io::compress::gzip.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

.Ve
.PP
To read from an existing Perl filehandle, \f(CW$input\fR, and write the
compressed data to a buffer, \f(CW$buffer\fR.
.PP
.Vb 4
\&    use strict ;
\&    use warnings ;
\&    use IO::Compress::Gzip qw(gzip $GzipError) ;
\&    use IO::File ;
\&
\&    my $input = new IO::File "<file1.txt"
\&        or die "Cannot open \*(Aqfile1.txt\*(Aq: $!\en" ;
\&    my $buffer ;
\&    gzip $input => \e$buffer 
\&        or die "gzip failed: $GzipError\en";
.Ve
.PP
To compress all files in the directory \*(L"/my/home\*(R" that match \*(L"*.txt\*(R"
and store the compressed data in the same directory
.PP
.Vb 3
\&    use strict ;
\&    use warnings ;
\&    use IO::Compress::Gzip qw(gzip $GzipError) ;
\&
\&    gzip \*(Aq</my/home/*.txt>\*(Aq => \*(Aq<*.gz>\*(Aq
\&        or die "gzip failed: $GzipError\en";
.Ve
.PP
and if you want to compress each file one at a time, this will do the trick
.PP
.Vb 3
\&    use strict ;
\&    use warnings ;
\&    use IO::Compress::Gzip qw(gzip $GzipError) ;
\&
\&    for my $input ( glob "/my/home/*.txt" )
\&    {
\&        my $output = "$input.gz" ;
\&        gzip $input => $output 
\&            or die "Error compressing \*(Aq$input\*(Aq: $GzipError\en";
\&    }
.Ve
.SH "OO Interface"
.IX Header "OO Interface"
.Sh "Constructor"
.IX Subsection "Constructor"
The format of the constructor for \f(CW\*(C`IO::Compress::Gzip\*(C'\fR is shown below
.PP
.Vb 2
\&    my $z = new IO::Compress::Gzip $output [,OPTS]
\&        or die "IO::Compress::Gzip failed: $GzipError\en";
.Ve
.PP
It returns an \f(CW\*(C`IO::Compress::Gzip\*(C'\fR object on success and undef on failure. 
The variable \f(CW$GzipError\fR will contain an error message on failure.
.PP
If you are running Perl 5.005 or better the object, \f(CW$z\fR, returned from 
IO::Compress::Gzip can be used exactly like an IO::File filehandle. 
This means that all normal output file operations can be carried out 
with \f(CW$z\fR. 
For example, to write to a compressed file/buffer you can use either of 
these forms
.PP
.Vb 2
\&    $z\->print("hello world\en");
\&    print $z "hello world\en";
.Ve
.PP
The mandatory parameter \f(CW$output\fR is used to control the destination
of the compressed data. This parameter can take one of these forms.
.IP "A filename" 5
.IX Item "A filename"
If the \f(CW$output\fR parameter is a simple scalar, it is assumed to be a
filename. This file will be opened for writing and the compressed data
will be written to it.
.IP "A filehandle" 5
.IX Item "A filehandle"
If the \f(CW$output\fR parameter is a filehandle, the compressed data will be
written to it.
The string '\-' can be used as an alias for standard output.
.IP "A scalar reference" 5
.IX Item "A scalar reference"
If \f(CW$output\fR is a scalar reference, the compressed data will be stored
in \f(CW$$output\fR.
.PP
If the \f(CW$output\fR parameter is any other type, \f(CW\*(C`IO::Compress::Gzip\*(C'\fR::new will
return undef.
.Sh "Constructor Options"
.IX Subsection "Constructor Options"
\&\f(CW\*(C`OPTS\*(C'\fR is any combination of the following options:
.ie n .IP """AutoClose => 0|1""" 5
.el .IP "\f(CWAutoClose => 0|1\fR" 5
.IX Item "AutoClose => 0|1"
This option is only valid when the \f(CW$output\fR parameter is a filehandle. If
specified, and the value is true, it will result in the \f(CW$output\fR being
closed once either the \f(CW\*(C`close\*(C'\fR method is called or the \f(CW\*(C`IO::Compress::Gzip\*(C'\fR
object is destroyed.
.Sp
This parameter defaults to 0.
.ie n .IP """Append => 0|1""" 5
.el .IP "\f(CWAppend => 0|1\fR" 5
.IX Item "Append => 0|1"
Opens \f(CW$output\fR in append mode.
.Sp
The behaviour of this option is dependent on the type of \f(CW$output\fR.
.RS 5
.IP "\(bu" 5
A Buffer
.Sp
If \f(CW$output\fR is a buffer and \f(CW\*(C`Append\*(C'\fR is enabled, all compressed data
will be append to the end if \f(CW$output\fR. Otherwise \f(CW$output\fR will be
cleared before any data is written to it.
.IP "\(bu" 5
A Filename
.Sp
If \f(CW$output\fR is a filename and \f(CW\*(C`Append\*(C'\fR 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.
.IP "\(bu" 5
A Filehandle
.Sp
If \f(CW$output\fR is a filehandle, the file pointer will be positioned to the
end of the file via a call to \f(CW\*(C`seek\*(C'\fR before any compressed data is written
to it.  Otherwise the file pointer will not be moved.
.RE
.RS 5
.Sp
This parameter defaults to 0.
.RE
.ie n .IP """Merge => 0|1""" 5
.el .IP "\f(CWMerge => 0|1\fR" 5
.IX Item "Merge => 0|1"
This option is used to compress input data and append it to an existing
compressed data stream in \f(CW$output\fR. The end result is a single compressed
data stream stored in \f(CW$output\fR.
.Sp
It is a fatal error to attempt to use this option when \f(CW$output\fR is not an
\&\s-1RFC\s0 1952 data stream.
.Sp
There are a number of other limitations with the \f(CW\*(C`Merge\*(C'\fR option:
.RS 5
.IP "1." 5
This module needs to have been built with zlib 1.2.1 or better to work. A
fatal error will be thrown if \f(CW\*(C`Merge\*(C'\fR is used with an older version of
zlib.
.IP "2." 5
If \f(CW$output\fR is a file or a filehandle, it must be seekable.
.RE
.RS 5
.Sp
This parameter defaults to 0.
.RE
.IP "\-Level" 5
.IX Item "-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.
.Sp
.Vb 4
\&   Z_NO_COMPRESSION
\&   Z_BEST_SPEED
\&   Z_BEST_COMPRESSION
\&   Z_DEFAULT_COMPRESSION
.Ve
.Sp
The default is Z_DEFAULT_COMPRESSION.
.Sp
Note, these constants are not imported by \f(CW\*(C`IO::Compress::Gzip\*(C'\fR by default.
.Sp
.Vb 3
\&    use IO::Compress::Gzip qw(:strategy);
\&    use IO::Compress::Gzip qw(:constants);
\&    use IO::Compress::Gzip qw(:all);
.Ve
.IP "\-Strategy" 5
.IX Item "-Strategy"
Defines the strategy used to tune the compression. Use one of the symbolic
constants defined below.
.Sp
.Vb 5
\&   Z_FILTERED
\&   Z_HUFFMAN_ONLY
\&   Z_RLE
\&   Z_FIXED
\&   Z_DEFAULT_STRATEGY
.Ve
.Sp
The default is Z_DEFAULT_STRATEGY.
.ie n .IP """Minimal => 0|1""" 5
.el .IP "\f(CWMinimal => 0|1\fR" 5
.IX Item "Minimal => 0|1"
If specified, this option will force the creation of the smallest possible
compliant gzip header (which is exactly 10 bytes long) as defined in
\&\s-1RFC\s0 1952.
.Sp
See the section titled \*(L"Compliance\*(R" in \s-1RFC\s0 1952 for a definition 
of the values used for the fields in the gzip header.
.Sp
All other parameters that control the content of the gzip header will
be ignored if this parameter is set to 1.
.Sp
This parameter defaults to 0.
.ie n .IP """Comment => $comment""" 5
.el .IP "\f(CWComment => $comment\fR" 5
.IX Item "Comment => $comment"
Stores the contents of \f(CW$comment\fR in the \s-1COMMENT\s0 field in
the gzip header.
By default, no comment field is written to the gzip file.
.Sp
If the \f(CW\*(C`\-Strict\*(C'\fR option is enabled, the comment can only consist of \s-1ISO\s0
8859\-1 characters plus line feed.
.Sp
If the \f(CW\*(C`\-Strict\*(C'\fR option is disabled, the comment field can contain any
character except \s-1NULL\s0. If any null characters are present, the field
will be truncated at the first \s-1NULL\s0.
.ie n .IP """Name => $string""" 5
.el .IP "\f(CWName => $string\fR" 5
.IX Item "Name => $string"
Stores the contents of \f(CW$string\fR in the gzip \s-1NAME\s0 header field. If
\&\f(CW\*(C`Name\*(C'\fR is not specified, no gzip \s-1NAME\s0 field will be created.
.Sp
If the \f(CW\*(C`\-Strict\*(C'\fR option is enabled, \f(CW$string\fR can only consist of \s-1ISO\s0
8859\-1 characters.
.Sp
If \f(CW\*(C`\-Strict\*(C'\fR is disabled, then \f(CW$string\fR can contain any character
except \s-1NULL\s0. If any null characters are present, the field will be
truncated at the first \s-1NULL\s0.
.ie n .IP """Time => $number""" 5
.el .IP "\f(CWTime => $number\fR" 5
.IX Item "Time => $number"
Sets the \s-1MTIME\s0 field in the gzip header to \f(CW$number\fR.
.Sp
This field defaults to the time the \f(CW\*(C`IO::Compress::Gzip\*(C'\fR object was created
if this option is not specified.
.ie n .IP """TextFlag => 0|1""" 5
.el .IP "\f(CWTextFlag => 0|1\fR" 5
.IX Item "TextFlag => 0|1"
This parameter controls the setting of the \s-1FLG\s0.FTEXT bit in the gzip
header. It is used to signal that the data stored in the gzip file/buffer
is probably text.
.Sp
The default is 0.
.ie n .IP """HeaderCRC => 0|1""" 5
.el .IP "\f(CWHeaderCRC => 0|1\fR" 5
.IX Item "HeaderCRC => 0|1"
When true this parameter will set the \s-1FLG\s0.FHCRC bit to 1 in the gzip header
and set the \s-1CRC16\s0 header field to the \s-1CRC\s0 of the complete gzip header
except the \s-1CRC16\s0 field itself.
.Sp
\&\fBNote\fR that gzip files created with the \f(CW\*(C`HeaderCRC\*(C'\fR flag set to 1 cannot
be read by most, if not all, of the the standard gunzip utilities, most
notably gzip version 1.2.4. You should therefore avoid using this option if
you want to maximize the portability of your gzip files.
.Sp
This parameter defaults to 0.
.ie n .IP """OS_Code => $value""" 5
.el .IP "\f(CWOS_Code => $value\fR" 5
.IX Item "OS_Code => $value"
Stores \f(CW$value\fR in the gzip \s-1OS\s0 header field. A number between 0 and 255 is
valid.
.Sp
If not specified, this parameter defaults to the \s-1OS\s0 code of the Operating
System this module was built on. The value 3 is used as a catch-all for all
Unix variants and unknown Operating Systems.
.ie n .IP """ExtraField => $data""" 5
.el .IP "\f(CWExtraField => $data\fR" 5
.IX Item "ExtraField => $data"
This parameter allows additional metadata to be stored in the ExtraField in
the gzip header. An \s-1RFC\s0 1952 compliant ExtraField consists of zero or more
subfields. Each subfield consists of a two byte header followed by the
subfield data.
.Sp
The list of subfields can be supplied in any of the following formats
.Sp
.Vb 12
\&    \-ExtraField => [$id1, $data1,
\&                    $id2, $data2,
\&                     ...
\&                   ]
\&    \-ExtraField => [ [$id1 => $data1],
\&                     [$id2 => $data2],
\&                     ...
\&                   ]
\&    \-ExtraField => { $id1 => $data1,
\&                     $id2 => $data2,
\&                     ...
\&                   }
.Ve
.Sp
Where \f(CW$id1\fR, \f(CW$id2\fR are two byte subfield \s-1ID\s0's. The second byte of
the \s-1ID\s0 cannot be 0, unless the \f(CW\*(C`Strict\*(C'\fR option has been disabled.
.Sp
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 \s-1ID\s0.
.Sp
Alternatively the list of subfields can by supplied as a scalar, thus
.Sp
.Vb 1
\&    \-ExtraField => $rawdata
.Ve
.Sp
If you use the raw format, and the \f(CW\*(C`Strict\*(C'\fR option is enabled,
\&\f(CW\*(C`IO::Compress::Gzip\*(C'\fR will check that \f(CW$rawdata\fR consists of zero or more
conformant sub-fields. When \f(CW\*(C`Strict\*(C'\fR is disabled, \f(CW$rawdata\fR can
consist of any arbitrary byte stream.
.Sp
The maximum size of the Extra Field 65535 bytes.
.ie n .IP """ExtraFlags => $value""" 5
.el .IP "\f(CWExtraFlags => $value\fR" 5
.IX Item "ExtraFlags => $value"
Sets the \s-1XFL\s0 byte in the gzip header to \f(CW$value\fR.
.Sp
If this option is not present, the value stored in \s-1XFL\s0 field will be
determined by the setting of the \f(CW\*(C`Level\*(C'\fR option.
.Sp
If \f(CW\*(C`Level => Z_BEST_SPEED\*(C'\fR has been specified then \s-1XFL\s0 is set to 2.
If \f(CW\*(C`Level => Z_BEST_COMPRESSION\*(C'\fR has been specified then \s-1XFL\s0 is set to 4.
Otherwise \s-1XFL\s0 is set to 0.
.ie n .IP """Strict => 0|1""" 5
.el .IP "\f(CWStrict => 0|1\fR" 5
.IX Item "Strict => 0|1"
\&\f(CW\*(C`Strict\*(C'\fR will optionally police the values supplied with other options
to ensure they are compliant with \s-1RFC1952\s0.
.Sp
This option is enabled by default.
.Sp
If \f(CW\*(C`Strict\*(C'\fR is enabled the following behaviour will be policed:
.RS 5
.IP "\(bu" 5
The value supplied with the \f(CW\*(C`Name\*(C'\fR option can only contain \s-1ISO\s0 8859\-1
characters.
.IP "\(bu" 5
The value supplied with the \f(CW\*(C`Comment\*(C'\fR option can only contain \s-1ISO\s0 8859\-1
characters plus line-feed.
.IP "\(bu" 5
The values supplied with the \f(CW\*(C`\-Name\*(C'\fR and \f(CW\*(C`\-Comment\*(C'\fR options cannot
contain multiple embedded nulls.
.IP "\(bu" 5