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.

If an \f(CW\*(C`ExtraField\*(C'\fR option is specified and it is a simple scalar,
it must conform to the sub-field structure as defined in \s-1RFC\s0 1952.
.IP "\(bu" 5
If an \f(CW\*(C`ExtraField\*(C'\fR option is specified the second byte of the \s-1ID\s0 will be
checked in each subfield to ensure that it does not contain the reserved
value 0x00.
.RE
.RS 5
.Sp
When \f(CW\*(C`Strict\*(C'\fR is disabled the following behaviour will be policed:
.IP "\(bu" 5
The value supplied with \f(CW\*(C`\-Name\*(C'\fR option can contain
any character except \s-1NULL\s0.
.IP "\(bu" 5
The value supplied with \f(CW\*(C`\-Comment\*(C'\fR option can contain any character
except \s-1NULL\s0.
.IP "\(bu" 5
The values supplied with the \f(CW\*(C`\-Name\*(C'\fR and \f(CW\*(C`\-Comment\*(C'\fR options can contain
multiple embedded nulls. The string written to the gzip header will
consist of the characters up to, but not including, the first embedded
\&\s-1NULL\s0.
.IP "\(bu" 5
If an \f(CW\*(C`ExtraField\*(C'\fR option is specified and it is a simple scalar, the
structure will not be checked. The only error is if the length is too big.
.IP "\(bu" 5
The \s-1ID\s0 header in an \f(CW\*(C`ExtraField\*(C'\fR sub-field can consist of any two bytes.
.RE
.RS 5
.RE
.Sh "Examples"
.IX Subsection "Examples"
\&\s-1TODO\s0
.SH "Methods"
.IX Header "Methods"
.Sh "print"
.IX Subsection "print"
Usage is
.PP
.Vb 2
\&    $z\->print($data)
\&    print $z $data
.Ve
.PP
Compresses and outputs the contents of the \f(CW$data\fR parameter. This
has the same behaviour as the \f(CW\*(C`print\*(C'\fR built-in.
.PP
Returns true if successful.
.Sh "printf"
.IX Subsection "printf"
Usage is
.PP
.Vb 2
\&    $z\->printf($format, $data)
\&    printf $z $format, $data
.Ve
.PP
Compresses and outputs the contents of the \f(CW$data\fR parameter.
.PP
Returns true if successful.
.Sh "syswrite"
.IX Subsection "syswrite"
Usage is
.PP
.Vb 3
\&    $z\->syswrite $data
\&    $z\->syswrite $data, $length
\&    $z\->syswrite $data, $length, $offset
.Ve
.PP
Compresses and outputs the contents of the \f(CW$data\fR parameter.
.PP
Returns the number of uncompressed bytes written, or \f(CW\*(C`undef\*(C'\fR if
unsuccessful.
.Sh "write"
.IX Subsection "write"
Usage is
.PP
.Vb 3
\&    $z\->write $data
\&    $z\->write $data, $length
\&    $z\->write $data, $length, $offset
.Ve
.PP
Compresses and outputs the contents of the \f(CW$data\fR parameter.
.PP
Returns the number of uncompressed bytes written, or \f(CW\*(C`undef\*(C'\fR if
unsuccessful.
.Sh "flush"
.IX Subsection "flush"
Usage is
.PP
.Vb 2
\&    $z\->flush;
\&    $z\->flush($flush_type);
.Ve
.PP
Flushes any pending compressed data to the output file/buffer.
.PP
This method takes an optional parameter, \f(CW$flush_type\fR, that controls
how the flushing will be carried out. By default the \f(CW$flush_type\fR
used is \f(CW\*(C`Z_FINISH\*(C'\fR. Other valid values for \f(CW$flush_type\fR are
\&\f(CW\*(C`Z_NO_FLUSH\*(C'\fR, \f(CW\*(C`Z_SYNC_FLUSH\*(C'\fR, \f(CW\*(C`Z_FULL_FLUSH\*(C'\fR and \f(CW\*(C`Z_BLOCK\*(C'\fR. It is
strongly recommended that you only set the \f(CW\*(C`flush_type\*(C'\fR parameter if
you fully understand the implications of what it does \- overuse of \f(CW\*(C`flush\*(C'\fR
can seriously degrade the level of compression achieved. See the \f(CW\*(C`zlib\*(C'\fR
documentation for details.
.PP
Returns true on success.
.Sh "tell"
.IX Subsection "tell"
Usage is
.PP
.Vb 2
\&    $z\->tell()
\&    tell $z
.Ve
.PP
Returns the uncompressed file offset.
.Sh "eof"
.IX Subsection "eof"
Usage is
.PP
.Vb 2
\&    $z\->eof();
\&    eof($z);
.Ve
.PP
Returns true if the \f(CW\*(C`close\*(C'\fR method has been called.
.Sh "seek"
.IX Subsection "seek"
.Vb 2
\&    $z\->seek($position, $whence);
\&    seek($z, $position, $whence);
.Ve
.PP
Provides a sub-set of the \f(CW\*(C`seek\*(C'\fR functionality, with the restriction
that it is only legal to seek forward in the output file/buffer.
It is a fatal error to attempt to seek backward.
.PP
Empty parts of the file/buffer will have \s-1NULL\s0 (0x00) bytes written to them.
.PP
The \f(CW$whence\fR parameter takes one the usual values, namely \s-1SEEK_SET\s0,
\&\s-1SEEK_CUR\s0 or \s-1SEEK_END\s0.
.PP
Returns 1 on success, 0 on failure.
.Sh "binmode"
.IX Subsection "binmode"
Usage is
.PP
.Vb 2
\&    $z\->binmode
\&    binmode $z ;
.Ve
.PP
This is a noop provided for completeness.
.Sh "opened"
.IX Subsection "opened"
.Vb 1
\&    $z\->opened()
.Ve
.PP
Returns true if the object currently refers to a opened file/buffer.
.Sh "autoflush"
.IX Subsection "autoflush"
.Vb 2
\&    my $prev = $z\->autoflush()
\&    my $prev = $z\->autoflush(EXPR)
.Ve
.PP
If the \f(CW$z\fR object is associated with a file or a filehandle, this method
returns the current autoflush setting for the underlying filehandle. If
\&\f(CW\*(C`EXPR\*(C'\fR is present, and is non-zero, it will enable flushing after every
write/print operation.
.PP
If \f(CW$z\fR is associated with a buffer, this method has no effect and always
returns \f(CW\*(C`undef\*(C'\fR.
.PP
\&\fBNote\fR that the special variable \f(CW$|\fR \fBcannot\fR be used to set or
retrieve the autoflush setting.
.Sh "input_line_number"
.IX Subsection "input_line_number"
.Vb 2
\&    $z\->input_line_number()
\&    $z\->input_line_number(EXPR)
.Ve
.PP
This method always returns \f(CW\*(C`undef\*(C'\fR when compressing.
.Sh "fileno"
.IX Subsection "fileno"
.Vb 2
\&    $z\->fileno()
\&    fileno($z)
.Ve
.PP
If the \f(CW$z\fR object is associated with a file or a filehandle, this method
will return the underlying file descriptor.
.PP
If the \f(CW$z\fR object is is associated with a buffer, this method will
return undef.
.Sh "close"
.IX Subsection "close"
.Vb 2
\&    $z\->close() ;
\&    close $z ;
.Ve
.PP
Flushes any pending compressed data and then closes the output file/buffer.
.PP
For most versions of Perl this method will be automatically invoked if
the IO::Compress::Gzip 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 \f(CW\*(C`close\*(C'\fR method will be called automatically, but
not until global destruction of all live objects when the program is
terminating.
.PP
Therefore, if you want your scripts to be able to run on all versions
of Perl, you should call \f(CW\*(C`close\*(C'\fR explicitly and not rely on automatic
closing.
.PP
Returns true on success, otherwise 0.
.PP
If the \f(CW\*(C`AutoClose\*(C'\fR option has been enabled when the IO::Compress::Gzip
object was created, and the object is associated with a file, the
underlying file will also be closed.
.Sh "newStream([\s-1OPTS\s0])"
.IX Subsection "newStream([OPTS])"
Usage is
.PP
.Vb 1
\&    $z\->newStream( [OPTS] )
.Ve
.PP
Closes the current compressed data stream and starts a new one.
.PP
\&\s-1OPTS\s0 consists of any of the the options that are available when creating
the \f(CW$z\fR object.
.PP
See the \*(L"Constructor Options\*(R" section for more details.
.Sh "deflateParams"
.IX Subsection "deflateParams"
Usage is
.PP
.Vb 1
\&    $z\->deflateParams
.Ve
.PP
\&\s-1TODO\s0
.SH "Importing"
.IX Header "Importing"
A number of symbolic constants are required by some methods in 
\&\f(CW\*(C`IO::Compress::Gzip\*(C'\fR. None are imported by default.
.IP ":all" 5
.IX Item ":all"
Imports \f(CW\*(C`gzip\*(C'\fR, \f(CW$GzipError\fR and all symbolic
constants that can be used by \f(CW\*(C`IO::Compress::Gzip\*(C'\fR. Same as doing this
.Sp
.Vb 1
\&    use IO::Compress::Gzip qw(gzip $GzipError :constants) ;
.Ve
.IP ":constants" 5
.IX Item ":constants"
Import all symbolic constants. Same as doing this
.Sp
.Vb 1
\&    use IO::Compress::Gzip qw(:flush :level :strategy) ;
.Ve
.IP ":flush" 5
.IX Item ":flush"
These symbolic constants are used by the \f(CW\*(C`flush\*(C'\fR method.
.Sp
.Vb 6
\&    Z_NO_FLUSH
\&    Z_PARTIAL_FLUSH
\&    Z_SYNC_FLUSH
\&    Z_FULL_FLUSH
\&    Z_FINISH
\&    Z_BLOCK
.Ve
.IP ":level" 5
.IX Item ":level"
These symbolic constants are used by the \f(CW\*(C`Level\*(C'\fR option in the constructor.
.Sp
.Vb 4
\&    Z_NO_COMPRESSION
\&    Z_BEST_SPEED
\&    Z_BEST_COMPRESSION
\&    Z_DEFAULT_COMPRESSION
.Ve
.IP ":strategy" 5
.IX Item ":strategy"
These symbolic constants are used by the \f(CW\*(C`Strategy\*(C'\fR option in the constructor.
.Sp
.Vb 5
\&    Z_FILTERED
\&    Z_HUFFMAN_ONLY
\&    Z_RLE
\&    Z_FIXED
\&    Z_DEFAULT_STRATEGY
.Ve
.PP
For
.SH "EXAMPLES"
.IX Header "EXAMPLES"
\&\s-1TODO\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Compress::Zlib, IO::Uncompress::Gunzip, IO::Compress::Deflate, IO::Uncompress::Inflate, IO::Compress::RawDeflate, IO::Uncompress::RawInflate, IO::Compress::Bzip2, IO::Uncompress::Bunzip2, IO::Compress::Lzop, IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::UnLzf, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress
.PP
Compress::Zlib::FAQ
.PP
File::GlobMapper, Archive::Zip,
Archive::Tar,
IO::Zlib
.PP
For \s-1RFC\s0 1950, 1951 and 1952 see 
\&\fIhttp://www.faqs.org/rfcs/rfc1950.html\fR,
\&\fIhttp://www.faqs.org/rfcs/rfc1951.html\fR and
\&\fIhttp://www.faqs.org/rfcs/rfc1952.html\fR
.PP
The \fIzlib\fR compression library was written by Jean-loup Gailly
\&\[e-mail]\fR and Mark Adler \[e-mail]\fR.
.PP
The primary site for the \fIzlib\fR compression library is
\&\fIhttp://www.zlib.org\fR.
.PP
The primary site for gzip is \fIhttp://www.gzip.org\fR.
.SH "AUTHOR"
.IX Header "AUTHOR"
This module was written by Paul Marquess, \[e-mail]\fR.
.SH "MODIFICATION HISTORY"
.IX Header "MODIFICATION HISTORY"
See the Changes file.
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright (c) 2005\-2007 Paul Marquess. All rights reserved.
.PP
This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.