Страницы справочника OS X

Эта страница руководства для  версии 10.9 Mac OS X

Читать страницы руководства

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, bzip2 and Compress::Zlib.

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 v5.16.2                                     2005-08-09                               Compress::Bzip2(3)