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.\" ========================================================================
.\"
.IX Title "EBook::Tools::LZSS 3pm"
.TH EBook::Tools::LZSS 3pm "2019-08-08" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
EBook::Tools::LZSS \- Lempel\-Ziv\-Storer\-Szymanski compression and decompression
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 5
\& use EBook::Tools::LZSS;
\& my $lzss = EBook::Tools::LZSS\->new(lengthbits => 3,
\&                                    offsetbits => 14,
\&                                    windowinit => \*(Aqthe man\*(Aq);
\& my $textref = $lzss\->uncompress(\e$data);
.Ve
.SH "CONSTRUCTOR AND INITIALIZATION"
.IX Header "CONSTRUCTOR AND INITIALIZATION"
.ie n .SS """new(%args)"""
.el .SS "\f(CWnew(%args)\fP"
.IX Subsection "new(%args)"
Instantiates a new EBook::Tools::LZSS object.
.PP
\fIArguments\fR
.IX Subsection "Arguments"
.PP
All arguments are optional, but must be identical between compression
and decompression for the result to be valid.
.IP "\(bu" 4
\&\f(CW\*(C`lengthbits\*(C'\fR
.Sp
The number of bits used to encode the length of a \s-1LZSS\s0 reference.  If
not specified defaults to 4 bits.
.Sp
The eBookwise .IMP format typically compresses with 3 length bits.
.Sp
Note that the actual length of the \s-1LZSS\s0 reference in bytes is greater
than the value stored in the length bits.  The actual number of bytes
returned is the decoded length bits value plus \f(CW\*(C`maxuncoded\*(C'\fR plus 1,
.IP "\(bu" 4
\&\f(CW\*(C`offsetbits\*(C'\fR
.Sp
The number of bits used to encode the offset to a \s-1LZSS\s0 reference.
This also determines the size of the sliding window of reference data.
If not specified, it defaults to 12 bits (4096\-byte window).
.Sp
The eBookwise .IMP format typically compresses with 14 offset bits
(16384\-byte window).
.IP "\(bu" 4
\&\f(CW\*(C`windowinit\*(C'\fR
.Sp
A string used to initalize the sliding window.  If specified, this
string \s-1MUST\s0 be the same length as the window size, or the subroutine
will croak.  If not specified, the window will be initialized with
spaces.
.IP "\(bu" 4
\&\f(CW\*(C`windowstart\*(C'\fR
.Sp
The first byte position in the window that will be overwritten by
decoded text.  If not specified, defaults to 0.
.IP "\(bu" 4
\&\f(CW\*(C`maxuncoded\*(C'\fR
.Sp
The maximum number of uncoded bytes (?).  This currently isn't used
for that purpose, but determines the actual length of a \s-1LZSS\s0 reference.
.IP "\(bu" 4
\&\f(CW\*(C`screwybits\*(C'\fR
.Sp
If set to true and the number of offset bits is greater than 8, then
the offset bits will be read first in a chunk of 8 for the least
significant bits, and then the remaining bits will be read and use as
the most significant bits.  This seems to be necessary for
compatibility with Michael Dipperstein's \s-1LZSS C\s0 compression library
but does not hold true for \s-1IMP\s0 e\-book \s-1LZSS\s0 decompression.
.IP "\(bu" 4
\&\f(CW\*(C`verbose\*(C'\fR
.Sp
If set to true, compression and uncompression will provide additional
status feedback on \s-1STDOUT.\s0
.SH "METHODS"
.IX Header "METHODS"
.ie n .SS """uncompress(\e$dataref)"""
.el .SS "\f(CWuncompress(\e$dataref)\fP"
.IX Subsection "uncompress($dataref)"
Takes a reference to a compressed data string, uncompresses the data
string and returns a reference to the uncompressed string.
.SH "BUGS AND LIMITATIONS"
.IX Header "BUGS AND LIMITATIONS"
.IP "\(bu" 4
Compression not yet implemented.
.IP "\(bu" 4
The \s-1LZSS\s0 algorithm isn't documented in the \s-1POD.\s0
.IP "\(bu" 4
Once compression is implemented and the algorithm is
documented, this module is a good candidate for being forked off into
its own project.  Relying on it to keep its current name may be
unwise.
.SH "AUTHOR"
.IX Header "AUTHOR"
Zed Pobre <zed@debian.org>
.PP
The design of this module was based on the C \s-1LZSS\s0 library by Michael
Dipperstein, version 0.5.2, at http://michael.dipperstein.com/lzss/
.SH "LICENSE AND COPYRIGHT"
.IX Header "LICENSE AND COPYRIGHT"
Copyright 2008 Zed Pobre
.PP
Licensed to the public under the terms of the \s-1GNU GPL,\s0 version 2.