compress::zlib.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.

When a dictionary is specified \fICompress::Zlib\fR will automatically
call \f(CW\*(C`deflateSetDictionary\*(C'\fR directly after calling \f(CW\*(C`deflateInit\*(C'\fR. The
Adler32 value for the dictionary can be obtained by calling the method 
\&\f(CW\*(C`$d\-\*(C'\fR\fIdict_adler()\fR>.
.Sp
The default is no dictionary.
.IP "\fB\-Bufsize\fR" 5
.IX Item "-Bufsize"
Sets the initial size for the deflation buffer. If the buffer has to be
reallocated to increase the size, it will grow in increments of
\&\f(CW\*(C`Bufsize\*(C'\fR.
.Sp
The default is 4096.
.PP
Here is an example of using the \f(CW\*(C`deflateInit\*(C'\fR optional parameter list
to override the default buffer size and compression level. All other
options will take their default values.
.PP
.Vb 2
\&    deflateInit( \-Bufsize => 300, 
\&                 \-Level => Z_BEST_SPEED  ) ;
.Ve
.ie n .Sh "\fB($out, \fP\fB$status\fP\fB) = \fP\f(BI$d\fP\fB\->deflate($buffer)\fP"
.el .Sh "\fB($out, \fP\f(CB$status\fP\fB) = \fP\f(CB$d\fP\fB\->deflate($buffer)\fP"
.IX Subsection "($out, $status) = $d->deflate($buffer)"
Deflates the contents of \f(CW$buffer\fR. The buffer can either be a scalar
or a scalar reference.  When finished, \f(CW$buffer\fR will be
completely processed (assuming there were no errors). If the deflation
was successful it returns the deflated output, \f(CW$out\fR, and a status
value, \f(CW$status\fR, of \f(CW\*(C`Z_OK\*(C'\fR.
.PP
On error, \f(CW$out\fR will be \fIundef\fR and \f(CW$status\fR will contain the
\&\fIzlib\fR error code.
.PP
In a scalar context \f(CW\*(C`deflate\*(C'\fR will return \f(CW$out\fR only.
.PP
As with the \fIdeflate\fR function in \fIzlib\fR, it is not necessarily the
case that any output will be produced by this method. So don't rely on
the fact that \f(CW$out\fR is empty for an error test.
.ie n .Sh "\fB($out, \fP\fB$status\fP\fB) = \fP\f(BI$d\fP\fB\->flush([flush_type])\fP"
.el .Sh "\fB($out, \fP\f(CB$status\fP\fB) = \fP\f(CB$d\fP\fB\->flush([flush_type])\fP"
.IX Subsection "($out, $status) = $d->flush([flush_type])"
Typically used to finish the deflation. Any pending output will be
returned via \f(CW$out\fR.
\&\f(CW$status\fR will have a value \f(CW\*(C`Z_OK\*(C'\fR if successful.
.PP
In a scalar context \f(CW\*(C`flush\*(C'\fR will return \f(CW$out\fR only.
.PP
Note that flushing can seriously degrade the compression ratio, so it
should only be used to terminate a decompression (using \f(CW\*(C`Z_FINISH\*(C'\fR) or
when you want to create a \fIfull flush point\fR (using \f(CW\*(C`Z_FULL_FLUSH\*(C'\fR).
.PP
By default the \f(CW\*(C`flush_type\*(C'\fR used is \f(CW\*(C`Z_FINISH\*(C'\fR. Other valid values
for \f(CW\*(C`flush_type\*(C'\fR are \f(CW\*(C`Z_NO_FLUSH\*(C'\fR, \f(CW\*(C`Z_PARTIAL_FLUSH\*(C'\fR, \f(CW\*(C`Z_SYNC_FLUSH\*(C'\fR
and \f(CW\*(C`Z_FULL_FLUSH\*(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. See the \f(CW\*(C`zlib\*(C'\fR documentation for details.
.ie n .Sh "\fB\fP\fB$status\fP\fB = \fP\f(BI$d\fP\fB\->deflateParams([\s-1OPT\s0])\fP"
.el .Sh "\fB\fP\f(CB$status\fP\fB = \fP\f(CB$d\fP\fB\->deflateParams([\s-1OPT\s0])\fP"
.IX Subsection "$status = $d->deflateParams([OPT])"
Change settings for the deflate stream \f(CW$d\fR.
.PP
The list of the valid options is shown below. Options not specified
will remain unchanged.
.IP "\fB\-Level\fR" 5
.IX Item "-Level"
Defines the compression level. Valid values are 0 through 9,
\&\f(CW\*(C`Z_NO_COMPRESSION\*(C'\fR, \f(CW\*(C`Z_BEST_SPEED\*(C'\fR, \f(CW\*(C`Z_BEST_COMPRESSION\*(C'\fR, and
\&\f(CW\*(C`Z_DEFAULT_COMPRESSION\*(C'\fR.
.IP "\fB\-Strategy\fR" 5
.IX Item "-Strategy"
Defines the strategy used to tune the compression. The valid values are
\&\f(CW\*(C`Z_DEFAULT_STRATEGY\*(C'\fR, \f(CW\*(C`Z_FILTERED\*(C'\fR and \f(CW\*(C`Z_HUFFMAN_ONLY\*(C'\fR.
.ie n .Sh "\fB\fP\fB$d\fP\fB\->\fP\f(BIdict_adler()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$d\fP\fB\->\fP\f(BIdict_adler()\fP\fB\fP"
.IX Subsection "$d->dict_adler()"
Returns the adler32 value for the dictionary.
.ie n .Sh "\fB\fP\fB$d\fP\fB\->\fP\f(BImsg()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$d\fP\fB\->\fP\f(BImsg()\fP\fB\fP"
.IX Subsection "$d->msg()"
Returns the last error message generated by zlib.
.ie n .Sh "\fB\fP\fB$d\fP\fB\->\fP\f(BItotal_in()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$d\fP\fB\->\fP\f(BItotal_in()\fP\fB\fP"
.IX Subsection "$d->total_in()"
Returns the total number of bytes uncompressed bytes input to deflate.
.ie n .Sh "\fB\fP\fB$d\fP\fB\->\fP\f(BItotal_out()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$d\fP\fB\->\fP\f(BItotal_out()\fP\fB\fP"
.IX Subsection "$d->total_out()"
Returns the total number of compressed bytes output from deflate.
.Sh "Example"
.IX Subsection "Example"
Here is a trivial example of using \f(CW\*(C`deflate\*(C'\fR. It simply reads standard
input, deflates it and writes it to standard output.
.PP
.Vb 2
\&    use strict ;
\&    use warnings ;
\&
\&    use Compress::Zlib ;
\&
\&    binmode STDIN;
\&    binmode STDOUT;
\&    my $x = deflateInit()
\&       or die "Cannot create a deflation stream\en" ;
\&
\&    my ($output, $status) ;
\&    while (<>)
\&    {
\&        ($output, $status) = $x\->deflate($_) ;
\&    
\&        $status == Z_OK
\&            or die "deflation failed\en" ;
\&    
\&        print $output ;
\&    }
\&    
\&    ($output, $status) = $x\->flush() ;
\&    
\&    $status == Z_OK
\&        or die "deflation failed\en" ;
\&    
\&    print $output ;
.Ve
.SH "Inflate Interface"
.IX Header "Inflate Interface"
This section defines the interface available that allows in-memory
uncompression using the \fIdeflate\fR interface provided by zlib.
.PP
Here is a definition of the interface:
.ie n .Sh "\fB($i, \fP\fB$status\fP\fB) = \fP\f(BIinflateInit()\fP\fB\fP"
.el .Sh "\fB($i, \fP\f(CB$status\fP\fB) = \fP\f(BIinflateInit()\fP\fB\fP"
.IX Subsection "($i, $status) = inflateInit()"
Initialises an inflation stream.
.PP
In a list context it returns the inflation stream, \f(CW$i\fR, and the
\&\fIzlib\fR status code in \f(CW$status\fR. In a scalar context it returns the
inflation stream only.
.PP
If successful, \f(CW$i\fR will hold the inflation stream and \f(CW$status\fR will
be \f(CW\*(C`Z_OK\*(C'\fR.
.PP
If not successful, \f(CW$i\fR will be \fIundef\fR and \f(CW$status\fR will hold the
\&\fIzlib\fR error code.
.PP
The function optionally takes a number of named options specified as
\&\f(CW\*(C`\-Name=>value\*(C'\fR pairs. This allows individual options to be
tailored without having to specify them all in the parameter list.
.PP
For backward compatibility, it is also possible to pass the parameters
as a reference to a hash containing the name=>value pairs.
.PP
The function takes one optional parameter, a reference to a hash.  The
contents of the hash allow the deflation interface to be tailored.
.PP
Here is a list of the valid options:
.IP "\fB\-WindowBits\fR" 5
.IX Item "-WindowBits"
To uncompress an \s-1RFC\s0 1950 data stream, set \f(CW\*(C`WindowBits\*(C'\fR to a positive number.
.Sp
To uncompress an \s-1RFC\s0 1951 data stream, set \f(CW\*(C`WindowBits\*(C'\fR to \f(CW\*(C`\-MAX_WBITS\*(C'\fR.
.Sp
For a full definition of the meaning and valid values for \f(CW\*(C`WindowBits\*(C'\fR refer
to the \fIzlib\fR documentation for \fIinflateInit2\fR.
.Sp
Defaults to \s-1MAX_WBITS\s0.
.IP "\fB\-Bufsize\fR" 5
.IX Item "-Bufsize"
Sets the initial size for the inflation buffer. If the buffer has to be
reallocated to increase the size, it will grow in increments of
\&\f(CW\*(C`Bufsize\*(C'\fR.
.Sp
Default is 4096.
.IP "\fB\-Dictionary\fR" 5
.IX Item "-Dictionary"
The default is no dictionary.
.PP
Here is an example of using the \f(CW\*(C`inflateInit\*(C'\fR optional parameter to
override the default buffer size.
.PP
.Vb 1
\&    inflateInit( \-Bufsize => 300 ) ;
.Ve
.ie n .Sh "\fB($out, \fP\fB$status\fP\fB) = \fP\f(BI$i\fP\fB\->inflate($buffer)\fP"
.el .Sh "\fB($out, \fP\f(CB$status\fP\fB) = \fP\f(CB$i\fP\fB\->inflate($buffer)\fP"
.IX Subsection "($out, $status) = $i->inflate($buffer)"
Inflates the complete contents of \f(CW$buffer\fR. The buffer can either be
a scalar or a scalar reference.
.PP
Returns \f(CW\*(C`Z_OK\*(C'\fR if successful and \f(CW\*(C`Z_STREAM_END\*(C'\fR if the end of the
compressed data has been successfully reached. 
If not successful, \f(CW$out\fR will be \fIundef\fR and \f(CW$status\fR will hold
the \fIzlib\fR error code.
.PP
The \f(CW$buffer\fR parameter is modified by \f(CW\*(C`inflate\*(C'\fR. On completion it
will contain what remains of the input buffer after inflation. This
means that \f(CW$buffer\fR will be an empty string when the return status is
\&\f(CW\*(C`Z_OK\*(C'\fR. When the return status is \f(CW\*(C`Z_STREAM_END\*(C'\fR the \f(CW$buffer\fR
parameter will contains what (if anything) was stored in the input
buffer after the deflated data stream.
.PP
This feature is useful when processing a file format that encapsulates
a  compressed data stream (e.g. gzip, zip).
.ie n .Sh "\fB\fP\fB$status\fP\fB = \fP\f(BI$i\fP\fB\->inflateSync($buffer)\fP"
.el .Sh "\fB\fP\f(CB$status\fP\fB = \fP\f(CB$i\fP\fB\->inflateSync($buffer)\fP"
.IX Subsection "$status = $i->inflateSync($buffer)"
Scans \f(CW$buffer\fR until it reaches either a \fIfull flush point\fR or the
end of the buffer.
.PP
If a \fIfull flush point\fR is found, \f(CW\*(C`Z_OK\*(C'\fR is returned and \f(CW$buffer\fR
will be have all data up to the flush point removed. This can then be
passed to the \f(CW\*(C`deflate\*(C'\fR method.
.PP
Any other return code means that a flush point was not found. If more
data is available, \f(CW\*(C`inflateSync\*(C'\fR can be called repeatedly with more
compressed data until the flush point is found.
.ie n .Sh "\fB\fP\fB$i\fP\fB\->\fP\f(BIdict_adler()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$i\fP\fB\->\fP\f(BIdict_adler()\fP\fB\fP"
.IX Subsection "$i->dict_adler()"
Returns the adler32 value for the dictionary.
.ie n .Sh "\fB\fP\fB$i\fP\fB\->\fP\f(BImsg()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$i\fP\fB\->\fP\f(BImsg()\fP\fB\fP"
.IX Subsection "$i->msg()"
Returns the last error message generated by zlib.
.ie n .Sh "\fB\fP\fB$i\fP\fB\->\fP\f(BItotal_in()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$i\fP\fB\->\fP\f(BItotal_in()\fP\fB\fP"
.IX Subsection "$i->total_in()"
Returns the total number of bytes compressed bytes input to inflate.
.ie n .Sh "\fB\fP\fB$i\fP\fB\->\fP\f(BItotal_out()\fP\fB\fP"
.el .Sh "\fB\fP\f(CB$i\fP\fB\->\fP\f(BItotal_out()\fP\fB\fP"
.IX Subsection "$i->total_out()"
Returns the total number of uncompressed bytes output from inflate.
.Sh "Example"
.IX Subsection "Example"
Here is an example of using \f(CW\*(C`inflate\*(C'\fR.
.PP
.Vb 2
\&    use strict ;
\&    use warnings ;
\&    
\&    use Compress::Zlib ;
\&    
\&    my $x = inflateInit()
\&       or die "Cannot create a inflation stream\en" ;
\&    
\&    my $input = \*(Aq\*(Aq ;
\&    binmode STDIN;
\&    binmode STDOUT;
\&    
\&    my ($output, $status) ;
\&    while (read(STDIN, $input, 4096))
\&    {
\&        ($output, $status) = $x\->inflate(\e$input) ;
\&    
\&        print $output 
\&            if $status == Z_OK or $status == Z_STREAM_END ;
\&    
\&        last if $status != Z_OK ;
\&    }
\&    
\&    die "inflation failed\en"
\&        unless $status == Z_STREAM_END ;
.Ve
.SH "CHECKSUM FUNCTIONS"
.IX Header "CHECKSUM FUNCTIONS"
Two functions are provided by \fIzlib\fR to calculate checksums. For the
Perl interface, the order of the two parameters in both functions has
been reversed. This allows both running checksums and one off
calculations to be done.
.PP
.Vb 2
\&    $crc = adler32($buffer [,$crc]) ;
\&    $crc = crc32($buffer [,$crc]) ;
.Ve
.PP
The buffer parameters can either be a scalar or a scalar reference.
.PP
If the \f(CW$crc\fR parameters is \f(CW\*(C`undef\*(C'\fR, the crc value will be reset.
.PP
If you have built this module with zlib 1.2.3 or better, two more
CRC-related functions are available.
.PP
.Vb 2
\&    $crc = adler32_combine($crc1, $crc2, $len2)l
\&    $crc = crc32_combine($adler1, $adler2, $len2)
.Ve
.PP
These functions allow checksums to be merged.
.SH "CONSTANTS"
.IX Header "CONSTANTS"
All the \fIzlib\fR constants are automatically imported when you make use
of \fICompress::Zlib\fR.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
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::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) 1995\-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.