IO::Compress::Zip(3p)

NAME
IO::Compress::Zip - Write zip files/buffers

SYNOPSIS
    use IO::Compress::Zip qw(zip $ZipError) ;

    my $status = zip $input => $output [,OPTS]
        or die "zip failed: $ZipError\n";

    my $z = IO::Compress::Zip->new( $output [,OPTS] )
        or die "zip failed: $ZipError\n";

    $z->print($string);
    $z->printf($format, $string);
    $z->write($string);
    $z->syswrite($string [, $length, $offset]);
    $z->flush();
    $z->tell();
    $z->eof();
    $z->seek($position, $whence);
    $z->binmode();
    $z->fileno();
    $z->opened();
    $z->autoflush();
    $z->input_line_number();
    $z->newStream( [OPTS] );

    $z->deflateParams();

    $z->close() ;

    $ZipError ;

    # IO::File mode

    print $z $string;
    printf $z $format, $string;
    tell $z
    eof $z
    seek $z, $position, $whence
    binmode $z
    fileno $z
    close $z ;

DESCRIPTION
This module provides a Perl interface that allows writing zip compressed data to files or buffer.

The primary purpose of this module is to provide streaming write access to zip files and buffers.

At present the following compression methods are supported by IO::Compress::Zip

Store (0)
Deflate (8)
Bzip2 (12)
    To write Bzip2 content, the module "IO::Uncompress::Bunzip2" must be installed.

Lzma (14)
    To write LZMA content, the module "IO::Uncompress::UnLzma" must be installed.

Zstandard (93)
    To write Zstandard content, the module "IO::Compress::Zstd" must be installed.

Xz (95)
    To write Xz content, the module "IO::Uncompress::UnXz" must be installed.

For reading zip files/buffers, see the companion module IO::Uncompress::Unzip.

Functional Interface
A top-level function, "zip", is provided to carry out "one-shot" compression between buffers and/or files. For finer control over the compression process, see the "OO Interface" section.

    use IO::Compress::Zip qw(zip $ZipError) ;

    zip $input_filename_or_reference => $output_filename_or_reference [,OPTS]
        or die "zip failed: $ZipError\n";

The functional interface needs Perl5.005 or better.

  zip $input_filename_or_reference => $output_filename_or_reference [, OPTS]
"zip" expects at least two parameters, $input_filename_or_reference and $output_filename_or_reference and zero or more optional parameters (see "Optional Parameters")

The $input_filename_or_reference parameter

The parameter, $input_filename_or_reference, is used to define the source of the uncompressed data.

It can take one of the following forms:

A filename
    If the $input_filename_or_reference parameter is a simple scalar, it is assumed to be a filename. This file will be opened for reading and the input data will be read from it.

A filehandle
    If the $input_filename_or_reference parameter is a filehandle, the input data will be read from it. The string '-' can be used as an alias for standard input.

A scalar reference
    If $input_filename_or_reference is a scalar reference, the input data will be read from $$input_filename_or_reference.

An array reference
    If $input_filename_or_reference is an array reference, each element in the array must be a filename.

    The input data will be read from each file in turn.

    The complete array will be walked to ensure that it only contains valid filenames before any data is compressed.

An Input FileGlob string
    If $input_filename_or_reference is a string that is delimited by the characters "<" and ">" "zip" will assume that it is an input fileglob string. The input is the list of files that match the fileglob.

    See File::GlobMapper for more details.

If the $input_filename_or_reference parameter is any other type, "undef" will be returned.

In addition, if $input_filename_or_reference is a simple filename, the default values for the "Name", "Time", "TextFlag", "ExtAttr", "exUnixN" and "exTime" options will be sourced from that file.

If you do not want to use these defaults they can be overridden by explicitly setting the "Name", "Time", "TextFlag", "ExtAttr", "exUnixN" and "exTime" options or by setting the "Minimal" parameter.

The $output_filename_or_reference parameter

The parameter $output_filename_or_reference is used to control the destination of the compressed data. This parameter can take one of these forms.

A filename
    If the $output_filename_or_reference parameter is a simple scalar, it is assumed to be a filename. This file will be opened for writing and the compressed data will be written to it.

A filehandle
    If the $output_filename_or_reference parameter is a filehandle, the compressed data will be written to it. The string '-' can be used as an alias for standard output.

A scalar reference
    If $output_filename_or_reference is a scalar reference, the compressed data will be stored in $$output_filename_or_reference.

An Array Reference
    If $output_filename_or_reference is an array reference, the compressed data will be pushed onto the array.

An Output FileGlob
    If $output_filename_or_reference is a string that is delimited by the characters "<" and ">" "zip" will assume that it is an output fileglob string. The output is the list of files that match the fileglob.

    When $output_filename_or_reference is an fileglob string, $input_filename_or_reference must also be a fileglob string. Anything else is an error.

    See File::GlobMapper for more details.

If the $output_filename_or_reference parameter is any other type, "undef" will be returned.

  Notes
When $input_filename_or_reference maps to multiple files/buffers and $output_filename_or_reference is a single file/buffer the input files/buffers will each be stored in $output_filename_or_reference as a distinct entry.

  Optional Parameters
The optional parameters for the one-shot function "zip" are (for the most part) identical to those used with the OO interface defined in the "Constructor Options" section. The exceptions are listed below

"AutoClose => 0|1"
    This option applies to any input or output data streams to "zip" 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 "zip" has completed.

    This parameter defaults to 0.

"BinModeIn => 0|1"
    This option is now a no-op. All files will be read in binmode.

"Append => 0|1"
    The behaviour of this option is dependent on the type of output data stream.

    •   A Buffer

        If "Append" is enabled, all compressed data will be append to the end of the output buffer. Otherwise the output buffer will be cleared before any compressed 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 compressed 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 compressed 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 compressed 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 compressed data. If the output is a filename, it will be opened for appending. If the output is a buffer, all compressed 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 compressed 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 compressed data is output.

    Defaults to 0.

  Examples
Here are a few example that show the capabilities of the module.

Streaming

This very simple command line example demonstrates the streaming capabilities of the module. The code reads data from STDIN, compresses it, and writes the compressed data to STDOUT.

    $ echo hello world | perl -MIO::Compress::Zip=zip -e 'zip \*STDIN => \*STDOUT' >output.zip

The special filename "-" can be used as a standin for both "\*STDIN" and "\*STDOUT", so the above can be rewritten as

    $ echo hello world | perl -MIO::Compress::Zip=zip -e 'zip "-" => "-"' >output.zip

One problem with creating a zip archive directly from STDIN can be demonstrated by looking at the contents of the zip file, output.zip, that we have just created.

    $ unzip -l output.zip
    Archive:  output.zip
    Length      Date    Time    Name
    ---------  ---------- -----   ----
        12  2019-08-16 22:21
    ---------                     -------
        12                     1 file

The archive member (filename) used is the empty string.

If that doesn't suit your needs, you can explicitly set the filename used in the zip archive by specifying the Name option, like so

    echo hello world | perl -MIO::Compress::Zip=zip -e 'zip "-" => "-", Name => "hello.txt"' >output.zip

Now the contents of the zip file looks like this

    $ unzip -l output.zip
    Archive:  output.zip
    Length      Date    Time    Name
    ---------  ---------- -----   ----
        12  2019-08-16 22:22   hello.txt
    ---------                     -------
        12                     1 file

Compressing a file from the filesystem

To read the contents of the file "file1.txt" and write the compressed data to the file "file1.txt.zip".

    use strict ;
    use warnings ;
    use IO::Compress::Zip qw(zip $ZipError) ;

    my $input = "file1.txt";
    zip $input => "$input.zip"
        or die "zip failed: $ZipError\n";

Reading from a Filehandle and writing to an in-memory buffer

To read from an existing Perl filehandle, $input, and write the compressed data to a buffer, $buffer.

    use strict ;
    use warnings ;
    use IO::Compress::Zip qw(zip $ZipError) ;
    use IO::File ;

    my $input = IO::File->new( "<file1.txt" )
        or die "Cannot open 'file1.txt': $!\n" ;
    my $buffer ;
    zip $input => \$buffer
        or die "zip failed: $ZipError\n";

Compressing multiple files

To create a zip file, "output.zip", that contains the compressed contents of the files "alpha.txt" and "beta.txt"

    use strict ;
    use warnings ;
    use IO::Compress::Zip qw(zip $ZipError) ;

    zip [ 'alpha.txt', 'beta.txt' ] => 'output.zip'
        or die "zip failed: $ZipError\n";

Alternatively, rather than having to explicitly name each of the files that you want to compress, you could use a fileglob to select all the "txt" files in the current directory, as follows

    use strict ;
    use warnings ;
    use IO::Compress::Zip qw(zip $ZipError) ;

    my @files = <*.txt>;
    zip \@files => 'output.zip'
        or die "zip failed: $ZipError\n";

or more succinctly

    zip [ <*.txt> ] => 'output.zip'
        or die "zip failed: $ZipError\n";

OO Interface

  Constructor
The format of the constructor for "IO::Compress::Zip" is shown below

    my $z = IO::Compress::Zip->new( $output [,OPTS] )
        or die "IO::Compress::Zip failed: $ZipError\n";

It returns an "IO::Compress::Zip" object on success and undef on failure. The variable $ZipError will contain an error message on failure.

If you are running Perl 5.005 or better the object, $z, returned from IO::Compress::Zip can be used exactly like an IO::File filehandle. This means that all normal output file operations can be carried out with $z. For example, to write to a compressed file/buffer you can use either of these forms

    $z->print("hello world\n");
    print $z "hello world\n";

The mandatory parameter $output is used to control the destination of the compressed 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 compressed data will be written to it.

A filehandle
    If the $output parameter is a filehandle, the compressed 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 compressed data will be stored in $$output.

If the $output parameter is any other type, "IO::Compress::Zip"::new will return undef.

  Constructor Options
"OPTS" is any combination of zero or more the following options:

"AutoClose => 0|1"
    This option is only valid when the $output parameter is a filehandle. If specified, and the value is true, it will result in the $output being closed once either the "close" method is called or the "IO::Compress::Zip" object is destroyed.

    This parameter defaults to 0.

"Append => 0|1"
    Opens $output in append mode.

    The behaviour of this option is dependent on the type of $output.

    •   A Buffer

        If $output is a buffer and "Append" is enabled, all compressed data will be append to the end of $output. Otherwise $output will be cleared before any data is written to it.

    •   A Filename

        If $output is a filename and "Append" is enabled, the file will be opened in append mode. Otherwise the contents of the file, if any, will be truncated before any compressed data is written to it.

    •   A Filehandle

        If $output is a filehandle, the file pointer will be positioned to the end of the file via a call to "seek" before any compressed data is written to it. Otherwise the file pointer will not be moved.

    This parameter defaults to 0.

File Naming Options

A quick bit of zip file terminology -- A zip archive consists of one or more archive members, where each member has an associated filename, known as the archive member name.

The options listed in this section control how the archive member name (or filename) is stored the zip archive.

"Name => $string"
    This option is used to explicitly set the archive member name in the zip archive to $string. Most of the time you don't need to make use of this option. By default when adding a filename to the zip archive, the archive member name will match the filename.

    You should only need to use this option if you want the archive member name to be different from the uncompressed filename or when the input is a filehandle or a buffer.

    The default behaviour for what archive member name is used when the "Name" option is not specified depends on the form of the $input parameter:

    •   If the $input parameter is a filename, the value of $input will be used for the archive member name .

    •   If the $input parameter is not a filename, the archive member name will be an empty string.

    Note that both the "CanonicalName" and "FilterName" options can modify the value used for the archive member name.

    Also note that you should set the "Efs" option to true if you are working with UTF8 filenames.

"CanonicalName => 0|1"
    This option controls whether the archive member name is normalized into Unix format before being written to the zip file.

    It is recommended that you enable this option unless you really need to create a non-standard Zip file.

    This is what APPNOTE.TXT has to say on what should be stored in the zip filename header field.

        The name of the file, with optional relative path.
        The path stored should not contain a drive or
        device letter, or a leading slash.  All slashes
        should be forward slashes '/' as opposed to
        backwards slashes '\' for compatibility with Amiga
        and UNIX file systems etc.

    This option defaults to false.

"FilterName => sub { ... }"
    This option allow the archive member name to be modified before it is written to the zip file.

    This option takes a parameter that must be a reference to a sub. On entry to the sub the $_ variable will contain the name to be filtered. If no filename is available $_ will contain an empty string.

    The value of $_ when the sub returns will be used as the archive member name.

    Note that if "CanonicalName" is enabled, a normalized filename will be passed to the sub.

    If you use "FilterName" to modify the filename, it is your responsibility to keep the filename in Unix format.

    Although this option can be used with the OO interface, it is of most use with the one-shot interface. For example, the code below shows how "FilterName" can be used to remove the path component from a series of filenames before they are stored in $zipfile.

        sub compressTxtFiles
        {
            my $zipfile = shift ;
            my $dir     = shift ;

            zip [ <$dir/*.txt> ] => $zipfile,
                FilterName => sub { s[^$dir/][] } ;
        }

"Efs => 0|1"
    This option controls setting of the "Language Encoding Flag" (EFS) in the zip archive. When set, the filename and comment fields for the zip archive MUST be valid UTF-8.

    If the string used for the filename and/or comment is not valid UTF-8 when this option is true, the script will die with a "wide character" error.

    Note that this option only works with Perl 5.8.4 or better.

    This option defaults to false.

Overall Zip Archive Structure

"Minimal => 1|0"
    If specified, this option will disable the creation of all extra fields in the zip local and central headers. So the "exTime", "exUnix2", "exUnixN", "ExtraFieldLocal" and "ExtraFieldCentral" options will be ignored.

    This parameter defaults to 0.

"Stream => 0|1"
    This option controls whether the zip file/buffer output is created in streaming mode.

    Note that when outputting to a file with streaming mode disabled ("Stream" is 0), the output file must be seekable.

    The default is 1.

"Zip64 => 0|1"
    Create a Zip64 zip file/buffer. This option is used if you want to store files larger than 4 Gig or store more than 64K files in a single zip archive.

    "Zip64" will be automatically set, as needed, if working with the one-shot interface when the input is either a filename or a scalar reference.

    If you intend to manipulate the Zip64 zip files created with this module using an external zip/unzip, make sure that it supports Zip64.

    In particular, if you are using Info-Zip you need to have zip version 3.x or better to update a Zip64 archive and unzip version 6.x to read a zip64 archive.

    The default is 0.

Deflate Compression Options

-Level
    Defines the compression level used by zlib. The value should either be a number between 0 and 9 (0 means no compression and 9 is maximum compression), or one of the symbolic constants defined below.

       Z_NO_COMPRESSION
       Z_BEST_SPEED
       Z_BEST_COMPRESSION
       Z_DEFAULT_COMPRESSION

    The default is Z_DEFAULT_COMPRESSION.

    Note, these constants are not imported by "IO::Compress::Zip" by default.

        use IO::Compress::Zip qw(:strategy);
        use IO::Compress::Zip qw(:constants);
        use IO::Compress::Zip qw(:all);

-Strategy
    Defines the strategy used to tune the compression. Use one of the symbolic constants defined below.

       Z_FILTERED
       Z_HUFFMAN_ONLY
       Z_RLE
       Z_FIXED
       Z_DEFAULT_STRATEGY

    The default is Z_DEFAULT_STRATEGY.

Bzip2 Compression Options

"BlockSize100K => number"
    Specify the number of 100K blocks bzip2 uses during compression.

    Valid values are from 1 to 9, where 9 is best compression.

    This option is only valid if the "Method" is ZIP_CM_BZIP2. It is ignored otherwise.

    The default is 1.

"WorkFactor => number"
    Specifies how much effort bzip2 should take before resorting to a slower fallback compression algorithm.

    Valid values range from 0 to 250, where 0 means use the default value 30.

    This option is only valid if the "Method" is ZIP_CM_BZIP2. It is ignored otherwise.

    The default is 0.

Lzma and Xz Compression Options

"Preset => number"
    Used to choose the LZMA compression preset.

    Valid values are 0-9 and "LZMA_PRESET_DEFAULT".

    0 is the fastest compression with the lowest memory usage and the lowest compression.

    9 is the slowest compression with the highest memory usage but with the best compression.

    This option is only valid if the "Method" is ZIP_CM_LZMA. It is ignored otherwise.

    Defaults to "LZMA_PRESET_DEFAULT" (6).

"Extreme => 0|1"
    Makes LZMA compression a lot slower, but a small compression gain.

    This option is only valid if the "Method" is ZIP_CM_LZMA. It is ignored otherwise.

    Defaults to 0.

Other Options

"Time => $number"
    Sets the last modified time field in the zip header to $number.

    This field defaults to the time the "IO::Compress::Zip" object was created if this option is not specified and the $input parameter is not a filename.

"ExtAttr => $attr"
    This option controls the "external file attributes" field in the central header of the zip file. This is a 4 byte field.

    If you are running a Unix derivative this value defaults to

        0100644 << 16

    This should allow read/write access to any files that are extracted from the zip file/buffer`.

    For all other systems it defaults to 0.

"exTime => [$atime, $mtime, $ctime]"
    This option expects an array reference with exactly three elements: $atime, "mtime" and $ctime. These correspond to the last access time, last modification time and creation time respectively.

    It uses these values to set the extended timestamp field (ID is "UT") in the local zip header using the three values, $atime, $mtime, $ctime. In addition it sets the extended timestamp field in the central zip header using $mtime.

    If any of the three values is "undef" that time value will not be used. So, for example, to set only the $mtime you would use this

        exTime => [undef, $mtime, undef]

    If the "Minimal" option is set to true, this option will be ignored.

    By default no extended time field is created.

"exUnix2 => [$uid, $gid]"
    This option expects an array reference with exactly two elements: $uid and $gid. These values correspond to the numeric User ID (UID) and Group ID (GID) of the owner of the files respectively.

    When the "exUnix2" option is present it will trigger the creation of a Unix2 extra field (ID is "Ux") in the local zip header. This will be populated with $uid and $gid. An empty Unix2 extra field will also be created in the central zip header.

    Note - The UID & GID are stored as 16-bit integers in the "Ux" field. Use "exUnixN" if your UID or GID are 32-bit.

    If the "Minimal" option is set to true, this option will be ignored.

    By default no Unix2 extra field is created.

"exUnixN => [$uid, $gid]"
    This option expects an array reference with exactly two elements: $uid and $gid. These values correspond to the numeric User ID (UID) and Group ID (GID) of the owner of the files respectively.

    When the "exUnixN" option is present it will trigger the creation of a UnixN extra field (ID is "ux") in both the local and central zip headers. This will be populated with $uid and $gid. The UID & GID are stored as 32-bit integers.

    If the "Minimal" option is set to true, this option will be ignored.

    By default no UnixN extra field is created.

"Comment => $comment"
    Stores the contents of $comment in the Central File Header of the zip file.

    Set the "Efs" option to true if you want to store a UTF8 comment.

    By default, no comment field is written to the zip file.

"ZipComment => $comment"
    Stores the contents of $comment in the End of Central Directory record of the zip file.

    By default, no comment field is written to the zip file.

"Method => $method"
    Controls which compression method is used. At present the compression methods supported are: Store (no compression at all), Deflate, Bzip2, Zstd, Xz and Lzma.

    The symbols ZIP_CM_STORE, ZIP_CM_DEFLATE, ZIP_CM_BZIP2, ZIP_CM_ZSTD, ZIP_CM_XZ and ZIP_CM_LZMA are used to select the compression method.

    These constants are not imported by "IO::Compress::Zip" by default.

        use IO::Compress::Zip qw(:zip_method);
        use IO::Compress::Zip qw(:constants);
        use IO::Compress::Zip qw(:all);

    Note that to create Bzip2 content, the module "IO::Compress::Bzip2" must be installed. A fatal error will be thrown if you attempt to create Bzip2 content when "IO::Compress::Bzip2" is not available.

    Note that to create Lzma content, the module "IO::Compress::Lzma" must be installed. A fatal error will be thrown if you attempt to create Lzma content when "IO::Compress::Lzma" is not available.

    Note that to create Xz content, the module "IO::Compress::Xz" must be installed. A fatal error will be thrown if you attempt to create Xz content when "IO::Compress::Xz" is not available.

    Note that to create Zstd content, the module "IO::Compress::Zstd" must be installed. A fatal error will be thrown if you attempt to create Zstd content when "IO::Compress::Zstd" is not available.

    The default method is ZIP_CM_DEFLATE.

"TextFlag => 0|1"
    This parameter controls the setting of a bit in the zip central header. It is used to signal that the data stored in the zip file/buffer is probably text.

    In one-shot mode this flag will be set to true if the Perl "-T" operator thinks the file contains text.

    The default is 0.

"ExtraFieldLocal => $data"
"ExtraFieldCentral => $data"
    The "ExtraFieldLocal" option is used to store additional metadata in the local header for the zip file/buffer. The "ExtraFieldCentral" does the same for the matching central header.

    An extra field consists of zero or more subfields. Each subfield consists of a two byte header followed by the subfield data.

    The list of subfields can be supplied in any of the following formats

        ExtraFieldLocal => [$id1, $data1,
                            $id2, $data2,
                             ...
                           ]

        ExtraFieldLocal => [ [$id1 => $data1],
                             [$id2 => $data2],
                             ...
                           ]

        ExtraFieldLocal => { $id1 => $data1,
                             $id2 => $data2,
                             ...
                           }

    Where $id1, $id2 are two byte subfield ID's.

    If you use the hash syntax, you have no control over the order in which the ExtraSubFields are stored, plus you cannot have SubFields with duplicate ID.

    Alternatively the list of subfields can by supplied as a scalar, thus

        ExtraField => $rawdata

    In this case "IO::Compress::Zip" will check that $rawdata consists of zero or more conformant sub-fields.

    The Extended Time field (ID "UT"), set using the "exTime" option, and the Unix2 extra field (ID "Ux), set using the "exUnix2" option, are examples of extra fields.

    If the "Minimal" option is set to true, this option will be ignored.

    The maximum size of an extra field 65535 bytes.

"Strict => 0|1"
    This is a placeholder option.

  Examples
TODO

Methods

  print
Usage is

    $z->print($data)
    print $z $data

Compresses and outputs the contents of the $data parameter. This has the same behaviour as the "print" built-in.

Returns true if successful.

  printf
Usage is

    $z->printf($format, $data)
    printf $z $format, $data

Compresses and outputs the contents of the $data parameter.

Returns true if successful.

  syswrite
Usage is

    $z->syswrite $data
    $z->syswrite $data, $length
    $z->syswrite $data, $length, $offset

Compresses and outputs the contents of the $data parameter.

Returns the number of uncompressed bytes written, or "undef" if unsuccessful.

  write
Usage is

    $z->write $data
    $z->write $data, $length
    $z->write $data, $length, $offset

Compresses and outputs the contents of the $data parameter.

Returns the number of uncompressed bytes written, or "undef" if unsuccessful.

  flush
Usage is

    $z->flush;
    $z->flush($flush_type);

Flushes any pending compressed data to the output file/buffer.

This method takes an optional parameter, $flush_type, that controls how the flushing will be carried out. By default the $flush_type used is "Z_FINISH". Other valid values for $flush_type are "Z_NO_FLUSH", "Z_SYNC_FLUSH", "Z_FULL_FLUSH" and "Z_BLOCK". It is strongly recommended that you only set the "flush_type" parameter if you fully understand the implications of what it does - overuse of "flush" can seriously degrade the level of compression achieved. See the "zlib" documentation for details.

Returns true on success.

  tell
Usage is

    $z->tell()
    tell $z

Returns the uncompressed file offset.

  eof
Usage is

    $z->eof();
    eof($z);

Returns true if the "close" method has been called.

  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 output file/buffer. It is a fatal error to attempt to seek backward.

Empty parts of the file/buffer will have NULL (0x00) bytes written to them.

The $whence parameter takes one the usual values, namely SEEK_SET, SEEK_CUR or SEEK_END.

Returns 1 on success, 0 on failure.

  binmode
Usage is

    $z->binmode
    binmode $z ;

This is a noop provided for completeness.

  opened
    $z->opened()

Returns true if the object currently refers to a opened file/buffer.

  autoflush
    my $prev = $z->autoflush()
    my $prev = $z->autoflush(EXPR)

If the $z object is associated with a file or a filehandle, this method returns the current autoflush setting for the underlying filehandle. If "EXPR" is present, and is non-zero, it will enable flushing after every write/print operation.

If $z is associated with a buffer, this method has no effect and always returns "undef".

Note that the special variable $| cannot be used to set or retrieve the autoflush setting.

  input_line_number
    $z->input_line_number()
    $z->input_line_number(EXPR)

This method always returns "undef" when compressing.

  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 ;

Flushes any pending compressed data and then closes the output file/buffer.

For most versions of Perl this method will be automatically invoked if the IO::Compress::Zip 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::Compress::Zip object was created, and the object is associated with a file, the underlying file will also be closed.

  newStream([OPTS])
Usage is

    $z->newStream( [OPTS] )

Closes the current compressed data stream and starts a new one.

OPTS consists of any of the options that are available when creating the $z object.

See the "Constructor Options" section for more details.

  deflateParams
Usage is

    $z->deflateParams

TODO

Importing
A number of symbolic constants are required by some methods in "IO::Compress::Zip". None are imported by default.

:all
    Imports "zip", $ZipError and all symbolic constants that can be used by "IO::Compress::Zip". Same as doing this

        use IO::Compress::Zip qw(zip $ZipError :constants) ;

:constants
    Import all symbolic constants. Same as doing this

        use IO::Compress::Zip qw(:flush :level :strategy :zip_method) ;

:flush
    These symbolic constants are used by the "flush" method.

        Z_NO_FLUSH
        Z_PARTIAL_FLUSH
        Z_SYNC_FLUSH
        Z_FULL_FLUSH
        Z_FINISH
        Z_BLOCK

:level
    These symbolic constants are used by the "Level" option in the constructor.

        Z_NO_COMPRESSION
        Z_BEST_SPEED
        Z_BEST_COMPRESSION
        Z_DEFAULT_COMPRESSION

:strategy
    These symbolic constants are used by the "Strategy" option in the constructor.

        Z_FILTERED
        Z_HUFFMAN_ONLY
        Z_RLE
        Z_FIXED
        Z_DEFAULT_STRATEGY

:zip_method
    These symbolic constants are used by the "Method" option in the constructor.

        ZIP_CM_STORE
        ZIP_CM_DEFLATE
        ZIP_CM_BZIP2

EXAMPLES

  Apache::GZip Revisited
See IO::Compress::FAQ

  Working with Net::FTP
See IO::Compress::FAQ

SUPPORT
General feedback/questions/bug reports should be sent to <https://github.com/pmqs/IO-Compress/issues> (preferred) or <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress>.

SEE ALSO
Compress::Zlib, IO::Compress::Gzip, IO::Uncompress::Gunzip, 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::Lzip, IO::Uncompress::UnLzip, IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::UnLzf, IO::Compress::Zstd, IO::Uncompress::UnZstd, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress

IO::Compress::FAQ

File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib

For RFC 1950, 1951 and 1952 see <https://datatracker.ietf.org/doc/html/rfc1950>, <https://datatracker.ietf.org/doc/html/rfc1951> and <https://datatracker.ietf.org/doc/html/rfc1952>

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) 2005-2022 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.