/usr/share/octave/packages/communications-1.1.1/lz77deco.m is in octave-communications-common 1.1.1-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 | ## Copyright (C) 2007 Gorka Lertxundi
##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{m} =} lz77deco (@var{c}, @var{alph}, @var{la}, @var{n})
## Lempel-Ziv 77 source algorithm decoding implementation. Where
##
## @table @asis
## @item @var{m}
## message decoded (1xN).
## @item @var{c}
## encoded message (Mx3).
## @item @var{alph}
## size of alphabet.
## @item @var{la}
## lookahead buffer size.
## @item @var{n}
## sliding window buffer size.
## @end table
## @seealso{lz77enco}
## @end deftypefn
function m = lz77deco(c, alph, la, n)
if (la <= 0 || n <= 0)
error("lz77deco: Lookahead buffer size and window size must be higher than 0.");
endif
if n - la < la
error("lz77deco: Unreachable configuration: n - la >= la.");
endif
if alph < 2
error("lz77deco: Alphabet size within less than 2 symbols? Is that possible?.");
endif
if columns(c) != 3
error("lz77deco: Encoded message must be a Nx3 matrix.");
endif
window = zeros(1,n);
x = length(c);
len = length(c);
for x=1:len
## update window
temp = n-la+c(x,2)-c(x,1);
for y=1:temp
window(n-la+y) = window(c(x,1)+y);
endfor
window(n-la+c(x,2)+1) = c(x,3);
## decoded message
m_deco = window(n-la+1:n-la+c(x,2)+1);
if x == 1
m = m_deco;
else
m = [m m_deco];
endif
## CCW shift
temp = c(x,2)+1;
window(1:n-la) = window(temp+1:n-la+temp);
endfor
endfunction
%!demo
%! lz77deco([8 2 1 ; 7 3 2 ; 6 7 2 ; 2 8 0],3,9,18)
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