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view main/comm/inst/lz77deco.m @ 8092:90a46621a91d octave-forge
More updates for the communications package for 3.4
author | adb014 |
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date | Sun, 22 May 2011 19:32:41 +0000 |
parents | 2de537641f94 |
children | 67d4cfc5eeb3 |
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## 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 2 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)