bz, $status) = bzdeflateInit( [PARAMS] ) ;
           ($out, $status) = $bz->bzdeflate($buffer) ;

           ($bz, $status) = bzinflateInit( [PARAMS] ) ;
           ($out, $status) = $bz->bzinflate($buffer) ;

           ($out, $status) = $bz->bzflush() ;
           ($out, $status) = $bz->bzclose() ;

           $dest = memBzip($source);
               alias compress
           $dest = memBunzip($source);
               alias decompress

           $bz = Compress::Bzip2->new( [PARAMS] );

           $bz = bzopen($filename or filehandle, $mode);
               alternate, with $bz created by new():
           $bz->bzopen($filename or filehandle, $mode);

           $bytesread = $bz->bzread($buffer [,$size]) ;
           $bytesread = $bz->bzreadline($line);
           $byteswritten = $bz->bzwrite($buffer [,$limit]);
           $errstring = $bz->bzerror();
           $status = $bz->bzeof();
           $status = $bz->bzflush();
           $status = $bz->bzclose() ;

           $status = $bz->bzsetparams( $param => $setting );

           $bz->total_in() ;
           $bz->total_out() ;

           $verstring = $bz->bzversion();

           $Compress::Bzip2::bzerrno


DESCRIPTION

       The Compress::Bzip2 module provides a Perl interface to the Bzip2
       compression library (see "AUTHOR" for details about where to get
       Bzip2). A relevant subset of the functionality provided by Bzip2 is
       available in Compress::Bzip2.

       All string parameters can either be a scalar or a scalar reference.

       The module can be split into two general areas of functionality, namely
       in-memory compression/decompression and read/write access to bzip2
       files. Each of these areas will be discussed separately below.


FILE READ/WRITE INTERFACE

       A number of functions are supplied in bzlib for reading and writing
       bzip2 files. Unfortunately, most of them are not suitable.  So, this
       module provides another interface, built over top of the low level
       bzlib methods.

       $bz = bzopen(filename or filehandle, mode)

       This function returns an object which is used to access the other bzip2
       methods.

       The mode parameter is used to specify both whether the file is opened
       for reading or writing, with "r" or "w" respectively.

       If a reference to an open filehandle is passed in place of the
       filename, it better be positioned to the start of a
       compression/decompression sequence.

       $bz = Compress::Bzip2->new( [PARAMS] )

       Create a Compress::Bzip2 object.  Optionally, provide
       compression/decompression parameters as a keyword => setting list.  See
       bzsetparams() for a description of the parameters.

       $bz->bzopen(filename or filehandle, mode)

       This is bzopen, but it uses an object previously created by the new
       method.  Other than that, it is identical to the above bzopen.

       $bytesread = $bz->bzread($buffer [, $size]) ;

       Reads $size bytes from the compressed file into $buffer. If $size is
       not specified, it will default to 4096. If the scalar $buffer is not
       large enough, it will be extended automatically.

       Returns the number of bytes actually read. On EOF it returns 0 and in
       the case of an error, -1.

       $bytesread = $bz->bzreadline($line) ;

       Reads the next line from the compressed file into $line.

       Returns the number of bytes actually read. On EOF it returns 0 and in
       the case of an error, -1.

       It IS legal to intermix calls to bzread and bzreadline.

       At this time bzreadline ignores the variable $/
       ($INPUT_RECORD_SEPARATOR or $RS when "English" is in use). The end of a
       line is denoted by the C character '\n'.

       $byteswritten = $bz->bzwrite($buffer [, $limit]) ;

       Writes the contents of $buffer to the compressed file. Returns the
       number of bytes actually written, or 0 on error.

       If $limit is given and non-zero, then only that many bytes from $buffer
       will be written.

       $status = $bz->bzflush($flush) ;

       Flushes all pending output to the compressed file.  Works identically
       to the zlib function it interfaces to. Note that the use of bzflush can
       degrade compression.

       Returns "BZ_OK" if $flush is "BZ_FINISH" and all output could be
       flushed. Otherwise the bzlib error code is returned.

       Refer to the bzlib documentation for the valid values of $flush.

       $status = $bz->bzeof() ;

       Returns 1 if the end of file has been detected while reading the input
       file, otherwise returns 0.

       $bz->bzclose

       Closes the compressed file. Any pending data is flushed to the file
       before it is closed.

       $bz->bzsetparams( [PARAMS] );

       Change settings for the deflate stream $bz.

       The list of the valid options is shown below. Options not specified
       will remain unchanged.

       -verbosity
            Defines the verbosity level. Valid values are 0 through 4,

            The default is "-verbosity => 0".

       -blockSize100k
            For bzip object opened for stream deflation or write.

            Defines the buffering factor of compression method.  The algorithm
            buffers all data until the buffer is full, then it flushes all the
            data out.  Use -blockSize100k to specify the size of the buffer.

            Valid settings are 1 through 9, representing a blocking in
            multiples of 100k.

            Note that each such block has an overhead of leading and trailing
            synchronization bytes.  bzip2 recovery uses this information to
            pull useable data out of a corrupted file.

            A streaming application would probably want to set the blocking
            low.

       -workFactor
            For bzip object opened for stream deflation or write.

            The workFactor setting tells the deflation algorithm how much work
            to invest to compensate for repetitive data.

            workFactor may be a number from 0 to 250 inclusive.  The default
            setting is 30.

            See the bzip documentation for more information.

       -small
            For bzip object opened for stream inflation or read.

            small may be 0 or 1.  Set "small" to one to use a slower, less
            memory intensive algorithm.

       $bz->bzerror

       Returns the bzlib error message or number for the last operation
       associated with $bz. The return value will be the bzlib error number
       when used in a numeric context and the bzlib error message when used in
       a string context. The bzlib error number constants, shown below, are
       available for use.

         BZ_CONFIG_ERROR
         BZ_DATA_ERROR
         BZ_DATA_ERROR_MAGIC
         BZ_FINISH
         BZ_FINISH_OK
         BZ_FLUSH
         BZ_FLUSH_OK
         BZ_IO_ERROR
         BZ_MAX_UNUSED
         BZ_MEM_ERROR
         BZ_OK
         BZ_OUTBUFF_FULL
         BZ_PARAM_ERROR
         BZ_RUN
         BZ_RUN_OK
         BZ_SEQUENCE_ERROR
         BZ_STREAM_END
         BZ_UNEXPECTED_EOF

       $bzerrno

       The $bzerrno scalar holds the error code associated with the most
       recent bzip2 routine. Note that unlike bzerror(), the error is not
       associated with a particular file.

       As with bzerror() it returns an error number in numeric context and an
       error message in string context. Unlike bzerror() though, the error
       message will correspond to the bzlib message when the error is
       associated with bzlib itself, or the UNIX error message when it is not
       (i.e. bzlib returned "Z_ERRORNO").

       As there is an overlap between the error numbers used by bzlib and
       UNIX, $bzerrno should only be used to check for the presence of an
       error in numeric context. Use bzerror() to check for specific bzlib
       errors. The bzcat example below shows how the variable can be used
       safely.


Compress::Bzip2 1.03 COMPATIBILITY

       While the 2.x thread forked off of 1.00, another line of development
       came to a head at 1.03.  The 1.03 version worked with bzlib 1.0.2, had
       improvements to the error handling, single buffer inflate/deflate, a
       streaming interface to inflate/deflate, and a cpan style test suite.

       $dest = compress( $string, [$level] )

       Alias to memBzip, this compresses string, using the optional
       compression level, 1 through 9, the default being 1.  Returns a string
       containing the compressed data.

       On error undef is returned.

       $dest = decompress($string)

       Alias to memBunzip, this decompresses the data in string, returning a
       string containing the decompressed data.

       On error undef is returned.

       $stream = compress_init( [PARAMS] )

       Alias to bzdeflateInit.  In addition to the named parameters documented
       for bzdeflateInit, the following are accepted:

          -level, alias to -blockSize100k
          -buffer, to set the buffer size.

       The -buffer option is ignored.  The intermediate buffer size is not
       changeable.

       $stream = decompress_init( [PARAMS] )

       Alias to bzinflateInit.  See bzinflateInit for a description of the
       parameters.  The option "-buffer" is accepted, but ignored.

       $output = $stream->add( $string )

       Add data to be compressed/decompressed.  Returns whatever output is
       available (possibly none, if it's still buffering it), or undef on
       error.

       $output = $stream->finish( [$string] )

       Finish the operation; takes an optional final data string.  Whatever is
       returned completes the output; returns undef on error.

       $stream->error

       Like the function, but applies to the current object only.  Note that
       errors in a stream object are also returned by the function.

       $stream->input_size

       Alias to total_in.  Total bytes passed to the stream.

       $stream->output_size

       Alias to total_out.  Total bytes received from the stream.


GZIP COMPATIBILITY INTERFACE

       Except for the exact state and error numbers, this package presents an
       interface very much like that given by the Compress::Zlib package.
       Mostly, if you take the method name, state or error number from
       Compress::Zlib and replace the "g" with a "b", your code should work.

       To make the interoperability even easier, all the Compress::Zlib method
       names have been used as aliases or cover functions for the bzip2
       methods.

       Therefore, most code that uses Compress::Zlib should be able to use
       this package, with a one line change.

       Simply change

          $gz = Compress::Zlib::gzopen( "filename", "w" );

       to

          $gz = Compress::Bzip2::gzopen( "filename", "w" );

       Some of the Compress::Zlib aliases don't return anything useful, like
       crc32 or adler32, cause bzip2 doesn't do that sort of thing.

        $gz = gzopen( $filename, $mode )

       Alias for bzopen.

        $gz->gzread( $buffer, [ $length ] )

       Alias for bzread.

        $gz->gzreadline( $buffer )

       Alias for bzreadline.

        $gz->gzwrite( $buffer )

       Alias for bzwrite.

        $gz->gzflush( [$flushtype] )

       Alias for bzflush, with return code translation.

        $gz->gzclose( )

       Alias for bzclose.

        $gz->gzeof( )

       Alias for bzeof.

        $gz->gzerror( )

       Alias for bzerror.

        $gz->gzsetparams( $level, $strategy )

       This is a no-op.

        $d = deflateInit( [OPTS] )

       Alias for bzdeflateInit, with return code translation.

       All OPTS are ignored.

        $d->deflate( $buffer )

       Alias for bzdeflate, with return code translation.

        $d->deflateParams( [OPTS] )

       This is a no-op.

        $d->flush( [$flushtype] )

       Cover function for bzflush or bzclose, depending on $flushtype.

       See the Compress::Zlib documentation for more information.

        $d->dict_adler( )

       This is a no-op.

        $d->msg( )

       This is a no-op.

        $d = inflateInit( [OPTS] )

       Alias for bzinflateInit, with return code translation.

       All OPTS are ignored.

        $d->inflate( )

       Alias for bzinflate, with return code translation.

        $d->inflateSync( )

       This is a no-op.

        $d->adler32( $crc )

       This is a no-op.

        $d->crc32( $crc )

       This is a no-op.

        $buffer = memGzip( $buffer )

       Alias for memBzip.

        $buffer = memGunzip( $buffer )

       Alias for memBunzip.


IN-MEMORY COMPRESS/UNCOMPRESS

       Two high-level functions are provided by bzlib to perform in-memory
       compression. They are memBzip and memBunzip. Two Perl subs are provided
       which provide similar functionality.

       $compressed = memBzip($buffer);

       Compresses $source. If successful it returns the compressed data.
       Otherwise it returns undef.

       The buffer parameter can either be a scalar or a scalar reference.

       Essentially, an in-memory bzip file is created. It creates a minimal
       bzip header.

       $uncompressed = memBunzip($buffer);

       Uncompresses $source. If successful it returns the uncompressed data.
       Otherwise it returns undef.

       The source buffer can either be a scalar or a scalar reference.

       The buffer parameter can either be a scalar or a scalar reference. The
       contents of the buffer parameter are destroyed after calling this
       function.


STREAM DEFLATE

       The Perl interface will always consume the complete input buffer before
       returning. Also the output buffer returned will be automatically grown
       to fit the amount of output available.

       Here is a definition of the interface available:

       ($d, $status) = bzdeflateInit( [PARAMS] )

       Initialises a deflation stream.

       If successful, it will return the initialised deflation stream, $d and
       $status of "BZ_OK" in a list context. In scalar context it returns the
       deflation stream, $d, only.

       If not successful, the returned deflation stream ($d) will be undef and
       $status will hold the exact bzip2 error code.

       The function optionally takes a number of named options specified as
       "-Name=>value" pairs. This allows individual options to be tailored
       without having to specify them all in the parameter list.

       Here is a list of the valid options:

       -verbosity
            Defines the verbosity level. Valid values are 0 through 4,

            The default is "-verbosity => 0".

       -blockSize100k
            Defines the buffering factor of compression method.  The algorithm
            buffers all data until the buffer is full, then it flushes all the
            data out.  Use -blockSize100k to specify the size of the buffer.

            Valid settings are 1 through 9, representing a blocking in
            multiples of 100k.

            Note that each such block has an overhead of leading and trailing
            synchronization bytes.  bzip2 recovery uses this information to
            pull useable data out of a corrupted file.

            A streaming application would probably want to set the blocking
            low.

       -workFactor
            The workFactor setting tells the deflation algorithm how much work
            to invest to compensate for repetitive data.

            workFactor may be a number from 0 to 250 inclusive.  The default
            setting is 30.

            See the bzip documentation for more information.

       Here is an example of using the deflateInit optional parameter list to
       override the default buffer size and compression level. All other
       options will take their default values.

           bzdeflateInit( -blockSize100k => 1, -verbosity => 1 );

       ($out, $status) = $d->bzdeflate($buffer)

       Deflates the contents of $buffer. The buffer can either be a scalar or
       a scalar reference.  When finished, $buffer will be completely
       processed (assuming there were no errors). If the deflation was
       successful it returns deflated output, $out, and a status value,
       $status, of "Z_OK".

       On error, $out will be undef and $status will contain the zlib error
       code.

       In a scalar context bzdeflate will return $out only.

       As with the internal buffering of the deflate function in bzip2, it is
       not necessarily the case that any output will be produced by this
       method. So don't rely on the fact that $out is empty for an error test.
       In fact, given the size of bzdeflates internal buffer, with most files
       it's likely you won't see any output at all until flush or close.

       ($out, $status) = $d->bzflush([flush_type])

       Typically used to finish the deflation. Any pending output will be
       returned via $out.  $status will have a value "BZ_OK" if successful.

       In a scalar context bzflush will return $out only.

       Note that flushing can seriously degrade the compression ratio, so it
       should only be used to terminate a decompression (using "BZ_FLUSH") or
       when you want to create a full flush point (using "BZ_FINISH").

       The allowable values for "flush_type" are "BZ_FLUSH" and "BZ_FINISH".

       For a handle opened for "w" (bzwrite), the default is "BZ_FLUSH".  For
       a stream, the default for "flush_type" is "BZ_FINISH" (which is
       essentially a close and reopen).

       It is strongly recommended that you only set the "flush_type" parameter
       if you fully understand the implications of what it does. See the
       "bzip2" documentation for details.

       Example

       Here is a trivial example of using bzdeflate. It simply reads standard
       input, deflates it and writes it to standard output.

           use strict ;
           use warnings ;

           use Compress::Bzip2 ;

           binmode STDIN;
           binmode STDOUT;
           my $x = bzdeflateInit()
              or die "Cannot create a deflation stream\n" ;

           my ($output, $status) ;
           while (<>)
           {
               ($output, $status) = $x->bzdeflate($_) ;

               $status == BZ_OK
                   or die "deflation failed\n" ;

               print $output ;
           }

           ($output, $status) = $x->bzclose() ;

           $status == BZ_OK
               or die "deflation failed\n" ;

           print $output ;


STREAM INFLATE

       Here is a definition of the interface:

       ($i, $status) = inflateInit()

       Initialises an inflation stream.

       In a list context it returns the inflation stream, $i, and the zlib
       status code ($status). In a scalar context it returns the inflation
       stream only.

       If successful, $i will hold the inflation stream and $status will be
       "BZ_OK".

       If not successful, $i will be undef and $status will hold the bzlib.h
       error code.

       The function optionally takes a number of named options specified as
       "-Name=>value" pairs. This allows individual options to be tailored
       without having to specify them all in the parameter list.

       For backward compatibility, it is also possible to pass the parameters
       as a reference to a hash containing the name=>value pairs.

       The function takes one optional parameter, a reference to a hash.  The
       contents of the hash allow the deflation interface to be tailored.

       Here is a list of the valid options:

       -small
            small may be 0 or 1.  Set "small" to one to use a slower, less
            memory intensive algorithm.

       -verbosity
            Defines the verbosity level. Valid values are 0 through 4,

            The default is "-verbosity => 0".

       Here is an example of using the bzinflateInit optional parameter.

           bzinflateInit( -small => 1, -verbosity => 1 );

       ($out, $status) = $i->bzinflate($buffer)

       Inflates the complete contents of $buffer. The buffer can either be a
       scalar or a scalar reference.

       Returns "BZ_OK" if successful and "BZ_STREAM_END" if the end of the
       compressed data has been successfully reached.  If not successful, $out
       will be undef and $status will hold the bzlib error code.

       The $buffer parameter is modified by "bzinflate". On completion it will
       contain what remains of the input buffer after inflation. This means
       that $buffer will be an empty string when the return status is "BZ_OK".
       When the return status is "BZ_STREAM_END" the $buffer parameter will
       contains what (if anything) was stored in the input buffer after the
       deflated data stream.

       This feature is useful when processing a file format that encapsulates
       a compressed data stream.

       Example

       Here is an example of using bzinflate.

           use strict ;
           use warnings ;

           use Compress::Bzip2;

           my $x = bzinflateInit()
              or die "Cannot create a inflation stream\n" ;

           my $input = '' ;
           binmode STDIN;
           binmode STDOUT;

           my ($output, $status) ;
           while (read(STDIN, $input, 4096))
           {
               ($output, $status) = $x->bzinflate(\$input) ;

               print $output
                   if $status == BZ_OK or $status == BZ_STREAM_END ;

               last if $status != BZ_OK ;
           }

           die "inflation failed\n"
               unless $status == BZ_STREAM_END ;


EXAMPLES

       Here are some example scripts of using the interface.

       A bzcat function

         use strict ;
         use warnings ;

         use Compress::Bzip2 ;

         die "Usage: bzcat file...\n" unless @ARGV ;

         my $file ;

         foreach $file (@ARGV) {
           my $buffer ;

           my $bz = bzopen($file, "rb")
              or die "Cannot open $file: $bzerrno\n" ;

           print $buffer while $bz->bzread($buffer) > 0 ;

           die "Error reading from $file: $bzerrno" . ($bzerrno+0) . "\n"
              if $bzerrno != BZ_STREAM_END ;

           $bz->bzclose() ;
         }

       A grep using bzreadline

         use strict ;
         use warnings ;

         use Compress::Bzip2 ;

         die "Usage: bzgrep pattern file...\n" unless @ARGV >= 2;

         my $pattern = shift ;

         my $file ;

         foreach $file (@ARGV) {
           my $bz = bzopen($file, "rb")
              or die "Cannot open $file: $bzerrno\n" ;

           while ($bz->bzreadline($_) > 0) {
             print if /$pattern/ ;
           }

           die "Error reading from $file: $bzerrno\n"
             if $bzerrno != Z_STREAM_END ;

           $bz->bzclose() ;
         }

       Streaming Compression

       This script, bzstream, does the opposite of the bzcat script above. It
       reads from standard input and writes a bzip file to standard output.

         use strict ;
         use warnings ;

         use Compress::Bzip2 ;

         binmode STDOUT;       # bzopen only sets it on the fd

         my $bz = bzopen(\*STDOUT, "wb")
            or die "Cannot open stdout: $bzerrno\n" ;

         while (<>) {
           $bz->bzwrite($_) or die "error writing: $bzerrno\n" ;
         }

         $bz->bzclose ;


EXPORT

       Use the tags :all, :utilities, :constants, :bzip1 and :gzip.

       Export tag :all

       This exports all the exportable methods.

       Export tag :constants

       This exports only the BZ_* constants.

       Export tag :bzip1

       This exports the Compress::Bzip2 1.x functions, for compatibility.

          compress
          decompress
          compress_init
          decompress_init
          version

       These are actually aliases to memBzip and memBunzip.

       Export tag :utilities

       This gives an interface to the bzip2 methods.

           bzopen
           bzinflateInit
           bzdeflateInit
           memBzip
           memBunzip
           bzip2
           bunzip2
           bzcat
           bzlibversion
           $bzerrno

       Export tag :gzip

       This gives compatibility with Compress::Zlib.

           gzopen
           gzinflateInit
           gzdeflateInit
           memGzip
           memGunzip
           $gzerrno


Exportable constants

       All the bzlib constants are automatically imported when you make use of
       Compress::Bzip2.

         BZ_CONFIG_ERROR
         BZ_DATA_ERROR
         BZ_DATA_ERROR_MAGIC
         BZ_FINISH
         BZ_FINISH_OK
         BZ_FLUSH
         BZ_FLUSH_OK
         BZ_IO_ERROR
         BZ_MAX_UNUSED
         BZ_MEM_ERROR
         BZ_OK
         BZ_OUTBUFF_FULL
         BZ_PARAM_ERROR
         BZ_RUN
         BZ_RUN_OK
         BZ_SEQUENCE_ERROR
         BZ_STREAM_END
         BZ_UNEXPECTED_EOF


SEE ALSO

       The documentation for zlib(3), bzip2(1) and Compress::Zlib(3).


AUTHOR

       Rob Janes, <arjay at cpan.org>


COPYRIGHT AND LICENSE

       Copyright (C) 2005 by Rob Janes

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself, either Perl version 5.8.3 or, at
       your option, any later version of Perl 5 you may have available.


AUTHOR

       The Compress::Bzip2 module was originally written by Gawdi Azem
       azemgi@rupert.informatik.uni-stuttgart.de.

       The first Compress::Bzip2 module was written by Gawdi Azem
       azemgi@rupert.informatik.uni-stuttgart.de.  It provided an interface to
       the in memory inflate and deflate routines.

       Compress::Bzip2 was subsequently passed on to Marco Carnut
       kiko@tempest.com.br who shepharded it through to version 1.03, a set of
       changes which included upgrades to handle bzlib 1.0.2, and improvements
       to the in memory inflate and deflate routines.  The streaming interface
       and error information were added by David Robins
       dbrobins@davidrobins.net.

       Version 2 of Compress::Bzip2 is due to Rob Janes, of arjay@cpan.org.
       This release is intended to give an interface close to that of
       Compress::Zlib.  It's development forks from 1.00, not 1.03, so the
       streaming interface is not the same as that in 1.03, although
       apparently compatible as it passes the 1.03 test suite.


MODIFICATION HISTORY

       See the Changes file.

       2.00 Second public release of Compress::Bzip2.


POD ERRORS

       Hey! The above document had some coding errors, which are explained
       below:

       Around line 746:
           You forgot a '=back' before '=head2'

       Around line 918:
           =back without =over

       Around line 929:
           You forgot a '=back' before '=head2'

       Around line 983:
           =back without =over

       Around line 1011:
           You forgot a '=back' before '=head2'

       Around line 1105:
           =back without =over

       Around line 1115:
           You forgot a '=back' before '=head2'

       Around line 1136:
           =back without =over

       Around line 1384:
           You forgot a '=back' before '=head2'

       Around line 1458:
           =back without =over



perl v5.10.0                      2005-08-09                Compress::Bzip2(3)

Mac OS X 10.6 - Generated Thu Sep 17 20:11:14 CDT 2009
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